linux-kernel - [PATCH v2 1/3] splice: always fsnotify_access(in), fsnotify

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Message-ID: <al4pxc2uftonry5vyunx5qblllbaakjsehrc74fbbk7pxddyv7@gn3k55eldmmp>
Date:   Tue, 27 Jun 2023 01:09:00 +0200
From:   Ahelenia Ziemiańska 
        <nabijaczleweli@...ijaczleweli.xyz>
To:     Amir Goldstein <amir73il@...il.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Christian Brauner <brauner@...nel.org>,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jan Kara <jack@...e.cz>,
        Chung-Chiang Cheng <cccheng@...ology.com>
Subject: [PATCH v2 1/3] 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 used inotify, like coreutils tail -f.

Fixes: 983652c69199 ("splice: report related fsnotify events")
Link: https://lore.kernel.org/linux-fsdevel/jbyihkyk5dtaohdwjyivambb2gffyjs3dodpofafnkkunxq7bu@jngkdxx65pux/t/#u
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@...ijaczleweli.xyz>
Reviewed-by: Amir Goldstein <amir73il@...il.com>
---
No changes since v1 (except in the message).

 fs/splice.c | 21 ++++++++++++---------
 1 file changed, 12 insertions(+), 9 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 3e06611d19ae..94fae24f9d54 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1154,7 +1154,8 @@ 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);
+		ret = splice_pipe_to_pipe(ipipe, opipe, len, flags);
+		goto notify;
 	}
 
 	if (ipipe) {
@@ -1182,15 +1183,12 @@ 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;
+		goto notify;
 	}
 
 	if (opipe) {
@@ -1209,18 +1207,23 @@ 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;
+		goto notify;
 	}
 
 	return -EINVAL;
+
+notify:
+	if (ret > 0) {
+		fsnotify_access(in);
+		fsnotify_modify(out);
+	}
+
+	return ret;
 }
 
 static long __do_splice(struct file *in, loff_t __user *off_in,
-- 
2.39.2


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