linux-kernel - [PATCH v2 3/8] pipe: refactor argument for account_pipe

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Date:   Mon, 29 Aug 2016 12:21:21 +1200
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     mtk.manpages@...il.com, Willy Tarreau <w@....eu>,
        Vegard Nossum <vegard.nossum@...cle.com>, socketpair@...il.com,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        Jens Axboe <axboe@...com>, Al Viro <viro@...iv.linux.org.uk>,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v2 3/8] pipe: refactor argument for account_pipe_buffers()

This is a preparatory patch for following work. account_pipe_buffers()
performs accounting in the 'user_struct'. There is no need to pass a
pointer to a 'pipe_inode_info' struct (which is then dereferenced to
obtain a pointer to the 'user' field). Instead, pass a pointer directly
to the 'user_struct'. This change is needed in preparation for a
subsequent patch that the fixes the limit checking in alloc_pipe_info()
(and the resulting code is a little more logical).

Cc: Willy Tarreau <w@....eu>
Cc: Vegard Nossum <vegard.nossum@...cle.com>
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>
Cc: linux-api@...r.kernel.org
Cc: linux-kernel@...r.kernel.org
Signed-off-by: Michael Kerrisk <mtk.manpages@...il.com>
---
 fs/pipe.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/fs/pipe.c b/fs/pipe.c
index 4b98fd0..37b7f5e 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -604,10 +604,10 @@ pipe_fasync(int fd, struct file *filp, int on)
 	return retval;
 }
 
-static void account_pipe_buffers(struct pipe_inode_info *pipe,
+static void account_pipe_buffers(struct user_struct *user,
                                  unsigned long old, unsigned long new)
 {
-	atomic_long_add(new - old, &pipe->user->pipe_bufs);
+	atomic_long_add(new - old, &user->pipe_bufs);
 }
 
 static bool too_many_pipe_buffers_soft(struct user_struct *user)
@@ -644,7 +644,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
 			pipe->r_counter = pipe->w_counter = 1;
 			pipe->buffers = pipe_bufs;
 			pipe->user = user;
-			account_pipe_buffers(pipe, 0, pipe_bufs);
+			account_pipe_buffers(user, 0, pipe_bufs);
 			mutex_init(&pipe->mutex);
 			return pipe;
 		}
@@ -659,7 +659,7 @@ void free_pipe_info(struct pipe_inode_info *pipe)
 {
 	int i;
 
-	account_pipe_buffers(pipe, pipe->buffers, 0);
+	account_pipe_buffers(pipe->user, pipe->buffers, 0);
 	free_uid(pipe->user);
 	for (i = 0; i < pipe->buffers; i++) {
 		struct pipe_buffer *buf = pipe->bufs + i;
@@ -1080,7 +1080,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
 			memcpy(bufs + head, pipe->bufs, tail * sizeof(struct pipe_buffer));
 	}
 
-	account_pipe_buffers(pipe, pipe->buffers, nr_pages);
+	account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
 	pipe->curbuf = 0;
 	kfree(pipe->bufs);
 	pipe->bufs = bufs;
-- 
2.5.5