[PATCH 2/3] NFS: Be more targeted about readdirplus use when doing lookup/revalidation

[Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>]

There is little point in setting NFS_INO_ADVISE_RDPLUS in nfs_lookup and
nfs_lookup_revalidate() unless a process is actually doing readdir on the
parent directory.
Furthermore, there is little point in using readdirplus if we're trying
to revalidate a negative dentry.

Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
---
 fs/nfs/dir.c | 28 +++++++++++++++++-----------
 1 file changed, 17 insertions(+), 11 deletions(-)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index 53e02b8bd9bd..5befd382be7d 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -455,14 +455,23 @@ bool nfs_use_readdirplus(struct inode *dir, struct dir_context *ctx)
 }
 
 /*
- * This function is called by the lookup code to request the use of
- * readdirplus to accelerate any future lookups in the same
+ * This function is called by the lookup and getattr code to request the
+ * use of readdirplus to accelerate any future lookups in the same
  * directory.
+ * Do this by checking if there is an active file descriptor
+ * and calling nfs_advise_use_readdirplus, then forcing a
+ * cache flush.
  */
 static
 void nfs_advise_use_readdirplus(struct inode *dir)
 {
-	set_bit(NFS_INO_ADVISE_RDPLUS, &NFS_I(dir)->flags);
+	struct nfs_inode *nfsi = NFS_I(dir);
+
+	if (nfs_server_capable(dir, NFS_CAP_READDIRPLUS) &&
+	    !list_empty(&nfsi->open_files)) {
+		set_bit(NFS_INO_ADVISE_RDPLUS, &nfsi->flags);
+		invalidate_mapping_pages(dir->i_mapping, 0, -1);
+	}
 }
 
 /*
@@ -475,10 +484,7 @@ void nfs_advise_use_readdirplus(struct inode *dir)
  */
 void nfs_force_use_readdirplus(struct inode *dir)
 {
-	if (!list_empty(&NFS_I(dir)->open_files)) {
-		nfs_advise_use_readdirplus(dir);
-		invalidate_mapping_pages(dir->i_mapping, 0, -1);
-	}
+	nfs_advise_use_readdirplus(dir);
 }
 
 static
@@ -1150,7 +1156,7 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 				return -ECHILD;
 			goto out_bad;
 		}
-		goto out_valid_noent;
+		goto out_valid;
 	}
 
 	if (is_bad_inode(inode)) {
@@ -1192,6 +1198,9 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 	if (IS_ERR(label))
 		goto out_error;
 
+	/* We need to force a revalidation: set a readdirplus hint */
+	nfs_advise_use_readdirplus(dir);
+
 	trace_nfs_lookup_revalidate_enter(dir, dentry, flags);
 	error = NFS_PROTO(dir)->lookup(dir, &dentry->d_name, fhandle, fattr, label);
 	trace_nfs_lookup_revalidate_exit(dir, dentry, flags, error);
@@ -1211,9 +1220,6 @@ static int nfs_lookup_revalidate(struct dentry *dentry, unsigned int flags)
 out_set_verifier:
 	nfs_set_verifier(dentry, nfs_save_change_attribute(dir));
  out_valid:
-	/* Success: notify readdir to use READDIRPLUS */
-	nfs_advise_use_readdirplus(dir);
- out_valid_noent:
 	if (flags & LOOKUP_RCU) {
 		if (parent != ACCESS_ONCE(dentry->d_parent))
 			return -ECHILD;
-- 
2.7.4

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