xfs
[Top] [All Lists]

Re: [PATCH] xfs: Don't flush inodes when project quota exceeded

To: Jan Kara <jack@xxxxxxx>
Subject: Re: [PATCH] xfs: Don't flush inodes when project quota exceeded
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Tue, 20 Nov 2012 11:04:28 +1100
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20121119213913.GB29498@xxxxxxxxxxxxx>
References: <1352766973-14197-1-git-send-email-jack@xxxxxxx> <20121119213913.GB29498@xxxxxxxxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Nov 19, 2012 at 10:39:13PM +0100, Jan Kara wrote:
> On Tue 13-11-12 01:36:13, Jan Kara wrote:
> > When project quota gets exceeded xfs_iomap_write_delay() ends up flushing
> > inodes because ENOSPC gets returned from xfs_bmapi_delay() instead of 
> > EDQUOT.
> > This makes handling of writes over project quota rather slow as a simple 
> > test
> > program shows:
> >     fd = open(argv[1], O_WRONLY | O_CREAT | O_TRUNC, 0644);
> >     for (i = 0; i < 50000; i++)
> >             pwrite(fd, buf, 4096, i*4096);
> > 
> > Writing 200 MB like this into a directory with 100 MB project quota takes
> > around 6 minutes while it takes about 2 seconds with this patch applied. 
> > This
> > actually happens in a real world load when nfs pushes data into a directory
> > which is over project quota.
> > 
> > Fix the problem by replacing XFS_QMOPT_ENOSPC flag with XFS_QMOPT_EPDQUOT.
> > That makes xfs_trans_reserve_quota_bydquots() return new error EPDQUOT when
> > project quota is exceeded. xfs_bmapi_delay() then uses this flag so that
> > xfs_iomap_write_delay() can distinguish real ENOSPC (requiring flushing)
> > from exceeded project quota (not requiring flushing).
> > 
> > As a side effect this patch fixes inconsistency where e.g. xfs_create()
> > returned EDQUOT even when project quota was exceeded.
>   Ping? Any opinions?

FWIW, it doesn't look like it'll apply to a current XFs tree:

> > @@ -441,8 +442,11 @@ retry:
> >      */
> >     if (nimaps == 0) {
> >             trace_xfs_delalloc_enospc(ip, offset, count);
> > -           if (flushed)
> > -                   return XFS_ERROR(error ? error : ENOSPC);
> > +           if (flushed) {
> > +                   if (error == 0 || error == EPDQUOT)
> > +                           error = ENOSPC;
> > +                   return XFS_ERROR(error);
> > +           }
> >  
> >             if (error == ENOSPC) {
> >                     xfs_iunlock(ip, XFS_ILOCK_EXCL);

This xfs_iomap_write_delay() looks like this now:

        /*
         * If bmapi returned us nothing, we got either ENOSPC or EDQUOT. Retry
         * without EOF preallocation.
         */
        if (nimaps == 0) {
                trace_xfs_delalloc_enospc(ip, offset, count);
                if (prealloc) {
                        prealloc = 0;
                        error = 0;
                        goto retry;
                }
                return XFS_ERROR(error ? error : ENOSPC);
        }

The flushing is now way up in xfs_file_buffered_aio_write(), and the
implementation of xfs_flush_inodes() has changed as well. Hence it
may or may not behave differently not....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

<Prev in Thread] Current Thread [Next in Thread>