| Age | Commit message (Collapse) | Author | Files | Lines |
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Notice now that the btree ops structure encodes btree geometry flags and
the magic number through the buffer ops. Refactor the btree block
initialization functions to use the btree ops so that we no longer have
to open code all that.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Expose these static btree ops structures so that we can reference them
in the AG initialization code in the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Add a new XFS_BTREE_ALLOCBT_ACTIVE flag to replace the active field.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Add a single xfs_alloc_lookup helper to sort out the argument passing and
setting of the active flag instead of duplicating the logic three times.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Just move the two flags into bc_flags where there is plenty of space.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Certain btree flags never change for the life of a btree cursor because
they describe the geometry of the btree itself. Encode these in the
btree ops structure and reduce the amount of code required in each btree
type's init_cursor functions. This also frees up most of the bits in
bc_flags.
A previous version of this patch also converted the open-coded flags
logic to helpers. This was removed due to the pending refactoring (that
follows this patch) to eliminate most of the state flags.
Conversion script:
sed \
-e 's/XFS_BTREE_LONG_PTRS/XFS_BTGEO_LONG_PTRS/g' \
-e 's/XFS_BTREE_ROOT_IN_INODE/XFS_BTGEO_ROOT_IN_INODE/g' \
-e 's/XFS_BTREE_LASTREC_UPDATE/XFS_BTGEO_LASTREC_UPDATE/g' \
-e 's/XFS_BTREE_OVERLAPPING/XFS_BTGEO_OVERLAPPING/g' \
-e 's/cur->bc_flags & XFS_BTGEO_/cur->bc_ops->geom_flags \& XFS_BTGEO_/g' \
-i $(git ls-files fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] fs/xfs/scrub/*.[ch])
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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A reviewer was confused by the init_sa logic in this function. Upon
checking the logic, I discovered that the code is imprecise. What we
want to do here is check that there is an ownership record in the rmap
btree for the AG that contains a btree block.
For an inode-rooted btree (e.g. the bmbt) the per-AG btree cursors have
not been initialized because inode btrees can span multiple AGs.
Therefore, we must initialize the per-AG btree cursors in sc->sa before
proceeding. That is what init_sa controls, and hence the logic should
be gated on XFS_BTREE_ROOT_IN_INODE, not XFS_BTREE_LONG_PTRS.
In practice, ROOT_IN_INODE and LONG_PTRS are coincident so this hasn't
mattered. However, we're about to refactor both of those flags into
separate btree_ops fields so we want this the logic to make sense
afterwards.
Fixes: 858333dcf021a ("xfs: check btree block ownership with bnobt/rmapbt when scrubbing btree")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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All existing btree types set XFS_BTREE_CRC_BLOCKS when running against a
V5 filesystem. All currently proposed btree types are V5 only and use
the richer XFS_BTREE_CRC_BLOCKS format. Therefore, we can drop this
flag and change the conditional to xfs_has_crc.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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This is a precursor to putting more static data in the btree ops structure.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Don't waste tracepoint segment memory on per-btree block allocation
tracepoints when we can do it from the generic btree code.
With this patch applied, two tracepoints are collapsed into one
tracepoint, with the following effects on objdump -hx xfs.ko output:
Before:
10 __tracepoints_ptrs 00000b38 0000000000000000 0000000000000000 001412f0 2**2
14 __tracepoints_strings 00005433 0000000000000000 0000000000000000 001689a0 2**5
29 __tracepoints 00010d30 0000000000000000 0000000000000000 0023fe00 2**5
After:
10 __tracepoints_ptrs 00000b34 0000000000000000 0000000000000000 001417b0 2**2
14 __tracepoints_strings 00005413 0000000000000000 0000000000000000 00168e80 2**5
29 __tracepoints 00010cd0 0000000000000000 0000000000000000 00240760 2**5
Column 3 is the section size in bytes; removing these two tracepoints
reduces the size of the ELF segments by 132 bytes.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Don't waste memory on extra per-btree block freeing tracepoints when we
can do it from the generic btree code.
