sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

sys: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

cluster_write(): do not access buffer after it is released

The issue was reported by
Alexander Lochmann <alexander.lochmann@tu-dortmund.de>,
who found the problem by performing lock analysis using LockDoc,
see https://doi.org/10.1145/3302424.3303948.

Reviewed by: mckusick
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D31780

Minor style tidy: if( -> if (

Fix a few 'if(' to be 'if (' in a few places, per style(9) and
overwhelming usage in the rest of the kernel / tree.

MFC After: 3 days
Sponsored by: Netflix

vnode: move write cluster support data to inodes.

The data is only needed by filesystems that
1. use buffer cache
2. utilize clustering write support.

Requested by: mjg
Reviewed by: asomers (previous version), fsu (ext2 parts), mckusick
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28679

Delete dead CLUSTERDEBUG config option.

Reviewed by: mckusick
Tested by: pho
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D28679

Make MAXPHYS tunable. Bump MAXPHYS to 1M.

Replace MAXPHYS by runtime variable maxphys. It is initialized from
MAXPHYS by default, but can be also adjusted with the tunable kern.maxphys.

Make b_pages[] array in struct buf flexible. Size b_pages[] for buffer
cache buffers exactly to atop(maxbcachebuf) (currently it is sized to
atop(MAXPHYS)), and b_pages[] for pbufs is sized to atop(maxphys) + 1.
The +1 for pbufs allow several pbuf consumers, among them vmapbuf(),
to use unaligned buffers still sized to maxphys, esp. when such
buffers come from userspace (*). Overall, we save significant amount
of otherwise wasted memory in b_pages[] for buffer cache buffers,
while bumping MAXPHYS to desired high value.

Eliminate all direct uses of the MAXPHYS constant in kernel and driver
sources, except a place which initialize maxphys. Some random (and
arguably weird) uses of MAXPHYS, e.g. in linuxolator, are converted
straight. Some drivers, which use MAXPHYS to size embeded structures,
get private MAXPHYS-like constant; their convertion is out of scope
for this work.

Changes to cam/, dev/ahci, dev/ata, dev/mpr, dev/mpt, dev/mvs,
dev/siis, where either submitted by, or based on changes by mav.

Suggested by: mav (*)
Reviewed by: imp, mav, imp, mckusick, scottl (intermediate versions)
Tested by: pho
Sponsored by: The FreeBSD Foundation
Differential revision: https://reviews.freebsd.org/D27225

vfs: fix trivial whitespace issues which don't interefere with blame

.. even without the -w switch

Remove duplicated empty lines from kern/*.c

No functional changes.

Do not use waitable allocation of pbuf when creating cluster for write.

Previously just ensuring that we do not sleep when clustering for
md(4) vnode was enough. Now, with the switch of the pbuf allocator to
uma and completely broken per-subsystem pbuf limits, it might cause
unbounded sleep even for non-md(4) vnodes.

Reported and tested by: pho
Reviewed by: markj
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D22899

Currently the breadn_flags() and getblkx() interfaces are passed
the vnode, logical block number, and size of data block that is
being requested. They then use the VOP_BMAP function to calculate
the mapping from logical block number to physical block number from
which to access the data. This change expands the interface to also
pass the physical block number in cases where the VOP_MAP function
may no longer work, for example when a file is being truncated.

No functional change.

Reviewed by: kib
Tested by: Peter Holm
Sponsored by: Netflix

Drop the object lock in vfs_bio and cluster where it is now safe to do so.

Recent changes to busy/valid/dirty have enabled page based synchronization
and the object lock is no longer required in many cases.

Reviewed by: kib
Sponsored by: Netflix, Intel
Differential Revision: https://reviews.freebsd.org/D21597

(4/6) Protect page valid with the busy lock.

Atomics are used for page busy and valid state when the shared busy is
held. The details of the locking protocol and valid and dirty
synchronization are in the updated vm_page.h comments.

Reviewed by: kib, markj
Tested by: pho
Sponsored by: Netflix, Intel
Differential Revision: https://reviews.freebsd.org/D21594

(1/6) Replace busy checks with acquires where it is trival to do so.

This is the first in a series of patches that promotes the page busy field
to a first class lock that no longer requires the object lock for
consistency.

Reviewed by: kib, markj
Tested by: pho
Sponsored by: Netflix, Intel
Differential Revision: https://reviews.freebsd.org/D21548

The VFS-level clustering code collects together sequential blocks
by issuing delayed-writes (bdwrite()) until a non-sequential block
is written or the maximum cluster size is reached. At that point
it collects the delayed buffers together (using bread()) to write
them in a single operation. The assumption was that since we just
looked at them they will still be in memory so there is no need to
check for a read error from bread(). Very occationally (apparently
every 10-hours or so when being pounded by Peter Holm's tests)
this assumption is wrong.

The fix is to check for errors from bread() and fail the cluster
write thus falling back to the default individual flushing of any
still dirty buffers.

Reported by: Peter Holm and Chuck Silvers
Reviewed by: kib
MFC after: 3 days

Use an atomic reference count for paging in progress so that callers do not
require the object lock.

Reviewed by: markj
Tested by: pho (as part of a larger branch)
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D21311

Allocate pager bufs from UMA instead of 80-ish mutex protected linked list.

o In vm_pager_bufferinit() create pbuf_zone and start accounting on how many
pbufs are we going to have set.
In various subsystems that are going to utilize pbufs create private zones
via call to pbuf_zsecond_create(). The latter calls uma_zsecond_create(),
and sets a limit on created zone. After startup preallocate pbufs according
to requirements of all pbuf zones.

Subsystems that used to have a private limit with old allocator now have
private pbuf zones: md(4), fusefs, NFS client, smbfs, VFS cluster, FFS,
swap, vnode pager.

The following subsystems use shared pbuf zone: cam(4), nvme(4), physio(9),
aio(4). They should have their private limits, but changing that is out of
scope of this commit.

o Fetch tunable value of kern.nswbuf from init_param2() and while here move
NSWBUF_MIN to opt_param.h and eliminate opt_swap.h, that was holding only
this option.
Default values aren't touched by this commit, but they probably should be
reviewed wrt to modern hardware.

This change removes a tight bottleneck from sendfile(2) operation, that
uses pbufs in vnode pager. Other pagers also would benefit from faster
allocation.

Together with: gallatin
Tested by: pho

ANSIfy sys/kern

Detect and optimize reads from the hole on UFS.

- Create getblkx(9) variant of getblk(9) which can return error.
- Add GB_NOSPARSE flag for getblk()/getblkx() which requests that BMAP
was performed before the buffer is created, and EJUSTRETURN returned
in case the requested block does not exist.
- Make ffs_read() use GB_NOSPARSE to avoid instantiating buffer (and
allocating the pages for it), copying from zero_region instead.

The end result is less page allocations and buffer recycling when a
hole is read, which is important for some benchmarks.

Requested and reviewed by: jeff
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Differential revision: https://reviews.freebsd.org/D14917

sys: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 3-Clause license.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

Move bogus_page declaration to vm_page.h and initialization to vm_page.c.

Reviewed by: kib

Add BUF_TRACKING and FULL_BUF_TRACKING buffer debugging

Upstream the BUF_TRACKING and FULL_BUF_TRACKING buffer debugging code.
This can be handy in tracking down what code touched hung bios and bufs
last. The full history is especially useful, but adds enough bloat that
it shouldn't be enabled in release builds.

Function names (or arbitrary string constants) are tracked in a
fixed-size ring in bufs. Bios gain a pointer to the upper buf for
tracking. SCSI CCBs gain a pointer to the upper bio for tracking.

Reviewed by: markj
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D8366

Renumber license clauses in sys/kern to avoid skipping #3

Remove b_pin_count from struct buf.

It was added in r153192 for XFS and doesn't appear to have been used for
anything else. XFS was disconnected in r241607 and removed entirely in
r247631.

Reported by: mlaier
Reviewed by: imp, kib
Differential Revision: https://reviews.freebsd.org/D7468

sys/kern: spelling fixes in comments.

No functional change.

kern: for pointers replace 0 with NULL.

These are mostly cosmetical, no functional change.

Found with devel/coccinelle.

Add four new RCTL resources - readbps, readiops, writebps and writeiops,
for limiting disk (actually filesystem) IO.

Note that in some cases these limits are not quite precise. It's ok,
as long as it's within some reasonable bounds.

Testing - and review of the code, in particular the VFS and VM parts - is
very welcome.

MFC after: 1 month
Relnotes: yes
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D5080

The bread() function was inconsistent about whether it would return
a buffer pointer in the event of an error (for some errors it would
return a buffer pointer and for other errors it would not return a
buffer pointer). The cluster_read() function was similarly inconsistent.

Clients of these functions were inconsistent in handling errors.
Some would assume that no buffer was returned after an error and
would thus lose buffers under certain error conditions. Others would
assume that brelse() should always be called after an error and
would thus panic the system under certain error conditions.

To correct both of these problems with minimal code churn, bread()
and cluster_write() now always free the buffer when returning an
error thus ensuring that buffers will never be lost. The brelse()
routine checks for being passed a NULL buffer pointer and silently
returns to avoid panics. Thus both approaches to handling error
returns from bread() and cluster_read() will work correctly.

Future code should be written assuming that bread() and cluster_read()
will never return a buffer with an error, so should not attempt to
brelse() the buffer when an error is returned.

Reviewed by: kib

Refactor unmapped buffer address handling.
- Use pointer assignment rather than a combination of pointers and
flags to switch buffers between unmapped and mapped. This eliminates
multiple flags and generally simplifies the logic.
- Eliminate b_saveaddr since it is only used with pager bufs which have
their b_data re-initialized on each allocation.
- Gather up some convenience routines in the buffer cache for
manipulating buf space and buf malloc space.
- Add an inline, buf_mapped(), to standardize checks around unmapped
buffers.

In collaboration with: mlaier
Reviewed by: kib
Tested by: pho (many small revisions ago)
Sponsored by: EMC / Isilon Storage Division

Remove several write-only variables, all reported by the gcc 4.9
buildkernel run.

