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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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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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The mount field is only passed to xfs_extent_busy_clear, which never uses
it.
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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Processing of busy extents requires the perag structure, so keep the
reference while they are in flight.
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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Replace the [mp,agno] tuple with the perag structure, which will become
more useful later.
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 helpers to convert an agino to an ino based on a pag structure.
This provides a simpler conversion and better type safety compared to the
existing code that passes the mount structure and the agno separately.
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 helpers to convert an agbno to a daddr or fsbno based on a pag
structure.
This provides a simpler conversion and better type safety compared to the
existing code that passes the mount structure and the agno separately.
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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xfs_free_ag_extent already has a pointer to the pag structure through
the agf buffer. Use that instead of passing the redundant argument,
and do the same for the tracepoint.
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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We'll want to use more than just the agno field in a bit.
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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pag_active_wq is only woken, but never waited for.
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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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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The for_each_perag helpers update the agno passed in for each iteration,
and thus the "if (pag->pag_agno == start_ag)" check will always be true.
Add another variable for the loop iterator so that the field is only
cleared after the first iteration.
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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In commit 11f4c3a53adde, we tried to simplify the extent lookup in
xfs_can_free_eofblocks so that it doesn't incur the overhead of all the
extra stuff that xfs_bmapi_read does around the iext lookup.
Unfortunately, this causes regressions on generic/603, xfs/108,
generic/219, xfs/173, generic/694, xfs/052, generic/230, and xfs/441
when always_cow is turned on. In all cases, the regressions take the
form of alwayscow files consuming rather more space than the golden
output is expecting. I observed that in all these cases, the cause of
the excess space usage was due to CoW fork delalloc reservations that go
beyond EOF.
For alwayscow files we allow posteof delalloc CoW reservations because
all writes go through the CoW fork. Recall that all extents in the CoW
fork are accounted for via i_delayed_blks, which means that prior to
this patch, we'd invoke xfs_free_eofblocks on first close if anything
was in the CoW fork. Now we don't do that.
Fix the problem by reverting the removal of the i_delayed_blks check.
Cc: <stable@vger.kernel.org> # v6.12-rc1
Fixes: 11f4c3a53adde ("xfs: simplify extent lookup in xfs_can_free_eofblocks")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
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Shared the regular buffered write iomap_ops with the page fault path
and just check for the IOMAP_FAULT flag to skip delalloc punching.
This keeps the delalloc punching checks in one place, and will make it
easier to convert iomap to an iter model where the begin and end
handlers are merged into a single callback.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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xfs_filemap_huge_fault only ever serves DAX faults, so hard code the
call to xfs_dax_read_fault and open code __xfs_filemap_fault in the
only remaining caller.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Only two of the callers of __xfs_filemap_fault every handle read faults.
Split the write_fault handling out of __xfs_filemap_fault so that all
callers call that directly either conditionally or unconditionally and
only leave the read fault handling in __xfs_filemap_fault.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Split the xfs_filemap_fault trace event into separate ones for read and
write faults and move them into the applicable locations.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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It's just read in from the superblock and used without doing any
validity checks at all on the value.
Fixes: fb4f2b4e5a82 ("xfs: add sparse inode chunk alignment superblock field")
Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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xfs_zero_extent does some really odd gymnstics to calculate the block
layer sectors numbers passed to blkdev_issue_zeroout. This is because it
used to call sb_issue_zeroout and the calculations in that helper got
open coded here in the rather misleadingly named commit 3dc29161070a
("dax: use sb_issue_zerout instead of calling dax_clear_sectors").
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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There are two invocations of xfs_alloc_log_agf in xfs_alloc_put_freelist.
The AGF does not change between the two calls. Although this does not pose
any practical problems, it seems like a small mistake. Therefore, fix it
by removing the first xfs_alloc_log_agf invocation.
Signed-off-by: Long Li <leo.lilong@huawei.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Set FMODE_CAN_ATOMIC_WRITE flag if we can atomic write for that inode.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Tested-by: Ojaswin Mujoo <ojaswin@linux.ibm.com> #On ppc64
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Validate that an atomic write adheres to length/offset rules. Currently
we can only write a single FS block.
For an IOCB with IOCB_ATOMIC set to get as far as xfs_file_write_iter(),
FMODE_CAN_ATOMIC_WRITE will need to be set for the file; for this,
ATOMICWRITES flags would also need to be set for the inode.
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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Support providing info on atomic write unit min and max for an inode.
For simplicity, currently we limit the min at the FS block size. As for
max, we limit also at FS block size, as there is no current method to
guarantee extent alignment or granularity for regular files.
