The patch titled
Subject: ocfs2: fix deadlock caused by ocfs2_defrag_extent()
has been added to the -mm tree. Its filename is
ocfs2-fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/ocfs2-fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/ocfs2-fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
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*** 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 backtrace 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 deadlock 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().
ocfs2_lock_allocators_move_extents() is referred 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/20181101071422.14470-1-lchen@xxxxxxxx
Signed-off-by: Larry Chen <lchen@xxxxxxxx>
Reviewed-by: Changwei Ge <ge.changwei@xxxxxxx>
Cc: Mark Fasheh <mark@xxxxxxxxxx>
Cc: Joel Becker <jlbec@xxxxxxxxxxxx>
Cc: Junxiao Bi <junxiao.bi@xxxxxxxxxx>
Cc: Joseph Qi <jiangqi903@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/ocfs2/move_extents.c | 47 +++++++++++++++++++++-----------------
1 file changed, 26 insertions(+), 21 deletions(-)
--- a/fs/ocfs2/move_extents.c~ocfs2-fix-dead-lock-caused-by-ocfs2_defrag_extent
+++ a/fs/ocfs2/move_extents.c
@@ -157,18 +157,14 @@ out:
}
/*
- * lock allocators, and reserving appropriate number of bits for
- * meta blocks and data clusters.
- *
- * in some cases, we don't need to reserve clusters, just let data_ac
- * be NULL.
+ * lock allocator, and reserve appropriate number of bits for
+ * meta blocks.
*/
-static int ocfs2_lock_allocators_move_extents(struct inode *inode,
+static int ocfs2_lock_meta_allocator_move_extents(struct inode *inode,
struct ocfs2_extent_tree *et,
u32 clusters_to_move,
u32 extents_to_split,
struct ocfs2_alloc_context **meta_ac,
- struct ocfs2_alloc_context **data_ac,
int extra_blocks,
int *credits)
{
@@ -193,13 +189,6 @@ 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);
@@ -259,10 +248,10 @@ static int ocfs2_defrag_extent(struct oc
}
}
- ret = ocfs2_lock_allocators_move_extents(inode, &context->et, *len, 1,
- &context->meta_ac,
- &context->data_ac,
- extra_blocks, &credits);
+ ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
+ *len, 1,
+ &context->meta_ac,
+ extra_blocks, &credits);
if (ret) {
mlog_errno(ret);
goto out;
@@ -285,6 +274,21 @@ static int ocfs2_defrag_extent(struct oc
}
}
+ /*
+ * Make sure ocfs2_reserve_cluster is called after
+ * __ocfs2_flush_truncate_log, otherwise, dead lock may happen.
+ *
+ * If ocfs2_reserve_cluster is called
+ * before __ocfs2_flush_truncate_log, dead lock on global bitmap
+ * may happen.
+ *
+ */
+ 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);
@@ -617,9 +621,10 @@ static int ocfs2_move_extent(struct ocfs
}
}
- ret = ocfs2_lock_allocators_move_extents(inode, &context->et, len, 1,
- &context->meta_ac,
- NULL, extra_blocks, &credits);
+ ret = ocfs2_lock_meta_allocator_move_extents(inode, &context->et,
+ len, 1,
+ &context->meta_ac,
+ extra_blocks, &credits);
if (ret) {
mlog_errno(ret);
goto out;
_
Patches currently in -mm which might be from lchen@xxxxxxxx are
ocfs2-fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
fix-dead-lock-caused-by-ocfs2_defrag_extent.patch