Some of them were write-only under some kernel options, e.g. variables
keeping values only used by CTR() macros. It costs nothing to the
code readability and correctness to eliminate the warnings in those
cases too by removing the local cached values used only for
single-access.

Review: https://reviews.freebsd.org/D2665
Reviewed by: rodrigc
Looked at by: bjk
Sponsored by: The FreeBSD Foundation
MFC after: 1 week

When allocating a pbuf for the cluster write, do not sleep waiting
for the available pbuf when passed vnode is backing md(4). Other i/o
directed to the same md device might already hold pbufs, and then we
could deadlock since only our progress can free a pbuf needed for
wakeup.

Obtained from: projects/vm6
Reminded and tested by: pho
MFC after: 1 week

Fix a whitespace.

Both cluster_rbuild() and cluster_wbuild() sometimes set the pages
shared busy without first draining the hard busy state. Previously it
went unnoticed since VPO_BUSY and m->busy fields were distinct, and
vm_page_io_start() did not verified that the passed page has VPO_BUSY
flag cleared, but such page state is wrong. New implementation is
more strict and catched this case.

Drain the busy state as needed, before calling vm_page_sbusy().

Tested by: pho, jkim
Sponsored by: The FreeBSD Foundation

The soft and hard busy mechanism rely on the vm object lock to work.
Unify the 2 concept into a real, minimal, sxlock where the shared
acquisition represent the soft busy and the exclusive acquisition
represent the hard busy.
The old VPO_WANTED mechanism becames the hard-path for this new lock
and it becomes per-page rather than per-object.
The vm_object lock becames an interlock for this functionality:
it can be held in both read or write mode.
However, if the vm_object lock is held in read mode while acquiring
or releasing the busy state, the thread owner cannot make any
assumption on the busy state unless it is also busying it.

Also:
- Add a new flag to directly shared busy pages while vm_page_alloc
and vm_page_grab are being executed. This will be very helpful
once these functions happen under a read object lock.
- Move the swapping sleep into its own per-object flag

The KPI is heavilly changed this is why the version is bumped.
It is very likely that some VM ports users will need to change
their own code.

Sponsored by: EMC / Isilon storage division
Discussed with: alc
Reviewed by: jeff, kib
Tested by: gavin, bapt (older version)
Tested by: pho, scottl

- Convert the bufobj lock to rwlock.
- Use a shared bufobj lock in getblk() and inmem().
- Convert softdep's lk to rwlock to match the bufobj lock.
- Move INFREECNT to b_flags and protect it with the buf lock.
- Remove unnecessary locking around bremfree() and BKGRDINPROG.

Sponsored by: EMC / Isilon Storage Division
Discussed with: mckusick, kib, mdf

Add a sysctl vfs.read_min to complement the exiting vfs.read_max. It
defaults to 1, meaning that it's off.

When read-ahead is enabled on a file, the vfs cluster code deliberately
breaks a read into 2 I/O transactions; one to satisfy the actual read,
and one to perform read-ahead. This makes sense in low-latency
circumstances, but often produces unbalanced i/o transactions that
penalize disks. By setting vfs.read_min, we can tell the algorithm to
fetch a larger transaction that what we asked for, achieving the same
effect as the read-ahead but without the doubled, unbalanced transaction
and the slightly lower latency. This significantly helps our workloads
with video streaming.

Submitted by: emax
Reviewed by: kib
Obtained from: Netflix

Implement the concept of the unmapped VMIO buffers, i.e. buffers which
do not map the b_pages pages into buffer_map KVA. The use of the
unmapped buffers eliminate the need to perform TLB shootdown for
mapping on the buffer creation and reuse, greatly reducing the amount
of IPIs for shootdown on big-SMP machines and eliminating up to 25-30%
of the system time on i/o intensive workloads.

The unmapped buffer should be explicitely requested by the GB_UNMAPPED
flag by the consumer. For unmapped buffer, no KVA reservation is
performed at all. The consumer might request unmapped buffer which
does have a KVA reserve, to manually map it without recursing into
buffer cache and blocking, with the GB_KVAALLOC flag.

When the mapped buffer is requested and unmapped buffer already
exists, the cache performs an upgrade, possibly reusing the KVA
reservation.

Unmapped buffer is translated into unmapped bio in g_vfs_strategy().
Unmapped bio carry a pointer to the vm_page_t array, offset and length
instead of the data pointer. The provider which processes the bio
should explicitely specify a readiness to accept unmapped bio,
otherwise g_down geom thread performs the transient upgrade of the bio
request by mapping the pages into the new bio_transient_map KVA
submap.

The bio_transient_map submap claims up to 10% of the buffer map, and
the total buffer_map + bio_transient_map KVA usage stays the
same. Still, it could be manually tuned by kern.bio_transient_maxcnt
tunable, in the units of the transient mappings. Eventually, the
bio_transient_map could be removed after all geom classes and drivers
can accept unmapped i/o requests.

Unmapped support can be turned off by the vfs.unmapped_buf_allowed
tunable, disabling which makes the buffer (or cluster) creation
requests to ignore GB_UNMAPPED and GB_KVAALLOC flags. Unmapped
buffers are only enabled by default on the architectures where
pmap_copy_page() was implemented and tested.

In the rework, filesystem metadata is not the subject to maxbufspace
limit anymore. Since the metadata buffers are always mapped, the
buffers still have to fit into the buffer map, which provides a
reasonable (but practically unreachable) upper bound on it. The
non-metadata buffer allocations, both mapped and unmapped, is
accounted against maxbufspace, as before. Effectively, this means that
the maxbufspace is forced on mapped and unmapped buffers separately.
The pre-patch bufspace limiting code did not worked, because
buffer_map fragmentation does not allow the limit to be reached.

By Jeff Roberson request, the getnewbuf() function was split into
smaller single-purpose functions.

Sponsored by: The FreeBSD Foundation
Discussed with: jeff (previous version)
Tested by: pho, scottl (previous version), jhb, bf
MFC after: 2 weeks

Some style fixes.

Sponsored by: The FreeBSD Foundation

Add currently unused flag argument to the cluster_read(),
cluster_write() and cluster_wbuild() functions. The flags to be
allowed are a subset of the GB_* flags for getblk().

Sponsored by: The FreeBSD Foundation
Tested by: pho

Switch the vm_object mutex to be a rwlock. This will enable in the
future further optimizations where the vm_object lock will be held
in read mode most of the time the page cache resident pool of pages
are accessed for reading purposes.

The change is mostly mechanical but few notes are reported:
* The KPI changes as follow:
- VM_OBJECT_LOCK() -> VM_OBJECT_WLOCK()
- VM_OBJECT_TRYLOCK() -> VM_OBJECT_TRYWLOCK()
- VM_OBJECT_UNLOCK() -> VM_OBJECT_WUNLOCK()
- VM_OBJECT_LOCK_ASSERT(MA_OWNED) -> VM_OBJECT_ASSERT_WLOCKED()
(in order to avoid visibility of implementation details)
- The read-mode operations are added:
VM_OBJECT_RLOCK(), VM_OBJECT_TRYRLOCK(), VM_OBJECT_RUNLOCK(),
VM_OBJECT_ASSERT_RLOCKED(), VM_OBJECT_ASSERT_LOCKED()
* The vm/vm_pager.h namespace pollution avoidance (forcing requiring
sys/mutex.h in consumers directly to cater its inlining functions
using VM_OBJECT_LOCK()) imposes that all the vm/vm_pager.h
consumers now must include also sys/rwlock.h.
* zfs requires a quite convoluted fix to include FreeBSD rwlocks into
the compat layer because the name clash between FreeBSD and solaris
versions must be avoided.
At this purpose zfs redefines the vm_object locking functions
directly, isolating the FreeBSD components in specific compat stubs.

The KPI results heavilly broken by this commit. Thirdy part ports must
be updated accordingly (I can think off-hand of VirtualBox, for example).

Sponsored by: EMC / Isilon storage division
Reviewed by: jeff
Reviewed by: pjd (ZFS specific review)
Discussed with: alc
Tested by: pho

Add barrier write capability to the VFS buffer interface. A barrier
write is a disk write request that tells the disk that the buffer
being written must be committed to the media along with any writes
that preceeded it before any future blocks may be written to the drive.

Barrier writes are provided by adding the functions bbarrierwrite
(bwrite with barrier) and babarrierwrite (bawrite with barrier).

Following a bbarrierwrite the client knows that the requested buffer
is on the media. It does not ensure that buffers written before that
buffer are on the media. It only ensure that buffers written before
that buffer will get to the media before any buffers written after
that buffer. A flush command must be sent to the disk to ensure that
all earlier written buffers are on the media.

Reviewed by: kib
Tested by: Peter Holm

Correct a KASSERT message.

Submitted by: bde

Unbreak detection of the async mode for clustered writes after r231075.

Submitted by: bde
MFC after: 12 days

The hardware has caught up; improvements are now observed even at 128,
but stay conservative and bump read_max to "only" 64 (it will probably be
a good idea to increase this to 128 after the next major release).

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Bumping the read-ahead count once more, to value equivalent to 512 KiB on
most system, based on benchmark results on a low-end fibre channel SAN
under VMWare:

vfs.read_max read performance
8 (historical default) 83 MB/s
16 (recent bump) 131 MB/s
32 (this version) 152 MB/s
64 157 MB/s

(results are +/- 3 MB/s)

As read-ahead is heuristic, based on past IO requests, it shouldn't be
problematic. The new default is still smaller then in other OSes.

To help with sequential read UFS performance on modern systems, increase
the vfs.read_max default. For most systems this means going from 128 KiB
to 256 KiB, which is still very conservative and lower than what most
other operating systems use, but as a sane default should not
interfere much with existing systems.

For systems with RAID volumes and/or virtualization envirnments, where
read performance is very important, increasing this sysctl tunable to 32
or even more will demonstratively yield additional performance benefits.

If MAXPHYS ever gets bumped up, it will probably be a good idea to slave
read_max to it.

Remove a stale comment. The very same revision (r85511) that introduced
this comment also implemented the proposed change to the code.

