linux-kernel - [PATCH 3.16 203/410] pipe: simplify logic in alloc_pipe

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Date:   Thu, 07 Jun 2018 15:05:21 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org,
        "Linus Torvalds" <torvalds@...ux-foundation.org>,
        "Tetsuo Handa" <penguin-kernel@...ove.SAKURA.ne.jp>,
        "Vegard Nossum" <vegard.nossum@...cle.com>,
        "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>,
        "" <socketpair@...il.com>, "Al Viro" <viro@...iv.linux.org.uk>,
        "Willy Tarreau" <w@....eu>, "Jens Axboe" <axboe@...com>
Subject: [PATCH 3.16 203/410] pipe: simplify logic in alloc_pipe_info()

3.16.57-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>

commit 09b4d1990094dd22c27fb0163534db419458569c upstream.

Replace an 'if' block that covers most of the code in this function
with a 'goto'. This makes the code a little simpler to read, and also
simplifies the next patch (fix limit checking in alloc_pipe_info())

Link: http://lkml.kernel.org/r/aef030c1-0257-98a9-4988-186efa48530c@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@...il.com>
Reviewed-by: Vegard Nossum <vegard.nossum@...cle.com>
Cc: Willy Tarreau <w@....eu>
Cc: <socketpair@...il.com>
Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@...com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
[bwh: Backported to 3.16:
 - Don't use GFP_KERNEL_ACCOUNT
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -611,31 +611,34 @@ static bool too_many_pipe_buffers_hard(s
 struct pipe_inode_info *alloc_pipe_info(void)
 {
 	struct pipe_inode_info *pipe;
+	unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
+	struct user_struct *user = get_current_user();
 
 	pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL);
-	if (pipe) {
-		unsigned long pipe_bufs = PIPE_DEF_BUFFERS;
-		struct user_struct *user = get_current_user();
+	if (pipe == NULL)
+		goto out_free_uid;
 
-		if (!too_many_pipe_buffers_hard(user)) {
-			if (too_many_pipe_buffers_soft(user))
-				pipe_bufs = 1;
-			pipe->bufs = kzalloc(sizeof(struct pipe_buffer) * pipe_bufs, GFP_KERNEL);
-		}
+	if (!too_many_pipe_buffers_hard(user)) {
+		if (too_many_pipe_buffers_soft(user))
+			pipe_bufs = 1;
+		pipe->bufs = kcalloc(pipe_bufs,
+				     sizeof(struct pipe_buffer),
+				     GFP_KERNEL);
+	}
 
-		if (pipe->bufs) {
-			init_waitqueue_head(&pipe->wait);
-			pipe->r_counter = pipe->w_counter = 1;
-			pipe->buffers = pipe_bufs;
-			pipe->user = user;
-			account_pipe_buffers(user, 0, pipe_bufs);
-			mutex_init(&pipe->mutex);
-			return pipe;
-		}
-		free_uid(user);
-		kfree(pipe);
+	if (pipe->bufs) {
+		init_waitqueue_head(&pipe->wait);
+		pipe->r_counter = pipe->w_counter = 1;
+		pipe->buffers = pipe_bufs;
+		pipe->user = user;
+		account_pipe_buffers(user, 0, pipe_bufs);
+		mutex_init(&pipe->mutex);
+		return pipe;
 	}
 
+	kfree(pipe);
+out_free_uid:
+	free_uid(user);
 	return NULL;
 }