MFC r308618:
Provide simple mutual exclusion between mount point update and unmount.
In the update path in ffs_mount(), drop vfs_busy() reference around namei().

MFC r308064:
Avoid possible overflow when calclating malloc size for auxillary
data structure sizes when mounting and reloading UFS/FFS filesystems.

MFC r305592:
Partially lift suspension when ffs_reload() finished with cgs and
going to re-read inodes.

MFC r300364:
Improve handling of rdev->si_mountpt on mount and unmount of FFS
volumes. Treat the field as a semaphore protecting availability of
the device for mounting. Do no access devvp->v_rdev without the vnode
lock owned.

Protect change of the devvp->v_bufobj bo_ops vector with the vnode
lock.

MFC r300084:
Do enable io accounting for read-only mounts and mounts which are
remounted to writeable after initial read-only. Assign to
dev->si_mountpt earlier to account the accesses done at the mount
time.

MFC r300030:
Fix comments.

MFC r297311:
Ensure that TRIMs are finished before unmount destroys ufsmount.

MFC of 291244, 291380, 291459, 291460, 291671, and 291743:

This MFC includes changes to better manage the vnode freelist
and to streamline the allocation and freeing of vnodes.

Note that to maintain the KPI the VI_AGE flag is left defined
in sys/vnode.h though its use is dropped as described in 291380.
To maintain KBI the vfs.vlru_alloc_cache_src sysctl variable
remains though it no longer has any effect as described in 291244.

MFC of 291244:
Move the comment about resident pages preventing vnode from leaving
active list, into the header comment for vdrop(), which is the
function that decides whether to leave the vnode on the list. Note
that dirty page write-out in vinactive() is asynchronous.

Discussed with: alc
Sponsored by: The FreeBSD Foundation

MFC of 291380:
Remove VI_AGE vnode iflag, it is unused.

Noted by: bde
Sponsored by: The FreeBSD Foundation

MFC of 291459:
For performance reasons, it is useful to have a single string used as
the name of a filesystem when setting it as the first parameter to the
getnewvnode() function. Most filesystems call getnewvnode from just one
place so can use a literal string as the first parameter. However, NFS
calls getnewvnode from two places, so we create a global constant string
that can be used by the two instances. This change also collapses two
instances of getnewvnode() in the UFS filesystem to a single call.

Reviewed by: kib
Tested by: Peter Holm

MFC of 291460:
As the kernel allocates and frees vnodes, it fully initializes them
on every allocation and fully releases them on every free. These
are not trivial costs: it starts by zeroing a large structure then
initializes a mutex, a lock manager lock, an rw lock, four lists,
and six pointers. And looking at vfs.vnodes_created, these operations
are being done millions of times an hour on a busy machine.

As a performance optimization, this code update uses the uma_init
and uma_fini routines to do these initializations and cleanups only
as the vnodes enter and leave the vnode_zone. With this change the
initializations are only done kern.maxvnodes times at system startup
and then only rarely again. The frees are done only if the vnode_zone
shrinks which never happens in practice. For those curious about the
avoided work, look at the vnode_init() and vnode_fini() functions in
kern/vfs_subr.c to see the code that has been removed from the main
vnode allocation/free path.

Reviewed by: kib
Tested by: Peter Holm

MFC of 291671:
We need to zero out the union of pointers in a freed vnode structure.

Fix from: Mateusz Guzik
Tested by: Jason Unovitch

MFC of 291743:
We need to zero out the clustering variables in a freed vnode structure.
For completeness add a VNASSERT that there are no threads waiting on a
range lock (this was previously checked on every vnode free).

Reported by; Rick Macklem
Fix from: Mateusz Guzik

MFC r284887:
Handle errors from background write of the cylinder group blocks.

MFC r284927:
Simplify code.

Approved by: re (gjb)

MFC r284495:
Keep a vnode which is freed but still owing inactivation, on the active list.
This closes a race where such vnode is not msync-ed until reboot.

MFC r283735:
Remove several write-only variables.

MFC of 269533:

Limit the number of cylinder groups that will be searched when
trying to build a cluster. The limit is tunable using the sysctl
vfs.ffs.maxclustersearch. The current limit is 10 cylinder groups
per block allocation. It was previously limited to the number of
cylinder groups in the filesystem per block allocation. When there
were no clusters of the needed size left, it repeatedly searched
the whole filesystem for a non-existent cluster on every block
allocation. The result was very slow filesystem allocation with
100% CPU utilization. The old behavior can be had by setting
vfs.ffs.maxclustersearch to a huge number (1,000,000).