Reviewed-by: "Darrick J. Wong" <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
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all failure exits prior to fdget() leave the scope, all matching fdput()
are immediately followed by leaving the scope.
[xfs_ioc_commit_range() chunk moved here as well]
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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XFS_IOC_FD_TO_HANDLE can grab a reference to copied ->f_path and
let the file go; results in simpler control flow - cleanup is
the same for both "by descriptor" and "by pathname" cases.
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Pull xfs fixes from Carlos Maiolino:
- fix a sysbot reported crash on filestreams
- Reduce cpu time spent searching for extents in a very fragmented FS
- Check for delayed allocations before setting extsize
* tag 'xfs-6.12-fixes-6' of git://git.kernel.org/pub/scm/fs/xfs/xfs-linux:
xfs: streamline xfs_filestream_pick_ag
xfs: fix finding a last resort AG in xfs_filestream_pick_ag
xfs: Reduce unnecessary searches when searching for the best extents
xfs: Check for delayed allocations before setting extsize
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gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs
Pull iomap fixes from Christian Brauner:
"Fixes for iomap to prevent data corruption bugs in the fallocate
unshare range implementation of fsdax and a small cleanup to turn
iomap_want_unshare_iter() into an inline function"
* tag 'vfs-6.12-rc6.iomap' of gitolite.kernel.org:pub/scm/linux/kernel/git/vfs/vfs:
iomap: turn iomap_want_unshare_iter into an inline function
fsdax: dax_unshare_iter needs to copy entire blocks
fsdax: remove zeroing code from dax_unshare_iter
iomap: share iomap_unshare_iter predicate code with fsdax
xfs: don't allocate COW extents when unsharing a hole
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Directly return the error from xfs_bmap_longest_free_extent instead
of breaking from the loop and handling it there, and use a done
label to directly jump to the exist when we found a suitable perag
structure to reduce the indentation level and pag/max_pag check
complexity in the tail of the function.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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When the main loop in xfs_filestream_pick_ag fails to find a suitable
AG it tries to just pick the online AG. But the loop for that uses
args->pag as loop iterator while the later code expects pag to be
set. Fix this by reusing the max_pag case for this last resort, and
also add a check for impossible case of no AG just to make sure that
the uninitialized pag doesn't even escape in theory.
Reported-by: syzbot+4125a3c514e3436a02e6@syzkaller.appspotmail.com
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: syzbot+4125a3c514e3436a02e6@syzkaller.appspotmail.com
Fixes: f8f1ed1ab3baba ("xfs: return a referenced perag from filestreams allocator")
Cc: <stable@vger.kernel.org> # v6.3
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Recently, we found that the CPU spent a lot of time in
xfs_alloc_ag_vextent_size when the filesystem has millions of fragmented
spaces.
The reason is that we conducted much extra searching for extents that
could not yield a better result, and these searches would cost a lot of
time when there were millions of extents to search through. Even if we
get the same result length, we don't switch our choice to the new one,
so we can definitely terminate the search early.
Since the result length cannot exceed the found length, when the found
length equals the best result length we already have, we can conclude
the search.
We did a test in that filesystem:
[root@localhost ~]# xfs_db -c freesp /dev/vdb
from to extents blocks pct
1 1 215 215 0.01
2 3 994476 1988952 99.99
Before this patch:
0) | xfs_alloc_ag_vextent_size [xfs]() {
0) * 15597.94 us | }
After this patch:
0) | xfs_alloc_ag_vextent_size [xfs]() {
0) 19.176 us | }
Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Extsize should only be allowed to be set on files with no data in it.
For this, we check if the files have extents but miss to check if
delayed extents are present. This patch adds that check.
While we are at it, also refactor this check into a helper since
it's used in some other places as well like xfs_inactive() or
xfs_ioctl_setattr_xflags()
**Without the patch (SUCCEEDS)**
$ xfs_io -c 'open -f testfile' -c 'pwrite 0 1024' -c 'extsize 65536'
wrote 1024/1024 bytes at offset 0
1 KiB, 1 ops; 0.0002 sec (4.628 MiB/sec and 4739.3365 ops/sec)
**With the patch (FAILS as expected)**
$ xfs_io -c 'open -f testfile' -c 'pwrite 0 1024' -c 'extsize 65536'
wrote 1024/1024 bytes at offset 0
1 KiB, 1 ops; 0.0002 sec (4.628 MiB/sec and 4739.3365 ops/sec)
xfs_io: FS_IOC_FSSETXATTR testfile: Invalid argument
Fixes: e94af02a9cd7 ("[XFS] fix old xfs_setattr mis-merge from irix; mostly harmless esp if not using xfs rt")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: John Garry <john.g.garry@oracle.com>
Signed-off-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Currently log recovery never updates the in-core perag values for the
last allocation group when they were grown by growfs. This leads to
btree record validation failures for the alloc, ialloc or finotbt
trees if a transaction references this new space.
