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Repair inconsistent symbolic link data.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Use the reverse-mapping btree information to rebuild an inode block map.
Update the btree bulk loading code as necessary to support inode rooted
btrees and fix some bitrot problems.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Reintroduce to xrep_reap_extents the ability to reap extents from any
AG. We dropped this before because it was buggy, but in the next patch
we will gain the ability to reap old bmap btrees, which can have blocks
in any AG. To do this, we require that sc->sa is uninitialized, so that
we can use it to hold all the per-AG context for a given extent.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Building off the rmap scanner that we added in the previous patch, we
can now find block 0 and try to use the information contained inside of
it to guess the mode of an inode if it's totally improper.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Determine if inode fork damage is responsible for the inode being unable
to pass the ifork verifiers in xfs_iget and zap the fork contents if
this is true. Once this is done the fork will be empty but we'll be
able to construct an in-core inode, and a subsequent call to the inode
fork repair ioctl will search the rmapbt to rebuild the records that
were in the fork.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Try to reinitialize corrupt inodes, or clear the reflink flag
if it's not needed.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Inodes aren't supposed to have a project id of -1U (aka 4294967295) but
the kernel hasn't always validated FSSETXATTR correctly. Flag this as
something for the sysadmin to check out.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Reconstruct the refcount data from the rmap btree.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Use the rmapbt to find inode chunks, query the chunks to compute
hole and free masks, and with that information rebuild the inobt
and finobt.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Back in the mists of time[1], I proposed this function to assist the
inode btree scrubbers in checking the inode btree contents against the
allocation state of the inode records. The original version performed a
direct lookup in the inode cache and returned the allocation status if
the cached inode hadn't been reused and wasn't in an intermediate state.
Brian thought it would be better to use the usual iget/irele mechanisms,
so that was changed for the final version.
Unfortunately, this hasn't aged well -- the IGET_INCORE flag only has
one user and clutters up the regular iget path, which makes it hard to
reason about how it actually works. Worse yet, the inode inactivation
series silently broke it because iget won't return inodes that are
anywhere in the inactivation machinery, even though the caller is
already required to prevent inode allocation and freeing. Inodes in the
inactivation machinery are still allocated, but the current code's
interactions with the iget code prevent us from being able to say that.
Now that I understand the inode lifecycle better than I did in early
2017, I now realize that as long as the cached inode hasn't been reused
and isn't actively being reclaimed, it's safe to access the i_mode field
(with the AGI, rcu, and i_flags locks held), and we don't need to worry
about the inode being freed out from under us.
Therefore, port the original version to modern code structure, which
fixes the brokennes w.r.t. inactivation. In the next patch we'll remove
IGET_INCORE since it's no longer necessary.
[1] https://lore.kernel.org/linux-xfs/149643868294.23065.8094890990886436794.stgit@birch.djwong.org/
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Rebuild the free space btrees from the gaps in the rmap btree.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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All online repair functions have the same structure: walk filesystem
metadata structures gathering enough data to rebuild the structure,
stage a new copy, and then commit the new copy.
The gathering steps do not write anything to disk, so they are peppered
with xchk_should_terminate calls to avoid softlockup warnings and to
provide an opportunity to abort the repair (by killing xfs_scrub).
However, it's not clear in the code base when is the last chance to
abort cleanly without having to undo a bunch of structure.
Therefore, add one more call to xchk_should_terminate (along with a
comment) providing the sysadmin with the ability to abort before it's
too late and to make it clear in the source code when it's no longer
convenient or safe to abort a repair. As there are only four repair
functions right now, this patch exists more to establish a precedent for
subsequent additions than to deliver practical functionality.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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While debugging other parts of online repair, I noticed that if someone
injects FORCE_SCRUB_REPAIR, starts an IFLAG_REPAIR scrub on a piece of
metadata, and the metadata repair fails, we'll log a message about
uncorrected errors in the filesystem.
This isn't strictly true if the scrub function didn't set OFLAG_CORRUPT
and we're only doing the repair because the error injection knob is set.
Repair functions are allowed to abort the entire operation at any point
before committing new metadata, in which case the piece of metadata is
in the same state as it was before. Therefore, the log message should
be gated on the results of the scrub. Refactor the predicate and
rearrange the code flow to make this happen.
