Messages in this thread | | | From | Changwei Ge <> | Subject | Re: [Ocfs2-devel] [PATCH V3] ocfs2: fix dead lock caused by ocfs2_defrag_extent | Date | Thu, 1 Nov 2018 11:52:06 +0000 |
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Hello Joseph,
On 2018/11/1 17:01, Joseph Qi wrote: > Hi Larry, > > On 18/11/1 15:14, Larry Chen wrote: >> 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. >> >> Change log: >> 1. Correct the function comment. >> 2. Remove unused argument from ocfs2_lock_meta_allocator_move_extents. >> >> Signed-off-by: Larry Chen <lchen@suse.com> >> --- >> fs/ocfs2/move_extents.c | 47 ++++++++++++++++++++++++++--------------------- >> 1 file changed, 26 insertions(+), 21 deletions(-) >>
> IMO, here clusters_to_move is only for data_ac, since we change this > function to only handle meta_ac, I'm afraid clusters_to_move related > logic has to been changed correspondingly.
I think we can't remove *clusters_to_move* from here as clusters can be reserved latter outsides this function, but we still have to reserve metadata(extents) in advance. So we need that argument.
Thanks, Changwei
> > Thanks, > Joseph >> u32 extents_to_split, >> struct ocfs2_alloc_context **meta_ac, >> - struct ocfs2_alloc_context **data_ac, >> int extra_blocks, >> int *credits) >> { >> @@ -192,13 +188,6 @@ 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); >> >> @@ -257,10 +246,10 @@ 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; >> @@ -283,6 +272,21 @@ 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); >> @@ -600,9 +604,10 @@ 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; >> > > _______________________________________________ > Ocfs2-devel mailing list > Ocfs2-devel@oss.oracle.com > https://oss.oracle.com/mailman/listinfo/ocfs2-devel >
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