linux-kernel - Re: [PATCH] CIFS: Fix readpages retrying on reconnects

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Date:	Thu, 2 Oct 2014 14:24:19 -0500
From:	Steve French <smfrench@...il.com>
To:	Pavel Shilovsky <piastry@...rsoft.ru>
Cc:	"linux-cifs@...r.kernel.org" <linux-cifs@...r.kernel.org>,
	Pavel Shilovsky <pshilovsky@...ba.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] CIFS: Fix readpages retrying on reconnects

Merged into cifs-2.6.git for-next (and for-linus)

I would like to get this and also
http://git.samba.org/?p=sfrench/cifs-2.6.git;a=commit;h=19e81573fca7b87ced7701e01ba164b968d929bd
upstream ASAP but timing is getting tight, will need to wait at least
a day for the normal linux-next build processes to complete and any
additional test results.

On Thu, Oct 2, 2014 at 11:13 AM, Pavel Shilovsky <piastry@...rsoft.ru> wrote:
> From: Pavel Shilovsky <pshilovsky@...ba.org>
>
> If we got a reconnect error from async readv we re-add pages back
> to page_list and continue loop. That is wrong because these pages
> have been already added to the pagecache but page_list has pages that
> have not been added to the pagecache yet. This ends up with a general
> protection fault in put_pages after readpages. Fix it by not retrying
> the read of these pages and falling back to readpage instead.
>
> Signed-off-by: Pavel Shilovsky <pshilovsky@...ba.org>
> ---
>  fs/cifs/file.c |    8 +-------
>  1 file changed, 1 insertion(+), 7 deletions(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 7c018a1..5f29354 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -3568,15 +3568,9 @@ static int cifs_readpages(struct file *file, struct address_space *mapping,
>                                 lru_cache_add_file(page);
>                                 unlock_page(page);
>                                 page_cache_release(page);
> -                               if (rc == -EAGAIN)
> -                                       list_add_tail(&page->lru, &tmplist);
>                         }
> +                       /* Fallback to the readpage in error/reconnect cases */
>                         kref_put(&rdata->refcount, cifs_readdata_release);
> -                       if (rc == -EAGAIN) {
> -                               /* Re-add pages to the page_list and retry */
> -                               list_splice(&tmplist, page_list);
> -                               continue;
> -                       }
>                         break;
>                 }
>
> --
> 1.7.10.4
>
> --
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-- 
Thanks,

Steve
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