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After various discussions on linux-fsdevel, it has been decided that it
is not necessary to cap the length of a dedupe request, and that
correctly-written userspace client programs will be able to absorb the
change. Therefore, remove the length clamping behavior.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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The on-disk field di_size is used to set i_size, which is a signed
integer of loff_t. If the high bit of di_size is set, we'll end up with
a negative i_size, which will cause all sorts of problems. Since the
VFS won't let us create a file with such length, we should catch them
here in the verifier too.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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We shouldn't assert if somehow we end up trying to add an attr fork to
an inode that apparently already has attr extents because this is an
indication of on-disk corruption. Instead, return an error code to
userspace.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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In xfs_dir3_data_read, we can encounter the situation where err == 0 and
*bpp == NULL if the given bno offset happens to be a hole; this leads to
a crash if we try to set the buffer type after the _da_read_buf call.
Holes can happen due to corrupt or malicious entries in the bmbt data,
so be a little more careful when we're handling buffers.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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When reading into memory all extents of a btree-format inode fork,
complain if the number of extents we find is not the same as the number
of extents reported in the inode core. This is needed to stop an IO
action from accessing the garbage areas of the in-core fork.
[dchinner: removed redundant assert]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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When we're reading a btree block, make sure that what we retrieved
matches the owner and level; and has a plausible number of records.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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There is no such thing as a zero-level AG btree since even a single-node
zero-records btree has one level. Btree cursor constructors read
cur_nlevels straight from disk and then access things like
cur_bufs[cur_nlevels - 1] which is /really/ bad if cur_nlevels is zero!
Therefore, strengthen the verifiers to prevent this possibility.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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There are a handful of xattr functions which now return
nothing but zero. They can be made void, chased through calling
functions, and error handling etc can be removed.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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By inspection, xfs_bmap_trace_exlist isn't handling cow forks,
and will trace the data fork instead.
Fix this by setting state appropriately if whichfork
== XFS_COW_FORK.
()___()
< @ @ >
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{o_o}
(|)
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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When xfs_bmap_trace_exlist called trace_xfs_extlist,
it sent in the "whichfork" var instead of the bmap "state"
as expected (even though state was already set up for this
purpose).
As a result, the xfs_bmap_class in tracing code used
"whichfork" not state in xfs_iext_state_to_fork(), and got
the wrong ifork pointer. It all goes downhill from
there, including an ASSERT when ifp_bytes is empty
by the time it reaches xfs_iext_get_ext():
XFS: Assertion failed: idx < ifp->if_bytes / sizeof(xfs_bmbt_rec_t)
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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We've missed properly setting the buffer type for
an AGI transaction in 3 spots now, so just move it
into xfs_read_agi() and set it if we are in a transaction
to avoid the problem in the future.
This is similar to how it is done in i.e. the dir3
and attr3 read functions.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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xlog_recover_clear_agi_bucket didn't set the
type to XFS_BLFT_AGI_BUF, so we got a warning during log
replay (or an ASSERT on a debug build).
XFS (md0): Unknown buffer type 0!
XFS (md0): _xfs_buf_ioapply: no ops on block 0xaea8802/0x1
Fix this, as was done in f19b872b for 2 other locations
with the same problem.
cc: <stable@vger.kernel.org> # 3.10 to current
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Straight switch over to using iomap for direct I/O - we already have the
non-COW dio path in write_begin for DAX and files with extent size hints,
so nothing to add there. The COW path is ported over from the old
get_blocks version and a bit of a mess, but I have some work in progress
to make it look more like the buffered I/O COW path.
This gets rid of xfs_get_blocks_direct and the last caller of
xfs_get_blocks with the create flag set, so all that code can be removed.
Last but not least I've removed a comment in xfs_filemap_fault that
refers to xfs_get_blocks entirely instead of updating it - while the
reference is correct, the whole DAX fault path looks different than
the non-DAX one, so it seems rather pointless.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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This patch drops the XFS-own i_iolock and uses the VFS i_rwsem which
recently replaced i_mutex instead. This means we only have to take
one lock instead of two in many fast path operations, and we can
also shrink the xfs_inode structure. Thanks to the xfs_ilock family
there is very little churn, the only thing of note is that we need
to switch to use the lock_two_directory helper for taking the i_rwsem
on two inodes in a few places to make sure our lock order matches
the one used in the VFS.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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xfs_file_iomap_begin_delay() implements post-eof speculative
preallocation by extending the block count of the requested delayed
allocation. Now that xfs_bmapi_reserve_delalloc() has been updated to
handle prealloc blocks separately and tag the inode, update
xfs_file_iomap_begin_delay() to use the new parameter and rely on the
former to tag the inode.
