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The branch, xfs-shift-extents-rework has been created
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commit 8b5279e33f241a074a9c8649bba8f77a2167b798
Author: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue Sep 23 15:39:05 2014 +1000
xfs: only writeback and truncate pages for the freed range
xfs_free_file_space() only affects the range of the file for which space
is being freed. It currently writes and truncates the page cache from
the start offset of the free to EOF.
Modify xfs_free_file_space() to write back and truncate page cache of
just the range being freed.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
commit f71721d061e872a39b2680d13f309c1eb6893438
Author: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue Sep 23 15:39:05 2014 +1000
xfs: writeback and inval. file range to be shifted by collapse
The collapse range operation currently writes the entire file before
starting the collapse to avoid changes in the in-core extent list due to
writeback causing the extent count to change. Now that collapse range is
fsb based rather than extent index based it can sustain changes in the
extent list during the shift sequence without disruption.
Modify xfs_collapse_file_space() to writeback and invalidate pages
associated with the range of the file to be shifted.
xfs_free_file_space() currently has similar behavior, but the space free
need only affect the region of the file that is freed and this could
change in the future.
Also update the comments to reflect the current implementation. We
retain the eofblocks trim permanently as a best option for dealing with
delalloc extents. We don't shift delalloc extents because this scenario
only occurs with post-eof preallocation (since data must be flushed such
that the cache can be invalidated and data can be shifted). That means
said space must also be initialized before being shifted into the
accessible region of the file only to be immediately truncated off as
the last part of the collapse. In other words, the eofblocks trim will
happen anyways, we just run it first to ensure the file remains in a
consistent state throughout the collapse.
Finally, detect and fail explicitly in the event of a delalloc extent
during the extent shift. The implementation does not support delalloc
extents and the caller is expected to prevent this scenario in advance
as is done by collapse.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
commit a979bdfea10a61dce0055b4d416d640f4f5f495e
Author: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue Sep 23 15:39:04 2014 +1000
xfs: refactor single extent shift into xfs_bmse_shift_one() helper
xfs_bmap_shift_extents() has a variety of conditions and error checks
that make the logic difficult to follow and indent heavy. Refactor the
loop body of this function into a new xfs_bmse_shift_one() helper. This
simplifies the error checks, eliminates index decrement on merge hack by
pushing the index increment down into the helper, and makes the code
more readable by reducing multiple levels of indentation.
This is a code refactor only. The behavior of extent shift and collapse
range is not modified.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
commit ddb19e3180fa42362a04e86771d758be1de0bb13
Author: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue Sep 23 15:38:09 2014 +1000
xfs: refactor shift-by-merge into xfs_bmse_merge() helper
The extent shift mechanism in xfs_bmap_shift_extents() is complicated
and handles several different, non-deterministic scenarios. These
include extent shifts, extent merges and potential btree updates in
either of the former scenarios.
Refactor the code to be more linear and readable. The loop logic in
xfs_bmap_shift_extents() and some initial error checking is adjusted
slightly. The associated btree lookup and update/delete operations are
condensed into single blocks of code. This reduces the number of
btree-specific blocks and facilitates the separation of the merge
operation into a new xfs_bmse_merge() and xfs_bmse_can_merge() helpers.
This is a code refactor only. The behavior of extent shift and collapse
range is not modified.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
commit 2c845f5a5f238f42376b6551a7f7716952c8f509
Author: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue Sep 23 15:37:09 2014 +1000
xfs: track collapse via file offset rather than extent index
The collapse range implementation uses a transaction per extent shift.
The progress of the overall operation is tracked via the current extent
index of the in-core extent list. This is racy because the ilock must be
dropped and reacquired for each transaction according to locking and log
reservation rules. Therefore, writeback to prior regions of the file is
possible and can change the extent count. This changes the extent to
which the current index refers and causes the collapse to fail mid
operation. To avoid this problem, the entire file is currently written
back before the collapse operation starts.
To eliminate the need to flush the entire file, use the file offset
(fsb) to track the progress of the overall extent shift operation rather
than the extent index. Modify xfs_bmap_shift_extents() to
unconditionally convert the start_fsb parameter to an extent index and
return the file offset of the extent where the shift left off, if
further extents exist. The bulk of ths function can remain based on
extent index as ilock is held by the caller. xfs_collapse_file_space()
now uses the fsb output as the starting point for the subsequent shift.
Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
Reviewed-by: Dave Chinner <dchinner@xxxxxxxxxx>
Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
commit 0d085a529b427d97710e6a41f8a4f23e1757cd12
Author: Dave Chinner <dchinner@xxxxxxxxxx>
Date: Tue Sep 23 15:36:27 2014 +1000
xfs: ensure WB_SYNC_ALL writeback handles partial pages correctly
XFS has been having trouble with stray delayed allocation extents
beyond EOF for a long time. Recent changes to the collapse range
code has triggered erroneous EBUSY errors on page invalidtion for
block size smaller than page size filesystems. These
have been caused by dirty buffers beyond EOF on a partial page which
do not get written to disk during a sync.
The issue is that write-ahead in xfs_cluster_write() finds such a
partial page and handles it by leaving the page dirty but pushing it
into a writeback state. This used to work just fine, as the
write_cache_pages() code would then find the dirty partial page in
the next mapping tree lookup as the dirty tag is still set.
Unfortunately, when we moved to a mark and sweep approach to
writeback to fix other writeback sync issues, we broken this. THe
act of marking the page as under writeback now clears the TOWRITE
tag in the radix tree, even though the page is still dirty. This
causes the TOWRITE tag to be cleared, and hence the next lookup on
the mapping tree does not find the dirty partial page and so doesn't
try to write it again.
This same writeback bug was found recently in ext4 and fixed in
commit 1c8349a ("ext4: fix data integrity sync in ordered mode")
without communication to the wider filesystem community. We can use
exactly the same fix here so the TOWRITE flag is not cleared on
partial page writes.
cc: stable@xxxxxxxxxxxxxxx # dependent on 1c8349a17137b93f0a83f276c764a6df1b9a116e
Root-cause-found-by: Brian Foster <bfoster@xxxxxxxxxx>
Signed-off-by: Dave Chinner <dchinner@xxxxxxxxxx>
Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx>
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