3 Commits

Author SHA1 Message Date
Darrick J. Wong
8559b21a64 xfs: implement live updates for directory repairs
While we're scanning the filesystem for parent pointers that we can turn
into dirents, we cannot hold the IOLOCK or ILOCK of the directory being
repaired.  Therefore, we need to set up a dirent hook so that we can
keep the temporary directory up to date with the rest of the filesystem.
Hence we add the ability to *remove* entries from the temporary dir.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2024-04-23 16:55:13 -07:00
Darrick J. Wong
34c9382c12 xfs: ask the dentry cache if it knows the parent of a directory
It's possible that the dentry cache can tell us the parent of a
directory.  Therefore, when repairing directory dot dot entries, query
the dcache as a last resort before scanning the entire filesystem.

A reviewer asks:

"How high is the chance that we actually have a valid dcache entry for a
file in a corrupted directory?"

There's a decent chance of this actually working.  Say you have a
1000-block directory foo, and block 980 gets corrupted.  Let's further
suppose that block 0 has a correct entry for ".." and "bar".  If someone
accesses /mnt/foo/bar, that will cause the dcache to create a dentry
from /mnt to /mnt/foo whose d_parent points back to /mnt.  If you then
want to rebuild the directory, XFS can obtain the parent from the dcache
without needing to wander into parent pointers or scan the filesystem to
find /mnt's connection to foo.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2024-04-15 14:58:56 -07:00
Darrick J. Wong
a07b455762 xfs: scan the filesystem to repair a directory dotdot entry
Teach the online directory repair code to scan the filesystem so that we
can set the dotdot entry when we're rebuilding a directory.  This
involves dropping ILOCK on the directory that we're repairing, which
means that the VFS can sneak in and tell us to update dotdot at any
time.  Deal with these races by using a dirent hook to absorb dotdot
updates, and be careful not to check the scan results until after we've
retaken the ILOCK.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
2024-04-15 14:58:56 -07:00