Note: If the repair function errors out after it commits the new
metadata, the transaction cancellation will shut down the filesystem,
which is an obvious sign of corrupt metadata.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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After an online repair function runs for a per-AG metadata structure,
sc->sick_mask is supposed to reflect the per-AG metadata that the repair
function fixed. Our next move is to re-check the metadata to assess
the completeness of our repair, so we don't want the rebuilt structure
to be excluded from the rescan just because the health system previously
logged a problem with the data structure.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Finish the realtime summary scrubber by adding the functions we need to
compute a fresh copy of the rtsummary info and comparing it to the copy
on disk.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Move the realtime summary file checking code to a separate file in
preparation to actually implement it.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Scrub tracks the resources that it's holding onto in the xfs_scrub
structure. This includes the inode being checked (if applicable) and
the inode lock state of that inode. Replace the open-coded structure
manipulation with a trivial helper to eliminate sources of error.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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When we want to scrub a file, get our own reference to the inode
unconditionally. This will make disposal rules simpler in the long run.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Create a simple 'big array' data structure for storage of fixed-size
metadata records that will be used to reconstruct a btree index. For
repair operations, the most important operations are append, iterate,
and sort.
Earlier implementations of the big array used linked lists and suffered
from severe problems -- pinning all records in kernel memory was not a
good idea and frequently lead to OOM situations; random access was very
inefficient; and record overhead for the lists was unacceptably high at
40-60%.
Therefore, the big memory array relies on the 'xfile' abstraction, which
creates a memfd file and stores the records in page cache pages. Since
the memfd is created in tmpfs, the memory pages can be pushed out to
disk if necessary and we have a built-in usage limit of 50% of physical
memory.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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We need to log EFIs for every extent that we allocate for the purpose of
staging a new btree so that if we fail then the blocks will be freed
during log recovery. Add a function to relog the EFIs, so that repair
can relog them all every time it creates a new btree block, which will
help us to avoid pinning the log tail.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Add some debug knobs so that we can control the leaf and node block
slack when rebuilding btrees.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Create a new xrep_newbt structure to encapsulate a fake root for
creating a staged btree cursor as well as to track all the blocks that
we need to reserve in order to build that btree.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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While stress-testing online repair of btrees, I noticed periodic
assertion failures from the buffer cache about buffer readers
encountering buffers with DELWRI_Q set, even though the btree bulk load
had already committed and the buffer itself wasn't on any delwri list.
I traced this to a misunderstanding of how the delwri lists work,
particularly with regards to the AIL's buffer list. If a buffer is
logged and committed, the buffer can end up on that AIL buffer list. If
btree repairs are run twice in rapid succession, it's possible that the
first repair will invalidate the buffer and free it before the next time
the AIL wakes up. This clears DELWRI_Q from the buffer state.
If the second repair allocates the same block, it will then recycle the
buffer to start writing the new btree block. Meanwhile, if the AIL
wakes up and walks the buffer list, it will ignore the buffer because it
can't lock it, and go back to sleep.
When the second repair calls delwri_queue to put the buffer on the
list of buffers to write before committing the new btree, it will set
DELWRI_Q again, but since the buffer hasn't been removed from the AIL's
buffer list, it won't add it to the bulkload buffer's list.
This is incorrect, because the bulkload caller relies on delwri_submit
to ensure that all the buffers have been sent to disk /before/
committing the new btree root pointer. This ordering requirement is
required for data consistency.
Worse, the AIL won't clear DELWRI_Q from the buffer when it does finally
drop it, so the next thread to walk through the btree will trip over a
debug assertion on that flag.
To fix this, create a new function that waits for the buffer to be
removed from any other delwri lists before adding the buffer to the
caller's delwri list.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Convert the xbitmap code to use interval trees instead of linked lists.
This reduces the amount of coding required to handle the disunion
operation and in the future will make it easier to set bits in arbitrary
order yet later be able to extract maximally sized extents, which we'll
need for rebuilding certain structures. We define our own interval tree
type so that it can deal with 64-bit indices even on 32-bit machines.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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When we're freeing extents that have been set in a bitmap, break the
bitmap extent into multiple sub-extents organized by fate, and reap the
extents. This enables us to dispose of old resources more efficiently
than doing them block by block.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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After an online repair, we need to invalidate buffers representing the
blocks from the old metadata that we're replacing. It's possible that
parts of a tree that were previously cached in memory are no longer
accessible due to media failure or other corruption on interior nodes,
so repair figures out the old blocks from the reverse mapping data and
scans the buffer cache directly.
