Messages in this thread | | | Date | Fri, 22 Oct 2021 23:32:16 +0800 | Subject | Re: [f2fs-dev] [PATCH] f2fs: remove circular locking between sb_internal and fs_reclaim | From | Chao Yu <> |
| |
On 2021/10/22 0:44, Daeho Jeong wrote: > There is a deadlock between sb_internal lock (sb_start_intwrite()) and > dquot related lock. > It's because we call f2fs_truncate(), which eventually calls > dquot_initialize(), while holding sb_internal lock. > So, I called dquot_initialize() in advance to make the 2nd calling of > it in f2fs_truncate() ineffective. > This is similar with the thing in f2fs_evict_inode() in inode.c
Well, if dquot_initialize() fails in f2fs_drop_inode(), will we still run into deadlock?
Thanks,
> > Thanks, > > On Thu, Oct 21, 2021 at 5:11 AM Chao Yu <chao@kernel.org> wrote: >> >> On 2021/10/15 3:05, Daeho Jeong wrote: >>> From: Daeho Jeong <daehojeong@google.com> >>> >>> We detected the below circular locking dependency between sb_internal >>> and fs_reclaim. So, removed it by calling dquot_initialize() before >>> sb_start_intwrite(). >>> >>> ====================================================== >>> WARNING: possible circular locking dependency detected >>> ------------------------------------------------------ >>> kswapd0/133 is trying to acquire lock: >>> ffffff80d5fb9680 (sb_internal#2){.+.+}-{0:0}, at: evict+0xd4/0x2f8 >>> >>> but task is already holding lock: >>> ffffffda597c93a8 (fs_reclaim){+.+.}-{0:0}, at: >>> __fs_reclaim_acquire+0x4/0x50 >>> >>> which lock already depends on the new lock. >>> ... >>> other info that might help us debug this: >>> >>> Chain exists of: >>> >>> sb_internal#2 --> &s->s_dquot.dqio_sem --> fs_reclaim >>> >>> Possible unsafe locking scenario: >>> >>> CPU0 CPU1 >>> ---- ---- >>> lock(fs_reclaim); >>> lock(&s->s_dquot.dqio_sem); >>> lock(fs_reclaim); >>> lock(sb_internal#2); >> >> Sorry, I still didn't get the root cause of this deadlock issue, could >> you please explain more about this? >> >> And why calling dquot_initialize() in drop_inode() could break the >> circular locking dependency? >> >> Thanks, >> >>> >>> Signed-off-by: Daeho Jeong <daehojeong@google.com> >>> --- >>> fs/f2fs/super.c | 2 ++ >>> 1 file changed, 2 insertions(+) >>> >>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c >>> index 86eeb019cc52..a133932333c5 100644 >>> --- a/fs/f2fs/super.c >>> +++ b/fs/f2fs/super.c >>> @@ -1370,6 +1370,8 @@ static int f2fs_drop_inode(struct inode *inode) >>> /* should remain fi->extent_tree for writepage */ >>> f2fs_destroy_extent_node(inode); >>> >>> + dquot_initialize(inode); >>> + >>> sb_start_intwrite(inode->i_sb); >>> f2fs_i_size_write(inode, 0); >>> >>>
| |