linux-sg2042/fs/xfs
Dave Chinner 9230a0b65b xfs: delalloc -> unwritten COW fork allocation can go wrong
Long saga. There have been days spent following this through dead end
after dead end in multi-GB event traces. This morning, after writing
a trace-cmd wrapper that enabled me to be more selective about XFS
trace points, I discovered that I could get just enough essential
tracepoints enabled that there was a 50:50 chance the fsx config
would fail at ~115k ops. If it didn't fail at op 115547, I stopped
fsx at op 115548 anyway.

That gave me two traces - one where the problem manifested, and one
where it didn't. After refining the traces to have the necessary
information, I found that in the failing case there was a real
extent in the COW fork compared to an unwritten extent in the
working case.

Walking back through the two traces to the point where the CWO fork
extents actually diverged, I found that the bad case had an extra
unwritten extent in it. This is likely because the bug it led me to
had triggered multiple times in those 115k ops, leaving stray
COW extents around. What I saw was a COW delalloc conversion to an
unwritten extent (as they should always be through
xfs_iomap_write_allocate()) resulted in a /written extent/:

xfs_writepage:        dev 259:0 ino 0x83 pgoff 0x17000 size 0x79a00 offset 0 length 0
xfs_iext_remove:      dev 259:0 ino 0x83 state RC|LF|RF|COW cur 0xffff888247b899c0/2 offset 32 block 152 count 20 flag 1 caller xfs_bmap_add_extent_delay_real
xfs_bmap_pre_update:  dev 259:0 ino 0x83 state RC|LF|RF|COW cur 0xffff888247b899c0/1 offset 1 block 4503599627239429 count 31 flag 0 caller xfs_bmap_add_extent_delay_real
xfs_bmap_post_update: dev 259:0 ino 0x83 state RC|LF|RF|COW cur 0xffff888247b899c0/1 offset 1 block 121 count 51 flag 0 caller xfs_bmap_add_ex

Basically, Cow fork before:

	0 1            32          52
	+H+DDDDDDDDDDDD+UUUUUUUUUUU+
	   PREV		RIGHT

COW delalloc conversion allocates:

	  1	       32
	  +uuuuuuuuuuuu+
	  NEW

And the result according to the xfs_bmap_post_update trace was:

	0 1            32          52
	+H+wwwwwwwwwwwwwwwwwwwwwwww+
	   PREV

Which is clearly wrong - it should be a merged unwritten extent,
not an unwritten extent.

That lead me to look at the LEFT_FILLING|RIGHT_FILLING|RIGHT_CONTIG
case in xfs_bmap_add_extent_delay_real(), and sure enough, there's
the bug.

It takes the old delalloc extent (PREV) and adds the length of the
RIGHT extent to it, takes the start block from NEW, removes the
RIGHT extent and then updates PREV with the new extent.

What it fails to do is update PREV.br_state. For delalloc, this is
always XFS_EXT_NORM, while in this case we are converting the
delayed allocation to unwritten, so it needs to be updated to
XFS_EXT_UNWRITTEN. This LF|RF|RC case does not do this, and so
the resultant extent is always written.

