linux-kernel - Re: [PATCH v2 2/4] afs: check function return

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Date:   Wed, 21 Jul 2021 09:59:11 -0300
From:   Marc Dionne <marc.dionne@...istor.com>
To:     David Howells <dhowells@...hat.com>
Cc:     linux-afs@...ts.infradead.org, Tom Rix <trix@...hat.com>,
        linux-fsdevel@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 2/4] afs: check function return

On Mon, Jul 12, 2021 at 1:28 PM David Howells <dhowells@...hat.com> wrote:
>
> From: Tom Rix <trix@...hat.com>
>
> Static analysis reports this problem
>
> write.c:773:29: warning: Assigned value is garbage or undefined
>   mapping->writeback_index = next;
>                            ^ ~~~~
> The call to afs_writepages_region() can return without setting
> next.  So check the function return before using next.
>
> Changes:
>  ver #2:
>    - Need to fix the range_cyclic case also[1].
>
> Fixes: e87b03f5830e ("afs: Prepare for use of THPs")
> Signed-off-by: Tom Rix <trix@...hat.com>
> Signed-off-by: David Howells <dhowells@...hat.com>
> Link: https://lore.kernel.org/r/20210430155031.3287870-1-trix@redhat.com
> Link: https://lore.kernel.org/r/162609464716.3133237.10354897554363093252.stgit@warthog.procyon.org.uk/ # v1
> Link: https://lore.kernel.org/r/CAB9dFdvHsLsw7CMnB+4cgciWDSqVjuij4mH3TaXnHQB8sz5rHw@mail.gmail.com/ [1]
> ---
>
>  fs/afs/write.c |   16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
>
> diff --git a/fs/afs/write.c b/fs/afs/write.c
> index 3104b62c2082..1ed62e0ccfe5 100644
> --- a/fs/afs/write.c
> +++ b/fs/afs/write.c
> @@ -771,13 +771,19 @@ int afs_writepages(struct address_space *mapping,
>         if (wbc->range_cyclic) {
>                 start = mapping->writeback_index * PAGE_SIZE;
>                 ret = afs_writepages_region(mapping, wbc, start, LLONG_MAX, &next);
> -               if (start > 0 && wbc->nr_to_write > 0 && ret == 0)
> -                       ret = afs_writepages_region(mapping, wbc, 0, start,
> -                                                   &next);
> -               mapping->writeback_index = next / PAGE_SIZE;
> +               if (ret == 0) {
> +                       mapping->writeback_index = next / PAGE_SIZE;
> +                       if (start > 0 && wbc->nr_to_write > 0) {
> +                               ret = afs_writepages_region(mapping, wbc, 0,
> +                                                           start, &next);
> +                               if (ret == 0)
> +                                       mapping->writeback_index =
> +                                               next / PAGE_SIZE;
> +                       }
> +               }
>         } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
>                 ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
> -               if (wbc->nr_to_write > 0)
> +               if (wbc->nr_to_write > 0 && ret == 0)
>                         mapping->writeback_index = next;
>         } else {
>                 ret = afs_writepages_region(mapping, wbc,
>
>

Reviewed-by: Marc Dionne <marc.dionne@...istor.com>

Marc