Messages in this thread Patch in this message | | | Date | Wed, 2 Dec 2020 22:07:03 -0800 | From | Jaegeuk Kim <> | Subject | Re: [f2fs-dev] [PATCH v3] f2fs: avoid race condition for shinker count |
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On 11/11, Jaegeuk Kim wrote: > Light reported sometimes shinker gets nat_cnt < dirty_nat_cnt resulting in > wrong do_shinker work. Let's avoid to get stale data by using nat_tree_lock. > > Reported-by: Light Hsieh <Light.Hsieh@mediatek.com> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > v3: > - fix to use NM_I(sbi) > > fs/f2fs/shrinker.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c > index d66de5999a26..555712ba06d8 100644 > --- a/fs/f2fs/shrinker.c > +++ b/fs/f2fs/shrinker.c > @@ -18,7 +18,11 @@ static unsigned int shrinker_run_no; > > static unsigned long __count_nat_entries(struct f2fs_sb_info *sbi) > { > - long count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt; > + long count; > + > + down_read(&NM_I(sbi)->nat_tree_lock); > + count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt; > + up_read(&NM_I(sbi)->nat_tree_lock);
I just fosund this can give kernel hang due to the following backtrace. f2fs_shrink_count shrink_slab shrink_node do_try_to_free_pages try_to_free_pages __alloc_pages_nodemask alloc_pages_current allocate_slab __slab_alloc __slab_alloc kmem_cache_alloc add_free_nid f2fs_flush_nat_entries f2fs_write_checkpoint
Let me just check like this.
From 971163330224449d90aac90957ea38f77d494f0f Mon Sep 17 00:00:00 2001 From: Jaegeuk Kim <jaegeuk@kernel.org> Date: Fri, 6 Nov 2020 13:22:05 -0800 Subject: [PATCH] f2fs: avoid race condition for shrinker count
Light reported sometimes shinker gets nat_cnt < dirty_nat_cnt resulting in wrong do_shinker work. Let's avoid to return insane overflowed value.
Reported-by: Light Hsieh <Light.Hsieh@mediatek.com> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org> --- fs/f2fs/shrinker.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/fs/f2fs/shrinker.c b/fs/f2fs/shrinker.c index d66de5999a26..75b5b4aaed99 100644 --- a/fs/f2fs/shrinker.c +++ b/fs/f2fs/shrinker.c @@ -18,9 +18,9 @@ static unsigned int shrinker_run_no; static unsigned long __count_nat_entries(struct f2fs_sb_info *sbi) { - long count = NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt; - - return count > 0 ? count : 0; + if (NM_I(sbi)->nat_cnt > NM_I(sbi)->dirty_nat_cnt) + return NM_I(sbi)->nat_cnt - NM_I(sbi)->dirty_nat_cnt; + return 0; } static unsigned long __count_free_nids(struct f2fs_sb_info *sbi) -- 2.29.2.454.gaff20da3a2-goog
> > return count > 0 ? count : 0; > } > -- > 2.29.2.299.gdc1121823c-goog > > > > _______________________________________________ > Linux-f2fs-devel mailing list > Linux-f2fs-devel@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
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