[PATCH] [RFC] fsnotify: Tell the user what part of the file mighthave changed

From: Alexey Zaytsev
Date: Sun Nov 14 2010 - 19:42:58 EST

Signed-off-by: Alexey Zaytsev <alexey.zaytsev@xxxxxxxxx>
---

Hi.

The patch adds fschange-like [1] modification ranges to
fsnotify events. Fanotify is made to pass the range
to the users.

This is useful for backup programs that work on huge files,
so that only a part of a modified file needs to be scanned
for changes.

Looking forwar for your coments on the approach.

You can also get the patch from
git://git.zaytsev.su/git/linux-2.6.git branch fsnotify

A modified fanotify-example is available from

git://git.zaytsev.su/git/fanotify-example.git branch range

[1] http://www.stefan.buettcher.org/cs/fschange/index.html

fs/nfsd/vfs.c | 2 +
fs/notify/fanotify/fanotify_user.c | 36 +++++++++++++++++++++--
fs/notify/fsnotify.c | 16 ++++++----
fs/notify/inode_mark.c | 2 +
fs/notify/inotify/inotify_user.c | 2 +
fs/notify/notification.c | 8 ++++-
fs/open.c | 2 +
fs/read_write.c | 4 +--
include/linux/fanotify.h | 15 +++++++++-
include/linux/fs.h | 10 ++++++
include/linux/fsnotify.h | 56 ++++++++++++++++++++++++++----------
include/linux/fsnotify_backend.h | 12 ++++++--
12 files changed, 128 insertions(+), 37 deletions(-)

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 184938f..d781014 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -1035,7 +1035,7 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
goto out_nfserr;
*cnt = host_err;
nfsdstats.io_write += host_err;
- fsnotify_modify(file);
+ fsnotify_modify(file, offset - host_err, host_err);

/* clear setuid/setgid flag after write */
if (inode->i_mode & (S_ISUID | S_ISGID))
diff --git a/fs/notify/fanotify/fanotify_user.c b/fs/notify/fanotify/fanotify_user.c
index 0632248..5d75dfa 100644
--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -31,6 +31,26 @@ struct fanotify_response_event {
struct fsnotify_event *event;
};

+#ifdef DEBUG
+static inline void dump_event_meta(const char *str, struct fanotify_event_metadata *meta)
+{
+ if (meta->mask & (FAN_MODIFY | FAN_CLOSE_WRITE))
+ printk("%s event_len=%d vers=%d mask=0x%lld fd=%d pid=%d"
+ " range_start=%lld range_end=%lld\n", str,
+ meta->event_len, meta->vers, meta->mask,
+ meta->fd, meta->pid, meta->range.start,
+ meta->range.end);
+ else
+ printk("%s event_len=%d vers=%d mask=0x%lld fd=%d pid=%d", str,
+ meta->event_len, meta->vers, meta->mask,
+ meta->fd, meta->pid);
+}
+#else
+static inline void dump_event_meta(const char *str, struct fanotify_event_metadata *meta)
+{
+}
+#endif
+
/*
* Get an fsnotify notification event if one exists and is small
* enough to fit in "count". Return an error pointer if the count
@@ -113,12 +133,20 @@ static ssize_t fill_event_metadata(struct fsnotify_group *group,
pr_debug("%s: group=%p metadata=%p event=%p\n", __func__,
group, metadata, event);

- metadata->event_len = FAN_EVENT_METADATA_LEN;
+ if (event->mask & (FS_MODIFY | FS_CLOSE_WRITE)) {
+ metadata->event_len = FAN_RANGE_EVENT_METADATA_LEN;
+ metadata->range.start = event->range.start;
+ metadata->range.end = event->range.end;
+ } else {
+ metadata->event_len = FAN_EVENT_METADATA_LEN;
+ }
+
metadata->vers = FANOTIFY_METADATA_VERSION;
metadata->mask = event->mask & FAN_ALL_OUTGOING_EVENTS;
metadata->pid = pid_vnr(event->tgid);
metadata->fd = create_fd(group, event);

+
return metadata->fd;
}

@@ -266,10 +294,12 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
goto out_close_fd;

ret = -EFAULT;
- if (copy_to_user(buf, &fanotify_event_metadata, FAN_EVENT_METADATA_LEN))
+ if (copy_to_user(buf, &fanotify_event_metadata, fanotify_event_metadata.event_len))
goto out_kill_access_response;

