> On Sep 14, 2020, at 4:53 PM, Chuck Lever <chuck.lever@xxxxxxxxxx> wrote:
>
>
>
>> On Sep 14, 2020, at 4:51 PM, J. Bruce Fields <bfields@xxxxxxxxxxxx> wrote:
>>
>> On Thu, Sep 10, 2020 at 03:45:12PM -0400, Chuck Lever wrote:
>>> I recently observed a significant slowdown in a long-running
>>> test on NFSv4.0 mounts.
>>>
>>> An OPEN for write seems to block the NFS server from offering
>>> delegations on that file for a few seconds. The problem is that
>>> when that file is closed, the filecache retains an open-for-write
>>> file descriptor until the laundrette runs. That keeps the inode's
>>> i_writecount positive until the cached file is finally unhashed
>>> and closed.
>>>
>>> Force the NFSv4 CLOSE logic to call filp_close() to eliminate
>>> the underlying cached open-for-write file as soon as the client
>>> closes the file.
>>>
>>> This minor change claws back about 80% of the performance
>>> regression.
>>
>> That's really useful to know. But mainly this makes me think that
>> nfsd4_check_conflicting_opens() is wrong.
>>
>> I'm trying to determine whether a given file has a non-nfsd writer by
>> counting the number of write opens nfsd holds on a given file and
>> subtracting that from i_writecount.
>>
>> But the way I'm counting write opens probably isn't correct.
>
> I entertained that possibility, but I couldn't figure out
> a better way to count opens-for-write.
Also, the regression started long before nfsd4_check_conflicting_opens
was added.
>> --b.
>>
>>>
>>> Signed-off-by: Chuck Lever <chuck.lever@xxxxxxxxxx>
>>> ---
>>> fs/nfsd/nfs4state.c | 8 ++++++--
>>> 1 file changed, 6 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
>>> index 3ac40ba7efe1..0b3059b8b36c 100644
>>> --- a/fs/nfsd/nfs4state.c
>>> +++ b/fs/nfsd/nfs4state.c
>>> @@ -613,10 +613,14 @@ static void __nfs4_file_put_access(struct nfs4_file *fp, int oflag)
>>> if (atomic_read(&fp->fi_access[1 - oflag]) == 0)
>>> swap(f2, fp->fi_fds[O_RDWR]);
>>> spin_unlock(&fp->fi_lock);
>>> - if (f1)
>>> + if (f1) {
>>> + nfsd_file_close_inode_sync(locks_inode(f1->nf_file));
>>> nfsd_file_put(f1);
>>> - if (f2)
>>> + }
>>> + if (f2) {
>>> + nfsd_file_close_inode_sync(locks_inode(f2->nf_file));
>>> nfsd_file_put(f2);
>>> + }
>>> }
>>> }
>
> --
> Chuck Lever
--
Chuck Lever