Note that this patch does not change behavior.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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COW fork reservation is implemented via delayed allocation. The code is
modeled after the traditional delalloc allocation code, but is slightly
different in terms of how preallocation occurs. Rather than post-eof
speculative preallocation, COW fork preallocation is implemented via a
COW extent size hint that is designed to minimize fragmentation as a
reflinked file is split over time.
xfs_reflink_reserve_cow() still uses logic that is oriented towards
dealing with post-eof speculative preallocation, however, and is stale
or not necessarily correct. First, the EOF alignment to the COW extent
size hint is implemented in xfs_bmapi_reserve_delalloc() (which does so
correctly by aligning the start and end offsets) and so is not necessary
in xfs_reflink_reserve_cow(). The backoff and retry logic on ENOSPC is
also ineffective for the same reason, as xfs_bmapi_reserve_delalloc()
will simply perform the same allocation request on the retry. Finally,
since the COW extent size hint aligns the start and end offset of the
range to allocate, the end_fsb != orig_end_fsb logic is not sufficient.
Indeed, if a write request happens to end on an aligned offset, it is
possible that we do not tag the inode for COW preallocation even though
xfs_bmapi_reserve_delalloc() may have preallocated at the start offset.
Kill the unnecessary, duplicate code in xfs_reflink_reserve_cow().
Remove the inode tag logic as well since xfs_bmapi_reserve_delalloc()
has been updated to tag the inode correctly.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Speculative preallocation is currently processed entirely by the callers
of xfs_bmapi_reserve_delalloc(). The caller determines how much
preallocation to include, adjusts the extent length and passes down the
resulting request.
While this works fine for post-eof speculative preallocation, it is not
as reliable for COW fork preallocation. COW fork preallocation is
implemented via the cowextszhint, which aligns the start offset as well
as the length of the extent. Further, it is difficult for the caller to
accurately identify when preallocation occurs because the returned
extent could have been merged with neighboring extents in the fork.
To simplify this situation and facilitate further COW fork preallocation
enhancements, update xfs_bmapi_reserve_delalloc() to take a separate
preallocation parameter to incorporate into the allocation request. The
preallocation blocks value is tacked onto the end of the request and
adjusted to accommodate neighboring extents and extent size limits.
Since xfs_bmapi_reserve_delalloc() now knows precisely how much
preallocation was included in the allocation, it can also tag the inodes
appropriately to support preallocation reclaim.
Note that xfs_bmapi_reserve_delalloc() callers are not yet updated to
use the preallocation mechanism. This patch should not change behavior
outside of correctly tagging reflink inodes when start offset
preallocation occurs (which the caller does not handle correctly).
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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It turns out that btrfs and xfs had differing interpretations of what
to do when the dedupe length is zero. Change xfs to follow btrfs'
semantics so that the userland interface is consistent.
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Declare the structure xfs_nameops as const as it is only stored in the
m_dirnameops field of a xfs_mount structure. This field is of type
const struct xfs_nameops *, so xfs_nameops structures having this
property can be declared as const.
Done using Coccinelle:
@r1 disable optional_qualifier @
identifier i;
position p;
@@
static struct xfs_nameops i@p = {...};
@ok1@
identifier r1.i;
position p;
struct xfs_mount mp;
@@
mp.m_dirnameops=&i@p
@bad@
position p!={r1.p,ok1.p};
identifier r1.i;
@@
i@p
@depends on !bad disable optional_qualifier@
identifier r1.i;
@@
static
+const
struct xfs_nameops i={...};
@depends on !bad disable optional_qualifier@
identifier r1.i;
@@
+const
struct xfs_nameops i;
File size before:
text data bss dec hex filename
5302 85 0 5387 150b fs/xfs/libxfs/xfs_dir2.o
File size after:
text data bss dec hex filename
5318 69 0 5387 150b fs/xfs/libxfs/xfs_dir2.o
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Declare the structure xfs_item_ops as const as it is only passed as an
argument to the function xfs_log_item_init. As this argument is of type
const struct xfs_item_ops *, so xfs_item_ops structures having this
property can be declared as const.
