[PATCH 5.12 214/292] nfsd: Reduce contention for the nfsd_file nf_rwsem

Greg Kroah-Hartman
2021-07-19T18:09:35Z

From: Trond Myklebust <trond.myklebust@hammerspace.com>

[ Upstream commit 474bc334698df98ce07c890f1898c7e7f389b0c7 ]

When flushing out the unstable file writes as part of a COMMIT call, try
to perform most of of the data writes and waits outside the semaphore.

This means that if the client is sending the COMMIT as part of a memory
reclaim operation, then it can continue performing I/O, with contention
for the lock occurring only once the data sync is finished.

Fixes: 5011af4c698a ("nfsd: Fix stable writes")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
Tested-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/nfsd/vfs.c | 18 ++++++++++++++++--
1 file changed, 16 insertions(+), 2 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index fd6be35a1642..f83a1d122505 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1123,6 +1123,19 @@ out:
}

#ifdef CONFIG_NFSD_V3
+static int
+nfsd_filemap_write_and_wait_range(struct nfsd_file *nf, loff_t offset,
+ loff_t end)
+{
+ struct address_space *mapping = nf->nf_file->f_mapping;
+ int ret = filemap_fdatawrite_range(mapping, offset, end);
+
+ if (ret)
+ return ret;
+ filemap_fdatawait_range_keep_errors(mapping, offset, end);
+ return 0;
+}
+
/*
* Commit all pending writes to stable storage.
*
@@ -1153,10 +1166,11 @@ nfsd_commit(struct svc_rqst *rqstp, struct svc_fh *fhp,
if (err)
goto out;
if (EX_ISSYNC(fhp->fh_export)) {
- int err2;
+ int err2 = nfsd_filemap_write_and_wait_range(nf, offset, end);

down_write(&nf->nf_rwsem);
- err2 = vfs_fsync_range(nf->nf_file, offset, end, 0);
+ if (!err2)
+ err2 = vfs_fsync_range(nf->nf_file, offset, end, 0);
switch (err2) {
case 0:
nfsd_copy_boot_verifier(verf, net_generic(nf->nf_net,
--
2.30.2