NFS: Reduce lock contention in nfs_page_find_head_request()



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>

parent 6d17d653

fs/nfs/write.c

+5 −3

Original line number	Diff line number	Diff line
		@@ -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;

		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;
		}