splice: abstract out actor data

For direct splicing (or private splicing), the output may not be a file.
So abstract out the handling into a specified actor function and put
the data in the splice_desc structure earlier, so we can build on top
of that.

This is the first step in better splice handling for drivers, and also
for implementing vmsplice _to_ user memory.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 70 insertions, 29 deletions

diff --git a/fs/splice.c b/fs/splice.c
index e7d7080de2f9..68f6328236a6 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -668,31 +668,24 @@ out_ret:
  * key here is the 'actor' worker passed in that actually moves the data
  * to the wanted destination. See pipe_to_file/pipe_to_sendpage above.
  */
-ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
-			   struct file *out, loff_t *ppos, size_t len,
-			   unsigned int flags, splice_actor *actor)
+ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
+			   splice_actor *actor)
 {
 	int ret, do_wakeup, err;
-	struct splice_desc sd;
 
 	ret = 0;
 	do_wakeup = 0;
 
-	sd.total_len = len;
-	sd.flags = flags;
-	sd.file = out;
-	sd.pos = *ppos;
-
 	for (;;) {
 		if (pipe->nrbufs) {
 			struct pipe_buffer *buf = pipe->bufs + pipe->curbuf;
 			const struct pipe_buf_operations *ops = buf->ops;
 
-			sd.len = buf->len;
-			if (sd.len > sd.total_len)
-				sd.len = sd.total_len;
+			sd->len = buf->len;
+			if (sd->len > sd->total_len)
+				sd->len = sd->total_len;
 
-			err = actor(pipe, buf, &sd);
+			err = actor(pipe, buf, sd);
 			if (err <= 0) {
 				if (!ret && err != -ENODATA)
 					ret = err;
@@ -704,10 +697,10 @@ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
 			buf->offset += err;
 			buf->len -= err;
 
-			sd.len -= err;
-			sd.pos += err;
-			sd.total_len -= err;
-			if (sd.len)
+			sd->len -= err;
+			sd->pos += err;
+			sd->total_len -= err;
+			if (sd->len)
 				continue;
 
 			if (!buf->len) {
@@ -719,7 +712,7 @@ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
 					do_wakeup = 1;
 			}
 
-			if (!sd.total_len)
+			if (!sd->total_len)
 				break;
 		}
 
@@ -732,7 +725,7 @@ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe,
 				break;
 		}
 
-		if (flags & SPLICE_F_NONBLOCK) {
+		if (sd->flags & SPLICE_F_NONBLOCK) {
 			if (!ret)
 				ret = -EAGAIN;
 			break;
@@ -772,6 +765,12 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 {
 	ssize_t ret;
 	struct inode *inode = out->f_mapping->host;
+	struct splice_desc sd = {
+		.total_len = len,
+		.flags = flags,
+		.pos = *ppos,
+		.file = out,
+	};
 
 	/*
 	 * The actor worker might be calling ->prepare_write and
@@ -780,7 +779,7 @@ ssize_t splice_from_pipe(struct pipe_inode_info *pipe, struct file *out,
 	 * pipe->inode, we have to order lock acquiry here.
 	 */
 	inode_double_lock(inode, pipe->inode);
-	ret = __splice_from_pipe(pipe, out, ppos, len, flags, actor);
+	ret = __splice_from_pipe(pipe, &sd, actor);
 	inode_double_unlock(inode, pipe->inode);
 
 	return ret;
@@ -804,6 +803,12 @@ generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 {
 	struct address_space *mapping = out->f_mapping;
 	struct inode *inode = mapping->host;
+	struct splice_desc sd = {
+		.total_len = len,
+		.flags = flags,
+		.pos = *ppos,
+		.file = out,
+	};
 	ssize_t ret;
 	int err;
 
@@ -811,7 +816,7 @@ generic_file_splice_write_nolock(struct pipe_inode_info *pipe, struct file *out,
 	if (unlikely(err))
 		return err;
 
-	ret = __splice_from_pipe(pipe, out, ppos, len, flags, pipe_to_file);
+	ret = __splice_from_pipe(pipe, &sd, pipe_to_file);
 	if (ret > 0) {
 		unsigned long nr_pages;
 
@@ -956,14 +961,17 @@ static long do_splice_to(struct file *in, loff_t *ppos,
 	return in->f_op->splice_read(in, ppos, pipe, len, flags);
 }
 
-long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
-		      size_t len, unsigned int flags)
+/*
+ * Splices from an input file to an actor, using a 'direct' pipe.
+ */
+ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
+			       splice_direct_actor *actor)
 {
 	struct pipe_inode_info *pipe;
 	long ret, bytes;
-	loff_t out_off;
 	umode_t i_mode;
-	int i;
+	size_t len;
+	int i, flags;
 
 	/*
 	 * We require the input being a regular file, as we don't want to
@@ -999,7 +1007,13 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 	 */
 	ret = 0;
 	bytes = 0;
-	out_off = 0;
+	len = sd->total_len;
+	flags = sd->flags;
+
+	/*
+	 * Don't block on output, we have to drain the direct pipe.
+	 */
+	sd->flags &= ~SPLICE_F_NONBLOCK;
 
 	while (len) {
 		size_t read_len, max_read_len;
@@ -1009,19 +1023,19 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 		 */
 		max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));
 
-		ret = do_splice_to(in, ppos, pipe, max_read_len, flags);
+		ret = do_splice_to(in, &sd->pos, pipe, max_read_len, flags);
 		if (unlikely(ret < 0))
 			goto out_release;
 
 		read_len = ret;
+		sd->total_len = read_len;
 
 		/*
 		 * NOTE: nonblocking mode only applies to the input. We
 		 * must not do the output in nonblocking mode as then we
 		 * could get stuck data in the internal pipe:
 		 */
-		ret = do_splice_from(pipe, out, &out_off, read_len,
-				     flags & ~SPLICE_F_NONBLOCK);
+		ret = actor(pipe, sd);
 		if (unlikely(ret < 0))
 			goto out_release;
 
@@ -1066,6 +1080,33 @@ out_release:
 		return bytes;
 
 	return ret;
+
+}
+EXPORT_SYMBOL(splice_direct_to_actor);
+
+static int direct_splice_actor(struct pipe_inode_info *pipe,
+			       struct splice_desc *sd)
+{
+	struct file *file = sd->file;
+
+	return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
+}
+
+long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
+		      size_t len, unsigned int flags)
+{
+	struct splice_desc sd = {
+		.len		= len,
+		.total_len	= len,
+		.flags		= flags,
+		.pos		= *ppos,
+		.file		= out,
+	};
+	size_t ret;
+
+	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);
+	*ppos = sd.pos;
+	return ret;
 }
 
 /*