[PATCH 3/3] sendfile: fix sendfile

[Changli Gao]

fix sendfile

the flags parameter of splice() doesn't mean non-block read of in file, but
non-block read/write of pipe. As the reader and writer of process internal
pipe is the process itself, we don't need this flags.

If output file is in non-block mode, in file should be seekable to avoid data
losing.

do_splice_from() shouldn't use sd->pos, as sd->pos is for file reading,
file->f_pos should be used instead.

Signed-off-by: Changli Gao <xiaosuo@xxxxxxxxx>
----
 fs/read_write.c    |   23 ++++++++---------------
 fs/splice.c        |   22 +++++-----------------
 include/linux/fs.h |    2 +-
 3 files changed, 14 insertions(+), 33 deletions(-)
diff --git a/fs/read_write.c b/fs/read_write.c
index 113386d..a844e2c 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -796,7 +796,7 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 	struct inode * in_inode, * out_inode;
 	loff_t pos;
 	ssize_t retval;
-	int fput_needed_in, fput_needed_out, fl;
+	int fput_needed_in, fput_needed_out;
 
 	/*
 	 * Get input file, and verify that it is ok..
@@ -808,11 +808,15 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 	if (!(in_file->f_mode & FMODE_READ))
 		goto fput_in;
 	retval = -ESPIPE;
-	if (!ppos)
+	if (!ppos) {
 		ppos = &in_file->f_pos;
-	else
+		if ((out_file->f_flags & O_NONBLOCK) &&
+		    !(in_file->f_mode & FMODE_PREAD))
+			goto fput_in;
+	} else {
 		if (!(in_file->f_mode & FMODE_PREAD))
 			goto fput_in;
+	}
 	retval = rw_verify_area(READ, in_file, ppos, count);
 	if (retval < 0)
 		goto fput_in;
@@ -846,18 +850,7 @@ static ssize_t do_sendfile(int out_fd, int in_fd, loff_t *ppos,
 		count = max - pos;
 	}
 
-	fl = 0;
-#if 0
-	/*
-	 * We need to debate whether we can enable this or not. The
-	 * man page documents EAGAIN return for the output at least,
-	 * and the application is arguably buggy if it doesn't expect
-	 * EAGAIN on a non-blocking file descriptor.
-	 */
-	if (in_file->f_flags & O_NONBLOCK)
-		fl = SPLICE_F_NONBLOCK;
-#endif
-	retval = do_splice_direct(in_file, ppos, out_file, count, fl);
+	retval = do_splice_direct(in_file, ppos, out_file, count);
 
 	if (retval > 0) {
 		add_rchar(current, retval);
diff --git a/fs/splice.c b/fs/splice.c
index 8137e23..e921d72 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -1125,7 +1125,7 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 	long ret, bytes;
 	umode_t i_mode;
 	size_t len;
-	int i, flags;
+	int i;
 
 	/*
 	 * We require the input being a regular file, as we don't want to
@@ -1162,29 +1162,18 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 	ret = 0;
 	bytes = 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;
 		loff_t pos = sd->pos, prev_pos = pos;
 
-		ret = do_splice_to(in, &pos, pipe, len, flags);
+		ret = do_splice_to(in, &pos, pipe, len, 0);
 		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 = actor(pipe, sd);
 		if (unlikely(ret <= 0)) {
 			sd->pos = prev_pos;
@@ -1232,7 +1221,8 @@ static int direct_splice_actor(struct pipe_inode_info *pipe,
 {
 	struct file *file = sd->u.file;
 
-	return do_splice_from(pipe, file, &sd->pos, sd->total_len, sd->flags);
+	return do_splice_from(pipe, file, &file->f_pos, sd->total_len,
+			      sd->flags);
 }
 
 /**
@@ -1241,7 +1231,6 @@ static int direct_splice_actor(struct pipe_inode_info *pipe,
  * @ppos:	input file offset
  * @out:	file to splice to
  * @len:	number of bytes to splice
- * @flags:	splice modifier flags
  *
  * Description:
  *    For use by do_sendfile(). splice can easily emulate sendfile, but
@@ -1251,12 +1240,11 @@ static int direct_splice_actor(struct pipe_inode_info *pipe,
  *
  */
 long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
-		      size_t len, unsigned int flags)
+		      size_t len)
 {
 	struct splice_desc sd = {
 		.len		= len,
 		.total_len	= len,
-		.flags		= flags,
 		.pos		= *ppos,
 		.u.file		= out,
 	};
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4079ef9..eb86433 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2224,7 +2224,7 @@ extern ssize_t generic_file_splice_write(struct pipe_inode_info *,
 extern ssize_t generic_splice_sendpage(struct pipe_inode_info *pipe,
 		struct file *out, loff_t *, size_t len, unsigned int flags);
 extern long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
-		size_t len, unsigned int flags);
+		size_t len);
 
 extern void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping);
--
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