Done using Coccinelle:
@r1 disable optional_qualifier @
identifier i;
position p;
@@
static struct xfs_item_ops i@p = {...};
@ok1@
identifier r1.i;
position p;
expression e1,e2,e3;
@@
xfs_log_item_init(e1,e2,e3,&i@p)
@bad@
position p!={r1.p,ok1.p};
identifier r1.i;
@@
i@p
@depends on !bad disable optional_qualifier@
identifier r1.i;
@@
static
+const
struct xfs_item_ops i={...};
@depends on !bad disable optional_qualifier@
identifier r1.i;
@@
+const
struct xfs_item_ops i;
File size before:
text data bss dec hex filename
737 64 8 809 329 fs/xfs/xfs_icreate_item.o
File size after:
text data bss dec hex filename
801 0 8 809 329 fs/xfs/xfs_icreate_item.o
Signed-off-by: Bhumika Goyal <bhumirks@gmail.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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When we're estimating the amount of space it's going to take to satisfy
a delalloc reservation, we need to include the space that we might need
to grow the rmapbt. This helps us to avoid running out of space later
when _iomap_write_allocate needs more space than we reserved. Eryu Guan
observed this happening on generic/224 when sunit/swidth were set.
Reported-by: Eryu Guan <eguan@redhat.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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When XBF_NO_IOACCT got added, it missed the translation
in XFS_BUF_FLAGS, so we see "0x8" in trace output rather
than the flag name. Fix it.
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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We only ever set a field to this constant for an impossible to reach
error case in xfs_bmap_search_extents. That functions has been removed,
so we can remove the constant as well.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Now that all users are gone.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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And remove the unused return value.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Use xfs_iext_lookup_extent to look up the extent, drop a useless check,
drop a unneeded return value and clean up the general style a little bit.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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And only lookup the previous extent inside xfs_iomap_prealloc_size
if we actually need it.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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We can easily lookup the previous extent for the cases where we need it,
which saves the callers from looking it up for us later in the series.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Rewrite the function using xfs_iext_lookup_extent and xfs_iext_get_extent,
and massage the flow into something easily understandable.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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xfs_iext_lookup_extent looks up a single extent at the passed in offset,
and returns the extent covering the area, or the one behind it in case
of a hole, as well as the index of the returned extent in arguments,
as well as a simple bool as return value that is set to false if no
extent could be found because the offset is behind EOF. It is a simpler
replacement for xfs_bmap_search_extent that leaves looking up the rarely
needed previous extent to the caller and has a nicer calling convention.
xfs_iext_get_extent is a helper for iterating over the extent list,
it takes an extent index as input, and returns the extent at that index
in it's expanded form in an argument if it exists. The actual return
value is a bool whether the index is valid or not.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Filesystem shutdown testing on an older distro kernel has uncovered an
imbalanced locking pattern for the inode flush lock in
xfs_reclaim_inode(). Specifically, there is a double unlock sequence
between the call to xfs_iflush_abort() and xfs_reclaim_inode() at the
"reclaim:" label.
This actually does not cause obvious problems on current kernels due to
the current flush lock implementation. Older kernels use a counting
based flush lock mechanism, however, which effectively breaks the lock
indefinitely when an already unlocked flush lock is repeatedly unlocked.
Though this only currently occurs on filesystem shutdown, it has
reproduced the effect of elevating an fs shutdown to a system-wide crash
or hang.
As it turns out, the flush lock is not actually required for the reclaim
logic in xfs_reclaim_inode() because by that time we have already cycled
the flush lock once while holding ILOCK_EXCL. Therefore, remove the
additional flush lock/unlock cycle around the 'reclaim:' label and
update branches into this label to release the flush lock where
appropriate. Add an assert to xfs_ifunlock() to help prevent future
occurences of the same problem.
Reported-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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Check the minimum block size on v5 filesystems.
[dchinner: cleaned up XFS_MIN_CRC_BLOCKSIZE check]
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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The open-coded pattern:
ifp->if_bytes / (uint)sizeof(xfs_bmbt_rec_t)
is all over the xfs code; provide a new helper
xfs_iext_count(ifp) to count the number of inline extents
in an inode fork.
