Commit 12ee4b66 authored by Ahelenia Ziemiańska's avatar Ahelenia Ziemiańska Committed by Christian Brauner
Browse files

splice: always fsnotify_access(in), fsnotify_modify(out) on success 

The current behaviour caused an asymmetry where some write APIs
(write, sendfile) would notify the written-to/read-from objects,
but splice wouldn't.

This affected userspace which uses inotify, most notably coreutils
tail -f, to monitor pipes.
If the pipe buffer had been filled by a splice-family function:
  * tail wouldn't know and thus wouldn't service the pipe, and
  * all writes to the pipe would block because it's full,
thus service was denied.
(For the particular case of tail -f this could be worked around
 with ---disable-inotify.)

Fixes: 983652c6 ("splice: report related fsnotify events")
Link: https://lore.kernel.org/linux-fsdevel/jbyihkyk5dtaohdwjyivambb2gffyjs3dodpofafnkkunxq7bu@jngkdxx65pux/t/#u
Link: https://bugs.debian.org/1039488


Signed-off-by: default avatarAhelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Acked-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarAmir Goldstein <amir73il@gmail.com>
Message-Id: <604ec704d933e0e0121d9e107ce914512e045fad.1688393619.git.nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: default avatarChristian Brauner <brauner@kernel.org>
parent ba38980a

fs/splice.c

+15 −17
Original line number Diff line number Diff line
@@ -1267,10 +1267,8 @@ long do_splice(struct file *in, loff_t *off_in, struct file *out, 
		if ((in->f_flags | out->f_flags) & O_NONBLOCK)

			flags |= SPLICE_F_NONBLOCK;



		return splice_pipe_to_pipe(ipipe, opipe, len, flags);

	}



	if (ipipe) {

		ret = splice_pipe_to_pipe(ipipe, opipe, len, flags);

	} else if (ipipe) {

		if (off_in)

			return -ESPIPE;

		if (off_out) {
@@ -1295,18 +1293,11 @@ long do_splice(struct file *in, loff_t *off_in, struct file *out, 
		ret = do_splice_from(ipipe, out, &offset, len, flags);

		file_end_write(out);



		if (ret > 0)

			fsnotify_modify(out);



		if (!off_out)

			out->f_pos = offset;

		else

			*off_out = offset;



		return ret;

	}



	if (opipe) {

	} else if (opipe) {

		if (off_out)

			return -ESPIPE;

		if (off_in) {
@@ -1322,18 +1313,25 @@ long do_splice(struct file *in, loff_t *off_in, struct file *out, 


		ret = splice_file_to_pipe(in, opipe, &offset, len, flags);



		if (ret > 0)

			fsnotify_access(in);



		if (!off_in)

			in->f_pos = offset;

		else

			*off_in = offset;

	} else {

		ret = -EINVAL;

	}



		return ret;

	if (ret > 0) {

		/*

		 * Generate modify out before access in:

		 * do_splice_from() may've already sent modify out,

		 * and this ensures the events get merged.

		 */

		fsnotify_modify(out);

		fsnotify_access(in);

	}



	return -EINVAL;

	return ret;

}



static long __do_splice(struct file *in, loff_t __user *off_in,