3.16.57-rc1 review patch. If anyone has any objections, please let me know.
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From: "Michael Kerrisk (man-pages)" mtk.manpages@gmail.com
commit 9c87bcf0a31b338dc8a69a5d251a037565a94e13 upstream.
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 Signed-off-by: Ben Hutchings ben@decadent.org.uk --- fs/pipe.c | 36 ++++++++++++++++++------------------ 1 file changed, 18 insertions(+), 18 deletions(-)
--- a/fs/pipe.c +++ b/fs/pipe.c @@ -590,22 +590,20 @@ pipe_fasync(int fd, struct file *filp, i 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) @@ -613,19 +611,20 @@ struct pipe_inode_info *alloc_pipe_info( 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); 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), @@ -641,7 +640,7 @@ struct pipe_inode_info *alloc_pipe_info( }
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); @@ -652,7 +651,7 @@ void free_pipe_info(struct pipe_inode_in { 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; @@ -1022,6 +1021,7 @@ static long pipe_set_size(struct pipe_in { struct pipe_buffer *bufs; unsigned int size, nr_pages; + unsigned long user_bufs; long ret = 0;
size = round_pipe_size(arg); @@ -1041,11 +1041,11 @@ static long pipe_set_size(struct pipe_in 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; @@ -1096,7 +1096,7 @@ static long pipe_set_size(struct pipe_in 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; }