pipe: add support for shrinking and growing pipes
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>
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 44f916a..7b155a0 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -3269,12 +3269,12 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
else
ret = 0;
/* TODO: block */
- return ret;
+ goto out;
}
ret = splice_to_pipe(pipe, &spd);
-
+ splice_shrink_spd(pipe, &spd);
+out:
return ret;
}