Unfortunately, the current buffer cache code triggers asserts if the
rhashtable lookup finds a non-stale buffer of a different length than
the key we searched for. For regular operation this is desirable, but
for this repair procedure, we don't care since we're going to forcibly
stale the buffer anyway. Add an internal lookup flag to avoid the
assert.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Rearrange the logic inside xrep_reap_block to make it more obvious that
crosslinked metadata blocks are handled differently. Add a couple of
tracepoints so that we can tell what's going on at the end of a btree
rebuild operation.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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It's not safe to edit bitmap intervals while we're iterating them with
for_each_xbitmap_extent. None of the existing callers actually need
that ability anyway, so drop the safe variable.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Remove the for_each_xbitmap_ macros in favor of proper iterator
functions. We'll soon be switching this data structure over to an
interval tree implementation, which means that we can't allow callers to
modify the bitmap during iteration without telling us.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Use deferred frees (EFIs) to reap the blocks of a btree that we just
replaced. This helps us to shrink the window in which those old blocks
could be lost due to a system crash, though we try to flush the EFIs
every few hundred blocks so that we don't also overflow the transaction
reservations during and after we commit the new btree.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Now that we've refactored btree cursors to require the caller to pass in
a perag structure, there are numerous problems in xrep_reap_extents if
it's being called to reap extents for an inode metadata repair. We
don't have any repair functions that can do that, so drop the support
for now.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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When we're discarding old btree blocks after a repair, only invalidate
the buffers for the ones that we're freeing -- if the metadata was
crosslinked with another data structure, we don't want to touch it.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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If we tried to repair something but the repair failed with -EDEADLOCK or
-EAGAIN, that means that the repair function couldn't grab some resource
it needed and wants us to try again. If we try again (with TRY_HARDER)
but still can't do it, exit back to userspace, since xfs_scrub_metadata
requires xrep_attempt to return -EAGAIN.
This makes the return value diagnostics look less weird, and fixes a
wart that remains from very early in the repair implementation.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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This function was created to help online repair deal with freeing blocks
from an old metadata structure after a repair completes. When
considering a block to free, we want to know if the rmap btree contains
records of any other owners. If yes, the block is crosslinked and we
merely want to drop the forward reference to the block and any rmap
record from the deleted structure. If no, then we should additionally
free the block.
The current version doesn't actually check file offsets properly, since
I hadn't built gotten that far with online repair. Now that I have, I
know that it should be performing a range comparison of the offsets and
not the simple offset check that it currently performs.
So, fix this deficiency ahead of the rest of online repair.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Currently, the code that performs CoW remapping after a write has this
odd behavior where it walks /backwards/ through the data fork to remap
extents in reverse order. Earlier, we rewrote the reflink remap
function to use deferred bmap log items instead of trying to cram as
much into the first transaction that we could. Now do the same for the
CoW remap code. There doesn't seem to be any performance impact; we're
just making better use of code that we added for the benefit of reflink.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Before to the introduction of deferred refcount operations, reflink
would try to cram refcount btree updates into the same transaction as an
allocation or a free event. Mainline XFS has never actually done that,
but we never refactored the transaction reservations to reflect that we
now do all refcount updates in separate transactions. Fix this to
reduce the transaction reservation size even farther, so that between
this patch and the previous one, we reduce the tr_write and tr_itruncate
sizes by 66%.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Back in the early days of reflink and rmap development I set the
transaction reservation sizes to be overly generous for rmap+reflink
filesystems, and a little under-generous for rmap-only filesystems.
Since we don't need *eight* transaction rolls to handle three new log
intent items, decrease the logcounts to what we actually need, and amend
the shadow reservation computation function to reflect what we used to
do so that the minimum log size doesn't change.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Every time someone changes the transaction reservation sizes, they
introduce potential compatibility problems if the changes affect the
minimum log size that we validate at mount time. If the minimum log
size gets larger (which should be avoided because doing so presents a
serious risk of log livelock), filesystems created with old mkfs will
not mount on a newer kernel; if the minimum size shrinks, filesystems
created with newer mkfs will not mount on older kernels.
Therefore, enable the creation of a shadow log reservation structure
where we can "undo" the effects of tweaks when computing minimum log
sizes. These shadow reservations should never be used in practice, but
they insulate us from perturbations in minimum log size.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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This raw call isn't necessary since we can always remove a full delalloc
extent.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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In commit e1a4e37cc7b6, we clamped the length of bunmapi calls on the
data forks of shared files to avoid two failure scenarios: one where the
extent being unmapped is so sparsely shared that we exceed the
transaction reservation with the sheer number of refcount btree updates
and EFI intent items; and the other where we attach so many deferred
updates to the transaction that we pin the log tail and later the log
head meets the tail, causing the log to livelock.