This change affects only the layout policy routines so is not able
to interfere with the integrity of the filesystem.

Reported by: Dmitry Sivachenko (demon@)
Tested by: Dmitry Sivachenko (demon@)

MFC: r281562
File systems that do not use the buffer cache (such as ZFS) must
use VOP_FSYNC() to perform the NFS server's Commit operation.
This patch adds a mnt_kern_flag called MNTK_USES_BCACHE which
is set by file systems that use the buffer cache. If this flag
is not set, the NFS server always does a VOP_FSYNC().
This should be ok for old file system modules that do not set
MNTK_USES_BCACHE, since calling VOP_FSYNC() is correct, although
it might not be optimal for file systems that use the buffer cache.

MFC r280760:
Fix the hand after the immediate reboot after the init binary is unlinked.

MFC r280763:
Fix build (with gcc).

MFC r270203:
Correct the test for condition to suspend UFS filesystem during unmount.

MFC r268612:
Add helper helper vfs_write_suspend_umnt().

Fix the bug in the FFS unmount, when suspension failed, the ufs
extattrs were not reinitialized.

MFC r262678;
ufs: small formatting fixes.

Cleanup some extra space.
Use of tabs vs. spaces.
No functional change.

Reviewed by: mckusick

MFC of 256801, 256803, 256808, 256812, 256817, 256845, and 256860.
This set of changes puts in place the infrastructure to allow soft
updates to be multi-threaded. It introduces no functional changes
from its current operation.

MFC of 256860:

Allow kernels without options SOFTUPDATES to build. This should fix the
embedded tinderboxes.

Reviewed by: emaste

MFC of 256845:

Fix build problem on ARM (which defaults to building without soft updates).

Reported by: Tinderbox
Sponsored by: Netflix

MFC of 256817:

Restructuring of the soft updates code to set it up so that the
single kernel-wide soft update lock can be replaced with a
per-filesystem soft-updates lock. This per-filesystem lock will
allow each filesystem to have its own soft-updates flushing thread
rather than being limited to a single soft-updates flushing thread
for the entire kernel.

Move soft update variables out of the ufsmount structure and into
their own mount_softdeps structure referenced by ufsmount field
um_softdep. Eventually the per-filesystem lock will be in this
structure. For now there is simply a pointer to the kernel-wide
soft updates lock.

Change all instances of ACQUIRE_LOCK and FREE_LOCK to pass the lock
pointer in the mount_softdeps structure instead of a pointer to the
kernel-wide soft-updates lock.

Replace the five hash tables used by soft updates with per-filesystem
copies of these tables allocated in the mount_softdeps structure.

Several functions that flush dependencies when too many are allocated
in the kernel used to operate across all filesystems. They are now
parameterized to flush dependencies from a specified filesystem.
For now, we stick with the round-robin flushing strategy when the
kernel as a whole has too many dependencies allocated.

While there are many lines of changes, there should be no functional
change in the operation of soft updates.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC of 256812:

Fourth of several cleanups to soft dependency implementation.
Add KASSERTS that soft dependency functions only get called
for filesystems running with soft dependencies. Calling these
functions when soft updates are not compiled into the system
become panic's.

No functional change.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC of 256808:

Third of several cleanups to soft dependency implementation.
Ensure that softdep_unmount() and softdep_setup_sbupdate()
only get called for filesystems running with soft dependencies.

No functional change.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC of 256803:

Second of several cleanups to soft dependency implementation.
Delete two unused functions in ffs_sofdep.c.

No functional change.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC of 256801:

First of several cleanups to soft dependency implementation.
Convert three functions exported from ffs_softdep.c to static
functions as they are not used outside of ffs_softdep.c.

No functional change.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC r284887:
Handle errors from background write of the cylinder group blocks.

MFC r284927:
Simplify code.

Approved by: re (gjb)

MFC r284495:
Keep a vnode which is freed but still owing inactivation, on the active list.
This closes a race where such vnode is not msync-ed until reboot.

MFC r283735:
Remove several write-only variables.

