On Tue 20-11-12 10:15:11, Ben Myers wrote: > Hi Jan, > > 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? > > I think that there may be good reason to flush inodes even in the project quota > case. Speculative allocation beyond EOF might need to be cleaned up. I'm all > for passing back some data about why we hit ENOSPC. Then we can combine this > with Brian Foster's work and flush only inodes that touch a given project, > user, or group quota. Yes, I agree flushing might be useful even for project quota but then why don't we flush inodes also for user quota? Also the performance impact is really huge - and here I agree that unless you are writing over NFS you won't notice because only NFS tries to push X MB to the filesystem page by page only to get ENOSPC each time... And NFS is arguably doing a stupid thing but it is a common setup and you don't always have the freedom to fix clients to be more clever. So I'd be happy if XFS accomodated such use. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
