[RFC PATCH v2 09/14] NFS: Only use and unuse an fscache cookie a single time based on NFS_INO_FSCACHE

[Dave Wysochanski <dwysocha@redhat.com>]

For NFS, we only want to make a decision whether to "use" a inode based
fscache cookie one time, not multiple times, and based on whether the
inode is open for write by any process.  Achieve this by gating the
call to fscache_use_cookie / fscache_unuse_cookie by the NFS_INO_FSCACHE
flag on the nfs_inode.

Signed-off-by: Dave Wysochanski <dwysocha@redhat.com>
---
 fs/nfs/fscache.c | 21 ++++++++++++++-------
 1 file changed, 14 insertions(+), 7 deletions(-)

diff --git a/fs/nfs/fscache.c b/fs/nfs/fscache.c
index 1c4ced273fb7..00bb720cccfa 100644
--- a/fs/nfs/fscache.c
+++ b/fs/nfs/fscache.c
@@ -285,8 +285,10 @@ void nfs_fscache_clear_inode(struct inode *inode)
 
 	dfprintk(FSCACHE, "NFS: clear cookie (0x%p/0x%p)\n", nfsi, cookie);
 
-	nfs_fscache_update_auxdata(&auxdata, nfsi);
-	fscache_unuse_cookie(cookie, &auxdata, NULL);
+	if (test_and_clear_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags)) {
+		nfs_fscache_update_auxdata(&auxdata, nfsi);
+		fscache_unuse_cookie(cookie, &auxdata, NULL);
+	}
 	fscache_relinquish_cookie(cookie, false);
 	nfsi->fscache = NULL;
 }
@@ -321,18 +323,23 @@ void nfs_fscache_open_file(struct inode *inode, struct file *filp)
 {
 	struct nfs_inode *nfsi = NFS_I(inode);
 	struct fscache_cookie *cookie = nfs_i_fscache(inode);
+	struct nfs_fscache_inode_auxdata auxdata;
 
 	if (!fscache_cookie_valid(cookie))
 		return;
 
 	if (inode_is_open_for_write(inode)) {
-		dfprintk(FSCACHE, "NFS: nfsi 0x%p disabling cache\n", nfsi);
-		clear_bit(NFS_INO_FSCACHE, &nfsi->flags);
+		if (test_and_clear_bit(NFS_INO_FSCACHE, &nfsi->flags)) {
+			dfprintk(FSCACHE, "NFS: nfsi 0x%p disabling cache\n", nfsi);
+			nfs_fscache_update_auxdata(&auxdata, nfsi);
+			fscache_unuse_cookie(cookie, &auxdata, NULL);
+		}
 	} else {
-		dfprintk(FSCACHE, "NFS: nfsi 0x%p enabling cache\n", nfsi);
-		set_bit(NFS_INO_FSCACHE, &NFS_I(inode)->flags);
+		if (!test_and_set_bit(NFS_INO_FSCACHE, &nfsi->flags)) {
+			dfprintk(FSCACHE, "NFS: nfsi 0x%p enabling cache\n", nfsi);
+			fscache_use_cookie(cookie, false);
+		}
 	}
-	fscache_use_cookie(cookie, false);
 }
 EXPORT_SYMBOL_GPL(nfs_fscache_open_file);
 
-- 
1.8.3.1