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| H A D | xfs_inode.c | diff bc56ad8c74b8588685c2875de0df8ab6974828ef Tue Sep 03 23:06:50 CDT 2019 kaixuxia <xiakaixu1987@gmail.com> xfs: Fix deadlock between AGI and AGF with RENAME_WHITEOUT
When performing rename operation with RENAME_WHITEOUT flag, we will
hold AGF lock to allocate or free extents in manipulating the dirents
firstly, and then doing the xfs_iunlink_remove() call last to hold
AGI lock to modify the tmpfile info, so we the lock order AGI->AGF.
The big problem here is that we have an ordering constraint on AGF
and AGI locking - inode allocation locks the AGI, then can allocate
a new extent for new inodes, locking the AGF after the AGI. Hence
the ordering that is imposed by other parts of the code is AGI before
AGF. So we get an ABBA deadlock between the AGI and AGF here.
Process A:
Call trace:
? __schedule+0x2bd/0x620
schedule+0x33/0x90
schedule_timeout+0x17d/0x290
__down_common+0xef/0x125
? xfs_buf_find+0x215/0x6c0 [xfs]
down+0x3b/0x50
xfs_buf_lock+0x34/0xf0 [xfs]
xfs_buf_find+0x215/0x6c0 [xfs]
xfs_buf_get_map+0x37/0x230 [xfs]
xfs_buf_read_map+0x29/0x190 [xfs]
xfs_trans_read_buf_map+0x13d/0x520 [xfs]
xfs_read_agf+0xa6/0x180 [xfs]
? schedule_timeout+0x17d/0x290
xfs_alloc_read_agf+0x52/0x1f0 [xfs]
xfs_alloc_fix_freelist+0x432/0x590 [xfs]
? down+0x3b/0x50
? xfs_buf_lock+0x34/0xf0 [xfs]
? xfs_buf_find+0x215/0x6c0 [xfs]
xfs_alloc_vextent+0x301/0x6c0 [xfs]
xfs_ialloc_ag_alloc+0x182/0x700 [xfs]
? _xfs_trans_bjoin+0x72/0xf0 [xfs]
xfs_dialloc+0x116/0x290 [xfs]
xfs_ialloc+0x6d/0x5e0 [xfs]
? xfs_log_reserve+0x165/0x280 [xfs]
xfs_dir_ialloc+0x8c/0x240 [xfs]
xfs_create+0x35a/0x610 [xfs]
xfs_generic_create+0x1f1/0x2f0 [xfs]
...
Process B:
Call trace:
? __schedule+0x2bd/0x620
? xfs_bmapi_allocate+0x245/0x380 [xfs]
schedule+0x33/0x90
schedule_timeout+0x17d/0x290
? xfs_buf_find+0x1fd/0x6c0 [xfs]
__down_common+0xef/0x125
? xfs_buf_get_map+0x37/0x230 [xfs]
? xfs_buf_find+0x215/0x6c0 [xfs]
down+0x3b/0x50
xfs_buf_lock+0x34/0xf0 [xfs]
xfs_buf_find+0x215/0x6c0 [xfs]
xfs_buf_get_map+0x37/0x230 [xfs]
xfs_buf_read_map+0x29/0x190 [xfs]
xfs_trans_read_buf_map+0x13d/0x520 [xfs]
xfs_read_agi+0xa8/0x160 [xfs]
xfs_iunlink_remove+0x6f/0x2a0 [xfs]
? current_time+0x46/0x80
? xfs_trans_ichgtime+0x39/0xb0 [xfs]
xfs_rename+0x57a/0xae0 [xfs]
xfs_vn_rename+0xe4/0x150 [xfs]
...
In this patch we move the xfs_iunlink_remove() call to
before acquiring the AGF lock to preserve correct AGI/AGF locking
order.
Signed-off-by: kaixuxia <kaixuxia@tencent.com>
Reviewed-by: Brian Foster <bfoster@redhat.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
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