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Date: Sat, 27 Sep 2008 01:18:15 -0500
From: Tom Zanussi <zanussi@...cast.net>
To: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: Martin Bligh <mbligh@...gle.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
prasad@...ux.vnet.ibm.com,
Linus Torvalds <torvalds@...ux-foundation.org>,
Thomas Gleixner <tglx@...utronix.de>,
Mathieu Desnoyers <compudj@...stal.dyndns.org>,
Steven Rostedt <rostedt@...dmis.org>, od@...e.com,
"Frank Ch. Eigler" <fche@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>, hch@....de,
David Wilder <dwilder@...ibm.com>
Subject: [RFC PATCH 7/10] relay - Remove padding-related code from
relay_read()/relay_splice_read() et al.
Remove padding-related code from relay_read()/relay_splice_read() et al.
Because we no longer write padding, we no longer have to read it or
account for it anywhere else, greatly simplifying the related code.
---
kernel/relay.c | 149 ++++++++------------------------------------------------
1 files changed, 20 insertions(+), 129 deletions(-)
diff --git a/kernel/relay.c b/kernel/relay.c
index d382528..b55466d 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -965,72 +965,13 @@ static void relay_file_read_consume(struct rchan_buf *buf,
size_t bytes_consumed)
{
size_t subbuf_size = buf->chan->subbuf_size;
- size_t n_subbufs = buf->chan->n_subbufs;
- size_t read_subbuf;
-
- if (buf->subbufs_produced == buf->subbufs_consumed &&
- buf->offset == buf->bytes_consumed)
- return;
-
- if (buf->bytes_consumed + bytes_consumed > subbuf_size) {
- relay_subbufs_consumed(buf->chan, buf->cpu, 1);
- buf->bytes_consumed = 0;
- }
buf->bytes_consumed += bytes_consumed;
- if (!read_pos)
- read_subbuf = buf->subbufs_consumed % n_subbufs;
- else
- read_subbuf = read_pos / buf->chan->subbuf_size;
- if (buf->bytes_consumed + buf->padding[read_subbuf] == subbuf_size) {
- if ((read_subbuf == buf->subbufs_produced % n_subbufs) &&
- (buf->offset == subbuf_size))
- return;
- relay_subbufs_consumed(buf->chan, buf->cpu, 1);
- buf->bytes_consumed = 0;
- }
-}
-/*
- * relay_file_read_avail - boolean, are there unconsumed bytes available?
- */
-static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
-{
- size_t subbuf_size = buf->chan->subbuf_size;
- size_t n_subbufs = buf->chan->n_subbufs;
- size_t produced = buf->subbufs_produced;
- size_t consumed = buf->subbufs_consumed;
-
- relay_file_read_consume(buf, read_pos, 0);
-
- consumed = buf->subbufs_consumed;
-
- if (unlikely(buf->offset > subbuf_size)) {
- if (produced == consumed)
- return 0;
- return 1;
- }
-
- if (unlikely(produced - consumed >= n_subbufs)) {
- consumed = produced - n_subbufs + 1;
- buf->subbufs_consumed = consumed;
+ if (buf->bytes_consumed == subbuf_size) {
+ relay_subbufs_consumed(buf->chan, buf->cpu, 1);
buf->bytes_consumed = 0;
}
-
- produced = (produced % n_subbufs) * subbuf_size + buf->offset;
- consumed = (consumed % n_subbufs) * subbuf_size + buf->bytes_consumed;
-
- if (consumed > produced)
- produced += n_subbufs * subbuf_size;
-
- if (consumed == produced) {
- if (buf->offset == subbuf_size &&
- buf->subbufs_produced > buf->subbufs_consumed)
- return 1;
- return 0;
- }
-
- return 1;
}
/**
@@ -1041,21 +982,19 @@ static int relay_file_read_avail(struct rchan_buf *buf, size_t read_pos)
static size_t relay_file_read_subbuf_avail(size_t read_pos,
struct rchan_buf *buf)
{
- size_t padding, avail = 0;
+ size_t avail;
size_t read_subbuf, read_offset, write_subbuf, write_offset;
size_t subbuf_size = buf->chan->subbuf_size;
write_subbuf = (buf->data - buf->start) / subbuf_size;
- write_offset = buf->offset > subbuf_size ? subbuf_size : buf->offset;
+ write_offset = buf->offset;
read_subbuf = read_pos / subbuf_size;
read_offset = read_pos % subbuf_size;
- padding = buf->padding[read_subbuf];
- if (read_subbuf == write_subbuf) {
- if (read_offset + padding < write_offset)
- avail = write_offset - (read_offset + padding);
- } else
- avail = (subbuf_size - padding) - read_offset;
+ avail = subbuf_size - read_offset;
+
+ if (read_subbuf == write_subbuf && read_offset < write_offset)
+ avail = write_offset - read_offset;
return avail;
}
@@ -1065,28 +1004,17 @@ static size_t relay_file_read_subbuf_avail(size_t read_pos,
* @read_pos: file read position
* @buf: relay channel buffer
*
- * If the @read_pos is in the middle of padding, return the
- * position of the first actually available byte, otherwise
- * return the original value.
+ * If the @read_pos is 0, return the position of the first
+ * unconsumed byte, otherwise return the original value.
