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xfs: fix BUG_ON in xfs_getbmap() 

JIRA: https://issues.redhat.com/browse/RHEL-25419

commit 8ee81ed581ff35882b006a5205100db0b57bf070
Author: Ye Bin <yebin10@huawei.com>
Date:   Wed Apr 12 15:49:44 2023 +1000

    xfs: fix BUG_ON in xfs_getbmap()

    There's issue as follows:
    XFS: Assertion failed: (bmv->bmv_iflags & BMV_IF_DELALLOC) != 0, file: fs/xfs/xfs_bmap_util.c, line: 329
    ------------[ cut here ]------------
    kernel BUG at fs/xfs/xfs_message.c:102!
    invalid opcode: 0000 [#1] PREEMPT SMP KASAN
    CPU: 1 PID: 14612 Comm: xfs_io Not tainted 6.3.0-rc2-next-20230315-00006-g2729d23ddb3b-dirty #422
    RIP: 0010:assfail+0x96/0xa0
    RSP: 0018:ffffc9000fa178c0 EFLAGS: 00010246
    RAX: 0000000000000000 RBX: 0000000000000001 RCX: ffff888179a18000
    RDX: 0000000000000000 RSI: ffff888179a18000 RDI: 0000000000000002
    RBP: 0000000000000000 R08: ffffffff8321aab6 R09: 0000000000000000
    R10: 0000000000000001 R11: ffffed1105f85139 R12: ffffffff8aacc4c0
    R13: 0000000000000149 R14: ffff888269f58000 R15: 000000000000000c
    FS:  00007f42f27a4740(0000) GS:ffff88882fc00000(0000) knlGS:0000000000000000
    CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
    CR2: 0000000000b92388 CR3: 000000024f006000 CR4: 00000000000006e0
    DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
    DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
    Call Trace:
     <TASK>
     xfs_getbmap+0x1a5b/0x1e40
     xfs_ioc_getbmap+0x1fd/0x5b0
     xfs_file_ioctl+0x2cb/0x1d50
     __x64_sys_ioctl+0x197/0x210
     do_syscall_64+0x39/0xb0
     entry_SYSCALL_64_after_hwframe+0x63/0xcd

    Above issue may happen as follows:
             ThreadA                       ThreadB
    do_shared_fault
     __do_fault
      xfs_filemap_fault
       __xfs_filemap_fault
        filemap_fault
                                 xfs_ioc_getbmap -> Without BMV_IF_DELALLOC flag
                                  xfs_getbmap
                                   xfs_ilock(ip, XFS_IOLOCK_SHARED);
                                   filemap_write_and_wait
     do_page_mkwrite
      xfs_filemap_page_mkwrite
       __xfs_filemap_fault
        xfs_ilock(XFS_I(inode), XFS_MMAPLOCK_SHARED);
        iomap_page_mkwrite
         ...
         xfs_buffered_write_iomap_begin
          xfs_bmapi_reserve_delalloc -> Allocate delay extent
                                  xfs_ilock_data_map_shared(ip)
                                  xfs_getbmap_report_one
                                   ASSERT((bmv->bmv_iflags & BMV_IF_DELALLOC) != 0)
                                    -> trigger BUG_ON

    As xfs_filemap_page_mkwrite() only hold XFS_MMAPLOCK_SHARED lock, there's
    small window mkwrite can produce delay extent after file write in xfs_getbmap().
    To solve above issue, just skip delalloc extents.

    Signed-off-by: Ye Bin <yebin10@huawei.com>
    Reviewed-by: Darrick J. Wong <djwong@kernel.org>
    Reviewed-by: Dave Chinner <dchinner@redhat.com>
    Signed-off-by: Dave Chinner <david@fromorbit.com>

Signed-off-by: Bill O'Donnell <bodonnel@redhat.com>
This commit is contained in:
Bill O'Donnell 2024-06-06 10:32:48 -05:00
parent a8cc7b7360
commit 3eb11f8212
1 changed files with 6 additions and 8 deletions
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14
fs/xfs/xfs_bmap_util.c
View File

@ -314,15 +314,13 @@ xfs_getbmap_report_one(
if (isnullstartblock(got->br_startblock) ||
got->br_startblock == DELAYSTARTBLOCK) {
/*
* Delalloc extents that start beyond EOF can occur due to
* speculative EOF allocation when the delalloc extent is larger
* than the largest freespace extent at conversion time. These
* extents cannot be converted by data writeback, so can exist
* here even if we are not supposed to be finding delalloc
* extents.
* Take the flush completion as being a point-in-time snapshot
* where there are no delalloc extents, and if any new ones
* have been created racily, just skip them as being 'after'
* the flush and so don't get reported.
*/
if (got->br_startoff < XFS_B_TO_FSB(ip->i_mount, XFS_ISIZE(ip)))
ASSERT((bmv->bmv_iflags & BMV_IF_DELALLOC) != 0);
if (!(bmv->bmv_iflags & BMV_IF_DELALLOC))
return 0;
p->bmv_oflags |= BMV_OF_DELALLOC;
p->bmv_block = -2;