- return FAN_EVENT_METADATA_LEN;
+ dump_event_meta("copy_event_to_user: ", &fanotify_event_metadata);
+
+ return fanotify_event_metadata.event_len;

out_kill_access_response:
remove_access_response(group, event, fd);
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 20dc218..81444c2 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -108,10 +108,10 @@ int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask)

if (path)
ret = fsnotify(p_inode, mask, path, FSNOTIFY_EVENT_PATH,
- dentry->d_name.name, 0);
+ dentry->d_name.name, 0, NULL);
else
ret = fsnotify(p_inode, mask, dentry->d_inode, FSNOTIFY_EVENT_INODE,
- dentry->d_name.name, 0);
+ dentry->d_name.name, 0, NULL);
}

dput(parent);
@@ -126,6 +126,7 @@ static int send_to_group(struct inode *to_tell, struct vfsmount *mnt,
__u32 mask, void *data,
int data_is, u32 cookie,
const unsigned char *file_name,
+ struct fsnotify_range *range,
struct fsnotify_event **event)
{
struct fsnotify_group *group = NULL;
@@ -183,7 +184,7 @@ static int send_to_group(struct inode *to_tell, struct vfsmount *mnt,
if (!*event) {
*event = fsnotify_create_event(to_tell, mask, data,
data_is, file_name,
- cookie, GFP_KERNEL);
+ cookie, range, GFP_KERNEL);
if (!*event)
return -ENOMEM;
}
@@ -197,7 +198,8 @@ static int send_to_group(struct inode *to_tell, struct vfsmount *mnt,
* notification event in whatever means they feel necessary.
*/
int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
- const unsigned char *file_name, u32 cookie)
+ const unsigned char *file_name, u32 cookie,
+ struct fsnotify_range *range)
{
struct hlist_node *inode_node = NULL, *vfsmount_node = NULL;
struct fsnotify_mark *inode_mark = NULL, *vfsmount_mark = NULL;
@@ -256,17 +258,17 @@ int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
if (inode_group > vfsmount_group) {
/* handle inode */
ret = send_to_group(to_tell, NULL, inode_mark, NULL, mask, data,
- data_is, cookie, file_name, &event);
+ data_is, cookie, file_name, range, &event);
/* we didn't use the vfsmount_mark */
vfsmount_group = NULL;
} else if (vfsmount_group > inode_group) {
ret = send_to_group(to_tell, mnt, NULL, vfsmount_mark, mask, data,
- data_is, cookie, file_name, &event);
+ data_is, cookie, file_name, range, &event);
inode_group = NULL;
} else {
ret = send_to_group(to_tell, mnt, inode_mark, vfsmount_mark,
mask, data, data_is, cookie, file_name,
- &event);
+ range, &event);
}

if (ret && (mask & ALL_FSNOTIFY_PERM_EVENTS))
diff --git a/fs/notify/inode_mark.c b/fs/notify/inode_mark.c
index 4c29fcf..cd39df7 100644
--- a/fs/notify/inode_mark.c
+++ b/fs/notify/inode_mark.c
@@ -295,7 +295,7 @@ void fsnotify_unmount_inodes(struct list_head *list)
iput(need_iput_tmp);

/* for each watch, send FS_UNMOUNT and then remove it */
- fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
+ fsnotify(inode, FS_UNMOUNT, inode, FSNOTIFY_EVENT_INODE, NULL, 0, NULL);

fsnotify_inode_delete(inode);

diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 444c305..a5c2c69 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -524,7 +524,7 @@ void inotify_ignored_and_remove_idr(struct fsnotify_mark *fsn_mark,

ignored_event = fsnotify_create_event(NULL, FS_IN_IGNORED, NULL,
FSNOTIFY_EVENT_NONE, NULL, 0,
- GFP_NOFS);
+ NULL, GFP_NOFS);
if (!ignored_event)
return;

diff --git a/fs/notify/notification.c b/fs/notify/notification.c
index f39260f..29b989f 100644
--- a/fs/notify/notification.c
+++ b/fs/notify/notification.c
@@ -395,7 +395,8 @@ struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event)
*/
struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask, void *data,
int data_type, const unsigned char *name,
- u32 cookie, gfp_t gfp)
+ u32 cookie, struct fsnotify_range *range,
+ gfp_t gfp)
{
struct fsnotify_event *event;

