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pipe: make account_pipe_buffers() return a value, and use it

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This is an optional patch, to provide a small performance
improvement.  Alter account_pipe_buffers() so that it returns the
new value in user->pipe_bufs. This means that we can refactor
too_many_pipe_buffers_soft() and too_many_pipe_buffers_hard() to
avoid the costs of repeated use of atomic_long_read() to get the
value user->pipe_bufs.

Link: http://lkml.kernel.org/r/93e5f193-1e5e-3e1f-3a20-eae79b7e1310@gmail.com
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Reviewed-by: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Willy Tarreau <w@1wt.eu>
Cc: <socketpair@gmail.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jens Axboe <axboe@fb.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Michael Kerrisk (man-pages) 2016-10-11 13:53:40 -07:00 committed by Linus Torvalds
parent a005ca0e68
commit 9c87bcf0a3
1 changed files with 18 additions and 18 deletions
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36
fs/pipe.c
View File

@ -601,22 +601,20 @@ pipe_fasync(int fd, struct file *filp, int on)
return retval;
}
static void account_pipe_buffers(struct user_struct *user,
static unsigned long account_pipe_buffers(struct user_struct *user,
unsigned long old, unsigned long new)
{
atomic_long_add(new - old, &user->pipe_bufs);
return atomic_long_add_return(new - old, &user->pipe_bufs);
}
static bool too_many_pipe_buffers_soft(struct user_struct *user)
static bool too_many_pipe_buffers_soft(unsigned long user_bufs)
{
return pipe_user_pages_soft &&
atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_soft;
return pipe_user_pages_soft && user_bufs >= pipe_user_pages_soft;
}
static bool too_many_pipe_buffers_hard(struct user_struct *user)
static bool too_many_pipe_buffers_hard(unsigned long user_bufs)
{
return pipe_user_pages_hard &&
atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_hard;
return pipe_user_pages_hard && user_bufs >= pipe_user_pages_hard;
}
struct pipe_inode_info *alloc_pipe_info(void)
@ -624,19 +622,20 @@ 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();
unsigned long user_bufs;
pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
if (pipe == NULL)
goto out_free_uid;
account_pipe_buffers(user, 0, pipe_bufs);
user_bufs = account_pipe_buffers(user, 0, pipe_bufs);
if (too_many_pipe_buffers_soft(user)) {
account_pipe_buffers(user, pipe_bufs, 1);
if (too_many_pipe_buffers_soft(user_bufs)) {
user_bufs = account_pipe_buffers(user, pipe_bufs, 1);
pipe_bufs = 1;
}
if (too_many_pipe_buffers_hard(user))
if (too_many_pipe_buffers_hard(user_bufs))
goto out_revert_acct;
pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
@ -652,7 +651,7 @@ struct pipe_inode_info *alloc_pipe_info(void)
}
out_revert_acct:
account_pipe_buffers(user, pipe_bufs, 0);
(void) account_pipe_buffers(user, pipe_bufs, 0);
kfree(pipe);
out_free_uid:
free_uid(user);
@ -663,7 +662,7 @@ void free_pipe_info(struct pipe_inode_info *pipe)
{
int i;
account_pipe_buffers(pipe->user, pipe->buffers, 0);
(void) 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;
@ -1034,6 +1033,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
{
struct pipe_buffer *bufs;
unsigned int size, nr_pages;
unsigned long user_bufs;
long ret = 0;
size = round_pipe_size(arg);
@ -1053,11 +1053,11 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
size > pipe_max_size && !capable(CAP_SYS_RESOURCE))
return -EPERM;
account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
user_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
if (nr_pages > pipe->buffers &&
(too_many_pipe_buffers_hard(pipe->user) ||
too_many_pipe_buffers_soft(pipe->user)) &&
(too_many_pipe_buffers_hard(user_bufs) ||
too_many_pipe_buffers_soft(user_bufs)) &&
!capable(CAP_SYS_RESOURCE) && !capable(CAP_SYS_ADMIN)) {
ret = -EPERM;
goto out_revert_acct;
@ -1109,7 +1109,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
return nr_pages * PAGE_SIZE;
out_revert_acct:
account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
(void) account_pipe_buffers(pipe->user, nr_pages, pipe->buffers);
return ret;
}