Approved by: re (kib)

Correct a long-standing performance bug in cluster_rbuild(). Specifically,
in the case of a file system with a block size that is less than the page
size, cluster_rbuild() looks at too many of the page's valid bits.
Consequently, it may terminate prematurely, resulting in poor performance.

Reported by: bde
Reviewed by: tegge
Approved by: re (kib)

Eliminate unnecessary obfuscation when testing a page's valid bits.

- Import the HEAD csup code which is the basis for the cvsmode work.

- Complete part of the unfinished bufobj work by consistently using
BO_LOCK/UNLOCK/MTX when manipulating the bufobj.
- Create a new lock in the bufobj to lock bufobj fields independently.
This leaves the vnode interlock as an 'identity' lock while the bufobj
is an io lock. The bufobj lock is ordered before the vnode interlock
and also before the mnt ilock.
- Exploit this new lock order to simplify softdep_check_suspend().
- A few sync related functions are marked with a new XXX to note that
we may not properly interlock against a non-zero bv_cnt when
attempting to sync all vnodes on a mountlist. I do not believe this
race is important. If I'm wrong this will make these locations easier
to find.

Reviewed by: kib (earlier diff)
Tested by: kris, pho (earlier diff)

- Move rusage from being per-process in struct pstats to per-thread in
td_ru. This removes the requirement for per-process synchronization in
statclock() and mi_switch(). This was previously supported by
sched_lock which is going away. All modifications to rusage are now
done in the context of the owning thread. reads proceed without locks.
- Aggregate exiting threads rusage in thread_exit() such that the exiting
thread's rusage is not lost.
- Provide a new routine, rufetch() to fetch an aggregate of all rusage
structures from all threads in a process. This routine must be used
in any place requiring a rusage from a process prior to it's exit. The
exited process's rusage is still available via p_ru.
- Aggregate tick statistics only on demand via rufetch() or when a thread
exits. Tick statistics are kept in the thread and protected by sched_lock
until it exits.

Initial patch by: attilio
Reviewed by: attilio, bde (some objections), arch (mostly silent)

Change these descriptions of memory types used in malloc(9), as their
current, rather long strings make output from vmstat -m look unpleasant.

Approved by: cognet (mentor)

Replace PG_BUSY with VPO_BUSY. In other words, changes to the page's
busy flag, i.e., VPO_BUSY, are now synchronized by the per-vm object
lock instead of the global page queues lock.

Add mnt_noasync counter to better handle interleaved calls to nmount(),
sync() and sync_fsync() without losing MNT_ASYNC. Add MNTK_ASYNC flag
which is set only when MNT_ASYNC is set and mnt_noasync is zero, and
check that flag instead of MNT_ASYNC before initiating async io.

Remove unused leaked debug function prototype.

Let snapshots make a copy of old contents for all buffers taking part in a
cluster instead of just the first buffer.

Delay buf_start() calls until snapshots have a copy of old content.

PR: kern/93942

Changes imported from XFS for FreeBSD project:
- add fields to struct buf (needed by XFS)
- 3 private fields: b_fsprivate1, b_fsprivate2, b_fsprivate3
- b_pin_count, count of pinned buffer

- add new B_MANAGED flag
- add breada() function to initiate asynchronous I/O on read-ahead blocks.
- add bufdone_finish(), bpin(), bunpin_wait() functions

Patches provided by: kan
Reviewed by: phk
Silence on: arch@

Normalize a significant number of kernel malloc type names:

- Prefer '_' to ' ', as it results in more easily parsed results in
memory monitoring tools such as vmstat.

- Remove punctuation that is incompatible with using memory type names
as file names, such as '/' characters.

- Disambiguate some collisions by adding subsystem prefixes to some
memory types.

- Generally prefer lower case to upper case.

- If the same type is defined in multiple architecture directories,
attempt to use the same name in additional cases.

Not all instances were caught in this change, so more work is required to
finish this conversion. Similar changes are required for UMA zone names.

Only set B_RAM (Read ahead mark) on an incore buffers if we can lock it.
This fixes a race condition caused by the unlocked write access to the
b_flags field.

MFC after: 3 days

Do not use vm_pager_init() to initialize vnode_pbuf_freecnt variable.
vm_pager_init() is run before required nswbuf variable has been set
to correct value. This caused system to run with single pbuf available
for vnode_pager. Handle both cluster_pbuf_freecnt and vnode_pbuf_freecnt
variable in the same way.

Reported by: ade
Obtained from: alc
MFC after: 2 days

Revert revision 1.164: pmap_qremove() does not require protection by
VM_LOCK_GIANT.

Discussed with: jeff

- Remove spls and comments relating to them.

- Call VM_LOCK_GIANT in cluster_callback() to protect some pmap calls. VFS
will not be acquiring Giant before calling this function anymore.

Sponsored by: Isilon Systems, Inc.

make cluster_callback() static

- Remove GIANT_REQUIRED where giant is no longer required.

Sponsored By: Isilon Systems, Inc.

Eliminate (now) unnecessary acquisition and release of the global page
queues lock.

Don't manually set b_bufobj, pbgetvp() does this for us.

Explicitly call pbrelvp()

Retire b_magic now, we have the bufobj containing the same hint.

Lock bp->b_bufobj->b_object instead of bp->b_object

Avoid using bp->b_vp when we already have the vnode by other means.

Synchronize access to the vm page's PG_BUSY flag using the containing vm
object's lock. In the same place, eliminate unnecessary checks for a NULL
vm object pointer.

Move the buffer method vector (buf->b_op) to the bufobj.

Extend it with a strategy method.

Add bufstrategy() which do the usual VOP_SPECSTRATEGY/VOP_STRATEGY
song and dance.

Rename ibwrite to bufwrite().

Move the two NFS buf_ops to more sensible places, add bufstrategy
to them.

Add inlines for bwrite() and bstrategy() which calls through
buf->b_bufobj->b_ops->b_{write,strategy}().

Replace almost all VOP_STRATEGY()/VOP_SPECSTRATEGY() calls with bstrategy().

Add b_bufobj to struct buf which eventually will eliminate the need for b_vp.

Initialize b_bufobj for all buffers.

Make incore() and gbincore() take a bufobj instead of a vnode.

Make inmem() local to vfs_bio.c

Change a lot of VI_[UN]LOCK(bp->b_vp) to BO_[UN]LOCK(bp->b_bufobj)
also VI_MTX() to BO_MTX(),

Make buf_vlist_add() take a bufobj instead of a vnode.

Eliminate other uses of bp->b_vp where bp->b_bufobj will do.

Various minor polishing: remove "register", turn panic into KASSERT,
use new function declarations, TAILQ_FOREACH_SAFE() etc.

Move the VI_BWAIT flag into no bo_flag element of bufobj and call it BO_WWAIT

Add bufobj_wref(), bufobj_wdrop() and bufobj_wwait() to handle the write
count on a bufobj. Bufobj_wdrop() replaces vwakeup().

Use these functions all relevant places except in ffs_softdep.c where
the use if interlocked_sleep() makes this impossible.

Rename b_vnbufs to b_bobufs now that we touch all the relevant files anyway.

Give cluster_write() an explicit vnode argument.

In the future a struct buf will not automatically point out a vnode for us.

Eliminate unused second argument to reassignbuf() and simplify it
accordingly.

Remove advertising clause from University of California Regent's license,
per letter dated July 22, 1999.

Approved by: core

Update the statfs structure with 64-bit fields to allow
accurate reporting of multi-terabyte filesystem sizes.

You should build and boot a new kernel BEFORE doing a `make world'
as the new kernel will know about binaries using the old statfs
structure, but an old kernel will not know about the new system
calls that support the new statfs structure. Running an old kernel
after a `make world' will cause programs such as `df' that do a
statfs system call to fail with a bad system call.

Reviewed by: Bruce Evans <bde@zeta.org.au>
Reviewed by: Tim Robbins <tjr@freebsd.org>
Reviewed by: Julian Elischer <julian@elischer.org>
Reviewed by: the hoards of <arch@freebsd.org>
Sponsored by: DARPA & NAI Labs.

Initialize the buf's b_object in pbgetvp(). Clear it in pbrelvp(). (This
facilitates synchronization of the vm page's valid field using the
vm object's lock.)

Suggested by: tegge

- Synchronize access to a vm page's valid field using the containing
vm object's lock.

DuH!

bp->b_iooffset (the spot on the disk), not bp->b_offset (the offset in
the file)

Initialize bp->b_offset before calling VOP_STRATEGY()

- Move BX_BKGRDWAIT and BX_BKGRDINPROG to BV_ and the b_vflags field.
- Surround all accesses of the BKGRD{WAIT,INPROG} flags with the vnode
interlock.
- Don't use the B_LOCKED flag and QUEUE_LOCKED for background write
buffers. Check for the BKGRDINPROG flag before recycling or throwing
away a buffer. We do this instead because it is not safe for us to move
the original buffer to a new queue from the callback on the background
write buffer.
- Remove the B_LOCKED flag and the locked buffer queue. They are no longer
used.
- The vnode interlock is used around checks for BKGRDINPROG where it may
not be strictly necessary. If we hold the buf lock the a back-ground
write will not be started without our knowledge, one may only be
completed while we're not looking. Rather than remove the code, Document
two of the places where this extra locking is done. A pass should be
done to verify and minimize the locking later.

Revert stuff which accidentally ended up in the previous commit.

Don't attempt to inline large functions mb_alloc() and mb_free(),
it more than doubles the text size of this file.

GCC has wisely ignored us on this previously

Use __FBSDID().

The IO_NOWDRAIN and B_NOWDRAIN hacks are no longer needed to prevent
deadlocks with vnode backed md(4) devices because md now uses a
kthread to run the bio requests instead of doing it directly from
the bio down path.

In cluster_wbuild(), initialise b_iocmd to BIO_WRITE before calling
buf_start() to avoid triggering a panic in softdep_disk_io_initiation()
if b_iocmd happened to be BIO_READ. The later initialisation of
b_iocmd in cluster_wbuild() could probably be moved to before the
buf_start() call, but this patch keeps the change as simple as
possible.

