6.5-stable review patch. If anyone has any objections, please let me know.
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From: Ahelenia Ziemiańska nabijaczleweli@nabijaczleweli.xyz
[ Upstream commit 12ee4b66af34f8e72f3b2fd93a946a955efe7c86 ]
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: 983652c69199 ("splice: report related fsnotify events") Link: https://lore.kernel.org/linux-fsdevel/jbyihkyk5dtaohdwjyivambb2gffyjs3dodpof... 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 Signed-off-by: Sasha Levin sashal@kernel.org --- fs/splice.c | 32 +++++++++++++++----------------- 1 file changed, 15 insertions(+), 17 deletions(-)
diff --git a/fs/splice.c b/fs/splice.c index 3e2a31e1ce6a8..53831eb0fefa8 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -1269,10 +1269,8 @@ 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) { @@ -1297,18 +1295,11 @@ 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) { @@ -1324,18 +1315,25 @@ 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,