With this patch applied, two tracepoints are collapsed into one
tracepoint, with the following effects on objdump -hx xfs.ko output:
Before:
10 __tracepoints_ptrs 00000b3c 0000000000000000 0000000000000000 00140eb0 2**2
14 __tracepoints_strings 00005453 0000000000000000 0000000000000000 00168540 2**5
29 __tracepoints 00010d90 0000000000000000 0000000000000000 0023f5e0 2**5
After:
10 __tracepoints_ptrs 00000b38 0000000000000000 0000000000000000 001412f0 2**2
14 __tracepoints_strings 00005433 0000000000000000 0000000000000000 001689a0 2**5
29 __tracepoints 00010d30 0000000000000000 0000000000000000 0023fe00 2**5
Column 3 is the section size in bytes; removing these two tracepoints
reduces the size of the ELF segments by 132 bytes.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Use the same summary counter calculation infrastructure to generate new
values for the in-core summary counters. The difference between the
scrubber and the repairer is that the repairer will freeze the fs during
setup, which means that the values should match exactly.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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If scrub finds that everything is ok with the filesystem, we need a way
to tell the health tracking that it can let go of indirect health flags,
since indirect flags only mean that at some point in the past we lost
some context.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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If an unhealthy inode gets inactivated, remember this fact in the
per-fs health summary.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Establish two more classes of health tracking bits:
* Indirect problems, which suggest problems in other health domains
that we weren't able to preserve.
* Secondary problems, which track state that's related to primary
evidence of health problems; and
The first class we'll use in an upcoming patch to record in the AG
health status the fact that we ran out of memory and had to inactivate
an inode with defective metadata. The second class we use to indicate
that repair knows that an inode is bad and we need to fix it later.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter XFS_IS_CORRUPT failures, we should report that to
the health monitoring system for later reporting.
I started with this semantic patch and massaged everything until it
built:
@@
expression mp, test;
@@
- if (XFS_IS_CORRUPT(mp, test)) return -EFSCORRUPTED;
+ if (XFS_IS_CORRUPT(mp, test)) { xfs_btree_mark_sick(cur); return -EFSCORRUPTED; }
@@
expression mp, test;
identifier label, error;
@@
- if (XFS_IS_CORRUPT(mp, test)) { error = -EFSCORRUPTED; goto label; }
+ if (XFS_IS_CORRUPT(mp, test)) { xfs_btree_mark_sick(cur); error = -EFSCORRUPTED; goto label; }
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter corrupt realtime metadat blocks, we should report
that to the health monitoring system for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter corrupt quota blocks, we should report that to the
health monitoring system for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter corrupt inode records, we should report that to
the health monitoring system for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter corrupt symbolic link blocks, we should report
that to the health monitoring system for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter corrupt directory or extended attribute blocks, we
should report that to the health monitoring system for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter corrupt btree blocks, we should report that to the
health monitoring system for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter a corrupt block mapping, we should report that to
the health monitoring system for later reporting.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter a corrupt AG header, we should report that to the
health monitoring system for later reporting. Buffer readers that don't
respond to corruption events with a _mark_sick call can be detected with
the following script:
#!/bin/bash
# Detect missing calls to xfs_*_mark_sick
filter=cat
tty -s && filter=less
git grep -A10 -E '( = xfs_trans_read_buf| = xfs_buf_read\()' fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Whenever we encounter corrupt fs metadata, we should report that to the
health monitoring system for later reporting. A convenient program for
identifying places to insert xfs_*_mark_sick calls is as follows:
#!/bin/bash
# Detect missing calls to xfs_*_mark_sick
filter=cat
tty -s && filter=less
git grep -B3 EFSCORRUPTED fs/xfs/*.[ch] fs/xfs/libxfs/*.[ch] fs/xfs/scrub/*.[ch] | awk '
BEGIN {
ignore = 0;
lineno = 0;
delete lines;
}
{
if ($0 == "--") {
if (!ignore) {
for (i = 0; i < lineno; i++) {
print(lines[i]);
}
printf("--\n");
}
delete lines;
lineno = 0;
ignore = 0;
} else if ($0 ~ /mark_sick/) {
ignore = 1;
} else if ($0 ~ /if .fa/) {
ignore = 1;
} else if ($0 ~ /failaddr/) {
ignore = 1;
} else if ($0 ~ /_verifier_error/) {
ignore = 1;
} else if ($0 ~ /^ \* .*EFSCORRUPTED/) {
ignore = 1;
} else if ($0 ~ /== -EFSCORRUPTED/) {
ignore = 1;
} else if ($0 ~ /!= -EFSCORRUPTED/) {
ignore = 1;
} else {
lines[lineno++] = $0;
}
}
' | $filter
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Split the setting of the sick and checked masks into separate functions
as part of preparing to add the ability for regular runtime fs code
(i.e. not scrub) to mark metadata structures sick when corruptions are
found. Improve the documentation of libxfs' requirements for helper
behavior.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Fix the file link counts since we just computed the correct ones.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create the necessary hooks in the directory operations
(create/link/unlink/rename) code so that our live nlink scrub code can
stay up to date with link count updates in the rest of the filesystem.
