Re: [RFC PATCH] network fs notification

[Miklos Szeredi <miklos@szeredi.hu>]

On Wed, May 01, 2019 at 04:55:41PM -0400, Miklos Szeredi wrote:
> This is a really really trivial first iteration, but I think it's enough to
> try out CIFS notification support.  Doesn't deal with mark deletion, but
> that's best effort anyway: fsnotify() will filter out unneeded events.

And this one actually does something for inotify.  I haven't tested fanotify
yet, but that one looks okay.

Note: FAN_MARK_MOUNT doesn't work yet, and we are not sure if it should work or
not.  FAN_MARK_FILESYSTEM would be a better candidate for remote notification,
since remote accesses are not associated with any particular local mount of the
filesystem.  But perhaps we need to turn on whole file notification for remote
due to the fact that applications rely on FAN_MARK_MOUNT already...  Btw, does the smb protocol support whole filesystem (or subtree) notifications?

Thanks,
Miklos

---
 fs/notify/fanotify/fanotify_user.c |    6 +++++-
 fs/notify/inotify/inotify_user.c   |    2 ++
 include/linux/fs.h                 |    1 +
 3 files changed, 8 insertions(+), 1 deletion(-)

--- a/fs/notify/fanotify/fanotify_user.c
+++ b/fs/notify/fanotify/fanotify_user.c
@@ -1041,9 +1041,13 @@ static int do_fanotify_mark(int fanotify
 		else if (mark_type == FAN_MARK_FILESYSTEM)
 			ret = fanotify_add_sb_mark(group, mnt->mnt_sb, mask,
 						   flags, fsid);
-		else
+		else {
 			ret = fanotify_add_inode_mark(group, inode, mask,
 						      flags, fsid);
+
+			if (!ret && inode->i_op->notify_update)
+				inode->i_op->notify_update(inode);
+		}
 		break;
 	case FAN_MARK_REMOVE:
 		if (mark_type == FAN_MARK_MOUNT)
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -754,6 +754,8 @@ SYSCALL_DEFINE3(inotify_add_watch, int,
 
 	/* create/update an inode mark */
 	ret = inotify_update_watch(group, inode, mask);
+	if (ret >= 0 && inode->i_op->notify_update)
+		inode->i_op->notify_update(inode);
 	path_put(&path);
 fput_and_out:
 	fdput(f);
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1852,6 +1852,7 @@ struct inode_operations {
 			   umode_t create_mode);
 	int (*tmpfile) (struct inode *, struct dentry *, umode_t);
 	int (*set_acl)(struct inode *, struct posix_acl *, int);
+	void (*notify_update)(struct inode *inode);
 } ____cacheline_aligned;
 
 static inline ssize_t call_read_iter(struct file *file, struct kiocb *kio,