linux-kernel - Re: [PATCH] Revert "f2fs: fix quota_sync failure due to f2fs_lock

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Date:   Sat, 30 May 2020 08:18:31 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-f2fs-devel@...ts.sourceforge.net,
        linux-kernel@...r.kernel.org, chao@...nel.org
Subject: Re: [PATCH] Revert "f2fs: fix quota_sync failure due to f2fs_lock_op"

On 05/30, Chao Yu wrote:
> On 2020/5/30 9:49, Jaegeuk Kim wrote:
> > On 05/30, Chao Yu wrote:
> >> On 2020/5/30 6:34, Jaegeuk Kim wrote:
> >>> On 05/29, Chao Yu wrote:
> >>>> Under heavy fsstress, we may triggle panic while issuing discard,
> >>>> because __check_sit_bitmap() detects that discard command may earse
> >>>> valid data blocks, the root cause is as below race stack described,
> >>>> since we removed lock when flushing quota data, quota data writeback
> >>>> may race with write_checkpoint(), so that it causes inconsistency in
> >>>> between cached discard entry and segment bitmap.
> >>>>
> >>>> - f2fs_write_checkpoint
> >>>>  - block_operations
> >>>>   - set_sbi_flag(sbi, SBI_QUOTA_SKIP_FLUSH)
> >>>>  - f2fs_flush_sit_entries
> >>>>   - add_discard_addrs
> >>>>    - __set_bit_le(i, (void *)de->discard_map);
> >>>> 						- f2fs_write_data_pages
> >>>> 						 - f2fs_write_single_data_page
> >>>> 						   : inode is quota one, cp_rwsem won't be locked
> >>>> 						  - f2fs_do_write_data_page
> >>>> 						   - f2fs_allocate_data_block
> >>>> 						    - f2fs_wait_discard_bio
> >>>> 						      : discard entry has not been added yet.
> >>>> 						    - update_sit_entry
> >>>>  - f2fs_clear_prefree_segments
> >>>>   - f2fs_issue_discard
> >>>>   : add discard entry
> >>>>
> >>>> This patch fixes this issue by reverting 435cbab95e39 ("f2fs: fix quota_sync
> >>>> failure due to f2fs_lock_op").
> >>>>
> >>>> Fixes: 435cbab95e39 ("f2fs: fix quota_sync failure due to f2fs_lock_op")
> >>>
> >>> The previous patch fixes quota_sync gets EAGAIN all the time.
> >>> How about this? It seems this works for fsstress test.
> >>>
> > 
> > Then this?
> > 
> > ---
> >  fs/f2fs/segment.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> > 
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index ebbadde6cbced..ed11dcf2d69ed 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -3107,6 +3107,14 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
> >  		type = CURSEG_COLD_DATA;
> >  	}
> >  
> > +	/*
> > +	 * We need to wait for node_write to avoid block allocation during
> > +	 * checkpoint. This can only happen to quota writes which can cause
> > +	 * the below discard race condition.
> > +	 */
> > +	if (IS_DATASEG(type))
> > +		down_write(&sbi->node_write);
> > +
> >  	down_read(&SM_I(sbi)->curseg_lock);
> >  
> >  	mutex_lock(&curseg->curseg_mutex);
> > @@ -3174,6 +3182,9 @@ void f2fs_allocate_data_block(struct f2fs_sb_info *sbi, struct page *page,
> 
> Minor thing: unlock order.
> 
> if (IS_DATASEG(type))
> 	up_write(&sbi->node_write);
> 
> Could you merge the diff into this patch?

Pushed in dev branch. Thanks.

> 
> >  
> >  	if (put_pin_sem)
> >  		up_read(&sbi->pin_sem);
> > +
> > +	if (IS_DATASEG(type))
> > +		up_write(&sbi->node_write);
> >  }
> >  
> >  static void update_device_state(struct f2fs_io_info *fio)
> >