This will be the means to keep our shadow link count information up to
date while the scan runs in real time.
In online fsck part 2, we'll use these same hooks to handle repairs
to directories and parent pointer information.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create the necessary scrub code to walk the filesystem's directory tree
so that we can compute file link counts. Similar to quotacheck, we
create an incore shadow array of link count information and then we walk
the filesystem a second time to compare the link counts. We need live
updates to keep the information up to date during the lengthy scan, so
this scrubber remains disabled until the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Report on the health of the inode link counts.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Use the shadow quota counters that live quotacheck creates to reset the
incore dquot counters.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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While running xfs/804 (quota repairs racing with fsstress), I observed a
filesystem shutdown in the primary sb write verifier:
run fstests xfs/804 at 2022-05-23 18:43:48
XFS (sda4): Mounting V5 Filesystem
XFS (sda4): Ending clean mount
XFS (sda4): Quotacheck needed: Please wait.
XFS (sda4): Quotacheck: Done.
XFS (sda4): EXPERIMENTAL online scrub feature in use. Use at your own risk!
XFS (sda4): SB ifree sanity check failed 0xb5 > 0x80
XFS (sda4): Metadata corruption detected at xfs_sb_write_verify+0x5e/0x100 [xfs], xfs_sb block 0x0
XFS (sda4): Unmount and run xfs_repair
The "SB ifree sanity check failed" message was a debugging printk that I
added to the kernel; observe that 0xb5 - 0x80 = 53, which is less than
one inode chunk.
I traced this to the xfs_log_sb calls from the online quota repair code,
which tries to clear the CHKD flags from the superblock to force a
mount-time quotacheck if the repair fails. On a V5 filesystem,
xfs_log_sb updates the ondisk sb summary counters with the current
contents of the percpu counters. This is done without quiescing other
writer threads, which means it could be racing with a thread that has
updated icount and is about to update ifree.
If the other write thread had incremented ifree before updating icount,
the repair thread will write icount > ifree into the logged update. If
the AIL writes the logged superblock back to disk before anyone else
fixes this siutation, this will lead to a write verifier failure, which
causes a filesystem shutdown.
Resolve this problem by updating the quota flags and calling
xfs_sb_to_disk directly, which does not touch the percpu counters.
While we're at it, we can elide the entire update if the selected qflags
aren't set.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create a shadow dqtrx system in the quotacheck code that hooks the
regular dquot counter update code. This will be the means to keep our
copy of the dquot counters up to date while the scan runs in real time.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create a new trio of scrub functions to check quota counters. While the
dquots themselves are filesystem metadata and should be checked early,
the dquot counter values are computed from other metadata and are
therefore summary counters. We don't plug these into the scrub dispatch
just yet, because we still need to be able to watch quota updates while
doing our scan.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create a new method to load an xfarray element from the xfile, but with
a twist. If we've never stored to the array index, zero the caller's
buffer. This will facilitate RMWs updates of records in a sparse array
without fuss, since the sparse xfarray convention is that uninitialized
array elements default to zeroes.
This is a separate patch to reduce the size of the upcoming quotacheck
patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create a helper to compute the number of blocks that a file has
allocated from the data realtime volumes. This patch was
split out to reduce the size of the upcoming quotacheck patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create a helper to initialize empty transactions on behalf of a scrub
operation.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Report the health of quota counts.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Repair might encounter an inode with a totally garbage i_mode. To fix
this problem, we have to figure out if the file was a regular file, a
directory, or a special file. One way to figure this out is to check if
there are any directories with entries pointing down to the busted file.
This patch recovers the file mode by scanning every directory entry on
the filesystem to see if there are any that point to the busted file.
If the ftype of all such dirents are consistent, the mode is recovered
from the ftype. If no dirents are found, the file becomes a regular
file. In all cases, ACLs are canceled and the file is made accessible
only by root.
A previous patch attempted to guess the mode by reading the beginning of
the file data. This was rejected by Christoph on the grounds that we
cannot trust user-controlled data blocks. Users do not have direct
control over the ondisk contents of directory entries, so this method
should be much safer.