Found by Brian's new growfs recovery stress test.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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__GFP_RETRY_MAYFAIL increases the likelyhood of allocations to fail,
which isn't really helpful during log recovery. Remove the flag and
stick to the default GFP_KERNEL policies.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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XFS currently does not support reducing the agcount, so error out if
a logged sb buffer tries to shrink the agcount.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Primary superblock buffers that change the file system geometry after a
growfs operation can affect the operation of later CIL checkpoints that
make use of the newly added space and allocation groups.
Apply the changes to the in-memory structures as part of recovery pass 2,
to ensure recovery works fine for such cases.
In the future we should apply the logic to other updates such as features
bits as well.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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There is no good reason to have two different routines for freeing perag
structures for the unmount and error cases. Add two arguments to specify
the range of AGs to free to xfs_free_perag, and use that to replace
xfs_free_unused_perag_range.
The addition RCU grace period for the error case is harmless, and the
extra check for the AG to actually exist is not required now that the
callers pass the exact known allocated range.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Currently only the new agcount is passed to xfs_initialize_perag, which
requires lookups of existing AGs to skip them and complicates error
handling. Also pass the previous agcount so that the range that
xfs_initialize_perag operates on is exactly defined. That way the
extra lookups can be avoided, and error handling can clean up the
exact range from the old count to the last added perag structure.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Fix a minor bug where we fail repairs on metadata files that do not have
attr forks because xrep_metadata_inode_subtype doesn't filter ENOENT.
Cc: stable@vger.kernel.org # v6.8
Fixes: 5a8e07e799721b ("xfs: repair the inode core and forks of a metadata inode")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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When ->iomap_end is called on a short write to the COW fork it needs to
punch stale delalloc data from the COW fork and not the data fork.
Ensure that IOMAP_F_NEW is set for new COW fork allocations in
xfs_buffered_write_iomap_begin, and then use the IOMAP_F_SHARED flag
in xfs_buffered_write_delalloc_punch to decide which fork to punch.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Change to always set xfs_buffered_write_iomap_begin for COW fork
allocations even if they don't overlap existing data fork extents,
which will allow the iomap_end callback to detect if it has to punch
stale delalloc blocks from the COW fork instead of the data fork. It
also means we sample the sequence counter for both the data and the COW
fork when writing to the COW fork, which ensures we properly revalidate
when only COW fork changes happens.
This is essentially a revert of commit 72a048c1056a ("xfs: only set
IOMAP_F_SHARED when providing a srcmap to a write"). This is fine because
the problem that the commit fixed has now been dealt with in iomap by
only looking at the actual srcmap and not the fallback to the write
iomap.
Note that the direct I/O path was never changed and has always set
IOMAP_F_SHARED for all COW fork allocations.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Introduce a local iomap_flags variable so that the code allocating new
delalloc blocks in the data fork can fall through to the found_imap
label and reuse the code to unlock and fill the iomap.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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xfs_buffered_write_iomap_begin can also create delallocate reservations
that need cleaning up, prepare for that by adding support for the COW
fork in xfs_bmap_punch_delalloc_range.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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All XFS callers of iomap_zero_range and iomap_file_unshare already hold
invalidate_lock, so we can't take it again in
iomap_file_buffered_write_punch_delalloc.
Use the passed in flags argument to detect if we're called from a zero
or unshare operation and don't take the lock again in this case.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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xfs_file_write_zero_eof is the only caller of xfs_zero_range that does
not take XFS_MMAPLOCK_EXCL (aka the invalidate lock). Currently that
is actually the right thing, as an error in the iomap zeroing code will
also take the invalidate_lock to clean up, but to fix that deadlock we
need a consistent locking pattern first.
The only extra thing that XFS_MMAPLOCK_EXCL will lock out are read
pagefaults, which isn't really needed here, but also not actively
harmful.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Split a helper from xfs_file_write_checks that just deal with the
post-EOF zeroing to keep the code readable.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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XFS (which currently is the only user of iomap_write_delalloc_release)
already holds invalidate_lock for most zeroing operations. To be able
to avoid a deadlock it needs to stop taking the lock, but doing so
in iomap would leak XFS locking details into iomap.