*/
static size_t relay_file_read_start_pos(size_t read_pos,
struct rchan_buf *buf)
{
- size_t read_subbuf, padding, padding_start, padding_end;
size_t subbuf_size = buf->chan->subbuf_size;
- size_t n_subbufs = buf->chan->n_subbufs;
- size_t consumed = buf->subbufs_consumed % n_subbufs;
+ size_t consumed = buf->subbufs_consumed % buf->chan->n_subbufs;
if (!read_pos)
read_pos = consumed * subbuf_size + buf->bytes_consumed;
- read_subbuf = read_pos / subbuf_size;
- padding = buf->padding[read_subbuf];
- padding_start = (read_subbuf + 1) * subbuf_size - padding;
- padding_end = (read_subbuf + 1) * subbuf_size;
- if (read_pos >= padding_start && read_pos < padding_end) {
- read_subbuf = (read_subbuf + 1) % n_subbufs;
- read_pos = read_subbuf * subbuf_size;
- }
return read_pos;
}
@@ -1101,17 +1029,9 @@ static size_t relay_file_read_end_pos(struct rchan_buf *buf,
size_t read_pos,
size_t count)
{
- size_t read_subbuf, padding, end_pos;
- size_t subbuf_size = buf->chan->subbuf_size;
- size_t n_subbufs = buf->chan->n_subbufs;
+ size_t end_pos = read_pos + count;
- read_subbuf = read_pos / subbuf_size;
- padding = buf->padding[read_subbuf];
- if (read_pos % subbuf_size + count + padding == subbuf_size)
- end_pos = (read_subbuf + 1) * subbuf_size;
- else
- end_pos = read_pos + count;
- if (end_pos >= subbuf_size * n_subbufs)
+ if (end_pos >= buf->chan->subbuf_size * buf->chan->n_subbufs)
end_pos = 0;
return end_pos;
@@ -1165,9 +1085,6 @@ static ssize_t relay_file_read_subbufs(struct file *filp, loff_t *ppos,
mutex_lock(&filp->f_path.dentry->d_inode->i_mutex);
do {
- if (!relay_file_read_avail(buf, *ppos))
- break;
-
read_start = relay_file_read_start_pos(*ppos, buf);
avail = relay_file_read_subbuf_avail(read_start, buf);
if (!avail)
@@ -1242,8 +1159,7 @@ static int subbuf_splice_actor(struct file *in,
loff_t *ppos,
struct pipe_inode_info *pipe,
size_t len,
- unsigned int flags,
- int *nonpad_ret)
+ unsigned int flags)
{
unsigned int pidx, poff, total_len, subbuf_pages, nr_pages, ret;
struct rchan_buf *rbuf = in->private_data;
@@ -1251,9 +1167,6 @@ static int subbuf_splice_actor(struct file *in,
uint64_t pos = (uint64_t) *ppos;
uint32_t alloc_size = (uint32_t) rbuf->chan->alloc_size;
size_t read_start = (size_t) do_div(pos, alloc_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 = {
@@ -1265,7 +1178,8 @@ static int subbuf_splice_actor(struct file *in,
.spd_release = relay_page_release,
};
- if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
+ if (rbuf->subbufs_produced == rbuf->subbufs_consumed &&
+ rbuf->offset == rbuf->bytes_consumed)
return 0;
/*
@@ -1280,46 +1194,25 @@ static int subbuf_splice_actor(struct file *in,
nr_pages = min_t(unsigned int, subbuf_pages, PIPE_BUFFERS);
for (total_len = 0; spd.nr_pages < nr_pages; spd.nr_pages++) {
- unsigned int this_len, this_end, private;
- unsigned int cur_pos = read_start + total_len;
+ unsigned int this_len;
if (!len)
break;
this_len = min_t(unsigned long, len, PAGE_SIZE - poff);
- private = this_len;
spd.pages[spd.nr_pages] = rbuf->page_array[pidx];
spd.partial[spd.nr_pages].offset = poff;
- 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;
len -= this_len;
total_len += this_len;
poff = 0;
pidx = (pidx + 1) % subbuf_pages;
-
- if (this_end >= nonpad_end) {
- spd.nr_pages++;
- break;
- }
}
- if (!spd.nr_pages)
- return 0;
-
- ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
- if (ret < 0 || ret < total_len)
- return ret;
-
- if (read_start + ret == nonpad_end)
- ret += padding;
+ ret = splice_to_pipe(pipe, &spd);
return ret;
}
@@ -1332,13 +1225,12 @@ static ssize_t relay_file_splice_read(struct file *in,
{
ssize_t spliced;
int ret;
- int nonpad_ret = 0;
ret = 0;
spliced = 0;
while (len && !spliced) {
- ret = subbuf_splice_actor(in, ppos, pipe, len, flags, &nonpad_ret);
+ ret = subbuf_splice_actor(in, ppos, pipe, len, flags);
if (ret < 0)
break;
else if (!ret) {
@@ -1355,8 +1247,7 @@ static ssize_t relay_file_splice_read(struct file *in,
len = 0;
else
len -= ret;
- spliced += nonpad_ret;
- nonpad_ret = 0;
+ spliced += ret;
}
if (spliced)
--
1.5.3.5
--
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