If all the dirents have the same ftype, then we can translate that back
into an S_IFMT flag and fix the file. If not, reset the mode to
S_IFREG.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create the XFS_DIR3_FTYPE_STR macro so that we can report ftype as
strings instead of numbers in tracepoints.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create a simple predicate to determine if two xfs_names are the same
objects or have the exact same name. The comparison is always case
sensitive.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Create an xfs_name_dot object so that upcoming scrub code can compare
against that. Offline repair already has such an object, so we're
really just hoisting it to the kernel.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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The inode scanner tries to reduce contention on the AGI header buffer
lock by grabbing references to consecutive allocated inodes. Batching
stops as soon as we encounter an unallocated inode. This is unfortunate
because in the worst case performance collapses to the old "one at a
time" behavior if every other inode is free.
This is correct behavior, but we could do better. Unallocated inodes by
definition have nothing to scan, which means the iscan can ignore them
as long as someone ensures that the scan data will reflect another
thread allocating the inode and adding interesting metadata to that
inode. That mechanism is, of course, the live update hooks.
Therefore, extend the batching mechanism to track unallocated inodes
adjacent to the scan cursor. The _want_live_update predicate can tell
the caller's live update hook to incorporate all live updates to what
the scanner thinks is an unallocated inode if (after dropping the AGI)
some other thread allocates one of those inodes and begins using it.
Note that we cannot just copy the ir_free bitmap into the scan cursor
because the batching stops if iget says the inode is in an intermediate
state (e.g. on the inactivation list) and cannot be igrabbed.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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After observing xfs_scrub taking forever to rebuild parent pointers on a
pptrs enabled filesystem, I decided to profile what the system was
doing. It turns out that when there are a lot of threads trying to scan
the filesystem, most of our time is spent contending on AGI buffer
locks. Given that we're walking the inobt records anyway, we can often
tell ahead of time when there's a bunch of (up to 64) consecutive inodes
that we could grab all at once.
Do this to amortize the cost of taking the AGI lock across as many
inodes as we possibly can. On the author's system this seems to improve
parallel throughput from barely one and a half cores to slightly
sublinear scaling. The obvious antipattern here of course is where the
freemask has every other bit set (e.g. all 0xA's)
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Online directory and parent repairs on parent-pointer equipped
filesystems have shown that starting a large number of parallel iscans
causes a lot of AGI buffer contention. Try to reduce this by making it
so that iscans scan wrap around the end of the filesystem, and using a
rotor to stagger where each scanner begins. Surprisingly, this boosts
CPU utilization (on the author's test machines) from effectively
single-threaded to 160%. Not great, but see the next patch.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Certain types of filesystem metadata can only be checked by scanning
every file in the entire filesystem. Specific examples of this include
quota counts, file link counts, and reverse mappings of file extents.
Directory and parent pointer reconstruction may also fall into this
category. File scanning is much trickier than scanning AG metadata
because we have to take inode locks in the same order as the rest of
[VX]FS, we can't be holding buffer locks when we do that, and scanning
the whole filesystem takes time.
Earlier versions of the online repair patchset relied heavily on
fsfreeze as a means to quiesce the filesystem so that we could take
locks in the proper order without worrying about concurrent updates from
other writers. Reviewers of those patches opined that freezing the
entire fs to check and repair something was not sufficiently better than
unmounting to run fsck offline. I don't agree with that 100%, but the
message was clear: find a way to repair things that minimizes the
quiet period where nobody can write to the filesystem.
Generally, building btree indexes online can be split into two phases: a
collection phase where we compute the records that will be put into the
new btree; and a construction phase, where we construct the physical
btree blocks and persist them. While it's simple to hold resource locks
for the entirety of the two phases to ensure that the new index is
consistent with the rest of the system, we don't need to hold resource
locks during the collection phase if we have a means to receive live
updates of other work going on elsewhere in the system.
The goal of this patch, then, is to enable online fsck to learn about
metadata updates going on in other threads while it constructs a shadow
copy of the metadata records to verify or correct the real metadata. To
minimize the overhead when online fsck isn't running, we use srcu
notifiers because they prioritize fast access to the notifier call chain
(particularly when the chain is empty) at a cost to configuring
notifiers. Online fsck should be relatively infrequent, so this is
acceptable.
The intended usage model is fairly simple. Code that modifies a
metadata structure of interest should declare a xfs_hook_chain structure
in some well defined place, and call xfs_hook_call whenever an update
happens. Online fsck code should define a struct notifier_block and use
xfs_hook_add to attach the block to the chain, along with a function to
be called. This function should synchronize with the fsck scanner to
update whatever in-memory data the scanner is collecting. When
finished, xfs_hook_del removes the notifier from the list and waits for
them all to complete.
