Commit 51a92c0f authored by Jens Axboe's avatar Jens Axboe
Browse files

splice: fix offset mangling with direct splicing (sendfile) 



If the output actor doesn't transfer the full amount of data, we will
increment ppos too much. Two related bugs in there:

- We need to break out and return actor() retval if it is shorted than
  what we spliced into the pipe.

- Adjust ppos only according to actor() return.

Also fix loop problem in generic_file_splice_read(), it should not keep
going when data has already been transferred.

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 29ce2058

fs/splice.c

+11 −23
Original line number Diff line number Diff line
@@ -492,7 +492,7 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos, 


	ret = 0;

	spliced = 0;

	while (len) {

	while (len && !spliced) {

		ret = __generic_file_splice_read(in, ppos, pipe, len, flags);



		if (ret < 0)
@@ -1060,15 +1060,10 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, 
	sd->flags &= ~SPLICE_F_NONBLOCK;



	while (len) {

		size_t read_len, max_read_len;



		/*

		 * Do at most PIPE_BUFFERS pages worth of transfer:

		 */

		max_read_len = min(len, (size_t)(PIPE_BUFFERS*PAGE_SIZE));

		size_t read_len;



		ret = do_splice_to(in, &sd->pos, pipe, max_read_len, flags);

		if (unlikely(ret < 0))

		ret = do_splice_to(in, &sd->pos, pipe, len, flags);

		if (unlikely(ret <= 0))

			goto out_release;



		read_len = ret;
@@ -1080,26 +1075,17 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd, 
		 * could get stuck data in the internal pipe:

		 */

		ret = actor(pipe, sd);

		if (unlikely(ret < 0))

		if (unlikely(ret <= 0))

			goto out_release;



		bytes += ret;

		len -= ret;



		/*

		 * In nonblocking mode, if we got back a short read then

		 * that was due to either an IO error or due to the

		 * pagecache entry not being there. In the IO error case

		 * the _next_ splice attempt will produce a clean IO error

		 * return value (not a short read), so in both cases it's

		 * correct to break out of the loop here:

		 */

		if ((flags & SPLICE_F_NONBLOCK) && (read_len < max_read_len))

			break;

		if (ret < read_len)

			goto out_release;

	}



	pipe->nrbufs = pipe->curbuf = 0;



	return bytes;



out_release:
@@ -1161,10 +1147,12 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out, 
		.pos		= *ppos,

		.u.file		= out,

	};

	size_t ret;

	long ret;



	ret = splice_direct_to_actor(in, &sd, direct_splice_actor);

	*ppos = sd.pos;

	if (ret > 0)

		*ppos += ret;



	return ret;

}

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