[PATCH] splice: speedups and optimizations

- Kill the local variables that cache ->nrbufs, they just take up space.

- Only set do_wakeup for a real pipe. This is a big win for direct splicing.

- Kill i_mutex lock around ->f_pos update, regular io paths don't do this
  either.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 13 insertions, 20 deletions

diff --git a/fs/splice.c b/fs/splice.c
index e30743c2c06a..36bc262dfbd5 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -150,8 +150,6 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
                 mutex_lock(&pipe->inode->i_mutex);
 
         for (;;) {
-                int bufs;
-
                 if (!pipe->readers) {
                         send_sig(SIGPIPE, current, 0);
                         if (!ret)
@@ -159,9 +157,8 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
                         break;
                 }
 
-                bufs = pipe->nrbufs;
-                if (bufs < PIPE_BUFFERS) {
-                        int newbuf = (pipe->curbuf + bufs) & (PIPE_BUFFERS - 1);
+                if (pipe->nrbufs < PIPE_BUFFERS) {
+                        int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
                         struct pipe_buffer *buf = pipe->bufs + newbuf;
                         struct page *page = pages[i++];
                         unsigned long this_len;
@@ -174,8 +171,9 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
                         buf->offset = offset;
                         buf->len = this_len;
                         buf->ops = &page_cache_pipe_buf_ops;
-                        pipe->nrbufs = ++bufs;
-                        do_wakeup = 1;
+                        pipe->nrbufs++;
+                        if (pipe->inode)
+                                do_wakeup = 1;
 
                         ret += this_len;
                         len -= this_len;
@@ -184,7 +182,7 @@ static ssize_t move_to_pipe(struct pipe_inode_info *pipe, struct page **pages,
                                 break;
                         if (!len)
                                 break;
-                        if (bufs < PIPE_BUFFERS)
+                        if (pipe->nrbufs < PIPE_BUFFERS)
                                 continue;
 
                         break;
@@ -581,11 +579,8 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                 mutex_lock(&pipe->inode->i_mutex);
 
         for (;;) {
-                int bufs = pipe->nrbufs;
-
-                if (bufs) {
-                        int curbuf = pipe->curbuf;
-                        struct pipe_buffer *buf = pipe->bufs + curbuf;
+                if (pipe->nrbufs) {
+                        struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
                         struct pipe_buf_operations *ops = buf->ops;
 
                         sd.len = buf->len;
@@ -606,10 +601,10 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                         if (!buf->len) {
                                 buf->ops = NULL;
                                 ops->release(pipe, buf);
-                                curbuf = (curbuf + 1) & (PIPE_BUFFERS - 1);
-                                pipe->curbuf = curbuf;
-                                pipe->nrbufs = --bufs;
-                                do_wakeup = 1;
+                                pipe->curbuf = (pipe->curbuf + 1) & (PIPE_BUFFERS - 1);
+                                pipe->nrbufs--;
+                                if (pipe->inode)
+                                        do_wakeup = 1;
                         }
 
                         sd.pos += sd.len;
@@ -618,7 +613,7 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                                 break;
                 }
 
-                if (bufs)
+                if (pipe->nrbufs)
                         continue;
                 if (!pipe->writers)
                         break;
@@ -660,9 +655,7 @@ static ssize_t move_from_pipe(struct pipe_inode_info *pipe, struct file *out,
                 kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT);
         }
 
-        mutex_lock(&out->f_mapping->host->i_mutex);
         out->f_pos = sd.pos;
-        mutex_unlock(&out->f_mapping->host->i_mutex);
         return ret;
 
 }