On Tue, May 22, 2012 at 1:46 PM, Myklebust, Trond
<Trond.Myklebust@xxxxxxxxxx> wrote:
> On Tue, 2012-05-22 at 16:30 +0000, Adamson, Andy wrote:
>> On May 22, 2012, at 12:24 PM, Myklebust, Trond wrote:
>>
>> > On Tue, 2012-05-22 at 08:09 -0400, andros@xxxxxxxxxx wrote:
>> >> From: Andy Adamson <andros@xxxxxxxxxx>
>> >>
>> >> Signed-off-by: Andy Adamson <andros@xxxxxxxxxx>
>> >> ---
>> >> fs/nfs/write.c | 2 ++
>> >> 1 files changed, 2 insertions(+), 0 deletions(-)
>> >>
>> >> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
>> >> index e6fe3d6..c7295de 100644
>> >> --- a/fs/nfs/write.c
>> >> +++ b/fs/nfs/write.c
>> >> @@ -1555,6 +1555,8 @@ static void nfs_commit_release_pages(struct nfs_commit_data *data)
>> >> /* We have a mismatch. Write the page again */
>> >> dprintk(" mismatch\n");
>> >> nfs_mark_request_dirty(req);
>> >> + nfs_unlock_request(req);
>> >> + continue;
>> >> next:
>> >> nfs_unlock_and_release_request(req);
>> >> }
>> >
>> > What is this patch trying to fix? As far as I can see it will lead to a
>> > reference leak.
>>
>> The release of the page drops the refcount to zero. Since it is a mismatch, we want to continue to use the page, so nfs_page_find_request_locked is called we get the WARNING in kref_get, and an Oops in various places in pnfs_update_layout.
>>
>> Here is the output of added printk's.
>>
>> -->Andy
>>
>> May 21 18:25:33 fedora-64-2 kernel: [ 152.988921] NFS: commit (0:35/2 4096@184320)
>> May 21 18:25:33 fedora-64-2 kernel: [ 152.988923] mismatch req ffff880042dbb800
>> May 21 18:25:33 fedora-64-2 kernel: [ 152.988927] nfs_release_request WB req ffff880042dbb800 wb_kref 1
>> May 21 18:25:33 fedora-64-2 kernel: [ 152.988932] put_lseg: lseg ffff880042d95380 ref 4 valid 0
>> May 21 18:25:33 fedora-64-2 kernel: [ 152.988945] nfs_page_find_request_locked req ffff88003e033800
>> May 21 18:25:33 fedora-64-2 kernel: [ 152.988949] nfs_page_find_request_locked WB req ffff88003e033800 wb_kref 0
>> May 21 18:25:33 fedora-64-2 kernel: [ 152.988953] ------------[ cut here ]------------
>> May 21 18:25:33 fedora-64-2 kernel: [ 152.989082] WARNING: at include/linux/kref.h:41 kref_get+0x20/0x2c [nfs]()
>
> Are these commit-to-ds requests?
Yes
-->Andy
> As far as I can see, there is a bug in
> transfer_commit_list() in that it locks the requests, but does not
> reference them.
>
> Fred?
>
> --
> Trond Myklebust
> Linux NFS client maintainer
>
> NetApp
> Trond.Myklebust@xxxxxxxxxx
> www.netapp.com
>
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