To avoid this require the caller to hold invalidate_lock when calling
iomap_write_delalloc_release instead of taking it there.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Currently iomap_file_buffered_write_punch_delalloc can be called from
XFS either with the invalidate lock held or not. To fix this while
keeping the locking in the file system and not the iomap library
code we'll need to life the locking up into the file system.
To prepare for that, open code iomap_file_buffered_write_punch_delalloc
in the only caller, and instead export iomap_write_delalloc_release.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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The variable declaration in this function predates the merge of the
nrext64 (aka 64-bit extent counters) feature, which means that the
variable declaration type is insufficient to avoid an integer overflow.
Fix that by redeclaring the variable to be xfs_extnum_t.
Coverity-id: 1630958
Fixes: 8f71bede8efd ("xfs: repair inode fork block mapping data structures")
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
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Jeff Layton <jlayton@kernel.org> says:
The VFS has always used coarse-grained timestamps when updating the
ctime and mtime after a change. This has the benefit of allowing
filesystems to optimize away a lot metadata updates, down to around 1
per jiffy, even when a file is under heavy writes.
Unfortunately, this has always been an issue when we're exporting via
NFSv3, which relies on timestamps to validate caches. A lot of changes
can happen in a jiffy, so timestamps aren't sufficient to help the
client decide when to invalidate the cache. Even with NFSv4, a lot of
exported filesystems don't properly support a change attribute and are
subject to the same problems with timestamp granularity. Other
applications have similar issues with timestamps (e.g backup
applications).
If we were to always use fine-grained timestamps, that would improve the
situation, but that becomes rather expensive, as the underlying
filesystem would have to log a lot more metadata updates.
What we need is a way to only use fine-grained timestamps when they are
being actively queried. Use the (unused) top bit in inode->i_ctime_nsec
as a flag that indicates whether the current timestamps have been
queried via stat() or the like. When it's set, we allow the kernel to
use a fine-grained timestamp iff it's necessary to make the ctime show
a different value.
This solves the problem of being able to distinguish the timestamp
between updates, but introduces a new problem: it's now possible for a
file being changed to get a fine-grained timestamp. A file that is
altered just a bit later can then get a coarse-grained one that appears
older than the earlier fine-grained time. This violates timestamp
ordering guarantees.
To remedy this, keep a global monotonic atomic64_t value that acts as a
timestamp floor. When we go to stamp a file, we first get the latter of
the current floor value and the current coarse-grained time. If the
inode ctime hasn't been queried then we just attempt to stamp it with
that value.
If it has been queried, then first see whether the current coarse time
is later than the existing ctime. If it is, then we accept that value.
If it isn't, then we get a fine-grained time and try to swap that into
the global floor. Whether that succeeds or fails, we take the resulting
floor time, convert it to realtime and try to swap that into the ctime.
We take the result of the ctime swap whether it succeeds or fails, since
either is just as valid.
Filesystems can opt into this by setting the FS_MGTIME fstype flag.
Others should be unaffected (other than being subject to the same floor
value as multigrain filesystems).
* patches from https://lore.kernel.org/r/20241002-mgtime-v10-0-d1c4717f5284@kernel.org:
tmpfs: add support for multigrain timestamps
btrfs: convert to multigrain timestamps
ext4: switch to multigrain timestamps
xfs: switch to multigrain timestamps
Documentation: add a new file documenting multigrain timestamps
fs: add percpu counters for significant multigrain timestamp events
fs: tracepoints around multigrain timestamp events
fs: handle delegated timestamps in setattr_copy_mgtime
fs: have setattr_copy handle multigrain timestamps appropriately
fs: add infrastructure for multigrain timestamps
Link: https://lore.kernel.org/r/20241002-mgtime-v10-0-d1c4717f5284@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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Enable multigrain timestamps, which should ensure that there is an
apparent change to the timestamp whenever it has been written after
being actively observed via getattr.
Also, anytime the mtime changes, the ctime must also change, and those
are now the only two options for xfs_trans_ichgtime. Have that function
unconditionally bump the ctime, and ASSERT that XFS_ICHGTIME_CHG is
always set.
Finally, stop setting STATX_CHANGE_COOKIE in getattr, since the ctime
should give us better semantics now.
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>
Tested-by: Randy Dunlap <rdunlap@infradead.org> # documentation bits
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Link: https://lore.kernel.org/r/20241002-mgtime-v10-9-d1c4717f5284@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
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