From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: with ECARTIS (v1.0.0; list xfs); Fri, 01 Sep 2006 06:20:49 -0700 (PDT) Received: from larry.melbourne.sgi.com (larry.melbourne.sgi.com [134.14.52.130]) by oss.sgi.com (8.12.10/8.12.10/SuSE Linux 0.7) with SMTP id k81DKDDW024104 for ; Fri, 1 Sep 2006 06:20:27 -0700 Date: Fri, 1 Sep 2006 23:19:13 +1000 From: David Chinner Subject: Re: vmsplice can't work well Message-ID: <20060901131913.GG5737019@melbourne.sgi.com> References: <44F4440F.1090300@gmail.com> <20060829140542.GN12257@kernel.dk> <44F5CC08.8010205@mnsu.edu> <20060830174815.GF7331@kernel.dk> <44F5D3C6.1010108@mnsu.edu> <20060831092440.GC5528@kernel.dk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20060831092440.GC5528@kernel.dk> Sender: xfs-bounce@oss.sgi.com Errors-To: xfs-bounce@oss.sgi.com List-Id: xfs To: Jens Axboe Cc: "Jeffrey E. Hundstad" , xfs@oss.sgi.com, nathans@sgi.com On Thu, Aug 31, 2006 at 11:24:41AM +0200, Jens Axboe wrote: > XFS list, > > On Wed, Aug 30 2006, Jeffrey E. Hundstad wrote: > > Jens Axboe wrote: > > >On Wed, Aug 30 2006, Jeffrey E. Hundstad wrote: > > > > > >>I tried your splie-git...tar.gz file and tried the splice-cp. It > > >>produced files that are the right length... but the files only contain > > >>nulls. Here's the straces: > > >> > > > > > >Works for me as well. Could be an fs issue, how large was the README and > > >what filesystem did you use? > > > > > > > > The file was 1130 bytes (it was the README in that directory.) The > > filesystem is XFS. > > > > I can reproduce this quite easily, doing: > > nelson:~ # splice-cp sda.blktrace.0 foo > > nelson:~ # md5sum sda.blktrace.0 foo > 4754070ae77091468c830ea23b125d68 sda.blktrace.0 > efdc7b9d00692fdfe91a691277209267 foo Busted write side - splice-in works fine, splice-out is an alias for /dev/zero. The reason it's full of NULLs: death:/mnt# xfs_bmap -vv foo foo: no extents death:/mnt# It's a hole. Nothing has been flushed out to disk. Interesting - the inode is leaving pipe_to_file() dirty, the page is dirty, the buffer head is dirty, delay, mapped and uptodate. The page is the only page in the radix tree and the radix tree is marked dirty. But it never gets flushed out. Even when I use dd to seek past the first disk block and write further into the file, I still end up with a hole in the range where the original splice write should be which means it was no longer in the page cache. Copying a large file I can see dirty memory increase to tens of megabytes. Nothing is going to disk, writeback is not going above zero. Interestingly, when the write completes, the size of the page cache drops by almost exactly the size of the file being written - almost like a truncate_inode_pages() is occuring on file close. Oh, look - we _are_ tossing away all the pages on close. xfs_splice_write() hasn't updated the xfs inode size when extending the file. The linux inode has the correct value, but xfs thinks that it's only got a speculative allocation EOF (i.e. 0) so we invalidate it before it gets to disk. The patch below just copies some code out of xfs_write() where it updates the xfs inode size and drops it in xfs_splice_write(). It's almost certainly not the right fix, but the bucket under the pipe will now catch most of the bits.... Cheers, Dave. -- Dave Chinner Principal Engineer SGI Australian Software Group --- fs/xfs/linux-2.6/xfs_lrw.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) Index: 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_lrw.c =================================================================== --- 2.6.x-xfs-new.orig/fs/xfs/linux-2.6/xfs_lrw.c 2006-08-31 16:17:47.000000000 +1000 +++ 2.6.x-xfs-new/fs/xfs/linux-2.6/xfs_lrw.c 2006-09-01 22:48:56.463190730 +1000 @@ -390,6 +390,8 @@ xfs_splice_write( xfs_inode_t *ip = XFS_BHVTOI(bdp); xfs_mount_t *mp = ip->i_mount; ssize_t ret; + struct inode *inode = outfilp->f_mapping->host; + xfs_fsize_t isize; XFS_STATS_INC(xs_write_calls); if (XFS_FORCED_SHUTDOWN(ip->i_mount)) @@ -416,6 +418,20 @@ xfs_splice_write( if (ret > 0) XFS_STATS_ADD(xs_write_bytes, ret); + isize = i_size_read(inode); + if (unlikely(ret < 0 && ret != -EFAULT && *ppos > isize)) + *ppos = isize; + + if (*ppos > ip->i_d.di_size) { + xfs_ilock(ip, XFS_ILOCK_EXCL); + if (*ppos > ip->i_d.di_size) { + ip->i_d.di_size = *ppos; + i_size_write(inode, *ppos); + ip->i_update_core = 1; + ip->i_update_size = 1; + } + xfs_iunlock(ip, XFS_ILOCK_EXCL); + } xfs_iunlock(ip, XFS_IOLOCK_EXCL); return ret; }