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/relay.c b/kernel/relay.c
index 3d97f28..4268287 100644
--- a/kernel/relay.c
+++ b/kernel/relay.c
@@ -1231,8 +1231,8 @@
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 page *pages[PIPE_DEF_BUFFERS];
+ struct partial_page partial[PIPE_DEF_BUFFERS];
struct splice_pipe_desc spd = {
.pages = pages,
.nr_pages = 0,
@@ -1245,6 +1245,8 @@
if (rbuf->subbufs_produced == rbuf->subbufs_consumed)
return 0;
+ if (splice_grow_spd(pipe, &spd))
+ return -ENOMEM;
/*
* Adjust read len, if longer than what is available
@@ -1255,7 +1257,7 @@
subbuf_pages = rbuf->chan->alloc_size >> PAGE_SHIFT;
pidx = (read_start / PAGE_SIZE) % subbuf_pages;
poff = read_start & ~PAGE_MASK;
- nr_pages = min_t(unsigned int, subbuf_pages, PIPE_BUFFERS);
+ 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;
@@ -1289,16 +1291,19 @@
}
}
+ ret = 0;
if (!spd.nr_pages)
- return 0;
+ goto out;
ret = *nonpad_ret = splice_to_pipe(pipe, &spd);
if (ret < 0 || ret < total_len)
- return ret;
+ goto out;
if (read_start + ret == nonpad_end)
ret += padding;
+out:
+ splice_shrink_spd(pipe, &spd);
return ret;
}
