From: Chuck Lever chuck.lever@oracle.com
[ Upstream commit ba838a75e73f55a780f1ee896b8e3ecb032dba0f ]
I measured a 50% throughput regression for large direct writes.
The observed on-the-wire behavior is that the client sends every NFS WRITE twice: once as an UNSTABLE WRITE plus a COMMIT, and once as a FILE_SYNC WRITE.
This is because the nfs_write_match_verf() check in nfs_direct_commit_complete() fails for every WRITE.
Buffered writes use nfs_write_completion(), which sets req->wb_verf correctly. Direct writes use nfs_direct_write_completion(), which does not set req->wb_verf at all. This leaves req->wb_verf set to all zeroes for every direct WRITE, and thus nfs_direct_commit_completion() always sets NFS_ODIRECT_RESCHED_WRITES.
This fix appears to restore nearly all of the lost performance.
Fixes: 1f28476dcb98 ("NFS: Fix O_DIRECT commit verifier handling") Signed-off-by: Chuck Lever chuck.lever@oracle.com Signed-off-by: Anna Schumaker Anna.Schumaker@Netapp.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/nfs/direct.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index a57e7c72c7f4..d49b1d197908 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -731,6 +731,8 @@ static void nfs_direct_write_completion(struct nfs_pgio_header *hdr) nfs_list_remove_request(req); if (request_commit) { kref_get(&req->wb_kref); + memcpy(&req->wb_verf, &hdr->verf.verifier, + sizeof(req->wb_verf)); nfs_mark_request_commit(req, hdr->lseg, &cinfo, hdr->ds_commit_idx); }