This is reported to fix occasional "softdep_disk_io_initiation: read"
panics, especially on NFS servers.

Reported by: Nick Hilliard <nick@netability.ie>
Tested by: Nick Hilliard <nick@netability.ie>
Approved by: re (rwatson)

- Lock the vm_object when performing vm_object_pip_add().

- We are not guaranteed that read ahead blocks are not in memory already.
Check for B_DELWRI as well as B_CACHED before issuing io on a buffer. This
is especially important since we are changing the b_iocmd.

Including <sys/stdint.h> is (almost?) universally only to be able to use
%j in printfs, so put a newsted include in <sys/systm.h> where the printf
prototype lives and save everybody else the trouble.

- Unlock the target bp and not the pager buf bp in a failure case in
cluster_wbuild(). This was causing strange panics that were widely
reported on current@.

Big Pointy Hat to: jeff

- Tune down read_max. For single disks we get no gain out of reading more
than a MAXPHYS size block ahead. Having this set too high just leaves
other processes starved for IO and screws up interactive response. Let the
users with RAID set it higher when they need it.

- Regularize variable usage in cluster_read().
- Issue the io that we will later block on prior to doing cluster read ahead
so that it is more likely to be ready when we block.
- Loop issuing clustered reads until we've exhausted the seq count supplied
by the file system.
- Use a sysctl tunable "vfs.read_max" to determine the maximum number of
blocks that we'll read ahead.

- Hold the buf lock while manipulating and inspecting its fields.
- Use gbincore() and not incore() so that we can drop the vnode interlock
as we acquire the buflock.
- Use GB_LOCK_NOWAIT when getting bufs for read ahead clusters so that we
don't block on locked bufs.
- Convert a while loop to a howmany() that will most likely be faster on
modern processors. There is another while loop divide that was left
near by because it is operating on a 64bit int and is most likely faster.
- Cleanup the cluster_read() code a little to get rid of a goto and make
the logic clearer.

Tested on: x86, alpha
Tested by: Steve Kargl <sgk@troutmask.apl.washington.edu>
Reviewd by: arch

- Add a new 'flags' parameter to getblk().
- Define one flag GB_LOCK_NOWAIT that tells getblk() to pass the LK_NOWAIT
flag to the initial BUF_LOCK(). This will eventually be used in cases
were we want to use a buffer only if it is not currently in use.
- Convert all consumers of the getblk() api to use this extra parameter.

Reviwed by: arch
Not objected to by: mckusick

- Add an interlock argument to BUF_LOCK and BUF_TIMELOCK.
- Remove the buftimelock mutex and acquire the buf's interlock to protect
these fields instead.
- Hold the vnode interlock while locking bufs on the clean/dirty queues.
This reduces some cases from one BUF_LOCK with a LK_NOWAIT and another
BUF_LOCK with a LK_TIMEFAIL to a single lock.

Reviewed by: arch, mckusick

Remove duplicate includes.

Submitted by: Cyril Nguyen-Huu <cyril@ci0.org>

Back out M_* changes, per decision of the TRB.

Approved by: trb

Remove M_TRYWAIT/M_WAITOK/M_WAIT. Callers should use 0.
Merge M_NOWAIT/M_DONTWAIT into a single flag M_NOWAIT.

- Use %j to print intmax_t values.
- Cast more daddr_t values to intmax_t when printing to quiet warnings.

- Use incore() where no other interlock locking is necessary.
- Lock access to numoutput.

Replace various spelling with FALLTHROUGH which is lint()able

o Lock page accesses by vm_page_io_start() with the page queues lock.
o Assert that the page queues lock is held in vm_page_io_start().

Replace the global buffer hash table with per-vnode splay trees using a
methodology similar to the vm_map_entry splay and the VM splay that Alan
Cox is working on. Extensive testing has appeared to have shown no
increase in overhead.

Disadvantages
Dirties more cache lines during lookups.

Not as fast as a hash table lookup (but still N log N and optimal
when there is locality of reference).

Advantages
vnode->v_dirtyblkhd is now perfectly sorted, making fsync/sync/filesystem
syncer operate more efficiently.

I get to rip out all the old hacks (some of which were mine) that tried
to keep the v_dirtyblkhd tailq sorted.

The per-vnode splay tree should be easier to lock / SMPng pushdown on
vnodes will be easier.

This commit along with another that Alan is working on for the VM page
global hash table will allow me to implement ranged fsync(), optimize
server-side nfs commit rpcs, and implement partial syncs by the
filesystem syncer (aka filesystem syncer would detect that someone is
trying to get the vnode lock, remembers its place, and skip to the
next vnode).

Note that the buffer cache splay is somewhat more complex then other splays
due to special handling of background bitmap writes (multiple buffers with
the same lblkno in the same vnode), and B_INVAL discontinuities between the
old hash table and the existence of the buffer on the v_cleanblkhd list.

Suggested by: alc

This commit adds basic support for the UFS2 filesystem. The UFS2
filesystem expands the inode to 256 bytes to make space for 64-bit
block pointers. It also adds a file-creation time field, an ability
to use jumbo blocks per inode to allow extent like pointer density,
and space for extended attributes (up to twice the filesystem block
size worth of attributes, e.g., on a 16K filesystem, there is space
for 32K of attributes). UFS2 fully supports and runs existing UFS1
filesystems. New filesystems built using newfs can be built in either
UFS1 or UFS2 format using the -O option. In this commit UFS1 is
the default format, so if you want to build UFS2 format filesystems,
you must specify -O 2. This default will be changed to UFS2 when
UFS2 proves itself to be stable. In this commit the boot code for
reading UFS2 filesystems is not compiled (see /sys/boot/common/ufsread.c)
as there is insufficient space in the boot block. Once the size of the
boot block is increased, this code can be defined.

Things to note: the definition of SBSIZE has changed to SBLOCKSIZE.
The header file <ufs/ufs/dinode.h> must be included before
<ufs/ffs/fs.h> so as to get the definitions of ufs2_daddr_t and
ufs_lbn_t.

Still TODO:
Verify that the first level bootstraps work for all the architectures.
Convert the utility ffsinfo to understand UFS2 and test growfs.
Add support for the extended attribute storage. Update soft updates
to ensure integrity of extended attribute storage. Switch the
current extended attribute interfaces to use the extended attribute
storage. Add the extent like functionality (framework is there,
but is currently never used).

Sponsored by: DARPA & NAI Labs.
Reviewed by: Poul-Henning Kamp <phk@freebsd.org>

Make daddr_t and u_daddr_t 64bits wide.
Retire daddr64_t and use daddr_t instead.

Sponsored by: DARPA & NAI Labs.

Remove __P.

Introduce the new 64-bit size disk block, daddr64_t. Change
the bio and buffer structures to have daddr64_t bio_pblkno,
b_blkno, and b_lblkno fields which allows access to disks
larger than a Terabyte in size. This change also requires
that the VOP_BMAP vnode operation accept and return daddr64_t
blocks. This delta should not affect system operation in
any way. It merely sets up the necessary interfaces to allow
the development of disk drivers that work with these larger
disk block addresses. It also allows for the development of
UFS2 which will use 64-bit block addresses.

Document all functions, global and static variables, and sysctls.
Includes some minor whitespace changes, and re-ordering to be able to document
properly (e.g, grouping of variables and the SYSCTL macro calls for them, where
the documentation has been added.)

Reviewed by: phk (but all errors are mine)

Implement IO_NOWDRAIN and B_NOWDRAIN - prevents the buffer cache from blocking
in wdrain during a write. This flag needs to be used in devices whos
strategy routines turn-around and issue another high level I/O, such as
when MD turns around and issues a VOP_WRITE to vnode backing store, in order
to avoid deadlocking the dirty buffer draining code.

Remove a vprintf() warning from MD when the backing vnode is found to be
in-use. The syncer of buf_daemon could be flushing the backing vnode at
the time of an MD operation so the warning is not correct.

MFC after: 1 week

In cluster_rbuild(), 'size' had better match buf->b_bcount and buf->b_bufsize
or the cluster will not be properly merged. Dup the code from
cluster_wbuild() and add some printf()s to see if bad cases are present.

MFC after: 2 weeks

Syntax cleanup and documentation, no operational changes.

MFC after: 1 day

Change the kernel's ucred API as follows:
- crhold() returns a reference to the ucred whose refcount it bumps.
- crcopy() now simply copies the credentials from one credential to
another and has no return value.
- a new crshared() primitive is added which returns true if a ucred's
refcount is > 1 and false (0) otherwise.

With Alfred's permission, remove vm_mtx in favor of a fine-grained approach
(this commit is just the first stage). Also add various GIANT_ macros to
formalize the removal of Giant, making it easy to test in a more piecemeal
fashion. These macros will allow us to test fine-grained locks to a degree
before removing Giant, and also after, and to remove Giant in a piecemeal
fashion via sysctl's on those subsystems which the authors believe can
operate without Giant.

This patch implements O_DIRECT about 80% of the way. It takes a patchset
Tor created a while ago, removes the raw I/O piece (that has cache coherency
problems), and adds a buffer cache / VM freeing piece.

Essentially this patch causes O_DIRECT I/O to not be left in the cache, but
does not prevent it from going through the cache, hence the 80%. For
the last 20% we need a method by which the I/O can be issued directly to
buffer supplied by the user process and bypass the buffer cache entirely,
but still maintain cache coherency.

I also have the code working under -stable but the changes made to sys/file.h
may not be MFCable, so an MFC is not on the table yet.

Submitted by: tegge, dillon

Introduce a global lock for the vm subsystem (vm_mtx).

vm_mtx does not recurse and is required for most low level
vm operations.

faults can not be taken without holding Giant.

Memory subsystems can now call the base page allocators safely.

Almost all atomic ops were removed as they are covered under the
vm mutex.

Alpha and ia64 now need to catch up to i386's trap handlers.

FFS and NFS have been tested, other filesystems will need minor
changes (grabbing the vm lock when twiddling page properties).

Reviewed (partially) by: jake, jhb

Revert consequences of changes to mount.h, part 2.

