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

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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: 983652c691 ("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: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Acked-by: Jan Kara <jack@suse.cz>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Message-Id: <604ec704d933e0e0121d9e107ce914512e045fad.1688393619.git.nabijaczleweli@nabijaczleweli.xyz>
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Ahelenia Ziemiańska 2023-07-03 16:42:13 +02:00 committed by Christian Brauner
parent ba38980add
commit 12ee4b66af
1 changed files with 16 additions and 18 deletions
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34
fs/splice.c
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@ -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;
return ret;
} else {
ret = -EINVAL;
}
return -EINVAL;
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 ret;
}
static long __do_splice(struct file *in, loff_t __user *off_in,