Re: [PATCH 1/2] NFSD: Fix duplicate fsnotify access events for iterator READs

[Chuck Lever]

On Wed, Aug 19, 2026, at 2:02 AM, Christoph Hellwig wrote:
> Well, that is the underlying bug here.  ->splice_read should not                                                                       
> skip fsnotify events and nfsd should not work around this as
> fsnotify is not the business of the users of VFS APIs.

I asked for the duplicate event to be split out of Ameer's larger
series as a backportable fix because there is clearly a bug here.
But NFSD might not be the correct place to address it.

Today the fsnotify event comes from the system call implementations,
not from the splice helpers. do_sendfile() calls fsnotify_access()
once do_splice_direct() returns, and do_splice() does the same for
splice(2), while vfs_splice_read() and splice_direct_to_actor()
emit nothing. vfs_iocb_iter_read() is the outlier, emitting from
inside the helper.

NFSD calls splice_direct_to_actor() directly, so on that path it
acts like do_sendfile() and emits the event itself. That is why
the fsnotify event counts differ between NFSD's two read paths.
Moving the fsnotify call site down into ->splice_read would double
up sendfile events unless the system call implementations stop
emitting it at the same time.

Jan, Amir, what are your thoughts?

-- 
Chuck Lever