[ 116/127] fuse: fix readdirplus Oops in fuse_dentry_revalidate

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.9-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Miklos Szeredi <mszeredi@suse.cz>

commit 28420dad233520811c0e0860e7fb4975ed863fc4 upstream.

Fix bug introduced by commit 4582a4ab2a "FUSE: Adapt readdirplus to application
usage patterns".

We need to check for a positive dentry; negative dentries are not added by
readdirplus.  Secondly we need to advise the use of readdirplus on the *parent*,
otherwise the whole thing is useless.  Thirdly all this is only relevant if
"readdirplus_auto" mode is selected by the filesystem.

We advise the use of readdirplus only if the dentry was still valid.  If we had
to redo the lookup then there was no use in doing the -plus version.

Reported-by: Bernd Schubert <bernd.schubert@itwm.fraunhofer.de>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
CC: Feng Shuo <steve.shuo.feng@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/fuse/dir.c   |   12 +++++++++---
 fs/fuse/inode.c |    7 ++++---
 2 files changed, 13 insertions(+), 6 deletions(-)

--- a/fs/fuse/dir.c
+++ b/fs/fuse/dir.c
@@ -180,6 +180,8 @@ u64 fuse_get_attr_version(struct fuse_co
 static int fuse_dentry_revalidate(struct dentry *entry, unsigned int flags)
 {
 	struct inode *inode;
+	struct dentry *parent;
+	struct fuse_conn *fc;
 
 	inode = ACCESS_ONCE(entry->d_inode);
 	if (inode && is_bad_inode(inode))
@@ -187,10 +189,8 @@ static int fuse_dentry_revalidate(struct
 	else if (fuse_dentry_time(entry) < get_jiffies_64()) {
 		int err;
 		struct fuse_entry_out outarg;
-		struct fuse_conn *fc;
 		struct fuse_req *req;
 		struct fuse_forget_link *forget;
-		struct dentry *parent;
 		u64 attr_version;
 
 		/* For negative dentries, always do a fresh lookup */
@@ -241,8 +241,14 @@ static int fuse_dentry_revalidate(struct
 				       entry_attr_timeout(&outarg),
 				       attr_version);
 		fuse_change_entry_timeout(entry, &outarg);
+	} else if (inode) {
+		fc = get_fuse_conn(inode);
+		if (fc->readdirplus_auto) {
+			parent = dget_parent(entry);
+			fuse_advise_use_readdirplus(parent->d_inode);
+			dput(parent);
+		}
 	}
-	fuse_advise_use_readdirplus(inode);
 	return 1;
 }
 
--- a/fs/fuse/inode.c
+++ b/fs/fuse/inode.c
@@ -864,10 +864,11 @@ static void process_init_reply(struct fu
 				fc->dont_mask = 1;
 			if (arg->flags & FUSE_AUTO_INVAL_DATA)
 				fc->auto_inval_data = 1;
-			if (arg->flags & FUSE_DO_READDIRPLUS)
+			if (arg->flags & FUSE_DO_READDIRPLUS) {
 				fc->do_readdirplus = 1;
-			if (arg->flags & FUSE_READDIRPLUS_AUTO)
-				fc->readdirplus_auto = 1;
+				if (arg->flags & FUSE_READDIRPLUS_AUTO)
+					fc->readdirplus_auto = 1;
+			}
 		} else {
 			ra_pages = fc->max_read / PAGE_CACHE_SIZE;
 			fc->no_lock = 1;