@@ -421,6 +422,9 @@ struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
event->sync_cookie = cookie;
event->to_tell = to_tell;
event->data_type = data_type;
+ /* The range struct might be allocated on stack. */
+ if (range)
+ event->range = *range;

switch (data_type) {
case FSNOTIFY_EVENT_PATH: {
@@ -453,7 +457,7 @@ __init int fsnotify_notification_init(void)
fsnotify_event_holder_cachep = KMEM_CACHE(fsnotify_event_holder, SLAB_PANIC);

q_overflow_event = fsnotify_create_event(NULL, FS_Q_OVERFLOW, NULL,
- FSNOTIFY_EVENT_NONE, NULL, 0,
+ FSNOTIFY_EVENT_NONE, NULL, 0, NULL,
GFP_KERNEL);
if (!q_overflow_event)
panic("unable to allocate fsnotify q_overflow_event\n");
diff --git a/fs/open.c b/fs/open.c
index 4197b9e..b3c5b0a 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -675,6 +675,8 @@ static struct file *__dentry_open(struct dentry *dentry, struct vfsmount *mnt,
f->f_path.mnt = mnt;
f->f_pos = 0;
f->f_op = fops_get(inode->i_fop);
+ f->f_whatchanged.start = -1;
+ f->f_whatchanged.end = 0;
file_sb_list_add(f, inode->i_sb);

error = security_dentry_open(f, cred);
diff --git a/fs/read_write.c b/fs/read_write.c
index 431a0ed..913915d 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -384,7 +384,7 @@ ssize_t vfs_write(struct file *file, const char __user *buf, size_t count, loff_
else
ret = do_sync_write(file, buf, count, pos);
if (ret > 0) {
- fsnotify_modify(file);
+ fsnotify_modify(file, (*pos) - ret, ret);
add_wchar(current, ret);
}
inc_syscw(current);
@@ -700,7 +700,7 @@ out:
if (type == READ)
fsnotify_access(file);
else
- fsnotify_modify(file);
+ fsnotify_modify(file, (*pos) - ret, ret);
}
return ret;
}
diff --git a/include/linux/fanotify.h b/include/linux/fanotify.h
index 0f01214..a599517 100644
--- a/include/linux/fanotify.h
+++ b/include/linux/fanotify.h
@@ -91,6 +91,14 @@ struct fanotify_event_metadata {
__aligned_u64 mask;
__s32 fd;
__s32 pid;
+
+ /* Optional. Check event_len.*/
+ union {
+ struct {
+ __aligned_u64 start;
+ __aligned_u64 end;
+ } range;
+ };
};

struct fanotify_response {
@@ -102,8 +110,13 @@ struct fanotify_response {
#define FAN_ALLOW 0x01
#define FAN_DENY 0x02

+#ifndef __KERNEL__
+#include <stddef.h> /* For the userspace offsetof */
+#endif
+
/* Helper functions to deal with fanotify_event_metadata buffers */
-#define FAN_EVENT_METADATA_LEN (sizeof(struct fanotify_event_metadata))
+#define FAN_EVENT_METADATA_LEN (offsetof(struct fanotify_event_metadata, range))
+#define FAN_RANGE_EVENT_METADATA_LEN (sizeof(struct fanotify_event_metadata))

#define FAN_EVENT_NEXT(meta, len) ((len) -= (meta)->event_len, \
(struct fanotify_event_metadata*)(((char *)(meta)) + \
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 334d68a..702d360 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -922,6 +922,12 @@ static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
index < ra->start + ra->size);
}

+/* fsnotify wants to know, what has been changed during the file's lifetime. */
+struct fsnotify_range {
+ loff_t start;
+ loff_t end;
+};
+
#define FILE_MNT_WRITE_TAKEN 1
#define FILE_MNT_WRITE_RELEASED 2

@@ -965,6 +971,10 @@ struct file {
#ifdef CONFIG_DEBUG_WRITECOUNT
unsigned long f_mnt_write_state;
#endif
+
+#ifdef CONFIG_FSNOTIFY
+ struct fsnotify_range f_whatchanged;
+#endif
};

