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SubjectRe: Possible NFS bug in 2.6.34...
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Trond Myklebust wrote:
> On Sat, 2010-05-22 at 09:18 -0700, Stuart Sheldon wrote:
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>> Hash: SHA256
>>
>> On 05/22/2010 09:09 AM, Trond Myklebust wrote:
>>> Do you see any more NFS traffic to the server when the above hang
>>> occurs? I'm wondering if we don't need something like the following
>>> patch.
>>>
>>> Cheers
>>> Trond
>>> --------------------------------------------------------------------------------
>>> From 0b574497e05f62fd49cfe26f1b97e3669525446c Mon Sep 17 00:00:00 2001
>>> From: Trond Myklebust <Trond.Myklebust@netapp.com>
>>> Date: Sat, 22 May 2010 11:49:19 -0400
>>> Subject: [PATCH] NFS: Ensure that we mark the inode as dirty if we exit early from commit
>>>
>>> If we exit from nfs_commit_inode() without ensuring that the COMMIT rpc
>>> call has been completed, we must re-mark the inode as dirty. Otherwise,
>>> future calls to sync_inode() with the WB_SYNC_ALL flag set will fail to
>>> ensure that the data is on the disk.
>>>
>>> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
>>> Cc: stable@kernel.org
>>> ---
>>> fs/nfs/write.c | 13 +++++++++++--
>>> 1 files changed, 11 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
>>> index 3aea3ca..b8a6d7a 100644
>>> --- a/fs/nfs/write.c
>>> +++ b/fs/nfs/write.c
>>> @@ -1386,7 +1386,7 @@ static int nfs_commit_inode(struct inode *inode, int how)
>>> int res = 0;
>>>
>>> if (!nfs_commit_set_lock(NFS_I(inode), may_wait))
>>> - goto out;
>>> + goto out_mark_dirty;
>>> spin_lock(&inode->i_lock);
>>> res = nfs_scan_commit(inode, &head, 0, 0);
>>> spin_unlock(&inode->i_lock);
>>> @@ -1398,9 +1398,18 @@ static int nfs_commit_inode(struct inode *inode, int how)
>>> wait_on_bit(&NFS_I(inode)->flags, NFS_INO_COMMIT,
>>> nfs_wait_bit_killable,
>>> TASK_KILLABLE);
>>> + else
>>> + goto out_mark_dirty;
>>> } else
>>> nfs_commit_clear_lock(NFS_I(inode));
>>> -out:
>>> + return res;
>>> + /* Note: If we exit without ensuring that the commit is complete,
>>> + * we must mark the inode as dirty. Otherwise, future calls to
>>> + * sync_inode() with the WB_SYNC_ALL flag set will fail to ensure
>>> + * that the data is on the disk.
>>> + */
>>> +out_mark_dirty:
>>> + __mark_inode_dirty(inode, I_DIRTY_DATASYNC);
>>> return res;
>>> }
>>>
>> Trond,
>>
>> When it occurred, it continues to throw those errors in the log, and all
>> access to the NFS mount stalled until I hard reset the client system.
>>
>> Do you want me to apply the patch and see if I can recreate the condition?
>
> Yes, please do. Could you also apply the following debugging patch on
> top of the above one, and see if the WARN_ON() triggers when both
> patches are applied?
>
> Cheers
> Trond
> ------------------------------------------------------------------------------------------------
> From 9883e35957468987f4338525c1d800d637bc05b7 Mon Sep 17 00:00:00 2001
> From: Trond Myklebust <Trond.Myklebust@netapp.com>
> Date: Sat, 22 May 2010 10:46:41 -0400
> Subject: [PATCH 2/2] NFS: debugging code for nfs_wb_page()
>
> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
> ---
> fs/nfs/write.c | 9 +++++++++
> 1 files changed, 9 insertions(+), 0 deletions(-)
>
> diff --git a/fs/nfs/write.c b/fs/nfs/write.c
> index b8a6d7a..0558fab 100644
> --- a/fs/nfs/write.c
> +++ b/fs/nfs/write.c
> @@ -1519,12 +1519,21 @@ int nfs_wb_page(struct inode *inode, struct page *page)
> int ret;
>
> while(PagePrivate(page)) {
> + unsigned dirty;
> + int syncing;
> +
> wait_on_page_writeback(page);
> if (clear_page_dirty_for_io(page)) {
> ret = nfs_writepage_locked(page, &wbc);
> if (ret < 0)
> goto out_error;
> + continue;
> }
> +
> + dirty = inode->i_state & I_DIRTY;
> + syncing = inode->i_state & I_SYNC;
> + WARN_ON(!syncing && !dirty && PagePrivate(page));
> +
> ret = sync_inode(inode, &wbc);
> if (ret < 0)
> goto out_error;

Ok,

I was able to reproduce the problem, and then repeat the test with the
patched kernel. The result with the patched kernel was that the system
did not crash, but I did not see any of the WARN_ON messages in the
logs. Also, I noticed that although the client did not crash, I did
notice long 'hangs' in the process...

Just a note, when I upgraded from 2.6.30.5 to 2.6.33.2 I noticed that
our overall network activity for NFS increase by about 40%. Also, I saw
longer delays when using commands like ls on a NFS mounted partition.
Not sure if anyone else noticed this or not, but I thought it worth
mentioning... :)

Stu


- --
Spider Pig, Spider Pig, Does whatever a Spider Pig does.
Can he swing, from a web, no he can't, he's a pig.
Look Oouuuut! He is a Spider Pig....
-- Matt Groening - "Spider Pig Lyrics"
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