Originally, I selected srcu notifiers over blocking notifiers to
implement live hooks because they seemed to have fewer impacts to
scalability. The per-call cost of srcu_notifier_call_chain is higher
(19ns) than blocking_notifier_ (4ns) in the single threaded case, but
blocking notifiers use an rwsem to stabilize the list. Cacheline
bouncing for that rwsem is costly to runtime code when there are a lot
of CPUs running regular filesystem operations. If there are no hooks
installed, this is a total waste of CPU time.
Therefore, I stuck with srcu notifiers, despite trading off single
threaded performance for multithreaded performance. I also wasn't
thrilled with the very high teardown time for srcu notifiers, since the
caller has to wait for the next rcu grace period. This can take a long
time if there are a lot of CPUs.
Then I discovered the jump label implementation of static keys.
Jump labels use kernel code patching to replace a branch with a nop sled
when the key is disabled. IOWs, they can eliminate the overhead of
_call_chain when there are no hooks enabled. This makes blocking
notifiers competitive again -- scrub runs faster because teardown of the
chain is a lot cheaper, and runtime code only pays the rwsem locking
overhead when scrub is actually running.
With jump labels enabled, calls to empty notifier chains are elided from
the call sites when there are no hooks registered, which means that the
overhead is 0.36ns when fsck is not running. This is perfect for most
of the architectures that XFS is expected to run on (e.g. x86, powerpc,
arm64, s390x, riscv).
For architectures that don't support jump labels (e.g. m68k) the runtime
overhead of checking the static key is an atomic counter read. This
isn't great, but it's still cheaper than taking a shared rwsem.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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This patch implements a live file scanner for online fsck functions that
require the ability to walk a filesystem to gather metadata records and
stay informed about metadata changes to files that have already been
visited.
The iscan structure consists of two inode number cursors: one to track
which inode we want to visit next, and a second one to track which
inodes have already been visited. This second cursor is key to
capturing live updates to files previously scanned while the main thread
continues scanning -- any inode greater than this value hasn't been
scanned and can go on its way; any other update must be incorporated
into the collected data. It is critical for the scanning thraad to hold
exclusive access on the inode until after marking the inode visited.
This new code is a separate patch from the patchsets adding callers for
the sake of enabling the author to move patches around his tree with
ease. The intended usage model for this code is roughly:
xchk_iscan_start(iscan, 0, 0);
while ((error = xchk_iscan_iter(sc, iscan, &ip)) == 1) {
xfs_ilock(ip, ...);
/* capture inode metadata */
xchk_iscan_mark_visited(iscan, ip);
xfs_iunlock(ip, ...);
xfs_irele(ip);
}
xchk_iscan_stop(iscan);
if (error)
return error;
Hook functions for live updates can then do:
if (xchk_iscan_want_live_update(...))
/* update the captured inode metadata */
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Replace the open-coded loop that recomputes freecount with a single call
to a bit weight function.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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A data corruption problem was reported by CoreOS image builders
when using reflink based disk image copies and then converting
them to qcow2 images. The converted images failed the conversion
verification step, and it was isolated down to the fact that
qemu-img uses SEEK_HOLE/SEEK_DATA to find the data it is supposed to
copy.
The reproducer allowed me to isolate the issue down to a region of
the file that had overlapping data and COW fork extents, and the
problem was that the COW fork extent was being reported in it's
entirity by xfs_seek_iomap_begin() and so skipping over the real
data fork extents in that range.
This was somewhat hidden by the fact that 'xfs_bmap -vvp' reported
all the extents correctly, and reading the file completely (i.e. not
using seek to skip holes) would map the file correctly and all the
correct data extents are read. Hence the problem is isolated to just
the xfs_seek_iomap_begin() implementation.
Instrumentation with trace_printk made the problem obvious: we are
passing the wrong length to xfs_trim_extent() in
xfs_seek_iomap_begin(). We are passing the end_fsb, not the
maximum length of the extent we want to trim the map too. Hence the
COW extent map never gets trimmed to the start of the next data fork
extent, and so the seek code treats the entire COW fork extent as
unwritten and skips entirely over the data fork extents in that
range.
Link: https://github.com/coreos/coreos-assembler/issues/3728
Fixes: 60271ab79d40 ("xfs: fix SEEK_DATA for speculative COW fork preallocation")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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These functions aren't used anymore, so get rid of them.
Signed-off-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Chandan Babu R <chandanbabu@kernel.org>
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