->splice_write() via ->write_iter()
iter_file_splice_write() - a ->splice_write() instance that gathers the
pipe buffers, builds a bio_vec-based iov_iter covering those and feeds
it to ->write_iter(). A bunch of simple cases coverted to that...
[AV: fixed the braino spotted by Cyrill]
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/splice.c b/fs/splice.c
index f99e420..f195a9b 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -32,6 +32,7 @@
#include <linux/gfp.h>
#include <linux/socket.h>
#include <linux/compat.h>
+#include <linux/aio.h>
#include "internal.h"
/*
@@ -1052,6 +1053,145 @@
EXPORT_SYMBOL(generic_file_splice_write);
+/**
+ * iter_file_splice_write - splice data from a pipe to a file
+ * @pipe: pipe info
+ * @out: file to write to
+ * @ppos: position in @out
+ * @len: number of bytes to splice
+ * @flags: splice modifier flags
+ *
+ * Description:
+ * Will either move or copy pages (determined by @flags options) from
+ * the given pipe inode to the given file.
+ * This one is ->write_iter-based.
+ *
+ */
+ssize_t
+iter_file_splice_write(struct pipe_inode_info *pipe, struct file *out,
+ loff_t *ppos, size_t len, unsigned int flags)
+{
+ struct splice_desc sd = {
+ .total_len = len,
+ .flags = flags,
+ .pos = *ppos,
+ .u.file = out,
+ };
+ int nbufs = pipe->buffers;
+ struct bio_vec *array = kcalloc(nbufs, sizeof(struct bio_vec),
+ GFP_KERNEL);
+ ssize_t ret;
+
+ if (unlikely(!array))
+ return -ENOMEM;
+
+ pipe_lock(pipe);
+
+ splice_from_pipe_begin(&sd);
+ while (sd.total_len) {
+ struct iov_iter from;
+ struct kiocb kiocb;
+ size_t left;
+ int n, idx;
+
+ ret = splice_from_pipe_next(pipe, &sd);
+ if (ret <= 0)
+ break;
+
+ if (unlikely(nbufs < pipe->buffers)) {
+ kfree(array);
+ nbufs = pipe->buffers;
+ array = kcalloc(nbufs, sizeof(struct bio_vec),
+ GFP_KERNEL);
+ if (!array) {
+ ret = -ENOMEM;
+ break;
+ }
+ }
+
+ /* build the vector */
+ left = sd.total_len;
+ for (n = 0, idx = pipe->curbuf; left && n < pipe->nrbufs; n++, idx++) {
+ struct pipe_buffer *buf = pipe->bufs + idx;
+ size_t this_len = buf->len;
+
+ if (this_len > left)
+ this_len = left;
+
+ if (idx == pipe->buffers - 1)
+ idx = -1;
+
+ ret = buf->ops->confirm(pipe, buf);
+ if (unlikely(ret)) {
+ if (ret == -ENODATA)
+ ret = 0;
+ goto done;
+ }
+
+ array[n].bv_page = buf->page;
+ array[n].bv_len = this_len;
+ array[n].bv_offset = buf->offset;
+ left -= this_len;
+ }
+
+ /* ... iov_iter */
+ from.type = ITER_BVEC | WRITE;
+ from.bvec = array;
+ from.nr_segs = n;
+ from.count = sd.total_len - left;
+ from.iov_offset = 0;
+
+ /* ... and iocb */
+ init_sync_kiocb(&kiocb, out);
+ kiocb.ki_pos = sd.pos;
+ kiocb.ki_nbytes = sd.total_len - left;
+
+ /* now, send it */
+ ret = out->f_op->write_iter(&kiocb, &from);
+ if (-EIOCBQUEUED == ret)
+ ret = wait_on_sync_kiocb(&kiocb);
+
+ if (ret <= 0)
+ break;
+
+ sd.num_spliced += ret;
+ sd.total_len -= ret;
+ *ppos = sd.pos = kiocb.ki_pos;
+
+ /* dismiss the fully eaten buffers, adjust the partial one */
+ while (ret) {
+ struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
+ if (ret >= buf->len) {
+ const struct pipe_buf_operations *ops = buf->ops;
+ ret -= buf->len;
+ buf->len = 0;
+ buf->ops = NULL;
+ ops->release(pipe, buf);
+ pipe->curbuf = (pipe->curbuf + 1) & (pipe->buffers - 1);
+ pipe->nrbufs--;
+ if (pipe->files)
+ sd.need_wakeup = true;
+ } else {
+ buf->offset += ret;
+ buf->len -= ret;
+ ret = 0;
+ }
+ }
+ }
+done:
+ kfree(array);
+ splice_from_pipe_end(pipe, &sd);
+
+ pipe_unlock(pipe);
+
+ if (sd.num_spliced)
+ ret = sd.num_spliced;
+
+ return ret;
+}
+
+EXPORT_SYMBOL(iter_file_splice_write);
+
static int write_pipe_buf(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
struct splice_desc *sd)
{