MFC of 269533:

Limit the number of cylinder groups that will be searched when
trying to build a cluster. The limit is tunable using the sysctl
vfs.ffs.maxclustersearch. The current limit is 10 cylinder groups
per block allocation. It was previously limited to the number of
cylinder groups in the filesystem per block allocation. When there
were no clusters of the needed size left, it repeatedly searched
the whole filesystem for a non-existent cluster on every block
allocation. The result was very slow filesystem allocation with
100% CPU utilization. The old behavior can be had by setting
vfs.ffs.maxclustersearch to a huge number (1,000,000).

This change affects only the layout policy routines so is not able
to interfere with the integrity of the filesystem.

Reported by: Dmitry Sivachenko (demon@)
Tested by: Dmitry Sivachenko (demon@)

MFC: r281562
File systems that do not use the buffer cache (such as ZFS) must
use VOP_FSYNC() to perform the NFS server's Commit operation.
This patch adds a mnt_kern_flag called MNTK_USES_BCACHE which
is set by file systems that use the buffer cache. If this flag
is not set, the NFS server always does a VOP_FSYNC().
This should be ok for old file system modules that do not set
MNTK_USES_BCACHE, since calling VOP_FSYNC() is correct, although
it might not be optimal for file systems that use the buffer cache.

MFC r280760:
Fix the hand after the immediate reboot after the init binary is unlinked.

MFC r280763:
Fix build (with gcc).

MFC r270203:
Correct the test for condition to suspend UFS filesystem during unmount.

MFC r268612:
Add helper helper vfs_write_suspend_umnt().

Fix the bug in the FFS unmount, when suspension failed, the ufs
extattrs were not reinitialized.

MFC r262678;
ufs: small formatting fixes.

Cleanup some extra space.
Use of tabs vs. spaces.
No functional change.

Reviewed by: mckusick

MFC of 256801, 256803, 256808, 256812, 256817, 256845, and 256860.
This set of changes puts in place the infrastructure to allow soft
updates to be multi-threaded. It introduces no functional changes
from its current operation.

MFC of 256860:

Allow kernels without options SOFTUPDATES to build. This should fix the
embedded tinderboxes.

Reviewed by: emaste

MFC of 256845:

Fix build problem on ARM (which defaults to building without soft updates).

Reported by: Tinderbox
Sponsored by: Netflix

MFC of 256817:

Restructuring of the soft updates code to set it up so that the
single kernel-wide soft update lock can be replaced with a
per-filesystem soft-updates lock. This per-filesystem lock will
allow each filesystem to have its own soft-updates flushing thread
rather than being limited to a single soft-updates flushing thread
for the entire kernel.

Move soft update variables out of the ufsmount structure and into
their own mount_softdeps structure referenced by ufsmount field
um_softdep. Eventually the per-filesystem lock will be in this
structure. For now there is simply a pointer to the kernel-wide
soft updates lock.

Change all instances of ACQUIRE_LOCK and FREE_LOCK to pass the lock
pointer in the mount_softdeps structure instead of a pointer to the
kernel-wide soft-updates lock.

Replace the five hash tables used by soft updates with per-filesystem
copies of these tables allocated in the mount_softdeps structure.

Several functions that flush dependencies when too many are allocated
in the kernel used to operate across all filesystems. They are now
parameterized to flush dependencies from a specified filesystem.
For now, we stick with the round-robin flushing strategy when the
kernel as a whole has too many dependencies allocated.

While there are many lines of changes, there should be no functional
change in the operation of soft updates.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC of 256812:

Fourth of several cleanups to soft dependency implementation.
Add KASSERTS that soft dependency functions only get called
for filesystems running with soft dependencies. Calling these
functions when soft updates are not compiled into the system
become panic's.

No functional change.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC of 256808:

Third of several cleanups to soft dependency implementation.
Ensure that softdep_unmount() and softdep_setup_sbupdate()
only get called for filesystems running with soft dependencies.

No functional change.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC of 256803:

Second of several cleanups to soft dependency implementation.
Delete two unused functions in ffs_sofdep.c.

No functional change.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix

MFC of 256801:

First of several cleanups to soft dependency implementation.
Convert three functions exported from ffs_softdep.c to static
functions as they are not used outside of ffs_softdep.c.

No functional change.

Tested by: Peter Holm and Scott Long
Sponsored by: Netflix