Requested by: bde

Correct #includes to work with fixed sys/mount.h.

This patch removes the VOP_BWRITE() vector.

VOP_BWRITE() was a hack which made it possible for NFS client
side to use struct buf with non-bio backing.

This patch takes a more general approach and adds a bp->b_op
vector where more methods can be added.

The success of this patch depends on bp->b_op being initialized
all relevant places for some value of "relevant" which is not
easy to determine. For now the buffers have grown a b_magic
element which will make such issues a tiny bit easier to debug.

Fix lockup for loopback NFS mounts. The pipelined I/O limitations could be
hit on the client side and prevent the server side from retiring writes.
Pipeline operations turned off for all READs (no big loss since reads are
usually synchronous) and for NFS writes, and left on for the default bwrite().
(MFC expected prior to 4.3 freeze)

Testing by: mjacob, dillon

Fix typo: teh -> the.

Do not cluster with B_LOCKED buffers.

This is an odd one. This patch appears to fix a panic related to background
bitmap writes (for FFS), though neither Kirk, Ian, or I can figure out how
B_CLUSTEROK could possibly be set on a bitmap block to cause the clustering
code to improperly cluster with a buffer undergoing a background write.

In anycase, the clustering code is very fragile and this patch helps with
that, as well as possibly fixing a bug Andre was having.

Suggested by: Ian Dowse <iedowse@maths.tcd.ie>
Testing by: Andre Albsmeier <andre.albsmeier@mchp.siemens.de>

This implements a better launder limiting solution. There was a solution
in 4.2-REL which I ripped out in -stable and -current when implementing the
low-memory handling solution. However, maxlaunder turns out to be the saving
grace in certain very heavily loaded systems (e.g. newsreader box). The new
algorithm limits the number of pages laundered in the first pageout daemon
pass. If that is not sufficient then suceessive will be run without any
limit.

Write I/O is now pipelined using two sysctls, vfs.lorunningspace and
vfs.hirunningspace. This prevents excessive buffered writes in the
disk queues which cause long (multi-second) delays for reads. It leads
to more stable (less jerky) and generally faster I/O streaming to disk
by allowing required read ops (e.g. for indirect blocks and such) to occur
without interrupting the write stream, amoung other things.

NOTE: eventually, filesystem write I/O pipelining needs to be done on a
per-device basis. At the moment it is globalized.

Implement a low-memory deadlock solution.

Removed most of the hacks that were trying to deal with low-memory
situations prior to now.

The new code is based on the concept that I/O must be able to function in
a low memory situation. All major modules related to I/O (except
networking) have been adjusted to allow allocation out of the system
reserve memory pool. These modules now detect a low memory situation but
rather then block they instead continue to operate, then return resources
to the memory pool instead of cache them or leave them wired.

Code has been added to stall in a low-memory situation prior to a vnode
being locked.

Thus situations where a process blocks in a low-memory condition while
holding a locked vnode have been reduced to near nothing. Not only will
I/O continue to operate, but many prior deadlock conditions simply no
longer exist.

Implement a number of VFS/BIO fixes

(found by Ian): in biodone(), bogus-page replacement code, the loop
was not properly incrementing loop variables prior to a continue
statement. We do not believe this code can be hit anyway but we
aren't taking any chances. We'll turn the whole section into a
panic (as it already is in brelse()) after the release is rolled.

In biodone(), the foff calculation was incorrectly
clamped to the iosize, causing the wrong foff to be calculated
for pages in the case of an I/O error or biodone() called without
initiating I/O. The problem always caused a panic before. Now it
doesn't. The problem is mainly an issue with NFS.

Fixed casts for ~PAGE_MASK. This code worked properly before only
because the calculations use signed arithmatic. Better to properly
extend PAGE_MASK first before inverting it for the 64 bit masking
op.

In brelse(), the bogus_page fixup code was improperly throwing
away the original contents of 'm' when it did the j-loop to
fix the bogus pages. The result was that it would potentially
invalidate parts of the *WRONG* page(!), leading to corruption.

There may still be cases where a background bitmap write is
being duplicated, causing potential corruption. We have identified
a potentially serious bug related to this but the fix is still TBD.
So instead this patch contains a KASSERT to detect the problem
and panic the machine rather then continue to corrupt the filesystem.
The problem does not occur very often.. it is very hard to
reproduce, and it may or may not be the cause of the corruption
people have reported.

Review by: (VFS/BIO: mckusick, Ian Dowse <iedowse@maths.tcd.ie>)
Testing by: (VM/Deadlock) Paul Saab <ps@yahoo-inc.com>

Don't attempt to cluster write buffers where the VMIO flag isn't set.

Virtualizes & untangles the bioops operations vector.

Ref: Message-ID: <18317.961014572@critter.freebsd.dk> To: current@

Separate the struct bio related stuff out of <sys/buf.h> into
<sys/bio.h>.

<sys/bio.h> is now a prerequisite for <sys/buf.h> but it shall
not be made a nested include according to bdes teachings on the
subject of nested includes.

Diskdrivers and similar stuff below specfs::strategy() should no
longer need to include <sys/buf.> unless they need caching of data.

Still a few bogus uses of struct buf to track down.

Repocopy by: peter

s/biowait/bufwait/g

Prodded by: several.

Complete the bio/buf divorce for all code below devfs::strategy

Exceptions:
Vinum untouched. This means that it cannot be compiled.
Greg Lehey is on the case.

CCD not converted yet, casts to struct buf (still safe)

atapi-cd casts to struct buf to examine B_PHYS

Move B_ERROR flag to b_ioflags and call it BIO_ERROR.

(Much of this done by script)

Move B_ORDERED flag to b_ioflags and call it BIO_ORDERED.

Move b_pblkno and b_iodone_chain to struct bio while we transition, they
will be obsoleted once bio structs chain/stack.

Add bio_queue field for struct bio aware disksort.

Address a lot of stylistic issues brought up by bde.

Change the write-behind code to take more care when starting
async I/O's. The sequential read heuristic has been extended to
cover writes as well. We continue to call cluster_write() normally,
thus blocks in the file will still be reallocated for large (but still
random) I/O's, but I/O will only be initiated for truely sequential
writes.

This solves a number of annoying situations, especially with DBM (hash
method) writes, and also has the side effect of fixing a number of
(stupid) benchmarks.

Reviewed-by: mckusick

Remove B_READ, B_WRITE and B_FREEBUF and replace them with a new
field in struct buf: b_iocmd. The b_iocmd is enforced to have
exactly one bit set.

B_WRITE was bogusly defined as zero giving rise to obvious coding
mistakes.

Also eliminate the redundant struct buf flag B_CALL, it can just
as efficiently be done by comparing b_iodone to NULL.

Should you get a panic or drop into the debugger, complaining about
"b_iocmd", don't continue. It is likely to write on your disk
where it should have been reading.

This change is a step in the direction towards a stackable BIO capability.

A lot of this patch were machine generated (Thanks to style(9) compliance!)

Vinum users: Greg has not had time to test this yet, be careful.

useracc() the prequel:

Merge the contents (less some trivial bordering the silly comments)
of <vm/vm_prot.h> and <vm/vm_inherit.h> into <vm/vm.h>. This puts
the #defines for the vm_inherit_t and vm_prot_t types next to their
typedefs.

This paves the road for the commit to follow shortly: change
useracc() to use VM_PROT_{READ|WRITE} rather than B_{READ|WRITE}
as argument.

Remove v_maxio from struct vnode.

Replace it with mnt_iosize_max in struct mount.

Nits from: bde

Initialize vp->v_maxio to its default in getnetvnode() rather than
four different places in vfs_cluster.c

If integration of a buffer into a cluster write operation fails, release
the buffer instead of creating a future deadlock.
PR: 12800
Submitted by: dillon

$Id$ -> $FreeBSD$

These changes appear to give us benefits with both small (32MB) and
large (1G) memory machine configurations. I was able to run 'dbench 32'
on a 32MB system without bring the machine to a grinding halt.

* buffer cache hash table now dynamically allocated. This will
have no effect on memory consumption for smaller systems and
will help scale the buffer cache for larger systems.

* minor enhancement to pmap_clearbit(). I noticed that
all the calls to it used constant arguments. Making
it an inline allows the constants to propogate to
deeper inlines and should produce better code.

* removal of inherent vfs_ioopt support through the emplacement
of appropriate #ifdef's, with John's permission. If we do not
find a use for it by the end of the year we will remove it entirely.

* removal of getnewbufloops* counters & sysctl's - no longer
necessary for debugging, getnewbuf() is now optimal.

* buffer hash table functions removed from sys/buf.h and localized
to vfs_bio.c

* VFS_BIO_NEED_DIRTYFLUSH flag and support code added
( bwillwrite() ), allowing processes to block when too many dirty
buffers are present in the system.

* removal of a softdep test in bdwrite() that is no longer necessary
now that bdwrite() no longer attempts to flush dirty buffers.

* slight optimization added to bqrelse() - there is no reason
to test for available buffer space on B_DELWRI buffers.

* addition of reverse-scanning code to vfs_bio_awrite().
vfs_bio_awrite() will attempt to locate clusterable areas
in both the forward and reverse direction relative to the
offset of the buffer passed to it. This will probably not
make much of a difference now, but I believe we will start
to rely on it heavily in the future if we decide to shift
some of the burden of the clustering closer to the actual
I/O initiation.

* Removal of the newbufcnt and lastnewbuf counters that Kirk
added. They do not fix any race conditions that haven't already
been fixed by the gbincore() test done after the only call
to getnewbuf(). getnewbuf() is a static, so there is no chance
of it being misused by other modules. ( Unless Kirk can think
of a specific thing that this code fixes. I went through it
very carefully and didn't see anything ).

* removal of VOP_ISLOCKED() check in flushbufqueues(). I do not
think this check is necessary, the buffer should flush properly
whether the vnode is locked or not. ( yes? ).

* removal of extra arguments passed to getnewbuf() that are not
necessary.

