[PATCH v7 06/18] fsnotify: pass optional file access range in pre-content event

[Josef Bacik <josef@toxicpanda.com>]

From: Amir Goldstein <amir73il@gmail.com>

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>
---
 fs/notify/fanotify/fanotify.c    | 11 +++++++++--
 fs/notify/fanotify/fanotify.h    |  2 ++
 include/linux/fsnotify.h         | 28 ++++++++++++++++++++++++----
 include/linux/fsnotify_backend.h | 32 ++++++++++++++++++++++++++++++++
 4 files changed, 67 insertions(+), 6 deletions(-)

diff --git a/fs/notify/fanotify/fanotify.c b/fs/notify/fanotify/fanotify.c
index 24c7c5df4998..2e6ba94ec405 100644
--- a/fs/notify/fanotify/fanotify.c
+++ b/fs/notify/fanotify/fanotify.c
@@ -548,9 +548,13 @@ static struct fanotify_event *fanotify_alloc_path_event(const struct path *path,
 	return &pevent->fae;
 }
 
-static struct fanotify_event *fanotify_alloc_perm_event(const struct path *path,
+static struct fanotify_event *fanotify_alloc_perm_event(const void *data,
+							int data_type,
 							gfp_t gfp)
 {
+	const struct path *path = fsnotify_data_path(data, data_type);
+	const struct file_range *range =
+			    fsnotify_data_file_range(data, data_type);
 	struct fanotify_perm_event *pevent;
 
 	pevent = kmem_cache_alloc(fanotify_perm_event_cachep, gfp);
@@ -564,6 +568,9 @@ static struct fanotify_event *fanotify_alloc_perm_event(const struct path *path,
 	pevent->hdr.len = 0;
 	pevent->state = FAN_EVENT_INIT;
 	pevent->path = *path;
+	/* NULL ppos means no range info */
+	pevent->ppos = range ? &range->pos : NULL;
+	pevent->count = range ? range->count : 0;
 	path_get(path);
 
 	return &pevent->fae;
@@ -801,7 +808,7 @@ static struct fanotify_event *fanotify_alloc_event(
 	old_memcg = set_active_memcg(group->memcg);
 
 	if (fanotify_is_perm_event(mask)) {
-		event = fanotify_alloc_perm_event(path, gfp);
+		event = fanotify_alloc_perm_event(data, data_type, gfp);
 	} else if (fanotify_is_error_event(mask)) {
 		event = fanotify_alloc_error_event(group, fsid, data,
 						   data_type, &hash);
diff --git a/fs/notify/fanotify/fanotify.h b/fs/notify/fanotify/fanotify.h
index e5ab33cae6a7..93598b7d5952 100644
--- a/fs/notify/fanotify/fanotify.h
+++ b/fs/notify/fanotify/fanotify.h
@@ -425,6 +425,8 @@ FANOTIFY_PE(struct fanotify_event *event)
 struct fanotify_perm_event {
 	struct fanotify_event fae;
 	struct path path;
+	const loff_t *ppos;		/* optional file range info */
+	size_t count;
 	u32 response;			/* userspace answer to the event */
 	unsigned short state;		/* state of the event */
 	int fd;		/* fd we passed to userspace for this event */
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 0f44cd60ac9a..7110bc2f5aa7 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -154,9 +154,16 @@ static inline int fsnotify_file(struct file *file, __u32 mask)
 }
 
 #ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
-static inline int fsnotify_pre_content(struct file *file)
+static inline int fsnotify_pre_content(const struct file *file,
+				       const loff_t *ppos, size_t count)
 {
 	struct inode *inode = file_inode(file);
+	struct file_range range;
+	const void *data;
+	int data_type;
+
+	if (!fsnotify_file_watchable(file, FS_PRE_ACCESS))
+		return 0;
 
 	/*
 	 * Pre-content events are only reported for regular files and dirs
@@ -168,7 +175,20 @@ static inline int fsnotify_pre_content(struct file *file)
 					       FSNOTIFY_PRIO_PRE_CONTENT))
 		return 0;
 
-	return fsnotify_file(file, FS_PRE_ACCESS);
+	/* Report page aligned range only when pos is known */
+	if (ppos) {
+		range.path = &file->f_path;
+		range.pos = PAGE_ALIGN_DOWN(*ppos);
+		range.count = PAGE_ALIGN(*ppos + count) - range.pos;
+		data = &range;
+		data_type = FSNOTIFY_EVENT_FILE_RANGE;
+	} else {
+		data = &file->f_path;
+		data_type = FSNOTIFY_EVENT_PATH;
+	}
+
+	return fsnotify_parent(file->f_path.dentry, FS_PRE_ACCESS,
+			       data, data_type);
 }
 
 /*
@@ -188,7 +208,7 @@ 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 (perm_mask & (MAY_READ | MAY_WRITE | MAY_ACCESS)) {
-		int ret = fsnotify_pre_content(file);
+		int ret = fsnotify_pre_content(file, ppos, count);
 
 		if (ret)
 			return ret;
@@ -205,7 +225,7 @@ 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..abd292edb48c 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
-- 
2.43.0