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Subject[PATCH 13/18] relay: use splice_to_pipe() instead of open-coding the pipe loop
Date
It cleans up the relay splice implementation a lot, and gets rid of
a lot of internal pipe knowledge that should not be in there.

Plus fixes for padding and partial first page (and lots more) from
Tom Zanussi.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
---
kernel/relay.c | 146 +++++++++++++++++++++-----------------------------------
1 files changed, 55 insertions(+), 91 deletions(-)

diff --git a/kernel/relay.c b/kernel/relay.c
index ae13040..0c2971e 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -1025,19 +1025,23 @@ static ssize_t relay_file_read(struct file *filp,
NULL, &desc);
}

+static void relay_consume_bytes(struct rchan_buf *rbuf, int bytes_consumed)
+{
+ rbuf->bytes_consumed += bytes_consumed;
+
+ if (rbuf->bytes_consumed >= rbuf->chan->subbuf_size) {
+ relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
+ rbuf->bytes_consumed %= rbuf->chan->subbuf_size;
+ }
+}
+
static void relay_pipe_buf_release(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
{
struct rchan_buf *rbuf;

rbuf = (struct rchan_buf *)page_private(buf->page);
-
- rbuf->bytes_consumed += PAGE_SIZE;
-
- if (rbuf->bytes_consumed == rbuf->chan->subbuf_size) {
- relay_subbufs_consumed(rbuf->chan, rbuf->cpu, 1);
- rbuf->bytes_consumed = 0;
- }
+ relay_consume_bytes(rbuf, buf->private);
}

static struct pipe_buf_operations relay_pipe_buf_ops = {
@@ -1060,118 +1064,79 @@ static int subbuf_splice_actor(struct file *in,
unsigned int flags,
int *nonpad_ret)
{
- unsigned int pidx, poff;
- unsigned int subbuf_pages;
- int ret = 0;
- int do_wakeup = 0;
+ unsigned int pidx, poff, total_len, subbuf_pages, ret;
struct rchan_buf *rbuf = in->private_data;
unsigned int subbuf_size = rbuf->chan->subbuf_size;
size_t read_start = ((size_t)*ppos) % rbuf->chan->alloc_size;
- size_t avail = subbuf_size - read_start % subbuf_size;
size_t read_subbuf = read_start / subbuf_size;
size_t padding = rbuf->padding[read_subbuf];
size_t nonpad_end = read_subbuf * subbuf_size + subbuf_size - padding;
+ struct page *pages[PIPE_BUFFERS];
+ struct partial_page partial[PIPE_BUFFERS];
+ struct splice_pipe_desc spd = {
+ .pages = pages,
+ .nr_pages = 0,
+ .partial = partial,
+ .flags = flags,
+ .ops = &relay_pipe_buf_ops,
+ };

if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
return 0;

- if (len > avail)
- len = avail;
-
- if (pipe->inode)
- mutex_lock(&pipe->inode->i_mutex);
+ /*
+ * Adjust read len, if longer than what is available
+ */
+ if (len > (subbuf_size - read_start % subbuf_size))
+ len = subbuf_size - read_start % subbuf_size;

subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
pidx = (read_start / PAGE_SIZE) % subbuf_pages;
poff = read_start & ~PAGE_MASK;

- for (;;) {
- unsigned int this_len;
- unsigned int this_end;
- int newbuf = (pipe->curbuf + pipe->nrbufs) & (PIPE_BUFFERS - 1);
- struct pipe_buffer *buf = pipe->bufs + newbuf;
+ for (total_len = 0; spd.nr_pages < subbuf_pages; spd.nr_pages++) {
+ unsigned int this_len, this_end, private;
+ unsigned int cur_pos = read_start + total_len;

- if (!pipe->readers) {
- send_sig(SIGPIPE, current, 0);
- if (!ret)
- ret = -EPIPE;
+ if (!len)
break;
- }
-
- if (pipe->nrbufs < PIPE_BUFFERS) {
- this_len = PAGE_SIZE - poff;
- if (this_len > avail)
- this_len = avail;
-
- buf->page = rbuf->page_array[pidx];
- buf->offset = poff;
- this_end = read_start + ret + this_len;
- if (this_end > nonpad_end) {
- if (read_start + ret >= nonpad_end)
- buf->len = 0;
- else
- buf->len = nonpad_end - (read_start + ret);
- } else
- buf->len = this_len;
-
- *nonpad_ret += buf->len;
-
- buf->ops = &relay_pipe_buf_ops;
- pipe->nrbufs++;

- avail -= this_len;
- ret += this_len;
- poff = 0;
- pidx = (pidx + 1) % subbuf_pages;
+ this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
+ private = this_len;

- if (pipe->inode)
- do_wakeup = 1;
+ spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
+ spd.partial[spd.nr_pages].offset = poff;

- if (!avail)
- break;
-
- if (pipe->nrbufs < PIPE_BUFFERS)
- continue;
-
- break;
+ this_end = cur_pos + this_len;
+ if (this_end >= nonpad_end) {
+ this_len = nonpad_end - cur_pos;
+ private = this_len + padding;
}
+ spd.partial[spd.nr_pages].len = this_len;
+ spd.partial[spd.nr_pages].private = private;

- if (flags & SPLICE_F_NONBLOCK) {
- if (!ret)
- ret = -EAGAIN;
- break;
- }
+ len -= this_len;
+ total_len += this_len;
+ poff = 0;
+ pidx = (pidx + 1) % subbuf_pages;

- if (signal_pending(current)) {
- if (!ret)
- ret = -ERESTARTSYS;
+ if (this_end >= nonpad_end) {
+ spd.nr_pages++;
break;
}
-
- if (do_wakeup) {
- smp_mb();
- if (waitqueue_active(&pipe->wait))
- wake_up_interruptible_sync(&pipe->wait);
- kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
- do_wakeup = 0;
- }
-
- pipe->waiting_writers++;
- pipe_wait(pipe);
- pipe->waiting_writers--;
}

- if (pipe->inode)
- mutex_unlock(&pipe->inode->i_mutex);
+ if (!spd.nr_pages)
+ return 0;

- if (do_wakeup) {
- smp_mb();
- if (waitqueue_active(&pipe->wait))
- wake_up_interruptible(&pipe->wait);
- kill_fasync(&pipe->fasync_readers, SIGIO, POLL_IN);
- }
+ ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
+ if (ret < 0 || ret < total_len)
+ return ret;

- return ret;
+ if (read_start + ret == nonpad_end)
+ ret += padding;
+
+ return ret;
}

static ssize_t relay_file_splice_read(struct file *in,
@@ -1192,7 +1157,6 @@ static ssize_t relay_file_splice_read(struct file *in,
if (ret < 0)
break;
else if (!ret) {
- break;
if (spliced)
break;
if (flags & SPLICE_F_NONBLOCK) {
--
1.5.2.1.174.gcd03
-
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