Re: [PATCH 2/3] f2fs: remove unsafe bitmap checking

[Jaegeuk Kim <jaegeuk@kernel.org>]

On 02/24, Chao Yu wrote:
> On 2017/2/23 17:18, Hou Pengyang wrote:
> > proc A:                      proc B:
> > - writeback_sb_inodes
> > - __writeback_single_inode   
> > - do_writepages
> > - f2fs_write_node_pages       
> > - f2fs_balance_fs_bg         - write_checkpoint
> > - build_free_nids            - flush_nat_entries
> > - __build_free_nids          - __flush_nat_entry_set
> > - ra_meta_pages              - get_next_nat_page
> > - current_nat_addr           - set_to_next_nat
> > [do nat_bitmap checking]     - f2fs_change_bit
> 
> Both flows were protected by nat_tree_lock, so we don't need to worry about such
> case?

The nat_tree_lock doesn't cover ra_meta_pages in proc A.

Thanks,

> 
> Thanks,
> 
> > 
> > For proc A, nat_bitmap and nat_bitmap_mir would be compared without lock_op and 
> > nm_i->nat_tree_lock, while proc B is changing nat_bitmap/nat_bitmap_ver in cp.
> > 
> > So it is normal for nat_bitmap/nat_bitmap diffrence under such scenario.
> > 
> > This patch fix this by removing the monitoring point.
> > 
> > [Fix: 599a09b f2fs: check in-memory nat version bitmap]
> > Signed-off-by: Hou Pengyang <houpengyang@huawei.com>
> > ---
> >  fs/f2fs/node.h | 6 ------
> >  1 file changed, 6 deletions(-)
> > 
> > diff --git a/fs/f2fs/node.h b/fs/f2fs/node.h
> > index d3d2893..3fc9c4b 100644
> > --- a/fs/f2fs/node.h
> > +++ b/fs/f2fs/node.h
> > @@ -209,12 +209,6 @@ static inline pgoff_t current_nat_addr(struct f2fs_sb_info *sbi, nid_t start)
> >  		(seg_off << sbi->log_blocks_per_seg << 1) +
> >  		(block_off & (sbi->blocks_per_seg - 1)));
> >  
> > -#ifdef CONFIG_F2FS_CHECK_FS
> > -	if (f2fs_test_bit(block_off, nm_i->nat_bitmap) !=
> > -			f2fs_test_bit(block_off, nm_i->nat_bitmap_mir))
> > -		f2fs_bug_on(sbi, 1);
> > -#endif
> > -
> >  	if (f2fs_test_bit(block_off, nm_i->nat_bitmap))
> >  		block_addr += sbi->blocks_per_seg;
> >  
> > 
> 
> 
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