[PATCH v3 4/7] fanotify: distinguish between fid encode error and null fid

[Amir Goldstein <amir73il@gmail.com>]

In fanotify_encode_fh(), both cases of NULL inode and failure to encode
ended up with fh type FILEID_INVALID.

Distiguish the case of NULL inode, by setting fh type to FILEID_ROOT.

This is needed because fanotify_fh_equal() treats FILEID_INVALID
specially and we are going to need fanotify_fh_equal() to return true
when comparing two null fids.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
---
 fs/notify/fanotify/fanotify.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 1e4a345155dd..bdafc76cc258 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -282,8 +282,11 @@ static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
 	void *buf = fh->buf;
 	int err;
 
+	/* FAN_DIR_MODIFY does not encode object fh */
+	fh->type = FILEID_ROOT;
+	fh->len = 0;
 	if (!inode)
-		goto out;
+		return;
 
 	dwords = 0;
 	err = -ENOENT;
@@ -318,7 +321,6 @@ static void fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
 			    type, bytes, err);
 	kfree(ext_buf);
 	*fanotify_fh_ext_buf_ptr(fh) = NULL;
-out:
 	/* Report the event without a file identifier on encode error */
 	fh->type = FILEID_INVALID;
 	fh->len = 0;
-- 
2.17.1