linux-ext4 - Re: [PATCH 1/5] ext4: fix race with setting free_inode/clusters

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Date:   Wed, 25 Jul 2018 08:38:19 +0800
From:   Wang Shilong <wangshilong1991@...il.com>
To:     "Theodore Ts'o" <tytso@....edu>, Andreas Dilger <adilger@...ger.ca>
Cc:     Ext4 Developers List <linux-ext4@...r.kernel.org>,
        Shuichi Ihara <sihara@....com>, Wang Shilong <wshilong@....com>
Subject: Re: [PATCH 1/5] ext4: fix race with setting free_inode/clusters_counter

Hi Ted,

Would you please consider this patchset for new merge windows?
They are all reviewed by Andreas at least.

Thanks,
Shilong

On Tue, Jun 5, 2018 at 2:00 AM, Andreas Dilger <adilger@...ger.ca> wrote:

> On May 29, 2018, at 5:45 AM, Wang Shilong <wangshilong1991@...il.com>
> wrote:
> >
> > From: Wang Shilong <wshilong@....com>
> >
> > Whenever we hit block or inode bitmap corruptions we set
> > bit and then reduce this block group free inode/clusters
> > counter to expose right available space.
> >
> > However some of ext4_mark_group_bitmap_corrupted() is called
> > inside group spinlock, some are not, this could make it happen
> > that we double reduce one block group free counters from system.
> >
> > Always hold group spinlock for it could fix it, but it looks
> > a little heavy, we could use test_and_set_bit() to fix race
> > problems here.
> >
> > Signed-off-by: Wang Shilong <wshilong@....com>
>
> Reviewed-by: Andreas Dilger <adilger@...ger.ca>
>
> > ---
> > fs/ext4/super.c | 22 +++++++++++-----------
> > 1 file changed, 11 insertions(+), 11 deletions(-)
> >
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index c1c5c87..d6fa6cf 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -770,26 +770,26 @@ void ext4_mark_group_bitmap_corrupted(struct
> super_block *sb,
> >       struct ext4_sb_info *sbi = EXT4_SB(sb);
> >       struct ext4_group_info *grp = ext4_get_group_info(sb, group);
> >       struct ext4_group_desc *gdp = ext4_get_group_desc(sb, group, NULL);
> > +     int ret;
> >
> > -     if ((flags & EXT4_GROUP_INFO_BBITMAP_CORRUPT) &&
> > -         !EXT4_MB_GRP_BBITMAP_CORRUPT(grp)) {
> > -             percpu_counter_sub(&sbi->s_freeclusters_counter,
> > -                                     grp->bb_free);
> > -             set_bit(EXT4_GROUP_INFO_BBITMAP_CORRUPT_BIT,
> > -                     &grp->bb_state);
> > +     if (flags & EXT4_GROUP_INFO_BBITMAP_CORRUPT) {
> > +             ret = ext4_test_and_set_bit(EXT4_
> GROUP_INFO_BBITMAP_CORRUPT_BIT,
> > +                                         &grp->bb_state);
> > +             if (!ret)
> > +                     percpu_counter_sub(&sbi->s_freeclusters_counter,
> > +                                        grp->bb_free);
> >       }
> >
> > -     if ((flags & EXT4_GROUP_INFO_IBITMAP_CORRUPT) &&
> > -         !EXT4_MB_GRP_IBITMAP_CORRUPT(grp)) {
> > -             if (gdp) {
> > +     if (flags & EXT4_GROUP_INFO_IBITMAP_CORRUPT) {
> > +             ret = ext4_test_and_set_bit(EXT4_
> GROUP_INFO_IBITMAP_CORRUPT_BIT,
> > +                                         &grp->bb_state);
> > +             if (!ret && gdp) {
> >                       int count;
> >
> >                       count = ext4_free_inodes_count(sb, gdp);
> >                       percpu_counter_sub(&sbi->s_freeinodes_counter,
> >                                          count);
> >               }
> > -             set_bit(EXT4_GROUP_INFO_IBITMAP_CORRUPT_BIT,
> > -                     &grp->bb_state);
> >       }
> > }
> >
> > --
> > 1.8.3.1
> >
>
>
> Cheers, Andreas
>
>
>
>
>
>

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