fsnotify: merge file_set_fsnotify_mode_from_watchers() with open perm hook

Create helper fsnotify_open_perm_and_set_mode() that moves the
fsnotify_open_perm() hook into file_set_fsnotify_mode_from_watchers().

This will allow some more optimizations.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/20250708143641.418603-2-amir73il@gmail.com

Author: amir73il

fs/file_table.c

@@ -196,7 +196,7 @@ static int init_file(struct file *f, int flags, const struct cred *cred)
 	file_ref_init(&f->f_ref, 1);
 	/*
 	 * Disable permission and pre-content events for all files by default.
-	 * They may be enabled later by file_set_fsnotify_mode_from_watchers().
+	 * They may be enabled later by fsnotify_open_perm_and_set_mode().
 	 */
 	file_set_fsnotify_mode(f, FMODE_NONOTIFY_PERM);
 	return 0;

fs/notify/fsnotify.c

@@ -656,20 +656,20 @@ EXPORT_SYMBOL_GPL(fsnotify);
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 /*
- * At open time we check fsnotify_sb_has_priority_watchers() and set the
- * FMODE_NONOTIFY_ mode bits accordignly.
+ * At open time we check fsnotify_sb_has_priority_watchers(), call the open perm
+ * hook and set the FMODE_NONOTIFY_ mode bits accordignly.
  * Later, fsnotify permission hooks do not check if there are permission event
  * watches, but that there were permission event watches at open time.
  */
-void file_set_fsnotify_mode_from_watchers(struct file *file)
+int fsnotify_open_perm_and_set_mode(struct file *file)
 {
 	struct dentry *dentry = file->f_path.dentry, *parent;
 	struct super_block *sb = dentry->d_sb;
 	__u32 mnt_mask, p_mask;
 
 	/* Is it a file opened by fanotify? */
 	if (FMODE_FSNOTIFY_NONE(file->f_mode))
-		return;
+		return 0;
 
 	/*
 	 * Permission events is a super set of pre-content events, so if there
@@ -679,7 +679,7 @@ void file_set_fsnotify_mode_from_watchers(struct file *file)
 	if (likely(!fsnotify_sb_has_priority_watchers(sb,
 						FSNOTIFY_PRIO_CONTENT))) {
 		file_set_fsnotify_mode(file, FMODE_NONOTIFY_PERM);
-		return;
+		return 0;
 	}
 
 	/*
@@ -689,8 +689,9 @@ void file_set_fsnotify_mode_from_watchers(struct file *file)
 	if ((!d_is_dir(dentry) && !d_is_reg(dentry)) ||
 	    likely(!fsnotify_sb_has_priority_watchers(sb,
 						FSNOTIFY_PRIO_PRE_CONTENT))) {
-		file_set_fsnotify_mode(file, FMODE_NONOTIFY | FMODE_NONOTIFY_PERM);
-		return;
+		file_set_fsnotify_mode(file, FMODE_NONOTIFY |
+				       FMODE_NONOTIFY_PERM);
+		goto open_perm;
 	}
 
 	/*
@@ -702,7 +703,7 @@ void file_set_fsnotify_mode_from_watchers(struct file *file)
 				     FSNOTIFY_PRE_CONTENT_EVENTS))) {
 		/* Enable pre-content events */
 		file_set_fsnotify_mode(file, 0);
-		return;
+		goto open_perm;
 	}
 
 	/* Is parent watching for pre-content events on this file? */
@@ -713,11 +714,14 @@ void file_set_fsnotify_mode_from_watchers(struct file *file)
 		if (p_mask & FSNOTIFY_PRE_CONTENT_EVENTS) {
 			/* Enable pre-content events */
 			file_set_fsnotify_mode(file, 0);
-			return;
+			goto open_perm;
 		}
 	}
 	/* Nobody watching for pre-content events from this file */
 	file_set_fsnotify_mode(file, FMODE_NONOTIFY | FMODE_NONOTIFY_PERM);
+
+open_perm:
+	return fsnotify_open_perm(file);
 }
 #endif
 

fs/open.c

@@ -943,12 +943,12 @@ static int do_dentry_open(struct file *f,
 		goto cleanup_all;
 
 	/*
-	 * Set FMODE_NONOTIFY_* bits according to existing permission watches.
+	 * Call fsnotify open permission hook and set FMODE_NONOTIFY_* bits
+	 * according to existing permission watches.
 	 * If FMODE_NONOTIFY mode was already set for an fanotify fd or for a
 	 * pseudo file, this call will not change the mode.
 	 */
-	file_set_fsnotify_mode_from_watchers(f);
-	error = fsnotify_open_perm(f);
+	error = fsnotify_open_perm_and_set_mode(f);
 	if (error)
 		goto cleanup_all;
 

include/linux/fsnotify.h

@@ -129,7 +129,7 @@ static inline int fsnotify_file(struct file *file, __u32 mask)
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
 
-void file_set_fsnotify_mode_from_watchers(struct file *file);
+int fsnotify_open_perm_and_set_mode(struct file *file);
 
 /*
  * fsnotify_file_area_perm - permission hook before access to file range
@@ -215,9 +215,6 @@ static inline int fsnotify_open_perm(struct file *file)
 {
 	int ret;
 
-	if (likely(!FMODE_FSNOTIFY_PERM(file->f_mode)))
-		return 0;
-
 	if (file->f_flags & __FMODE_EXEC) {
 		ret = fsnotify_path(&file->f_path, FS_OPEN_EXEC_PERM);
 		if (ret)
@@ -228,8 +225,9 @@ static inline int fsnotify_open_perm(struct file *file)
 }
 
 #else
-static inline void file_set_fsnotify_mode_from_watchers(struct file *file)
+static inline int fsnotify_open_perm_and_set_mode(struct file *file)
 {
+	return 0;
 }
 
 static inline int fsnotify_file_area_perm(struct file *file, int perm_mask,