* missed cluster_wbuild() that had to be a cluster_wbuild_wb() in
vfs_cluster.c

* vn_write() now calls bwillwrite() *PRIOR* to locking the vnode,
which should greatly aid flushing operations in heavy load
situations - both the pageout and update daemons will be able
to operate more efficiently.

* removal of b_usecount. We may add it back in later but for now
it is useless. Prior implementations of the buffer cache never
had enough buffers for it to be useful, and current implementations
which make more buffers available might not benefit relative to
the amount of sophistication required to implement a b_usecount.
Straight LRU should work just as well, especially when most things
are VMIO backed. I expect that (even though John will not like
this assumption) directories will become VMIO backed some point soon.

Submitted by: Matthew Dillon <dillon@backplane.com>
Reviewed by: Kirk McKusick <mckusick@mckusick.com>

The vfs.write_behind sysctl and related code support has been added to
allow changes to the filesystem's write_behind behavior. By the
default the filesystem aggressively issues write_behind's. Three values
may be specified for vfs.write_behind. 0 disables write_behind, 1 results
in historical operation (agressive write_behind), and 2 is an experimental
backed-off write_behind. The values of 0 and 1 are recommended. The value
of 0 is recommended in conjuction with an increase in the number of
NBUF's and the number of dirty buffers allowed (vfs.{lo,hi}dirtybuffers).
Note that a value of 0 will radically increase the dirty buffer load on
the system. Future work on write_behind behavior will use values 2 and
greater for testing purposes.

Submitted by: Matthew Dillon <dillon@apollo.backplane.com>
Reviewed by: Kirk McKusick <mckusick@mckusick.com>

Hopefully fix the remaining glitches with the BUF_*() changes. This should
(really this time) fix pageout to swap and a couple of clustering cases.

This simplifies BUF_KERNPROC() so that it unconditionally reassigns the
lock owner rather than testing B_ASYNC and having the caller decide when
to do the reassign. At present this is required because some places use
B_CALL/b_iodone to free the buffers without B_ASYNC being set. Also,
vfs_cluster.c explicitly calls BUF_KERNPROC() when attaching the buffers
rather than the parent walking the cluster_head tailq.

Reviewed by: Kirk McKusick <mckusick@mckusick.com>

Convert buffer locking from using the B_BUSY and B_WANTED flags to using
lockmgr locks. This commit should be functionally equivalent to the old
semantics. That is, all buffer locking is done with LK_EXCLUSIVE
requests. Changes to take advantage of LK_SHARED and LK_RECURSIVE will
be done in future commits.

Reformat comment to match indentation of code around it.

Changed trypbuf to a getpbuf to work around a problem where redundant writes
would occur when clustering them - caused by running out of buffers
and taking a degenerate code path as a result. It appears that waiting
instead for buffers to become available is okay.

Submitted by: Matthew Dillon <dillon@apollo.backplane.com>
Discovered by: Craig A Soules <soules+@andrew.cmu.edu>

The VFS/BIO subsystem contained a number of hacks in order to optimize
piecemeal, middle-of-file writes for NFS. These hacks have caused no
end of trouble, especially when combined with mmap(). I've removed
them. Instead, NFS will issue a read-before-write to fully
instantiate the struct buf containing the write. NFS does, however,
optimize piecemeal appends to files. For most common file operations,
you will not notice the difference. The sole remaining fragment in
the VFS/BIO system is b_dirtyoff/end, which NFS uses to avoid cache
coherency issues with read-merge-write style operations. NFS also
optimizes the write-covers-entire-buffer case by avoiding the
read-before-write. There is quite a bit of room for further
optimization in these areas.

The VM system marks pages fully-valid (AKA vm_page_t->valid =
VM_PAGE_BITS_ALL) in several places, most noteably in vm_fault. This
is not correct operation. The vm_pager_get_pages() code is now
responsible for marking VM pages all-valid. A number of VM helper
routines have been added to aid in zeroing-out the invalid portions of
a VM page prior to the page being marked all-valid. This operation is
necessary to properly support mmap(). The zeroing occurs most often
when dealing with file-EOF situations. Several bugs have been fixed
in the NFS subsystem, including bits handling file and directory EOF
situations and buf->b_flags consistancy issues relating to clearing
B_ERROR & B_INVAL, and handling B_DONE.

getblk() and allocbuf() have been rewritten. B_CACHE operation is now
formally defined in comments and more straightforward in
implementation. B_CACHE for VMIO buffers is based on the validity of
the backing store. B_CACHE for non-VMIO buffers is based simply on
whether the buffer is B_INVAL or not (B_CACHE set if B_INVAL clear,
and vise-versa). biodone() is now responsible for setting B_CACHE
when a successful read completes. B_CACHE is also set when a bdwrite()
is initiated and when a bwrite() is initiated. VFS VOP_BWRITE
routines (there are only two - nfs_bwrite() and bwrite()) are now
expected to set B_CACHE. This means that bowrite() and bawrite() also
set B_CACHE indirectly.

There are a number of places in the code which were previously using
buf->b_bufsize (which is DEV_BSIZE aligned) when they should have
been using buf->b_bcount. These have been fixed. getblk() now clears
B_DONE on return because the rest of the system is so bad about
dealing with B_DONE.

Major fixes to NFS/TCP have been made. A server-side bug could cause
requests to be lost by the server due to nfs_realign() overwriting
other rpc's in the same TCP mbuf chain. The server's kernel must be
recompiled to get the benefit of the fixes.

Submitted by: Matthew Dillon <dillon@apollo.backplane.com>

Reviewed by: Many at differnt times in differnt parts,
including alan, john, me, luoqi, and kirk
Submitted by: Matt Dillon <dillon@frebsd.org>

This change implements a relatively sophisticated fix to getnewbuf().
There were two problems with getnewbuf(). First, the writerecursion
can lead to a system stack overflow when you have NFS and/or VN
devices in the system. Second, the free/dirty buffer accounting was
completely broken. Not only did the nfs routines blow it trying to
manually account for the buffer state, but the accounting that was
done did not work well with the purpose of their existance: figuring
out when getnewbuf() needs to sleep.

The meat of the change is to kern/vfs_bio.c. The remaining diffs are
all minor except for NFS, which includes both the fixes for bp
interaction AND fixes for a 'biodone(): buffer already done' lockup.
Sys/buf.h also contains a chaining structure which is not used by
this patchset but is used by other patches that are coming soon.
This patch deliniated by tags PRE_MAT_GETBUF and POST_MAT_GETBUF.
(sorry for the missing T matt)

Fix warnings in preparation for adding -Wall -Wcast-qual to the
kernel compile

This is a rather large commit that encompasses the new swapper,
changes to the VM system to support the new swapper, VM bug
fixes, several VM optimizations, and some additional revamping of the
VM code. The specific bug fixes will be documented with additional
forced commits. This commit is somewhat rough in regards to code
cleanup issues.

Reviewed by: "John S. Dyson" <root@dyson.iquest.net>, "David Greenman" <dg@root.com>

KNFize, by bde.

Split DIAGNOSTIC -> DIAGNOSTIC, INVARIANTS, and INVARIANT_SUPPORT as
discussed on -hackers.

Introduce 'KASSERT(assertion, ("panic message", args))' for simple
check + panic.

Reviewed by: msmith

Even the most recently allocated buffer may not have its b_blkno
field properly filled in, so we must do a VOP_BMAP on that buffer
as well if it is not resolved.
Submitted by: Luoqi Chen <luoqi@watermarkgroup.com>

Because buffers may be tossed and recreated at will under the new VM
system, the mapping from logical to physical block number may be lost.
Hence we have to check for a reconstituted buffer and redo the call to
VOP_BMAP if the physical block number has been lost.

Fixed a missing include. <sys/kernel.h> is needed by the new
MALLOC_DEFINE() and MALLOC_DEFINE() is needed by the recently
reenabled "reallocblks" code, but <sys/kernel.h> was only included
if CLUSTERDEBUG was defined. This was too harmless. gcc only
warns about garbage like `SYSINIT(blech);' at file scope ...

Restored the "reallocblks" code to its former glory. What this does is
basically do a on-the-fly defragmentation of the FFS filesystem, changing
file block allocations to make them contiguous. Thanks to Kirk McKusick
for providing hints on what needed to be done to get this working.

Nitpicking and dusting performed on a train. Removes trivial warnings
about unused variables, labels and other lint.

Cosmetic changes to the PAGE_XXX macros to make them consistent with
the other objects in vm.

Change various syscalls to use size_t arguments instead of u_int.

Add some overflow checks to read/write (from bde).

Change all modifications to vm_page::flags, vm_page::busy, vm_object::flags
and vm_object::paging_in_progress to use operations which are not
interruptable.

Reviewed by: Bruce Evans <bde@zeta.org.au>

Protect all modifications to v_numoutput with splbio().

Protect all modifications to paging_in_progress with splvm(). The i386
managed to avoid corruption of this variable by luck (the compiler used a
memory read-modify-write instruction which wasn't interruptable) but other
architectures cannot.

With this change, I am now able to 'make buildworld' on the alpha (sfx: the
crowd goes wild...)

Fixed printf format errors.

Fixed printf format errors.

Don't depend on gcc's feature of casting lvalues.

VOP_STRATEGY grows an (struct vnode *) argument
as the value in b_vp is often not really what you want.
(and needs to be frobbed). more cleanups will follow this.
Reviewed by: Bruce Evans <bde@freebsd.org>

Make flushing dirty pages work correctly on filesystems that
unexpectedly do not complete writes even with sync I/O requests.
This should help the behavior of mmaped files when using
softupdates (and perhaps in other circumstances also.)

Partially fixed write clustering for cases where cluster_wbuild() is
called from vfs_bio_awrite() without going through cluster_write()
or ufs_bmaparray(), in particular for all writes to block disk devices.
Only ufs_bmaparray() sets vp->v_maxio in a correct way, and it doesn't
seem to be called early enough even for regular files.

In kern_physio.c fix tsleep priority messup.

