[02/20] NFS: Reduce lock contention in nfs_page_find_head_request()
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Message ID 20170719220955.58210-3-trond.myklebust@primarydata.com
State New
Headers show

Commit Message

Trond Myklebust July 19, 2017, 10:09 p.m. UTC
Add a lockless check for whether or not the page might be carrying
an existing writeback before we grab the inode->i_lock.

Reported-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
---
 fs/nfs/write.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

Patch
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diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index 1d447e37f472..06e150c4e315 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -190,9 +190,11 @@  static struct nfs_page *nfs_page_find_head_request(struct page *page)
 	struct inode *inode = page_file_mapping(page)->host;
 	struct nfs_page *req = NULL;
 
-	spin_lock(&inode->i_lock);
-	req = nfs_page_find_head_request_locked(NFS_I(inode), page);
-	spin_unlock(&inode->i_lock);
+	if (PagePrivate(page) || PageSwapCache(page)) {
+		spin_lock(&inode->i_lock);
+		req = nfs_page_find_head_request_locked(NFS_I(inode), page);
+		spin_unlock(&inode->i_lock);
+	}
 	return req;
 }