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Date:   Tue, 27 Jun 2023 01:08:38 +0200
From:   =?utf-8?B?0L3QsNCx?= <nabijaczleweli@nabijaczleweli.xyz>
To:     Amir Goldstein <amir73il@gmail.com>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Christian Brauner <brauner@kernel.org>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        Jan Kara <jack@suse.cz>,
        Chung-Chiang Cheng <cccheng@synology.com>
Subject: [PATCH v2 0/3] fanotify accounting for fs/splice.c
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"people just forget to add inotify hooks to their I/O routines as a rule"?
Guess what I did, fully knowing that some are missing in this file :)

=3D=3D> te.c <=3D=3D
#define _GNU_SOURCE
#include <fcntl.h>
#include <stdio.h>
int main() {
  ssize_t rd, acc =3D 0;
  while ((rd =3D tee(0, 1, 128 * 1024 * 1024, 0)) > 0)
    acc +=3D rd;
  fprintf(stderr, "te=3D%zd: %m\n", acc);
}

=3D=3D> vm.c <=3D=3D
#define _GNU_SOURCE
#include <fcntl.h>
#include <stdio.h>
#include <string.h>
static char sb[1024 * 1024];
int main() {
  memcpy(sb, "=C5=BCupan", sizeof("=C5=BCupan"));
  ssize_t rd =3D
      vmsplice(1, &(struct iovec){.iov_base =3D sb, .iov_len =3D sizeof(sb)=
}, 1,
               SPLICE_F_GIFT);
  fprintf(stderr, "vm=3D%zd: %m\n", rd);
}


echo zupa | ./te > fifo tees a few times and then blocks when the pipe
fills, at which point we get into the broken state.

Similarly, ./vm > fifo (with the default 64k F_GETPIPE_SZ) enters that
same state instantly.

With 2/3 and 3/3, they instead do
  1: mask=3D2, cook=3D0, len=3D0, name=3D
  rd=3D80
  1: mask=3D2, cook=3D0, len=3D0, name=3D
  rd=3D80
  ...
in a loop, as-expected, and=20
  # ./vm > fifo
  vm=3D65200: Success
  1: mask=3D2, cook=3D0, len=3D0, name=3D
  rd=3D65200

I took the liberty of marking 2/3 and 3/3 as Fixes: of the original
fanotify-in-splice commit as well, I think they fit the bill.

Ahelenia Ziemia=C5=84ska (3):
  splice: always fsnotify_access(in), fsnotify_modify(out) on success
  splice: fsnotify_modify(fd) in vmsplice
  splice: fsnotify_access(in), fsnotify_modify(out) on success in tee

 fs/splice.c | 29 ++++++++++++++++++++---------
 1 file changed, 20 insertions(+), 9 deletions(-)

--=20
2.39.2

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