xfs: refactor dir format helpers

Add a new enum and a xfs_dir2_format helper that returns it to allow
the code to switch on the format of a directory in a single operation
and switch all helpers of xfs_dir2_isblock and xfs_dir2_isleaf to it.

This also removes the explicit xfs_iread_extents call in a few of the
call sites given that xfs_bmap_last_offset already takes care of it
underneath.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

xfs: factor out a xfs_dir_lookup_args helper

Add a helper to switch between the different directory formats for
lookup and to handle the -EEXIST return for a successful lookup.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

xfs: deferred scrub of dirents

If the trylock-based parent pointer check fails, retain those dirents
and check them at the end. This may involve dropping the locks on the
file being scanned, so yay.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

xfs: online repair of directories

If a directory looks like it's in bad shape, try to sift through the
rubble to find whatever directory entries we can, scan the directory
tree for the parent (if needed), stage the new directory contents in a
temporary file and use the atomic extent swapping mechanism to commit
the results in bulk.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

xfs: validate explicit directory block buffer owners

Port the existing directory block header checking function to accept an
owner number instead of an xfs_inode, then update the callsites to use
xfs_da_args.owner when possible.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

xfs: validate explicit directory data buffer owners

Port the existing directory data header checking function to accept an
owner number instead of an xfs_inode, then update the callsites to use
xfs_da_args.owner when possible.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

xfs: add an explicit owner field to xfs_da_args

Add an explicit owner field to xfs_da_args, which will make it easier
for online fsck to set the owner field of the temporary directory and
xattr structures that it builds to repair damaged metadata.

Note: I hopefully found all the xfs_da_args definitions by looking for
automatic stack variable declarations and xfs_da_args.dp assignments:

git grep -E '(args.*dp =|struct xfs_da_args[[:space:]]*[a-z0-9][a-z0-9]*)'

Note that callers of xfs_attr_{get,set,change} can set the owner to zero
(or leave it unset) to have the default set to args->dp.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>

xfs: Replace xfs_isilocked with xfs_assert_ilocked

To use the new rwsem_assert_held()/rwsem_assert_held_write(), we can't
use the existing ASSERT macro. Add a new xfs_assert_ilocked() and
convert all the callers.

Fix an apparent bug in xfs_isilocked(): If the caller specifies
XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL, xfs_assert_ilocked() will check both
the IOLOCK and the ILOCK are held for write. xfs_isilocked() only
checked that the ILOCK was held for write.

xfs_assert_ilocked() is always on, even if DEBUG or XFS_WARN aren't
defined. It's a cheap check, so I don't think it's worth defining
it away.

Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

xfs: make if_data a void pointer

The xfs_ifork structure currently has a union of the if_root void pointer
and the if_data char pointer. In either case it is an opaque pointer
that depends on the fork format. Replace the union with a single if_data
void pointer as that is what almost all callers want. Only the symlink
NULL termination code in xfs_init_local_fork actually needs a new local
variable now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>

xfs: streamline the directory iteration code for scrub

Currently, online scrub reuses the xfs_readdir code to walk every entry
in a directory. This isn't awesome for performance, since we end up
cycling the directory ILOCK needlessly and coding around the particular
quirks of the VFS dir_context interface.

Create a streamlined version of readdir that keeps the ILOCK (since the
walk function isn't going to copy stuff to userspace), skips a whole lot
of directory walk cursor checks (since we start at 0 and walk to the
end) and has a sane way to return error codes.

Note: Porting the dotdot checking code is left for a subsequent patch.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>