linux-ext4 - [PATCH RFC 02/15] fanotify: Split fsid check from other fid mode checks

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Date:   Mon, 26 Apr 2021 14:41:48 -0400
From:   Gabriel Krisman Bertazi <krisman@...labora.com>
To:     amir73il@...il.com, tytso@....edu, djwong@...nel.org
Cc:     david@...morbit.com, jack@...e.com, dhowells@...hat.com,
        khazhy@...gle.com, linux-fsdevel@...r.kernel.org,
        linux-ext4@...r.kernel.org,
        Gabriel Krisman Bertazi <krisman@...labora.com>,
        kernel@...labora.com
Subject: [PATCH RFC 02/15] fanotify: Split fsid check from other fid mode checks

FAN_ERROR will require fsid, but not necessarily require the filesystem
to expose a file handle.  Split those checks into different functions, so
they can be used separately when creating a mark.

Signed-off-by: Gabriel Krisman Bertazi <krisman@...labora.com>
---
 fs/notify/fanotify/fanotify_user.c | 35 +++++++++++++++++++-----------
 1 file changed, 22 insertions(+), 13 deletions(-)

diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 0332c4afeec3..e0d113e3b65c 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1055,7 +1055,23 @@ SYSCALL_DEFINE2(fanotify_init, unsigned int, flags, unsigned int, event_f_flags)
 }
 
 /* Check if filesystem can encode a unique fid */
-static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
+static int fanotify_test_fid(struct path *path)
+{
+	/*
+	 * We need to make sure that the file system supports at least
+	 * encoding a file handle so user can use name_to_handle_at() to
+	 * compare fid returned with event to the file handle of watched
+	 * objects. However, name_to_handle_at() requires that the
+	 * filesystem also supports decoding file handles.
+	 */
+	if (!path->dentry->d_sb->s_export_op ||
+	    !path->dentry->d_sb->s_export_op->fh_to_dentry)
+		return -EOPNOTSUPP;
+
+	return 0;
+}
+
+static int fanotify_check_path_fsid(struct path *path, __kernel_fsid_t *fsid)
 {
 	__kernel_fsid_t root_fsid;
 	int err;
@@ -1082,17 +1098,6 @@ static int fanotify_test_fid(struct path *path, __kernel_fsid_t *fsid)
 	    root_fsid.val[1] != fsid->val[1])
 		return -EXDEV;
 
-	/*
-	 * We need to make sure that the file system supports at least
-	 * encoding a file handle so user can use name_to_handle_at() to
-	 * compare fid returned with event to the file handle of watched
-	 * objects. However, name_to_handle_at() requires that the
-	 * filesystem also supports decoding file handles.
-	 */
-	if (!path->dentry->d_sb->s_export_op ||
-	    !path->dentry->d_sb->s_export_op->fh_to_dentry)
-		return -EOPNOTSUPP;
-
 	return 0;
 }
 
@@ -1230,7 +1235,11 @@ static int do_fanotify_mark(int fanotify_fd, unsigned int flags, __u64 mask,
 	}
 
 	if (fid_mode) {
-		ret = fanotify_test_fid(&path, &__fsid);
+		ret = fanotify_check_path_fsid(&path, &__fsid);
+		if (ret)
+			goto path_put_and_out;
+
+		ret = fanotify_test_fid(&path);
 		if (ret)
 			goto path_put_and_out;
 
-- 
2.31.0