From 0d4c4d4ea443babab6ec1a79f481260963fc969a Mon Sep 17 00:00:00 2001 From: Amir Goldstein Date: Tue, 8 Jul 2025 16:36:41 +0200 Subject: fsnotify: optimize FMODE_NONOTIFY_PERM for the common cases The most unlikely watched permission event is FAN_ACCESS_PERM, because at the time that it was introduced there were no evictable ignore mark, so subscribing to FAN_ACCESS_PERM would have incured a very high overhead. Yet, when we set the fmode to FMODE_NOTIFY_HSM(), we never skip trying to send FAN_ACCESS_PERM, which is almost always a waste of cycles. We got to this logic because of bundling FAN_OPEN*_PERM and FAN_ACCESS_PERM in the same category and because FAN_OPEN_PERM is a commonly used event. By open coding fsnotify_open_perm() in fsnotify_open_perm_and_set_mode(), we no longer need to regard FAN_OPEN*_PERM when calculating fmode. This leaves the case of having pre-content events and not having any other permission event in the object masks a more likely case than the other way around. Rework the fmode macros and code so that their meaning now refers only to hooks on an already open file: - FMODE_NOTIFY_NONE() skip all events - FMODE_NOTIFY_ACCESS_PERM() send all permission events including FAN_ACCESS_PERM - FMODE_NOTIFY_HSM() send pre-content permission events Signed-off-by: Amir Goldstein Signed-off-by: Jan Kara Link: https://patch.msgid.link/20250708143641.418603-3-amir73il@gmail.com --- include/linux/fs.h | 12 ++++++------ include/linux/fsnotify.h | 27 ++------------------------- 2 files changed, 8 insertions(+), 31 deletions(-) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index b085f161ed22..bc92fdb8bfcc 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -200,12 +200,12 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, /* * The two FMODE_NONOTIFY* define which fsnotify events should not be generated - * for a file. These are the possible values of (f->f_mode & - * FMODE_FSNOTIFY_MASK) and their meaning: + * for an open file. These are the possible values of + * (f->f_mode & FMODE_FSNOTIFY_MASK) and their meaning: * * FMODE_NONOTIFY - suppress all (incl. non-permission) events. * FMODE_NONOTIFY_PERM - suppress permission (incl. pre-content) events. - * FMODE_NONOTIFY | FMODE_NONOTIFY_PERM - suppress only pre-content events. + * FMODE_NONOTIFY | FMODE_NONOTIFY_PERM - suppress only FAN_ACCESS_PERM. */ #define FMODE_FSNOTIFY_MASK \ (FMODE_NONOTIFY | FMODE_NONOTIFY_PERM) @@ -213,13 +213,13 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, #define FMODE_FSNOTIFY_NONE(mode) \ ((mode & FMODE_FSNOTIFY_MASK) == FMODE_NONOTIFY) #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS -#define FMODE_FSNOTIFY_PERM(mode) \ +#define FMODE_FSNOTIFY_HSM(mode) \ ((mode & FMODE_FSNOTIFY_MASK) == 0 || \ (mode & FMODE_FSNOTIFY_MASK) == (FMODE_NONOTIFY | FMODE_NONOTIFY_PERM)) -#define FMODE_FSNOTIFY_HSM(mode) \ +#define FMODE_FSNOTIFY_ACCESS_PERM(mode) \ ((mode & FMODE_FSNOTIFY_MASK) == 0) #else -#define FMODE_FSNOTIFY_PERM(mode) 0 +#define FMODE_FSNOTIFY_ACCESS_PERM(mode) 0 #define FMODE_FSNOTIFY_HSM(mode) 0 #endif diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h index 8c1fa617d375..28a9cb13fbfa 100644 --- a/include/linux/fsnotify.h +++ b/include/linux/fsnotify.h @@ -147,9 +147,6 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, if (!(perm_mask & (MAY_READ | MAY_WRITE | MAY_ACCESS))) return 0; - if (likely(!FMODE_FSNOTIFY_PERM(file->f_mode))) - return 0; - /* * read()/write() and other types of access generate pre-content events. */ @@ -160,7 +157,8 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask, return ret; } - if (!(perm_mask & MAY_READ)) + if (!(perm_mask & MAY_READ) || + likely(!FMODE_FSNOTIFY_ACCESS_PERM(file->f_mode))) return 0; /* @@ -208,22 +206,6 @@ static inline int fsnotify_file_perm(struct file *file, int perm_mask) return fsnotify_file_area_perm(file, perm_mask, NULL, 0); } -/* - * fsnotify_open_perm - permission hook before file open - */ -static inline int fsnotify_open_perm(struct file *file) -{ - int ret; - - if (file->f_flags & __FMODE_EXEC) { - ret = fsnotify_path(&file->f_path, FS_OPEN_EXEC_PERM); - if (ret) - return ret; - } - - return fsnotify_path(&file->f_path, FS_OPEN_PERM); -} - #else static inline int fsnotify_open_perm_and_set_mode(struct file *file) { @@ -251,11 +233,6 @@ static inline int fsnotify_file_perm(struct file *file, int perm_mask) { return 0; } - -static inline int fsnotify_open_perm(struct file *file) -{ - return 0; -} #endif /* -- cgit v1.2.3