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...@1wt.eu> Cc: Vegard Nossum <vegard.nos...@oracle.com> Cc: socketp...@gmail.com Cc: Tetsuo Handa <penguin-ker...@i-love.sakura.ne.jp> Cc: Jens Axboe <ax...@fb.com> Cc: Al Viro <v...@zeniv.linux.org.uk> Cc: linux-...@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: Michael Kerrisk <mtk.manpa...@gmail.com> --- 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