xfs: punch all delalloc blocks beyond EOF on write failure.
I've been seeing regular ASSERT failures in xfstests when running fsstress based tests over the past month. xfs_getbmap() has been failing this test: XFS: Assertion failed: ((iflags & BMV_IF_DELALLOC) != 0) || (map[i].br_startblock != DELAYSTARTBLOCK), file: fs/xfs/xfs_bmap.c, line: 5650 where it is encountering a delayed allocation extent after writing all the dirty data to disk and then walking the extent map atomically by holding the XFS_IOLOCK_SHARED to prevent new delayed allocation extents from being created. Test 083 on a 512 byte block size filesystem was used to reproduce the problem, because it only had a 5s run timeand would usually fail every 3-4 runs. This test is exercising ENOSPC behaviour by running fsstress on a nearly full filesystem. The following trace extract shows the final few events on the inode that tripped the assert: xfs_ilock: flags ILOCK_EXCL caller xfs_setfilesize xfs_setfilesize: isize 0x180000 disize 0x12d400 offset 0x17e200 count 7680 file size updated to 0x180000 by IO completion xfs_ilock: flags ILOCK_EXCL caller xfs_iomap_write_delay xfs_iext_insert: state idx 3 offset 3072 block 4503599627239432 count 1 flag 0 caller xfs_bmap_add_extent_hole_delay xfs_get_blocks_alloc: size 0x180000 offset 0x180000 count 512 type startoff 0xc00 startblock -1 blockcount 0x1 xfs_ilock: flags ILOCK_EXCL caller __xfs_get_blocks delalloc write, adding a single block at offset 0x180000 xfs_delalloc_enospc: isize 0x180000 disize 0x180000 offset 0x180200 count 512 ENOSPC trying to allocate a dellalloc block at offset 0x180200 xfs_ilock: flags ILOCK_EXCL caller xfs_iomap_write_delay xfs_get_blocks_alloc: size 0x180000 offset 0x180200 count 512 type startoff 0xc00 startblock -1 blockcount 0x2 And succeeding on retry after flushing dirty inodes. xfs_ilock: flags ILOCK_EXCL caller __xfs_get_blocks xfs_delalloc_enospc: isize 0x180000 disize 0x180000 offset 0x180400 count 512 ENOSPC trying to allocate a dellalloc block at offset 0x180400 xfs_ilock: flags ILOCK_EXCL caller xfs_iomap_write_delay xfs_delalloc_enospc: isize 0x180000 disize 0x180000 offset 0x180400 count 512 And failing the retry, giving a real ENOSPC error. xfs_ilock: flags ILOCK_EXCL caller xfs_vm_write_failed ^^^^^^^^^^^^^^^^^^^ The smoking gun - the write being failed and cleaning up delalloc blocks beyond EOF allocated by the failed write. xfs_getattr: xfs_ilock: flags IOLOCK_SHARED caller xfs_getbmap xfs_ilock: flags ILOCK_SHARED caller xfs_ilock_map_shared And that's where we died almost immediately afterwards. xfs_bmapi_read() found delalloc extent beyond current file in memory file size. Some debug I added to xfs_getbmap() showed the state just before the assert failure: ino 0x80e48: off 0xc00, fsb 0xffffffffffffffff, len 0x1, size 0x180000 start_fsb 0x106, end_fsb 0x638 ino flags 0x2 nex 0xd bmvcnt 0x555, len 0x3c58a6f23c0bf1, start 0xc00 ext 0: off 0x1fc, fsb 0x24782, len 0x254 ext 1: off 0x450, fsb 0x40851, len 0x30 ext 2: off 0x480, fsb 0xd99, len 0x1b8 ext 3: off 0x92f, fsb 0x4099a, len 0x3b ext 4: off 0x96d, fsb 0x41844, len 0x98 ext 5: off 0xbf1, fsb 0x408ab, len 0xf which shows that we found a single delalloc block beyond EOF (first line of output) when we were returning the map for a length somewhere around 10^16 bytes long (second line), and the on-disk extents showed they didn't go past EOF (last lines). Further debug added to xfs_vm_write_failed() showed this happened when punching out delalloc blocks beyond the end of the file after the failed write: [ 132.606693] ino 0x80e48: vwf to 0x181000, sze 0x180000 [ 132.609573] start_fsb 0xc01, end_fsb 0xc08 It punched the range 0xc01 -> 0xc08, but the range we really need to punch is 0xc00 -> 0xc07 (8 blocks from 0xc00) as this testing was run on a 512 byte block size filesystem (8 blocks per page). the punch from is 0xc00. So end_fsb is correct, but start_fsb is wrong as we punch from start_fsb for (end_fsb - start_fsb) blocks. Hence we are not punching the delalloc block beyond EOF in the case. The fix is simple - it's a silly off-by-one mistake in calculating the range. It's especially silly because the macro used to calculate the start_fsb already takes into account the case where the inode size is an exact multiple of the filesystem block size... Signed-off-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Eric Sandeen <sandeen@redhat.com> Signed-off-by: Ben Myers <bpm@sgi.com>
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@ -1434,7 +1434,7 @@ xfs_vm_write_failed(
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* Check if there are any blocks that are outside of i_size
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* that need to be trimmed back.
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*/
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start_fsb = XFS_B_TO_FSB(ip->i_mount, inode->i_size) + 1;
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start_fsb = XFS_B_TO_FSB(ip->i_mount, inode->i_size);
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end_fsb = XFS_B_TO_FSB(ip->i_mount, to);
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if (end_fsb <= start_fsb)
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return;
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