And that's the bug I've been chasing for a week - a bmap btree bug,
not a reflink/dedupe/copy_file_range bug, but a BMBT bug introduced
with the recent in core extent tree scalability enhancements.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
2018-11-21 10:10:53 -08:00
..
libxfs xfs: delalloc -> unwritten COW fork allocation can go wrong 2018-11-21 10:10:53 -08:00
scrub xfs: fix buffer state management in xrep_findroot_block 2018-10-18 17:20:35 +11:00
Kconfig xfs: implement the metadata repair ioctl flag 2018-05-15 18:12:50 -07:00
Makefile xfs: move the repair extent list into its own file 2018-07-29 22:37:09 -07:00
kmem.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
kmem.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
mrlock.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs.h xfs: remove b_last_holder & associated macros 2018-08-12 08:37:31 -07:00
xfs_acl.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_acl.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_aops.c xfs: remove XFS_IO_INVALID 2018-10-18 17:17:50 +11:00
xfs_aops.h xfs: remove XFS_IO_INVALID 2018-10-18 17:17:50 +11:00
xfs_attr_inactive.c xfs: remove all boilerplate defer init/finish code 2018-07-26 10:15:15 -07:00
xfs_attr_list.c xfs: substitute spaces with tabs 2018-08-02 23:05:14 -07:00
xfs_bmap_item.c xfs: pass transaction to xfs_defer_add() 2018-08-02 23:05:14 -07:00
xfs_bmap_item.h xfs: use transaction for intent recovery instead of raw dfops 2018-08-02 23:05:13 -07:00
xfs_bmap_util.c xfs: flush removing page cache in xfs_reflink_remap_prep 2018-11-21 10:10:53 -08:00
xfs_bmap_util.h xfs: flush removing page cache in xfs_reflink_remap_prep 2018-11-21 10:10:53 -08:00
xfs_buf.c xfs: clear ail delwri queued bufs on unmount of shutdown fs 2018-10-18 17:21:49 +11:00
xfs_buf.h xfs: always assign buffer verifiers when one is provided 2018-10-18 17:20:30 +11:00
xfs_buf_item.c xfs: fix transient reference count error in xfs_buf_resubmit_failed_buffers 2018-11-20 10:36:01 -08:00
xfs_buf_item.h xfs: refactor xfs_buf_log_item reference count handling 2018-09-29 13:45:26 +10:00
xfs_dir2_readdir.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_discard.c xfs: trivial xfs_btree_del_cursor cleanups 2018-07-23 09:08:00 -07:00
xfs_discard.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xfs_dquot.c xfs: remove dead error handling code in xfs_dquot_disk_alloc() 2018-08-07 10:57:13 -07:00
xfs_dquot.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_dquot_item.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_dquot_item.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_error.c xfs: force summary counter recalc at next mount 2018-07-23 09:08:01 -07:00
xfs_error.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_export.c xfs: clean up IRELE/iput callsites 2018-07-26 10:15:16 -07:00
xfs_export.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_extent_busy.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_extent_busy.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_extfree_item.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_extfree_item.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_file.c xfs: make xfs_file_remap_range() static 2018-11-19 13:30:38 -08:00
xfs_filestream.c xfs: replace dop_low with transaction flag 2018-08-02 23:05:13 -07:00
xfs_filestream.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_fsmap.c xfs: trivial xfs_btree_del_cursor cleanups 2018-07-23 09:08:00 -07:00
xfs_fsmap.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_fsops.c xfs: issue log message on user force shutdown 2018-10-18 17:20:39 +11:00
xfs_fsops.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_globals.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_icache.c xfs: introduce a new xfs_inode_has_cow_data helper 2018-07-30 07:57:48 -07:00
xfs_icache.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_icreate_item.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_icreate_item.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_inode.c xfs: remove last of unnecessary xfs_defer_cancel() callers 2018-09-29 13:41:58 +10:00
xfs_inode.h xfs: fold dfops into the transaction 2018-08-02 23:05:14 -07:00
xfs_inode_item.c xfs: remove if_real_bytes 2018-07-30 07:57:48 -07:00
xfs_inode_item.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_ioctl.c xfs: Fix error code in 'xfs_ioc_getbmap()' 2018-11-06 07:50:50 -08:00
xfs_ioctl.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_ioctl32.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_ioctl32.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_iomap.c xfs: remove the unused trimmed argument from xfs_reflink_trim_around_shared 2018-10-18 17:19:48 +11:00
