[PATCH v8 08/19] fsnotify: pass optional file access range in pre-content event

Josef Bacik
2024-11-15T15:31:35Z

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 ++
fs/notify/fsnotify.c | 18 ++++++++++++++
include/linux/fsnotify.h | 4 ++--
include/linux/fsnotify_backend.h | 40 ++++++++++++++++++++++++++++++++
5 files changed, 71 insertions(+), 4 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/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index d128cb7dee62..538aacf990ca 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -225,6 +225,24 @@ __u32 fsnotify_file_object_watched(struct file *file, __u32 events_mask)
}
EXPORT_SYMBOL_GPL(fsnotify_file_object_watched);

+/* Report pre-content event with optional range info */
+int fsnotify_pre_content(const struct path *path, const loff_t *ppos,
+ size_t count)
+{
+ struct file_range range;
+
+ /* Report page aligned range only when pos is known */
+ if (!ppos)
+ return fsnotify_path(path, FS_PRE_ACCESS);
+
+ range.path = path;
+ range.pos = PAGE_ALIGN_DOWN(*ppos);
+ range.count = PAGE_ALIGN(*ppos + count) - range.pos;
+
+ return fsnotify_parent(path->dentry, FS_PRE_ACCESS, &range,
+ FSNOTIFY_EVENT_FILE_RANGE);
+}
+
/*
* Notify this dentry's parent about a child's events with child name info
* if parent is watching or if inode/sb/mount are interested in events with
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 994d7a322369..ce189b4778a5 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -201,7 +201,7 @@ 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;
@@ -218,7 +218,7 @@ 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 33880de72ef3..89f351193d8f 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
@@ -865,6 +897,8 @@ static inline void fsnotify_init_event(struct fsnotify_event *event)
}

__u32 fsnotify_file_object_watched(struct file *file, __u32 mask);
+int fsnotify_pre_content(const struct path *path, const loff_t *ppos,
+ size_t count);

#else

@@ -873,6 +907,12 @@ static inline __u32 fsnotify_file_object_watched(struct file *file, __u32 mask)
return 0;
}

+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)
--
2.43.0