We avoid triggering the first problem by tracking the number of ops in
the refcount btree cursor and forcing a requeue of the refcount intent
item any time we think that we might be close to overflowing. This has
been baked into XFS since before the original e1a4 patch.
A recent patchset fixed the second problem by changing the deferred ops
code to finish all the work items created by each round of trying to
complete a refcount intent item, which eliminates the long chains of
deferred items (27dad); and causing long-running transactions to relog
their intent log items when space in the log gets low (74f4d).
Because this clamp affects /any/ unmapping request regardless of the
sharing factors of the component blocks, it degrades the performance of
all large unmapping requests -- whereas with an unshared file we can
unmap millions of blocks in one go, shared files are limited to
unmapping a few thousand blocks at a time, which causes the upper level
code to spin in a bunmapi loop even if it wasn't needed.
This also eliminates one more place where log recovery behavior can
differ from online behavior, because bunmapi operations no longer need
to requeue.
Partial-revert-of: e1a4e37cc7b6 ("xfs: try to avoid blowing out the transaction reservation when bunmaping a shared extent")
Depends: 27dada070d59 ("xfs: change the order in which child and parent defer ops ar finished")
Depends: 74f4d6a1e065 ("xfs: only relog deferred intent items if free space in the log gets low")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Reverse mapping on a reflink-capable filesystem has some pretty high
overhead when performing file operations. This is because the rmap
records for logically and physically adjacent extents might not be
adjacent in the rmap index due to data block sharing. As a result, we
use expensive overlapped-interval btree search, which walks every record
that overlaps with the supplied key in the hopes of finding the record.
However, profiling data shows that when the index contains a record that
is an exact match for a query key, the non-overlapped btree search
function can find the record much faster than the overlapped version.
Try the non-overlapped lookup first when we're trying to find the left
neighbor rmap record for a given file mapping, which makes unwritten
extent conversion and remap operations run faster if data block sharing
is minimal in this part of the filesystem.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Reverse mapping on a reflink-capable filesystem has some pretty high
overhead when performing file operations. This is because the rmap
records for logically and physically adjacent extents might not be
adjacent in the rmap index due to data block sharing. As a result, we
use expensive overlapped-interval btree search, which walks every record
that overlaps with the supplied key in the hopes of finding the record.
However, profiling data shows that when the index contains a record that
is an exact match for a query key, the non-overlapped btree search
function can find the record much faster than the overlapped version.
Try the non-overlapped lookup first, which will make scrub run much
faster.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Most callers of xfs_rmap_lookup_le will retrieve the btree record
immediately if the lookup succeeds. The overlapped version of this
function (xfs_rmap_lookup_le_range) will return the record if the lookup
succeeds, so make the regular version do it too. Get rid of the useless
len argument, since it's not part of the lookup key.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Gaps in the reference count btree are also significant -- for these
regions, there must not be any overlapping reverse mappings. We don't
currently check this, so make the refcount scrubber more complete.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Teach scrub to flag quota files containing unwritten extents.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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When scrub is checking file fork mappings against rmap records and
the rmap record starts before or ends after the bmap record, check the
adjacent bmap records to make sure that they're adjacent to the one
we're checking. This helps us to detect cases where the rmaps cover
territory that the bmaps do not.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Teach the summary count checker to count the number of free realtime
extents and compare that to the superblock copy.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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When scrub is checking a non-root btree block, it should make sure that
the keys in the parent btree block accurately capture the keyspace that
the child block stores.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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The current directory parent scrubbing code could be tighter in its
checking -- when we've dropped all the directory iolocks, it's not
necessary to trylock the first of a nested pair, so we can eliminate the
first call to xchk_ilock_inverted on those grounds.
Second, if the child directory's parent changes during the lock cycling,
we know that the new parent has stamped the correct parent into the
dotdot entry, so we can conclude that the parent entry is correct.
Therefore, we don't need the second xchk_ilock_inverted call at all.
We can spin in a lock/trylock loop until we can grab both locks and
recheck the child directory afterwards. This eliminates an entire
source of -EDEADLOCK-based "retry harder" code executions.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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The current implementation of xfs_btree_has_record returns true if it
finds /any/ record within the given range. Unfortunately, that's not
what the predicate is supposed to do -- it's supposed to test if the
/entire/ range is covered by records.
Therefore, enhance the routine to check that the first record it
encounters starts earlier or at the same point as the low key, the last
record ends at or after the same point as the high key, and that there
aren't any gaps in the records.
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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