xfs_iomap.h xfs: avoid COW fork extent lookups in writeback if the fork didn't change 2018-07-31 13:18:09 -07:00
xfs_iops.c xfs: don't crash the vfs on a garbage inline symlink 2018-09-29 13:40:40 +10:00
xfs_iops.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_itable.c xfs: clean up IRELE/iput callsites 2018-07-26 10:15:16 -07:00
xfs_itable.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_linux.h xfs: replace do_mod with native operations 2018-06-08 10:07:52 -07:00
xfs_log.c xfs: fix a comment in xfs_log_reserve 2018-08-03 08:17:54 -07:00
xfs_log.h xfs: refactor log recovery check 2018-08-01 07:40:48 -07:00
xfs_log_cil.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_log_priv.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_log_recover.c xfs: remove invalid log recovery first/last cycle check 2018-09-29 13:50:41 +10:00
xfs_message.c xfs: print buffer offsets when dumping corrupt buffers 2018-11-06 07:50:50 -08:00
xfs_message.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xfs_mount.c xfs: recalculate summary counters at mount time if icount is bad 2018-08-13 07:58:27 -07:00
xfs_mount.h xfs: remove deprecated barrier/nobarrier mount 2018-07-26 10:15:17 -07:00
xfs_mru_cache.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_mru_cache.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_ondisk.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_pnfs.c xfs: prepare xfs_break_layouts() for another layout type 2018-05-22 07:19:08 -07:00
xfs_pnfs.h xfs: prepare xfs_break_layouts() for another layout type 2018-05-22 07:19:08 -07:00
xfs_qm.c xfs: clean up IRELE/iput callsites 2018-07-26 10:15:16 -07:00
xfs_qm.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_qm_bhv.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_qm_syscalls.c xfs: clean up IRELE/iput callsites 2018-07-26 10:15:16 -07:00
xfs_quota.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_quotaops.c xfs: clean up IRELE/iput callsites 2018-07-26 10:15:16 -07:00
xfs_refcount_item.c xfs: pass transaction to xfs_defer_add() 2018-08-02 23:05:14 -07:00
xfs_refcount_item.h xfs: use transaction for intent recovery instead of raw dfops 2018-08-02 23:05:13 -07:00
xfs_reflink.c xfs: flush removing page cache in xfs_reflink_remap_prep 2018-11-21 10:10:53 -08:00
xfs_reflink.h vfs: rework data cloning infrastructure 2018-11-02 09:33:08 -07:00
xfs_rmap_item.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_rmap_item.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_rtalloc.c xfs: clean up IRELE/iput callsites 2018-07-26 10:15:16 -07:00
xfs_rtalloc.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_stats.c xfs: use offsetof() in place of offset macros for __xfsstats 2018-10-18 17:21:39 +11:00
xfs_stats.h xfs: use offsetof() in place of offset macros for __xfsstats 2018-10-18 17:21:39 +11:00
xfs_super.c xfs: add a define for statfs magic to uapi 2018-10-18 17:20:19 +11:00
xfs_super.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_symlink.c xfs: automatic dfops inode relogging 2018-08-02 23:05:14 -07:00
xfs_symlink.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_sysctl.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_sysctl.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_sysfs.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_sysfs.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_trace.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_trace.h xfs: uncached buffer tracing needs to print bno 2018-11-20 10:35:05 -08:00
xfs_trans.c xfs: avoid lockdep false positives in xfs_trans_alloc 2018-09-29 13:46:21 +10:00
xfs_trans.h xfs: fix buffer state management in xrep_findroot_block 2018-10-18 17:20:35 +11:00
xfs_trans_ail.c xfs: clear ail delwri queued bufs on unmount of shutdown fs 2018-10-18 17:21:49 +11:00
xfs_trans_bmap.c xfs: drop dop param from xfs_defer_op_type ->finish_item() callback 2018-08-02 23:05:14 -07:00
xfs_trans_buf.c xfs: fix buffer state management in xrep_findroot_block 2018-10-18 17:20:35 +11:00
xfs_trans_dquot.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_trans_extfree.c xfs: drop dop param from xfs_defer_op_type ->finish_item() callback 2018-08-02 23:05:14 -07:00
xfs_trans_inode.c vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
xfs_trans_priv.h xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00
xfs_trans_refcount.c xfs: drop dop param from xfs_defer_op_type ->finish_item() callback 2018-08-02 23:05:14 -07:00
xfs_trans_rmap.c xfs: drop dop param from xfs_defer_op_type ->finish_item() callback 2018-08-02 23:05:14 -07:00
xfs_xattr.c xfs: convert to SPDX license tags 2018-06-06 14:17:53 -07:00