[dchinner: pick up several missed conversions]
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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There have been several reports over the years of NULL pointer
dereferences in xfs_trans_log_inode during xfs_fsr processes,
when the process is doing an fput and tearing down extents
on the temporary inode, something like:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000018
PID: 29439 TASK: ffff880550584fa0 CPU: 6 COMMAND: "xfs_fsr"
[exception RIP: xfs_trans_log_inode+0x10]
#9 [ffff8800a57bbbe0] xfs_bunmapi at ffffffffa037398e [xfs]
#10 [ffff8800a57bbce8] xfs_itruncate_extents at ffffffffa0391b29 [xfs]
#11 [ffff8800a57bbd88] xfs_inactive_truncate at ffffffffa0391d0c [xfs]
#12 [ffff8800a57bbdb8] xfs_inactive at ffffffffa0392508 [xfs]
#13 [ffff8800a57bbdd8] xfs_fs_evict_inode at ffffffffa035907e [xfs]
#14 [ffff8800a57bbe00] evict at ffffffff811e1b67
#15 [ffff8800a57bbe28] iput at ffffffff811e23a5
#16 [ffff8800a57bbe58] dentry_kill at ffffffff811dcfc8
#17 [ffff8800a57bbe88] dput at ffffffff811dd06c
#18 [ffff8800a57bbea8] __fput at ffffffff811c823b
#19 [ffff8800a57bbef0] ____fput at ffffffff811c846e
#20 [ffff8800a57bbf00] task_work_run at ffffffff81093b27
#21 [ffff8800a57bbf30] do_notify_resume at ffffffff81013b0c
#22 [ffff8800a57bbf50] int_signal at ffffffff8161405d
As it turns out, this is because the i_itemp pointer, along
with the d_ops pointer, has been overwritten with zeros
when we tear down the extents during truncate. When the in-core
inode fork on the temporary inode used by xfs_fsr was originally
set up during the extent swap, we mistakenly looked at di_nextents
to determine whether all extents fit inline, but this misses extents
generated by speculative preallocation; we should be using if_bytes
instead.
This mistake corrupts the in-memory inode, and code in
xfs_iext_remove_inline eventually gets bad inputs, causing
it to memmove and memset incorrect ranges; this became apparent
because the two values in ifp->if_u2.if_inline_ext[1] contained
what should have been in d_ops and i_itemp; they were memmoved due
to incorrect array indexing and then the original locations
were zeroed with memset, again due to an array overrun.
Fix this by properly using i_df.if_bytes to determine the number
of extents, not di_nextents.
Thanks to dchinner for looking at this with me and spotting the
root cause.
Cc: stable@vger.kernel.org
Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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We've had reports of generic/095 causing XFS to BUG() in
__xfs_get_blocks() due to the existence of delalloc blocks on a
direct I/O read. generic/095 issues a mix of various types of I/O,
including direct and memory mapped I/O to a single file. This is
clearly not supported behavior and is known to lead to such
problems. E.g., the lack of exclusion between the direct I/O and
write fault paths means that a write fault can allocate delalloc
blocks in a region of a file that was previously a hole after the
direct read has attempted to flush/inval the file range, but before
it actually reads the block mapping. In turn, the direct read
discovers a delalloc extent and cannot proceed.
While the appropriate solution here is to not mix direct and memory
mapped I/O to the same regions of the same file, the current
BUG_ON() behavior is probably overkill as it can crash the entire
system. Instead, localize the failure to the I/O in question by
returning an error for a direct I/O that cannot be handled safely
due to delalloc blocks. Be careful to allow the case of a direct
write to post-eof delalloc blocks. This can occur due to speculative
preallocation and is safe as post-eof blocks are not accompanied by
dirty pages in pagecache (conversely, preallocation within eof must
have been zeroed, and thus dirtied, before the inode size could have
been increased beyond said blocks).
Finally, provide an additional warning if a direct I/O write occurs
while the file is memory mapped. This may not catch all problematic
scenarios, but provides a hint that some known-to-be-problematic I/O
methods are in use.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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The cowblocks background scanner currently clears the cowblocks tag
for inodes without any real allocations in the cow fork. This
excludes inodes with only delalloc blocks in the cow fork. While we
might never expect to clear delalloc blocks from the cow fork in the
background scanner, it is not necessarily correct to clear the
cowblocks tag from such inodes.
For example, if the background scanner happens to process an inode
between a buffered write and writeback, the scanner catches the
inode in a state after delalloc blocks have been allocated to the
cow fork but before the delalloc blocks have been converted to real
blocks by writeback. The background scanner then incorrectly clears
the cowblocks tag, even if part of the aforementioned delalloc
reservation will not be remapped to the data fork (i.e., extra
blocks due to the cowextsize hint). This means that any such
additional blocks in the cow fork might never be reclaimed by the
background scanner and could persist until the inode itself is
reclaimed.
To address this problem, only skip and clear inodes without any cow
fork allocations whatsoever from the background scanner. While we
generally do not want to cancel delalloc reservations from the
background scanner, the pagecache dirty check following the
cowblocks check should prevent that situation. If we do end up with
delalloc cow fork blocks without a dirty address space mapping, this
is probably an indication that something has gone wrong and the
blocks should be reclaimed, as they may never be converted to a real
allocation.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Dave Chinner <david@fromorbit.com>
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