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.
Cc: Willy Tarreau <w@xxxxxx>
Cc: Vegard Nossum <vegard.nossum@xxxxxxxxxx>
Cc: socketpair@xxxxxxxxx
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: linux-api@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
Signed-off-by: Michael Kerrisk <mtk.manpages@xxxxxxxxx>
---
fs/pipe.c | 34 +++++++++++++++++-----------------
1 file changed, 17 insertions(+), 17 deletions(-)
diff --git a/fs/pipe.c b/fs/pipe.c
index 705d79f..ada1777 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -604,22 +604,20 @@ 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 num_bufs)
{
- return pipe_user_pages_soft &&
- atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_soft;
+ return pipe_user_pages_soft && num_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 num_bufs)
{
- return pipe_user_pages_hard &&
- atomic_long_read(&user->pipe_bufs) >= pipe_user_pages_hard;
+ return pipe_user_pages_hard && num_bufs >= pipe_user_pages_hard;
}
struct pipe_inode_info *alloc_pipe_info(void)
@@ -627,17 +625,18 @@ 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 num_bufs;
pipe = kzalloc(sizeof(struct pipe_inode_info), GFP_KERNEL_ACCOUNT);
if (pipe == NULL)
goto out_free_uid;
- if (too_many_pipe_buffers_soft(user))
+ if (too_many_pipe_buffers_soft(atomic_long_read(&user->pipe_bufs)))
pipe_bufs = 1;
- account_pipe_buffers(user, 0, pipe_bufs);
+ num_bufs = account_pipe_buffers(user, 0, pipe_bufs);
- if (too_many_pipe_buffers_hard(user))
+ if (too_many_pipe_buffers_hard(num_bufs))
goto out_revert_acct;
pipe->bufs = kcalloc(pipe_bufs, sizeof(struct pipe_buffer),
@@ -653,7 +652,7 @@ 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);
@@ -664,7 +663,7 @@ 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;
@@ -1035,6 +1034,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
{
struct pipe_buffer *bufs;
unsigned int size, nr_pages;
+ unsigned long num_bufs;
long ret = 0;
size = round_pipe_size(arg);
@@ -1043,7 +1043,7 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
if (!nr_pages)
return -EINVAL;
- account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
+ num_bufs = account_pipe_buffers(pipe->user, pipe->buffers, nr_pages);
/*
* If trying to increase the pipe capacity, check that an
@@ -1055,8 +1055,8 @@ static long pipe_set_size(struct pipe_inode_info *pipe, unsigned long arg)
if (!capable(CAP_SYS_RESOURCE) && size > pipe_max_size) {
ret = -EPERM;
goto out_revert_acct;
- } else if ((too_many_pipe_buffers_hard(pipe->user) ||
- too_many_pipe_buffers_soft(pipe->user)) &&
+ } else if ((too_many_pipe_buffers_hard(num_bufs) ||
+ too_many_pipe_buffers_soft(num_bufs)) &&
!capable(CAP_SYS_RESOURCE) &&
!capable(CAP_SYS_ADMIN)) {
ret = -EPERM;
@@ -1110,7 +1110,7 @@ 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;
}
--
2.5.5
--
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