linux-ext4 - [PATCH v6 11/21] fanotify: Allow file handle encoding for unhashed events

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Message-Id: <20210812214010.3197279-12-krisman@collabora.com>
Date:   Thu, 12 Aug 2021 17:40:00 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     amir73il@...il.com, jack@...e.com
Cc:     linux-api@...r.kernel.org, linux-ext4@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, khazhy@...gle.com,
        dhowells@...hat.com, david@...morbit.com, tytso@....edu,
        djwong@...nel.org, repnop@...gle.com,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com, Jan Kara <jack@...e.cz>
Subject: [PATCH v6 11/21] fanotify: Allow file handle encoding for unhashed events

FAN_FS_ERROR will report a file handle, but it is an unhashed event.
Allow passing a NULL hash to fanotify_encode_fh and avoid calculating
the hash if not needed.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
Reviewed-by: Jan Kara <jack@...e.cz>
---
 fs/notify/fanotify/fanotify.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index acf78c0ed219..50fce4fec0d6 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -403,8 +403,12 @@ static int fanotify_encode_fh(struct fanotify_fh *fh, struct inode *inode,
 	fh->type = type;
 	fh->len = fh_len;
 
-	/* Mix fh into event merge key */
-	*hash ^= fanotify_hash_fh(fh);
+	/*
+	 * Mix fh into event merge key.  Hash might be NULL in case of
+	 * unhashed FID events (i.e. FAN_FS_ERROR).
+	 */
+	if (hash)
+		*hash ^= fanotify_hash_fh(fh);
 
 	return FANOTIFY_FH_HDR_LEN + fh_len;
 
-- 
2.32.0