splice: lift pipe_lock out of splice_to_pipe()
* splice_to_pipe() stops at pipe overflow and does *not* take pipe_lock
* ->splice_read() instances do the same
* vmsplice_to_pipe() and do_splice() (ultimate callers of splice_to_pipe())
arrange for waiting, looping, etc. themselves.
That should make pipe_lock the outermost one.
Unfortunately, existing rules for the amount passed by vmsplice_to_pipe()
and do_splice() are quite ugly _and_ userland code can be easily broken
by changing those. It's not even "no more than the maximal capacity of
this pipe" - it's "once we'd fed pipe->nr_buffers pages into the pipe,
leave instead of waiting".
Considering how poorly these rules are documented, let's try "wait for some
space to appear, unless given SPLICE_F_NONBLOCK, then push into pipe
and if we run into overflow, we are done".
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/splice.c b/fs/splice.c
index 31c52e0..2ca7e69 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -183,79 +183,41 @@
struct splice_pipe_desc *spd)
{
unsigned int spd_pages = spd->nr_pages;
- int ret, do_wakeup, page_nr;
+ int ret = 0, page_nr = 0;
if (!spd_pages)
return 0;
- ret = 0;
- do_wakeup = 0;
- page_nr = 0;
-
- pipe_lock(pipe);
-
- for (;;) {
- if (!pipe->readers) {
- send_sig(SIGPIPE, current, 0);
- if (!ret)
- ret = -EPIPE;
- break;
- }
-
- if (pipe->nrbufs < pipe->buffers) {
- int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
- struct pipe_buffer *buf = pipe->bufs + newbuf;
-
- buf->page = spd->pages[page_nr];
- buf->offset = spd->partial[page_nr].offset;
- buf->len = spd->partial[page_nr].len;
- buf->private = spd->partial[page_nr].private;
- buf->ops = spd->ops;
- if (spd->flags & SPLICE_F_GIFT)
- buf->flags |= PIPE_BUF_FLAG_GIFT;
-
- pipe->nrbufs++;
- page_nr++;
- ret += buf->len;
-
- if (pipe->files)
- do_wakeup = 1;
-
- if (!--spd->nr_pages)
- break;
- if (pipe->nrbufs < pipe->buffers)
- continue;
-
- break;
- }
-
- if (spd->flags & SPLICE_F_NONBLOCK) {
- if (!ret)
- ret = -EAGAIN;
- break;
- }
-
- if (signal_pending(current)) {
- if (!ret)
- ret = -ERESTARTSYS;
- break;
- }
-
- if (do_wakeup) {
- wakeup_pipe_readers(pipe);
- do_wakeup = 0;
- }
-
- pipe->waiting_writers++;
- pipe_wait(pipe);
- pipe->waiting_writers--;
+ if (unlikely(!pipe->readers)) {
+ send_sig(SIGPIPE, current, 0);
+ ret = -EPIPE;
+ goto out;
}
- pipe_unlock(pipe);
+ while (pipe->nrbufs < pipe->buffers) {
+ int newbuf = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1);
+ struct pipe_buffer *buf = pipe->bufs + newbuf;
- if (do_wakeup)
- wakeup_pipe_readers(pipe);
+ buf->page = spd->pages[page_nr];
+ buf->offset = spd->partial[page_nr].offset;
+ buf->len = spd->partial[page_nr].len;
+ buf->private = spd->partial[page_nr].private;
+ buf->ops = spd->ops;
+ if (spd->flags & SPLICE_F_GIFT)
+ buf->flags |= PIPE_BUF_FLAG_GIFT;
+ pipe->nrbufs++;
+ page_nr++;
+ ret += buf->len;
+
+ if (!--spd->nr_pages)
+ break;
+ }
+
+ if (!ret)
+ ret = -EAGAIN;
+
+out:
while (page_nr < spd_pages)
spd->spd_release(spd, page_nr++);
@@ -1339,6 +1301,20 @@
}
EXPORT_SYMBOL(do_splice_direct);
+static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
+{
+ while (pipe->nrbufs == pipe->buffers) {
+ if (flags & SPLICE_F_NONBLOCK)
+ return -EAGAIN;
+ if (signal_pending(current))
+ return -ERESTARTSYS;
+ pipe->waiting_writers++;
+ pipe_wait(pipe);
+ pipe->waiting_writers--;
+ }
+ return 0;
+}
+
static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
struct pipe_inode_info *opipe,
size_t len, unsigned int flags);
@@ -1421,8 +1397,13 @@
offset = in->f_pos;
}
- ret = do_splice_to(in, &offset, opipe, len, flags);
-
+ pipe_lock(opipe);
+ ret = wait_for_space(opipe, flags);
+ if (!ret)
+ ret = do_splice_to(in, &offset, opipe, len, flags);
+ pipe_unlock(opipe);
+ if (ret > 0)
+ wakeup_pipe_readers(opipe);
if (!off_in)
in->f_pos = offset;
else if (copy_to_user(off_in, &offset, sizeof(loff_t)))
@@ -1546,14 +1527,20 @@
return -ENOMEM;
}
- spd.nr_pages = get_iovec_page_array(&from, spd.pages,
- spd.partial,
- spd.nr_pages_max);
- if (spd.nr_pages <= 0)
- ret = spd.nr_pages;
- else
- ret = splice_to_pipe(pipe, &spd);
-
+ pipe_lock(pipe);
+ ret = wait_for_space(pipe, flags);
+ if (!ret) {
+ spd.nr_pages = get_iovec_page_array(&from, spd.pages,
+ spd.partial,
+ spd.nr_pages_max);
+ if (spd.nr_pages <= 0)
+ ret = spd.nr_pages;
+ else
+ ret = splice_to_pipe(pipe, &spd);
+ }
+ pipe_unlock(pipe);
+ if (ret > 0)
+ wakeup_pipe_readers(pipe);
splice_shrink_spd(&spd);
kfree(iov);
return ret;