fsnotify: pass optional file access range in pre-content event

We would like to add file range information to pre-content events.

Pass a struct file_range with offset and length to event handler
along with pre-content permission event.

The offset and length are aligned to page size, but we may need to
align them to minimum folio size for filesystems with large block size.

Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://patch.msgid.link/88eddee301231d814aede27fb4d5b41ae37c9702.1731684329.git.josef@toxicpanda.com

2 files changed, 42 insertions, 2 deletions

diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index d91aa064f0e4..87044acf8e79 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -154,7 +154,7 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask,
 	 * read()/write() and other types of access generate pre-content events.
 	 */
 	if (unlikely(FMODE_FSNOTIFY_HSM(file->f_mode))) {
-		int ret = fsnotify_path(&file->f_path, FS_PRE_ACCESS);
+		int ret = fsnotify_pre_content(&file->f_path, ppos, count);
 
 		if (ret)
 			return ret;
@@ -171,7 +171,7 @@ static inline int fsnotify_file_area_perm(struct file *file, int perm_mask,
 }
 
 /*
- * fsnotify_file_perm - permission hook before file access
+ * fsnotify_file_perm - permission hook before file access (unknown range)
  */
 static inline int fsnotify_file_perm(struct file *file, int perm_mask)
 {
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 9bda354b5538..0d24a21a8e60 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -294,6 +294,7 @@ static inline void fsnotify_group_assert_locked(struct fsnotify_group *group)
 /* When calling fsnotify tell it if the data is a path or inode */
 enum fsnotify_data_type {
 	FSNOTIFY_EVENT_NONE,
+	FSNOTIFY_EVENT_FILE_RANGE,
 	FSNOTIFY_EVENT_PATH,
 	FSNOTIFY_EVENT_INODE,
 	FSNOTIFY_EVENT_DENTRY,
@@ -306,6 +307,17 @@ struct fs_error_report {
 	struct super_block *sb;
 };
 
+struct file_range {
+	const struct path *path;
+	loff_t pos;
+	size_t count;
+};
+
+static inline const struct path *file_range_path(const struct file_range *range)
+{
+	return range->path;
+}
+
 static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
 {
 	switch (data_type) {
@@ -315,6 +327,8 @@ static inline struct inode *fsnotify_data_inode(const void *data, int data_type)
 		return d_inode(data);
 	case FSNOTIFY_EVENT_PATH:
 		return d_inode(((const struct path *)data)->dentry);
+	case FSNOTIFY_EVENT_FILE_RANGE:
+		return d_inode(file_range_path(data)->dentry);
 	case FSNOTIFY_EVENT_ERROR:
 		return ((struct fs_error_report *)data)->inode;
 	default:
@@ -330,6 +344,8 @@ static inline struct dentry *fsnotify_data_dentry(const void *data, int data_typ
 		return (struct dentry *)data;
 	case FSNOTIFY_EVENT_PATH:
 		return ((const struct path *)data)->dentry;
+	case FSNOTIFY_EVENT_FILE_RANGE:
+		return file_range_path(data)->dentry;
 	default:
 		return NULL;
 	}
@@ -341,6 +357,8 @@ static inline const struct path *fsnotify_data_path(const void *data,
 	switch (data_type) {
 	case FSNOTIFY_EVENT_PATH:
 		return data;
+	case FSNOTIFY_EVENT_FILE_RANGE:
+		return file_range_path(data);
 	default:
 		return NULL;
 	}
@@ -356,6 +374,8 @@ static inline struct super_block *fsnotify_data_sb(const void *data,
 		return ((struct dentry *)data)->d_sb;
 	case FSNOTIFY_EVENT_PATH:
 		return ((const struct path *)data)->dentry->d_sb;
+	case FSNOTIFY_EVENT_FILE_RANGE:
+		return file_range_path(data)->dentry->d_sb;
 	case FSNOTIFY_EVENT_ERROR:
 		return ((struct fs_error_report *) data)->sb;
 	default:
@@ -375,6 +395,18 @@ static inline struct fs_error_report *fsnotify_data_error_report(
 	}
 }
 
+static inline const struct file_range *fsnotify_data_file_range(
+							const void *data,
+							int data_type)
+{
+	switch (data_type) {
+	case FSNOTIFY_EVENT_FILE_RANGE:
+		return (struct file_range *)data;
+	default:
+		return NULL;
+	}
+}
+
 /*
  * Index to merged marks iterator array that correlates to a type of watch.
  * The type of watched object can be deduced from the iterator type, but not
@@ -863,9 +895,17 @@ static inline void fsnotify_init_event(struct fsnotify_event *event)
 {
 	INIT_LIST_HEAD(&event->list);
 }
+int fsnotify_pre_content(const struct path *path, const loff_t *ppos,
+			 size_t count);
 
 #else
 
+static inline int fsnotify_pre_content(const struct path *path,
+				       const loff_t *ppos, size_t count)
+{
+	return 0;
+}
+
 static inline int fsnotify(__u32 mask, const void *data, int data_type,
 			   struct inode *dir, const struct qstr *name,
 			   struct inode *inode, u32 cookie)