Fwd: [PATCH] cifs: bugfix for unreclaimed writeback pages in cifs_writev_requeue()

[Steve French <smfrench-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Forwarding to the current cifs development mailing list


---------- Forwarded message ----------
From:  <jiang.biao2-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>
Date: Wed, Feb 6, 2013 at 12:26 AM
Subject: [PATCH] cifs: bugfix for unreclaimed writeback pages in
cifs_writev_requeue()
To: Steve French <sfrench-eUNUBHrolfbYtjvyW6yDsg@public.gmane.org>, linux-cifs-client-w/Ol4Ecudpl8XjKLYN78aQ@public.gmane.org



    This patch applies to the kernel version of linux-3.8-rc6.

    Pages get the PG_writeback flag set before cifs sends its request
to SMB server
    in cifs_writepages(), if the SMB service goes down, cifs may try
to recommit the
    writing requests in cifs_writev_requeue(). However, it does not
clean its PG_writeback
    flag and relaimed the pages even if it fails again in
cifs_writev_requeue(), which
    may lead to the hanging of the processes accessing the cifs
directory. This patch
    just cleans the PG_writeback flags and reclaims the pages under
that circumstances.

    Steps to reproduce the bug(trying serveral times may trigger the issue):
    1.Write from cifs client continuously.(e.g dd if=/dev/zero of=<cifs file>)
    2.Stop SMB service from server.(e.g service smb stop)
    3.Wait for two minutes， and then start SMB service from
server.(e.g service smb start)
    4.The processes which are accessing cifs directory may hang up.

    Signed-off-by: Ouyang Maochun <ouyang.maochun-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>
    Signed-off-by: Jiang Yong <jian.yong5-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>
    Tested-by: Zhang Xianwei <zhang.xianwei8-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>
    Reviewed-by: Wang Liang <wang.liang82-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>
    Reviewed-by: Cai Qu <cai.qu-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>
    Reviewed-by: Jiang Biao <jiang.biao2-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>

diff -uprN linux-3.8-rc6/fs/cifs/cifssmb.c linux-3.8-rc6_new/fs/cifs/cifssmb.c
--- linux-3.8-rc6/fs/cifs/cifssmb.c        2013-02-01 09:08:14.000000000 +0800
+++ linux-3.8-rc6_new/fs/cifs/cifssmb.c        2013-02-04
15:44:09.869254397 +0800
@@ -1909,8 +1909,11 @@ cifs_writev_requeue(struct cifs_writedat
         } while (rc == -EAGAIN);

         for (i = 0; i < wdata->nr_pages; i++) {
-                if (rc != 0)
+                if (rc != 0){
                         SetPageError(wdata->pages[i]);
+                         end_page_writeback(wdata->pages[i]);
+                         page_cache_release(wdata->pages[i]);
+                 }
                 unlock_page(wdata->pages[i]);
         }


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-- 
Thanks,

Steve