#define get_file(x) atomic_long_inc(&(x)->f_count)
diff --git a/include/linux/fsnotify.h b/include/linux/fsnotify.h
index 5c185fa..5c5cbaa 100644
--- a/include/linux/fsnotify.h
+++ b/include/linux/fsnotify.h
@@ -57,7 +57,8 @@ static inline int fsnotify_perm(struct file *file, int mask)
if (ret)
return ret;

- return fsnotify(inode, fsnotify_mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
+ return fsnotify(inode, fsnotify_mask, path, FSNOTIFY_EVENT_PATH,
+ NULL, 0, NULL);
}

/*
@@ -78,7 +79,7 @@ static inline void fsnotify_d_move(struct dentry *dentry)
*/
static inline void fsnotify_link_count(struct inode *inode)
{
- fsnotify(inode, FS_ATTRIB, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
+ fsnotify(inode, FS_ATTRIB, inode, FSNOTIFY_EVENT_INODE, NULL, 0, NULL);
}

/*
@@ -102,14 +103,17 @@ static inline void fsnotify_move(struct inode *old_dir, struct inode *new_dir,
new_dir_mask |= FS_ISDIR;
}

- fsnotify(old_dir, old_dir_mask, old_dir, FSNOTIFY_EVENT_INODE, old_name, fs_cookie);
- fsnotify(new_dir, new_dir_mask, new_dir, FSNOTIFY_EVENT_INODE, new_name, fs_cookie);
+ fsnotify(old_dir, old_dir_mask, old_dir, FSNOTIFY_EVENT_INODE,
+ old_name, fs_cookie, NULL);
+ fsnotify(new_dir, new_dir_mask, new_dir, FSNOTIFY_EVENT_INODE,
+ new_name, fs_cookie, NULL);

if (target)
fsnotify_link_count(target);

if (source)
- fsnotify(source, FS_MOVE_SELF, moved->d_inode, FSNOTIFY_EVENT_INODE, NULL, 0);
+ fsnotify(source, FS_MOVE_SELF, moved->d_inode, FSNOTIFY_EVENT_INODE,
+ NULL, 0, NULL);
audit_inode_child(moved, new_dir);
}

@@ -147,7 +151,7 @@ static inline void fsnotify_nameremove(struct dentry *dentry, int isdir)
*/
static inline void fsnotify_inoderemove(struct inode *inode)
{
- fsnotify(inode, FS_DELETE_SELF, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
+ fsnotify(inode, FS_DELETE_SELF, inode, FSNOTIFY_EVENT_INODE, NULL, 0, NULL);
__fsnotify_inode_delete(inode);
}

@@ -158,7 +162,8 @@ static inline void fsnotify_create(struct inode *inode, struct dentry *dentry)
{
audit_inode_child(dentry, inode);

- fsnotify(inode, FS_CREATE, dentry->d_inode, FSNOTIFY_EVENT_INODE, dentry->d_name.name, 0);
+ fsnotify(inode, FS_CREATE, dentry->d_inode, FSNOTIFY_EVENT_INODE,
+ dentry->d_name.name, 0, NULL);
}

/*
@@ -171,7 +176,8 @@ static inline void fsnotify_link(struct inode *dir, struct inode *inode, struct
fsnotify_link_count(inode);
audit_inode_child(new_dentry, dir);

- fsnotify(dir, FS_CREATE, inode, FSNOTIFY_EVENT_INODE, new_dentry->d_name.name, 0);
+ fsnotify(dir, FS_CREATE, inode, FSNOTIFY_EVENT_INODE,
+ new_dentry->d_name.name, 0, NULL);
}

/*
@@ -184,7 +190,8 @@ static inline void fsnotify_mkdir(struct inode *inode, struct dentry *dentry)

audit_inode_child(dentry, inode);

- fsnotify(inode, mask, d_inode, FSNOTIFY_EVENT_INODE, dentry->d_name.name, 0);
+ fsnotify(inode, mask, d_inode, FSNOTIFY_EVENT_INODE,
+ dentry->d_name.name, 0, NULL);
}

/*
@@ -201,25 +208,41 @@ static inline void fsnotify_access(struct file *file)

if (!(file->f_mode & FMODE_NONOTIFY)) {
fsnotify_parent(path, NULL, mask);
- fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
+ fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0, NULL);
}
}

