From: Changwei Ge <ge.changwei@h3c.com>
To: Andrew Morton <akpm@linux-foundation.org>, Larry Chen <lchen@suse.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"ocfs2-devel@oss.oracle.com" <ocfs2-devel@oss.oracle.com>
Subject: Re: [Ocfs2-devel] [PATCH V2] ocfs2: fix dead lock caused by ocfs2_defrag_extent
Date: Thu, 1 Nov 2018 03:11:57 +0000 [thread overview]
Message-ID: <63ADC13FD55D6546B7DECE290D39E37301277DDF02@H3CMLB12-EX.srv.huawei-3com.com> (raw)
In-Reply-To: 20181031142632.c523108bc137caa8cb1c6282@linux-foundation.org
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 <lchen@suse.com>
> 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.
>
> [lchen@suse.com: 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 <lchen@suse.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>
> Cc: Changwei Ge <ge.changwei@h3c.com>
> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
> ---
>
> 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
> Ocfs2-devel@oss.oracle.com
> https://oss.oracle.com/mailman/listinfo/ocfs2-devel
>
next prev parent reply other threads:[~2018-11-01 3:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-02 9:14 [PATCH V2] ocfs2: fix dead lock caused by ocfs2_defrag_extent Larry Chen
2018-10-31 21:26 ` Andrew Morton
2018-11-01 3:11 ` Changwei Ge [this message]
2018-11-01 4:12 ` [Ocfs2-devel] " Larry Chen
2018-11-01 7:25 ` Joseph Qi
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