Why was the XFS filesystem corrupted and set to read-only? The message "XFS: Internal error XFS_WANT_CORRUPTED_GOTO" is seen in the log file.

Issue

• An XFS filesystem became read-only after logging the following in /var/log/messages:

 kernel: XFS internal error XFS_WANT_CORRUPTED_GOTO at line 1518 of file fs/xfs/xfs_alloc.c.  Caller 0xffffffffa023a532
 kernel: Pid: 6135, comm: mv Not tainted 2.6.32-131.17.1.el6.x86_64 #1
 kernel: Call Trace:
 kernel: [<ffffffffa0262163>] ? xfs_error_report+0x43/0x50 [xfs]
 kernel: [<ffffffffa023a532>] ? xfs_free_extent+0xa2/0xc0 [xfs]
 kernel: [<ffffffffa02385da>] ? xfs_free_ag_extent+0x56a/0x7e0 [xfs]
 kernel: [<ffffffffa023a532>] ? xfs_free_extent+0xa2/0xc0 [xfs]
 kernel: [<ffffffffa0243edd>] ? xfs_bmap_finish+0x15d/0x1a0 [xfs]
 kernel: [<ffffffffa0269cf3>] ? xfs_itruncate_finish+0x183/0x390 [xfs]
 kernel: [<ffffffffa0284dc8>] ? xfs_inactive+0x358/0x4e0 [xfs]
 kernel: [<ffffffff814dc34e>] ? mutex_lock+0x1e/0x50
 kernel: [<ffffffffa0294fa0>] ? xfs_fs_clear_inode+0xa0/0xe0 [xfs]
 kernel: [<ffffffff8118cb7f>] ? clear_inode+0x8f/0x110
 kernel: [<ffffffff8118d326>] ? generic_delete_inode+0x196/0x1d0
 kernel: [<ffffffff8118d3c5>] ? generic_drop_inode+0x65/0x80
 kernel: [<ffffffff8118c232>] ? iput+0x62/0x70
 kernel: [<ffffffff811835e2>] ? do_unlinkat+0x112/0x1c0
 kernel: [<ffffffff81177e36>] ? sys_newfstatat+0x36/0x50
 kernel: [<ffffffff811837f2>] ? sys_unlinkat+0x22/0x40
 kernel: [<ffffffff8100b172>] ? system_call_fastpath+0x16/0x1b
 kernel: xfs_force_shutdown(drbd1,0x8) called from line 4011 of file fs/xfs/xfs_bmap.c.  Return address = 0xffffffffa0243f16
 kernel: Filesystem "drbd1": Corruption of in-memory data detected.  Shutting down filesystem: drbd1
 kernel: Please umount the filesystem, and rectify the problem(s) 

• The above error may sometimes be followed by this error:

 kernel: XFS (dm-#): xfs_log_force: error 5 returned.