+static inline void fsnotify_update_range(struct file *f, loff_t orig_fpos, size_t len)
+{
+ /* -1 => first modification. */
+ if (f->f_whatchanged.start == -1)
+ f->f_whatchanged.start = orig_fpos;
+ else
+ f->f_whatchanged.start = min(orig_fpos, f->f_whatchanged.start);
+
+ f->f_whatchanged.end = max(orig_fpos + len, f->f_whatchanged.start);
+}
+
/*
* fsnotify_modify - file was modified
*/
-static inline void fsnotify_modify(struct file *file)
+static inline void fsnotify_modify(struct file *file, loff_t original, size_t count)
{
struct path *path = &file->f_path;
struct inode *inode = path->dentry->d_inode;
__u32 mask = FS_MODIFY;
+ struct fsnotify_range range = {
+ .start = original,
+ .end = original + count,
+ };

+ fsnotify_update_range(file, original, count);
if (S_ISDIR(inode->i_mode))
mask |= FS_ISDIR;

if (!(file->f_mode & FMODE_NONOTIFY)) {
fsnotify_parent(path, NULL, mask);
- fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
+ fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0, &range);
}
}

@@ -239,7 +262,7 @@ static inline void fsnotify_open(struct file *file)
file->f_mode &= ~FMODE_NONOTIFY;

fsnotify_parent(path, NULL, mask);
- fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
+ fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0, NULL);
}

/*
@@ -257,7 +280,8 @@ static inline void fsnotify_close(struct file *file)

if (!(file->f_mode & FMODE_NONOTIFY)) {
fsnotify_parent(path, NULL, mask);
- fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH, NULL, 0);
+ fsnotify(inode, mask, path, FSNOTIFY_EVENT_PATH,
+ NULL, 0, &file->f_whatchanged);
}
}

@@ -273,7 +297,7 @@ static inline void fsnotify_xattr(struct dentry *dentry)
mask |= FS_ISDIR;

fsnotify_parent(NULL, dentry, mask);
- fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
+ fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE, NULL, 0, NULL);
}

/*
@@ -308,7 +332,7 @@ static inline void fsnotify_change(struct dentry *dentry, unsigned int ia_valid)
mask |= FS_ISDIR;

fsnotify_parent(NULL, dentry, mask);
- fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE, NULL, 0);
+ fsnotify(inode, mask, inode, FSNOTIFY_EVENT_INODE, NULL, 0, NULL);
}
}

diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 0a68f92..5348b54 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -240,6 +240,8 @@ struct fsnotify_event {
size_t name_len;
struct pid *tgid;

+ struct fsnotify_range range; /* What has been modified */
+
#ifdef CONFIG_FANOTIFY_ACCESS_PERMISSIONS
__u32 response; /* userspace answer to question */
#endif /* CONFIG_FANOTIFY_ACCESS_PERMISSIONS */
@@ -305,7 +307,8 @@ struct fsnotify_mark {

/* main fsnotify call to send events */
extern int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
- const unsigned char *name, u32 cookie);
+ const unsigned char *name, u32 cookie,
+ struct fsnotify_range *range);
extern int __fsnotify_parent(struct path *path, struct dentry *dentry, __u32 mask);
extern void __fsnotify_inode_delete(struct inode *inode);
extern void __fsnotify_vfsmount_delete(struct vfsmount *mnt);
@@ -420,7 +423,9 @@ extern void fsnotify_unmount_inodes(struct list_head *list);
extern struct fsnotify_event *fsnotify_create_event(struct inode *to_tell, __u32 mask,
void *data, int data_is,
const unsigned char *name,
- u32 cookie, gfp_t gfp);
+ u32 cookie,
+ struct fsnotify_range *range,
+ gfp_t gfp);

/* fanotify likes to change events after they are on lists... */
extern struct fsnotify_event *fsnotify_clone_event(struct fsnotify_event *old_event);
@@ -430,7 +435,8 @@ extern int fsnotify_replace_event(struct fsnotify_event_holder *old_holder,
#else

static inline int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
- const unsigned char *name, u32 cookie)
+ const unsigned char *name, u32 cookie,
+ struct fsnotify_range *range)
{
return 0;
}

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