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pipe: add support for shrinking and growing pipes

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This patch adds F_GETPIPE_SZ and F_SETPIPE_SZ fcntl() actions for
growing and shrinking the size of a pipe and adjusts pipe.c and splice.c
(and relay and network splice) usage to work with these larger (or smaller)
pipes.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe
2010-05-20 10:43:18 +02:00
parent 3d42b36128
commit 35f3d14dbb
9 changed files with 293 additions and 109 deletions
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60
kernel/trace/trace.c
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@@ -3269,12 +3269,12 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
size_t len,
unsigned int flags)
{
struct page *pages[PIPE_BUFFERS];
struct partial_page partial[PIPE_BUFFERS];
struct page *pages_def[PIPE_DEF_BUFFERS];
struct partial_page partial_def[PIPE_DEF_BUFFERS];
struct trace_iterator *iter = filp->private_data;
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.pages = pages_def,
.partial = partial_def,
.nr_pages = 0, /* This gets updated below. */
.flags = flags,
.ops = &tracing_pipe_buf_ops,
@@ -3285,6 +3285,9 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
size_t rem;
unsigned int i;
if (splice_grow_spd(pipe, &spd))
return -ENOMEM;
/* copy the tracer to avoid using a global lock all around */
mutex_lock(&trace_types_lock);
if (unlikely(old_tracer != current_trace && current_trace)) {
@@ -3315,23 +3318,23 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
trace_access_lock(iter->cpu_file);
/* Fill as many pages as possible. */
for (i = 0, rem = len; i < PIPE_BUFFERS && rem; i++) {
pages[i] = alloc_page(GFP_KERNEL);
if (!pages[i])
for (i = 0, rem = len; i < pipe->buffers && rem; i++) {
spd.pages[i] = alloc_page(GFP_KERNEL);
if (!spd.pages[i])
break;
rem = tracing_fill_pipe_page(rem, iter);
/* Copy the data into the page, so we can start over. */
ret = trace_seq_to_buffer(&iter->seq,
page_address(pages[i]),
page_address(spd.pages[i]),
iter->seq.len);
if (ret < 0) {
__free_page(pages[i]);
__free_page(spd.pages[i]);
break;
}
partial[i].offset = 0;
partial[i].len = iter->seq.len;
spd.partial[i].offset = 0;
spd.partial[i].len = iter->seq.len;
trace_seq_init(&iter->seq);
}
@@ -3342,12 +3345,14 @@ static ssize_t tracing_splice_read_pipe(struct file *filp,
spd.nr_pages = i;
return splice_to_pipe(pipe, &spd);
ret = splice_to_pipe(pipe, &spd);
out:
splice_shrink_spd(pipe, &spd);
return ret;
out_err:
mutex_unlock(&iter->mutex);
return ret;
goto out;
}
static ssize_t
@@ -3746,11 +3751,11 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
unsigned int flags)
{
struct ftrace_buffer_info *info = file->private_data;
struct partial_page partial[PIPE_BUFFERS];
struct page *pages[PIPE_BUFFERS];
struct partial_page partial_def[PIPE_DEF_BUFFERS];
struct page *pages_def[PIPE_DEF_BUFFERS];
struct splice_pipe_desc spd = {
.pages = pages,
.partial = partial,
.pages = pages_def,
.partial = partial_def,
.flags = flags,
.ops = &buffer_pipe_buf_ops,
.spd_release = buffer_spd_release,
@@ -3759,22 +3764,28 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
int entries, size, i;
size_t ret;
if (splice_grow_spd(pipe, &spd))
return -ENOMEM;
if (*ppos & (PAGE_SIZE - 1)) {
WARN_ONCE(1, "Ftrace: previous read must page-align\n");
return -EINVAL;
ret = -EINVAL;
goto out;
}
if (len & (PAGE_SIZE - 1)) {
WARN_ONCE(1, "Ftrace: splice_read should page-align\n");
if (len < PAGE_SIZE)
return -EINVAL;
if (len < PAGE_SIZE) {
ret = -EINVAL;
goto out;
}
len &= PAGE_MASK;
}
trace_access_lock(info->cpu);
entries = ring_buffer_entries_cpu(info->tr->buffer, info->cpu);
for (i = 0; i < PIPE_BUFFERS && len && entries; i++, len -= PAGE_SIZE) {
for (i = 0; i < pipe->buffers && len && entries; i++, len -= PAGE_SIZE) {
struct page *page;
int r;
@@ -3829,11 +3840,12 @@ tracing_buffers_splice_read(struct file *file, loff_t *ppos,
else
ret = 0;
/* TODO: block */
return ret;
goto out;
}
ret = splice_to_pipe(pipe, &spd);
splice_shrink_spd(pipe, &spd);
out:
return ret;
}