From: Jeff Layton <jlayton@redhat.com> Date: Tue, 4 Jan 2011 18:38:37 -0500 Subject: [fs] nfs: pure nfs client performance using odirect Message-id: <1294166317-5086-1-git-send-email-jlayton@redhat.com> Patchwork-id: 31033 O-Subject: [RHEL5.7 PATCH] BZ#643441: nfs: pure nfs client performance using odirect. Bugzilla: 643441 RH-Acked-by: J. Bruce Fields <bfields@redhat.com> From: Arun Bharadwaj <arun@linux.vnet.ibm.com> An application that's doing O_DIRECT can't return from a write call without ensuring that the server has committed it to disk. What the client typically does is issue all of the WRITE calls that it can and then a COMMIT before returning. If the writes are smaller than the wsize however, it'll just do stable write call to the server so that it won't have to follow up with a commit. There's a corner case in the code however, we currently will do the unstable write/commit when we could get away with a stable write. This (fairly obvious) patch fixes that corner case. IBM pushed the upstream version of this patch to Trond and it's slated for inclusion in 2.6.37. -----------------------[snip]------------------- When an application opens a file with O_DIRECT flag, if the size of the data that is written is equal to wsize, the client sends a WRITE RPC with stable flag set to UNSTABLE followed by a single COMMIT RPC rather than sending a single WRITE RPC with the stable flag set to FILE_SYNC. This a bug. Patch to fix this. Signed-off-by: Arun R Bharadwaj <arun@linux.vnet.ibm.com> Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> Upstream-commit: b47d19de2c714020ba8f5545a6e7d4968f37eb45 diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index 83aaf42..4421dc8 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -720,7 +720,7 @@ static ssize_t nfs_direct_write(struct kiocb *iocb, unsigned long user_addr, siz goto out; nfs_alloc_commit_data(dreq); - if (dreq->commit_data == NULL || count < wsize) + if (dreq->commit_data == NULL || count <= wsize) sync = FLUSH_STABLE; dreq->inode = inode;
