The patch titled
Subject: ocfs2: fix deadlock caused by ocfs2_defrag_extent
has been added to the -mm tree. Its filename is
fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Larry Chen <lchen@xxxxxxxx>
Subject: ocfs2: fix deadlock caused by ocfs2_defrag_extent
ocfs2_defrag_extent may fall into deadlock.
ocfs2_ioctl_move_extents
ocfs2_ioctl_move_extents
ocfs2_move_extents
ocfs2_defrag_extent
ocfs2_lock_allocators_move_extents
ocfs2_reserve_clusters
inode_lock GLOBAL_BITMAP_SYSTEM_INODE
__ocfs2_flush_truncate_log
inode_lock GLOBAL_BITMAP_SYSTEM_INODE
As back trace shows above, ocfs2_reserve_clusters will call inode_lock
against the global bitmap if local allocator has not sufficient cluters.
Once global bitmap could meet the demand, ocfs2_reserve_cluster will
return success with global bitmap locked.
After ocfs2_reserve_cluster, if truncate log is full,
__ocfs2_flush_truncate_log will definitely fall into dead lock because it
needs to inode_lock global bitmap, which has already been locked.
To fix this bug, we could remove from ocfs2_lock_allocators_move_extents
the code which intends to lock global allocator, and put the removed code
after __ocfs2_flush_truncate_log
The ocfs2_lock_allocators_move_extents has been refered by 2 places, one
is here, the other does not need the data allocator context, which means
this patch does not affect the caller so far.
Link: http://lkml.kernel.org/r/20180827080121.31145-1-lchen@xxxxxxxx
Signed-off-by: Larry Chen <lchen@xxxxxxxx>
Cc: Mark Fasheh <mark@xxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Joseph Qi <jiangqi903@xxxxxxxxx>
Cc: Changwei Ge <ge.changwei@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ocfs2/move_extents.c | 13 ++++++-------
1 file changed, 6 insertions(+), 7 deletions(-)
--- a/fs/ocfs2/move_extents.c~fix-dead-lock-caused-by-ocfs2_defrag_extent
+++ a/fs/ocfs2/move_extents.c
@@ -192,13 +192,6 @@ static int ocfs2_lock_allocators_move_ex
goto out;
}
- if (data_ac) {
- ret = ocfs2_reserve_clusters(osb, clusters_to_move, data_ac);
- if (ret) {
- mlog_errno(ret);
- goto out;
- }
- }
*credits += ocfs2_calc_extend_credits(osb->sb, et->et_root_el);
@@ -283,6 +276,12 @@ static int ocfs2_defrag_extent(struct oc
}
}
+ ret = ocfs2_reserve_clusters(osb, *len, &context->data_ac);
+ if (ret) {
+ mlog_errno(ret);
+ goto out_unlock_mutex;
+ }
+
handle = ocfs2_start_trans(osb, credits);
if (IS_ERR(handle)) {
ret = PTR_ERR(handle);
_
Patches currently in -mm which might be from lchen@xxxxxxxx are
fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