In vfs_bio.c, remove b_generation count usage,
remove redundant reassignbuf,
remove redundant spl(s),
manage page PG_ZERO flags more correctly,
utilize in invalid value for b_offset until it
is properly initialized. Add asserts
for #ifdef DIAGNOSTIC, when b_offset is
improperly used.
when a process is not performing I/O, and just waiting
on a buffer generally, make the sleep priority
low.
only check page validity in getblk for B_VMIO buffers.

In vfs_cluster, add b_offset asserts, correct pointer calculation
for clustered reads. Improve readability of certain parts of
the code. Remove redundant spl(s).

In vfs_subr, correct usage of vfs_bio_awrite (From Andrew Gallatin
<gallatin@cs.duke.edu>). More vtruncbuf problems fixed.

Remove a soft-update hook that was accidentally added to the READ path.
also add some comments, and a couple of very minor cosmetic changes.

Some VM improvements, including elimination of alot of Sig-11
problems. Tor Egge and others have helped with various VM bugs
lately, but don't blame him -- blame me!!!

pmap.c:
1) Create an object for kernel page table allocations. This
fixes a bogus allocation method previously used for such, by
grabbing pages from the kernel object, using bogus pindexes.
(This was a code cleanup, and perhaps a minor system stability
issue.)

pmap.c:
2) Pre-set the modify and accessed bits when prudent. This will
decrease bus traffic under certain circumstances.

vfs_bio.c, vfs_cluster.c:
3) Rather than calculating the beginning virtual byte offset
multiple times, stick the offset into the buffer header, so
that the calculated offset can be reused. (Long long multiplies
are often expensive, and this is a probably unmeasurable performance
improvement, and code cleanup.)

vfs_bio.c:
4) Handle write recursion more intelligently (but not perfectly) so
that it is less likely to cause a system panic, and is also
much more robust.

vfs_bio.c:
5) getblk incorrectly wrote out blocks that are incorrectly sized.
The problem is fixed, and writes blocks out ONLY when B_DELWRI
is true.

vfs_bio.c:
6) Check that already constituted buffers have fully valid pages. If
not, then make sure that the B_CACHE bit is not set. (This was
a major source of Sig-11 type problems.)

vfs_bio.c:
7) Fix a potential system deadlock due to an incorrectly specified
sleep priority while waiting for a buffer write operation. The
change that I made opens the system up to serious problems, and
we need to examine the issue of process sleep priorities.

vfs_cluster.c, vfs_bio.c:
8) Make clustered reads work more correctly (and more completely)
when buffers are already constituted, but not fully valid.
(This was another system reliability issue.)

vfs_subr.c, ffs_inode.c:
9) Create a vtruncbuf function, which is used by filesystems that
can truncate files. The vinvalbuf forced a file sync type operation,
while vtruncbuf only invalidates the buffers past the new end of file,
and also invalidates the appropriate pages. (This was a system reliabiliy
and performance issue.)

10) Modify FFS to use vtruncbuf.

vm_object.c:
11) Make the object rundown mechanism for OBJT_VNODE type objects work
more correctly. Included in that fix, create pager entries for
the OBJT_DEAD pager type, so that paging requests that might slip
in during race conditions are properly handled. (This was a system
reliability issue.)

vm_page.c:
12) Make some of the page validation routines be a little less picky
about arguments passed to them. Also, support page invalidation
change the object generation count so that we handle generation
counts a little more robustly.

vm_pageout.c:
13) Further reduce pageout daemon activity when the system doesn't
need help from it. There should be no additional performance
decrease even when the pageout daemon is running. (This was
a significant performance issue.)

vnode_pager.c:
14) Teach the vnode pager to handle race conditions during vnode
deallocations.

Reviewed by: dyson@freebsd.org (john Dyson), dg@root.com (david greenman)
Submitted by: Kirk McKusick (mcKusick@mckusick.com)
Obtained from: WHistle development tree

This mega-commit is meant to fix numerous interrelated problems. There
has been some bitrot and incorrect assumptions in the vfs_bio code. These
problems have manifest themselves worse on NFS type filesystems, but can
still affect local filesystems under certain circumstances. Most of
the problems have involved mmap consistancy, and as a side-effect broke
the vfs.ioopt code. This code might have been committed seperately, but
almost everything is interrelated.

1) Allow (pmap_object_init_pt) prefaulting of buffer-busy pages that
are fully valid.
2) Rather than deactivating erroneously read initial (header) pages in
kern_exec, we now free them.
3) Fix the rundown of non-VMIO buffers that are in an inconsistent
(missing vp) state.
4) Fix the disassociation of pages from buffers in brelse. The previous
code had rotted and was faulty in a couple of important circumstances.
5) Remove a gratuitious buffer wakeup in vfs_vmio_release.
6) Remove a crufty and currently unused cluster mechanism for VBLK
files in vfs_bio_awrite. When the code is functional, I'll add back
a cleaner version.
7) The page busy count wakeups assocated with the buffer cache usage were
incorrectly cleaned up in a previous commit by me. Revert to the
original, correct version, but with a cleaner implementation.
8) The cluster read code now tries to keep data associated with buffers
more aggressively (without breaking the heuristics) when it is presumed
that the read data (buffers) will be soon needed.
9) Change to filesystem lockmgr locks so that they use LK_NOPAUSE. The
delay loop waiting is not useful for filesystem locks, due to the
length of the time intervals.
10) Correct and clean-up spec_getpages.
11) Implement a fully functional nfs_getpages, nfs_putpages.
12) Fix nfs_write so that modifications are coherent with the NFS data on
the server disk (at least as well as NFS seems to allow.)
13) Properly support MS_INVALIDATE on NFS.
14) Properly pass down MS_INVALIDATE to lower levels of the VM code from
vm_map_clean.
15) Better support the notion of pages being busy but valid, so that
fewer in-transit waits occur. (use p->busy more for pageouts instead
of PG_BUSY.) Since the page is fully valid, it is still usable for
reads.
16) It is possible (in error) for cached pages to be busy. Make the
page allocation code handle that case correctly. (It should probably
be a printf or panic, but I want the system to handle coding errors
robustly. I'll probably add a printf.)
17) Correct the design and usage of vm_page_sleep. It didn't handle
consistancy problems very well, so make the design a little less
lofty. After vm_page_sleep, if it ever blocked, it is still important
to relookup the page (if the object generation count changed), and
verify it's status (always.)
18) In vm_pageout.c, vm_pageout_clean had rotted, so clean that up.
19) Push the page busy for writes and VM_PROT_READ into vm_pageout_flush.
20) Fix vm_pager_put_pages and it's descendents to support an int flag
instead of a boolean, so that we can pass down the invalidate bit.

Back out DIAGNOSTIC changes.

Turn DIAGNOSTIC into a new-style option.

Change the busy page mgmt, so that when pages are freed, they
MUST be PG_BUSY. It is bogus to free a page that isn't busy,
because it is in a state of being "unavailable" when being
freed. The additional advantage is that the page_remove code
has a better cross-check that the page should be busy and
unavailable for other use. There were some minor problems
with the collapse code, and this plugs those subtile "holes."

Also, the vfs_bio code wasn't checking correctly for PG_BUSY
pages. I am going to develop a more consistant scheme for
grabbing pages, busy or otherwise. For now, we are stuck
with the current morass.

Make the debug options new-style.

This also zaps a DPT option from lint; it wasn't referenced from
anywhere.

Add better support for larger I/O clusters, including larger physical
I/O. The support is not mature yet, and some of the underlying implementation
needs help. However, support does exist for IDE devices now.

Make our v_usecount vnode reference count work identically to the
original BSD code. The association between the vnode and the vm_object
no longer includes reference counts. The major difference is that
vm_object's are no longer freed gratuitiously from the vnode, and so
once an object is created for the vnode, it will last as long as the
vnode does.

When a vnode object reference count is incremented, then the underlying
vnode reference count is incremented also. The two "objects" are now
more intimately related, and so the interactions are now much less
complex.

When vnodes are now normally placed onto the free queue with an object still
attached. The rundown of the object happens at vnode rundown time, and
happens with exactly the same filesystem semantics of the original VFS
code. There is absolutely no need for vnode_pager_uncache and other
travesties like that anymore.

A side-effect of these changes is that SMP locking should be much simpler,
the I/O copyin/copyout optimizations work, NFS should be more ponderable,
and further work on layered filesystems should be less frustrating, because
of the totally coherent management of the vnode objects and vnodes.

Please be careful with your system while running this code, but I would
greatly appreciate feedback as soon a reasonably possible.

Remove a bunch of variables which were unused both in GENERIC and LINT.

Found by: -Wunused

Removed unused #includes.

Fix a problem with the VN device. Specifically, the VN device can
cause a problem of spiraling death due to buffer resource limitations.
The vfs_bio code in general had little ability to handle buffer resource
management, and now it does. Also, there are a lot more knobs for tuning the
vfs_bio code now. The knobs came free because of the need that there
always be some immediately available buffers (non-delayed or locked) for
use. Note that the buffer cache code is much less likely to get bogged
down with lots of delayed writes, even more so than before.

Don't zero b_dirtyoff and b_dirtyend on error.

Submitted by: Hidetoshi Shimokawa <simokawa@sat.t.u-tokyo.ac.jp>

Don't allow partial buffers to be cluster-comitted.
Zero the b_dirty{off,end} after cluster-comitting a group of buffers.

With these fixes, I was able to complete a 'make world' with remote src
and obj directories.

Use OID_AUTO instead of magic number for the old sysctl debug.rcluster.
The magic number conflicted with the rotting disabled one in ext2fs for
debug.doasyncfree.

Removed messy debugging variable/constant/sysctl debug.doreallocblks.
Lite2 removed it, and we don't use the code that it controls.

Remove unnecessary check for vp->v_mount being null. Pointed
out by BDE.

Back out part 1 of the MCFH that changed $Id$ to $FreeBSD$. We are not
ready for it yet.

Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.

This commit is the embodiment of some VFS read clustering improvements.
Firstly, now our read-ahead clustering is on a file descriptor basis and not
on a per-vnode basis. This will allow multiple processes reading the
same file to take advantage of read-ahead clustering. Secondly, there
previously was a problem with large reads still using the ramp-up
algorithm. Of course, that was bogus, and now we read the entire
"chunk" off of the disk in one operation. The read-ahead clustering
algorithm should use less CPU than the previous also (I hope :-)).

