Hi Larry, I still have a few tiny comments for your patch, please refer to them.
On 2018/11/1 5:28, Andrew Morton wrote: > > Folks, could we please review this patch for upstream inclusion? > > Thanks. > > > From: Larry Chen <[email protected]> > 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 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. > > [[email protected]: rename ocfs2_lock_allocators_move_extents() to > ocfs2_lock_meta_allocator_move_extents(), add some comments] > Link: > https://urldefense.proofpoint.com/v2/url?u=http-3A__lkml.kernel.org_r_20180902091455.23862-2D1-2Dlchen-40suse.com&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=C7gAd4uDxlAvTdc0vmU6X8CMk6L2iDY8-HD0qT6Fo7Y&m=K8aRgOiMescamJW-IuHq-cW4mWedGQv2JTT-2KPy1RI&s=3fQHFtwgixirPeQ5Px4fRBnd_UcSx3rvSsLKLidwESo&e= > Link: > https://urldefense.proofpoint.com/v2/url?u=http-3A__lkml.kernel.org_r_20180827080121.31145-2D1-2Dlchen-40suse.com&d=DwICAg&c=RoP1YumCXCgaWHvlZYR8PZh8Bv7qIrMUB65eapI_JnE&r=C7gAd4uDxlAvTdc0vmU6X8CMk6L2iDY8-HD0qT6Fo7Y&m=K8aRgOiMescamJW-IuHq-cW4mWedGQv2JTT-2KPy1RI&s=PQOJREyeElsg_1IlINdSGefNqA6w_cUrI1ezdVxyi7o&e= > Signed-off-by: Larry Chen <[email protected]> > Cc: Mark Fasheh <[email protected]> > Cc: Joel Becker <[email protected]> > Cc: Junxiao Bi <[email protected]> > Cc: Joseph Qi <[email protected]> > Cc: Changwei Ge <[email protected]> > Signed-off-by: Andrew Morton <[email protected]> > --- > > fs/ocfs2/move_extents.c | 40 +++++++++++++++++++++++--------------- > 1 file changed, 25 insertions(+), 15 deletions(-) > > --- a/fs/ocfs2/move_extents.c~fix-dead-lock-caused-by-ocfs2_defrag_extent > +++ a/fs/ocfs2/move_extents.c > @@ -162,7 +162,7 @@ out: > * in some cases, we don't need to reserve clusters, just let data_ac > * be NULL. > */ > -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, After removing 'reserving clusters logic' out of this function, I suggest to also change the function header comments. And I think there is no need for arguments _data_ac_ now. Otherwise this patch looks sane to me. Thanks, Changwei > @@ -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); > > @@ -257,10 +250,11 @@ 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, > + &context->data_ac, > + extra_blocks, &credits); > if (ret) { > mlog_errno(ret); > goto out; > @@ -283,6 +277,21 @@ 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); > @@ -600,9 +609,10 @@ 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, > + NULL, extra_blocks, &credits); > if (ret) { > mlog_errno(ret); > goto out; > _ > > > _______________________________________________ > Ocfs2-devel mailing list > [email protected] > https://oss.oracle.com/mailman/listinfo/ocfs2-devel >
