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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@suse.com
Signed-off-by: Larry Chen <lchen@suse.com>
Reviewed-by: Changwei Ge <ge.changwei@h3c.com>
Cc: Mark Fasheh <mark@fasheh.com>
Cc: Joel Becker <jlbec@evilplan.org>
Cc: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <jiangqi903@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Larry Chen 2018-11-30 14:08:56 -08:00 committed by Linus Torvalds
parent 08be37b798
commit e21e57445a
1 changed files with 26 additions and 21 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
fs/ocfs2/move_extents.c
View File

@ -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_extents(struct inode *inode,
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 ocfs2_move_extents_context *context,
}
}
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 ocfs2_move_extents_context *context,
}
}
/*
* 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 ocfs2_move_extents_context *context,
}
}
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;