NOTE: THAT LKMS MUST BE REBUILT!!!

Implement a new totally dynamic (up to MAXPHYS) buffer kva allocation
scheme. Additionally, add the capability for checking for unexpected
kernel page faults. The maximum amount of kva space for buffers hasn't
been decreased from where it is, but it will now be possible to do so.

This scheme manages the kva space similar to the buffers themselves. If
there isn't enough kva space because of usage or fragementation, buffers
will be reclaimed until a buffer allocation is successful. This scheme
should be very resistant to fragmentation problems until/if the LFS code
is fixed and uses the bogus buffer locking scheme -- but a 'fixed' LFS
is not likely to use such a scheme.

Now there should be NO problem allocating buffers up to MAXPHYS.

Fix 4 problems:
Major: When blocking occurs in allocbuf() for VMIO files,
excess wire counts could accumulate.
Major: Pages are incorrectly accumulated into the physical
buffer for clustered reads. This happens when bogus
page is needed.
Minor: When reclaiming buffers, the async flag on the buffer
needs to be zero, or the reclaim is not optimal.
Minor: The age flag should be cleared, if a buffer is wanted.

Modification to vfs_cluster to allow clustering of NFS delayed writes.
Submitted by: Doug Rabson <dfr@render.com>

Fix an error when B_MALLOC buffers are returned from the cluster read
code without the B_READ flag being set. This is a problem when the
data is not cached, and the result will be a bogus attempted write.
Submitted by: Kato Takenori <kato@eclogite.eps.nagoya-u.ac.jp>

Import 4.4BSD-Lite2 onto the vendor branch, note that in the kernel, all
files are off the vendor branch, so this should not change anything.

A "U" marker generally means that the file was not changed in between
the 4.4Lite and Lite-2 releases, and does not need a merge. "C" generally
means that there was a change.
[note new unused (in this form) syscalls.conf, to be 'cvs rm'ed]

1) Fix a bug that a buffer is removed from a queue, but the
queue type is not set to QUEUE_NONE. This appears to have
caused a hang bug that has been lurking.
2) Fix bugs that brelse'ing locked buffers do not "free" them, but the
code assumes so. This can cause hangs when LFS is used.
3) Use malloced memory for directories when applicable. The amount
of malloced memory is seriously limited, but should decrease the
amount of memory used by an average directory to 1/4 - 1/2 previous.
This capability is fully tunable. (Note that there is no config
parameter, and might never be.)
4) Bias slightly the buffer cache usage towards non-VMIO buffers. Since
the data in VMIO buffers is not lost when the buffer is reclaimed, this
will help performance. This is adjustable also.

An earlier modification had decreased CPU usage, but also
decreased performance. This essentially undoes that change.

Previous commit to vfs_cluster accidentally disabled read-ahead. Problem
fixed by initializing "alreadyincore" to 0 in the case of
sequential reads.

Eliminated many redundant vm_map_lookup operations for vm_mmap.
Speed up for vfs_bio -- addition of a routine bqrelse to greatly diminish
overhead for merged cache.
Efficiency improvement for vfs_cluster. It used to do alot of redundant
calls to cluster_rbuild.
Correct the ordering for vrele of .text and release of credentials.
Use the selective tlb update for 486/586/P6.
Numerous fixes to the size of objects allocated for files. Additionally,
fixes in the various pagers.
Fixes for proper positioning of vnode_pager_setsize in msdosfs and ext2fs.
Fixes in the swap pager for exhausted resources. The pageout code
will not as readily thrash.
Change the page queue flags (PG_ACTIVE, PG_INACTIVE, PG_FREE, PG_CACHE) into
page queue indices (PQ_ACTIVE, PQ_INACTIVE, PQ_FREE, PQ_CACHE),
thereby improving efficiency of several routines.
Eliminate even more unnecessary vm_page_protect operations.
Significantly speed up process forks.
Make vm_object_page_clean more efficient, thereby eliminating the pause
that happens every 30seconds.
Make sequential clustered writes B_ASYNC instead of B_DELWRI even in the
case of filesystems mounted async.
Fix a panic with busy pages when write clustering is done for non-VMIO
buffers.

Fixed bugs and finished staticization for things inside `#ifdef DEBUG'.
Moved most of these things inside `#ifdef notyet_block_reallocation_enabled'
where they may never be used again.

Changes to support 1Tb filesizes. Pages are now named by an
(object,index) pair instead of (object,offset) pair.

Untangled the vm.h include file spaghetti.

Yet another small block FS bug fix.

Fix more clustering bugs for FSes with block sizes < PAGE_SIZE.

Changed an incorrect splhigh to splbio.

General fixes to the vfs clustring code:

1) Make cluster buffer list be a non-malloced chain. This eliminates
yet another 'evil' M_WAITOK and generally cleans up the code.
2) Fix write clustering for ext2fs. It was just broken. Also, ffs
clustering had an efficiency problem that more bawrites were happening
than should have been.
3) Make changes to buf.h to support the above, plus remove b_pfcent
at the request of David Greenman.
Reviewed by: davidg (partially)

Change some of the debug sysctl vars. The semantics of these will change.

Second batch of cleanup changes.
This time mostly making a lot of things static and some unused
variables here and there.

Work-around a problem in the clustering code on non-VMIO buffers. The
write-side needs rewriting, but this makes a ktrace panic go away for
now.

These changes fix a bug in the clustering code that I made worse when adding
support for EXT2FS. Note that the Sig-11 problems appear to be caused by
this, but there is still probably an underlying VM problem that let this
clustering bug cause vnode objects to appear to be corrupted.

The direct manifestation of this bug would have been severely mis-read
files. It is possible that processes would Sig-11 on very damaged
input files and might explain the mysterious differences in system
behaviour when phk's malloc is being used.

Added VOP_GETPAGES/VOP_PUTPAGES and also the "backwards" block count
for VOP_BMAP. Updated affected filesystems...

VOP_BMAP will eventually need an additional argument, but not yet. This
backs out that modification to minimize the window during which this
is not yet correct.

Improvements to the cluster code, minor vfs_bio efficiency:
Better performance -- more aggressive read-ahead
under certain circumstanses.

Mods to support clustering on small
( < PAGE_SIZE) block size filesystems (e.g. ext2fs,
msdosfs.)

Don't include vm_pageout.h.

Remove trailing whitespace.

Check for case of blkno already known to avoid unnecessary VOP_BMAP's.

Submitted by: John Dyson

Fix from Doug Rabson: Don't try to release a pbuf we didn't get.
Minor style change by me.

Add and move declarations to fix all of the warnings from `gcc -Wimplicit'
(except in netccitt, netiso and netns) and most of the warnings from
`gcc -Wnested-externs'. Fix all the bugs found. There were no serious
ones.

Removed obsolete vtrace() remnants.

Don't try to cluster busy buffers.

Submitted by: John Dyson

vfs_cluster.c:
Various more tweaks from John Dyson to improve read ahead calculations.

vfs_subr.c:
Only wakeup if numoutput is 0 in vwakeup().

Submitted by: John Dyson

Fixed a variety of deadlock and panic bugs, removed the bypass code, and
implemented the ability to limit bufferspace by memory consumed. (vfs_bio.c)
Fixed recently introduced bugs that caused extra I/O to happen in some
cases. (vfs_cluster.c)

Submitted by: John Dyson

These changes embody the support of the fully coherent merged VM buffer cache,
much higher filesystem I/O performance, and much better paging performance. It
represents the culmination of over 6 months of R&D.

The majority of the merged VM/cache work is by John Dyson.

The following highlights the most significant changes. Additionally, there are
(mostly minor) changes to the various filesystem modules (nfs, msdosfs, etc) to
support the new VM/buffer scheme.

vfs_bio.c:
Significant rewrite of most of vfs_bio to support the merged VM buffer cache
scheme. The scheme is almost fully compatible with the old filesystem
interface. Significant improvement in the number of opportunities for write
clustering.

vfs_cluster.c, vfs_subr.c
Upgrade and performance enhancements in vfs layer code to support merged
VM/buffer cache. Fixup of vfs_cluster to eliminate the bogus pagemove stuff.

vm_object.c:
Yet more improvements in the collapse code. Elimination of some windows that
can cause list corruption.

vm_pageout.c:
Fixed it, it really works better now. Somehow in 2.0, some "enhancements"
broke the code. This code has been reworked from the ground-up.

vm_fault.c, vm_page.c, pmap.c, vm_object.c
Support for small-block filesystems with merged VM/buffer cache scheme.

pmap.c vm_map.c
Dynamic kernel VM size, now we dont have to pre-allocate excessive numbers of
kernel PTs.

vm_glue.c
Much simpler and more effective swapping code. No more gratuitous swapping.

proc.h
Fixed the problem that the p_lock flag was not being cleared on a fork.

swap_pager.c, vnode_pager.c
Removal of old vfs_bio cruft to support the past pseudo-coherency. Now the
code doesn't need it anymore.

machdep.c
Changes to better support the parameter values for the merged VM/buffer cache
scheme.

machdep.c, kern_exec.c, vm_glue.c
Implemented a seperate submap for temporary exec string space and another one
to contain process upages. This eliminates all map fragmentation problems
that previously existed.

ffs_inode.c, ufs_inode.c, ufs_readwrite.c
Changes for merged VM/buffer cache. Add "bypass" support for sneaking in on
busy buffers.

Submitted by: John Dyson and David Greenman

Fix possible off by one in b_save allocation size.

Cosmetics: added ()'s and fixed prinf-formats to make gcc silent.

Temporarily (?) disable block reallocation until either the real bug is
found or we throw out the vfs cluster code entirely.

Changed B_AGE policy to work correctly in a world with relatively large
buffer caches. The old policy generally ended up caching nothing.

Added $Id$

The big 4.4BSD Lite to FreeBSD 2.0.0 (Development) patch.

Reviewed by: Rodney W. Grimes
Submitted by: John Dyson and David Greenman

BSD 4.4 Lite Kernel Sources