linux-kernel - Re: [f2fs-dev] [PATCH] f2fs: fix null page reference in redirty

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Date:   Tue, 5 Jan 2021 11:10:59 +0900
From:   Daeho Jeong <daeho43@...il.com>
To:     Chao Yu <yuchao0@...wei.com>
Cc:     linux-kernel@...r.kernel.org,
        linux-f2fs-devel@...ts.sourceforge.net, kernel-team@...roid.com,
        Colin Ian King <colin.king@...onical.com>,
        Daeho Jeong <daehojeong@...gle.com>
Subject: Re: [f2fs-dev] [PATCH] f2fs: fix null page reference in redirty_blocks

Yes, it's better~ :)

2021년 1월 5일 (화) 오전 10:44, Chao Yu <yuchao0@...wei.com>님이 작성:
>
> On 2021/1/5 9:28, Daeho Jeong wrote:
> > From: Daeho Jeong <daehojeong@...gle.com>
> >
> > Fixed null page reference when find_lock_page() fails in
> > redirty_blocks().
> >
> > Signed-off-by: Daeho Jeong <daehojeong@...gle.com>
> > Reported-by: Colin Ian King <colin.king@...onical.com>
> > Fixes: 5fdb322ff2c2 ("f2fs: add F2FS_IOC_DECOMPRESS_FILE and F2FS_IOC_COMPRESS_FILE")
> > ---
> >   fs/f2fs/file.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
> > index 9e5275716be8..bf6682a52433 100644
> > --- a/fs/f2fs/file.c
> > +++ b/fs/f2fs/file.c
> > @@ -4060,8 +4060,10 @@ static int redirty_blocks(struct inode *inode, pgoff_t page_idx, int len)
> >
> >       for (i = 0; i < page_len; i++, redirty_idx++) {
> >               page = find_lock_page(mapping, redirty_idx);
> > -             if (!page)
> > +             if (!page) {
> >                       ret = -ENOENT;
>
> ret = -ENOMEM;
>
> > +                     continue;
>
> How about breaking the loop for out-of-memory case, because in such condition
> we have less chance to dirty whole cluster due to no memory, and continue to
> allocate pages for target file will make system suffer more memory pressure,
> it will make many thing slower.
>
> Thnaks,
>
> > +             }
> >               set_page_dirty(page);
> >               f2fs_put_page(page, 1);
> >               f2fs_put_page(page, 0);
> >