[RFC PATCH] splice: Convert longs and some ints into ssize_t

[David Howells <dhowells@redhat.com>]

Christoph Hellwig <hch@infradead.org> wrote:

> The (pre-existing) long here is odd given that ->splice_read
> returns a ssize_t.  This might be a good time to fix that up.

Here's a patch to do that.  I'm not sure yet that I've got all the places that
need changing as there are a couple of function pointer-taking functions where
the pointed-to function return value should be changed.

There are a couple of potential bugs fixed here too, where something takes a
size_t length, but counts the data spliced in an int.  iter_to_pipe() for
example.

David
---
splice: Convert longs and some ints into ssize_t

Convert 'long' and some 'int' into ssize_t in the code involved in splice.

Suggested-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Christoph Hellwig <hch@lst.de>
cc: Jens Axboe <axboe@kernel.dk>
cc: Al Viro <viro@zeniv.linux.org.uk>
cc: John Hubbard <jhubbard@nvidia.com>
cc: David Hildenbrand <david@redhat.com>
cc: Matthew Wilcox <willy@infradead.org>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/ZBCvdKQskS46qyV3@infradead.org/
---
 drivers/char/mem.c            |    4 -
 drivers/char/virtio_console.c |    7 +-
 fs/splice.c                   |  119 +++++++++++++++++++++---------------------
 include/linux/splice.h        |   24 ++++----
 4 files changed, 78 insertions(+), 76 deletions(-)

diff --git a/drivers/char/mem.c b/drivers/char/mem.c
index ffb101d349f0..230b72e12c54 100644
--- a/drivers/char/mem.c
+++ b/drivers/char/mem.c
@@ -468,8 +468,8 @@ static ssize_t write_iter_null(struct kiocb *iocb, struct iov_iter *from)
 	return count;
 }
 
-static int pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
-			struct splice_desc *sd)
+static ssize_t pipe_to_null(struct pipe_inode_info *info, struct pipe_buffer *buf,
+			    struct splice_desc *sd)
 {
 	return sd->len;
 }
diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index d5ac4d955bc8..d38bee859d5c 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -854,11 +854,12 @@ struct sg_list {
 	struct scatterlist *sg;
 };
 
-static int pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
-			struct splice_desc *sd)
+static ssize_t pipe_to_sg(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
+			  struct splice_desc *sd)
 {
 	struct sg_list *sgl = sd->u.data;
-	unsigned int offset, len;
+	ssize_t len;
+	size_t offset;
 
 	if (sgl->n == sgl->size)
 		return 0;
diff --git a/fs/splice.c b/fs/splice.c
index f46dd1fb367b..2bfa94d21346 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -186,7 +186,8 @@ ssize_t splice_to_pipe(struct pipe_inode_info *pipe,
 	unsigned int tail = pipe->tail;
 	unsigned int head = pipe->head;
 	unsigned int mask = pipe->ring_size - 1;
-	int ret = 0, page_nr = 0;
+	ssize_t ret = 0;
+	int page_nr = 0;
 
 	if (!spd_pages)
 		return 0;
@@ -232,7 +233,7 @@ ssize_t add_to_pipe(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
 	unsigned int head = pipe->head;
 	unsigned int tail = pipe->tail;
 	unsigned int mask = pipe->ring_size - 1;
-	int ret;
+	ssize_t ret;
 
 	if (unlikely(!pipe->readers)) {
 		send_sig(SIGPIPE, current, 0);
@@ -414,8 +415,8 @@ EXPORT_SYMBOL(nosteal_pipe_buf_ops);
  * Send 'sd->len' bytes to socket from 'sd->file' at position 'sd->pos'
  * using sendpage(). Return the number of bytes sent.
  */
-static int pipe_to_sendpage(struct pipe_inode_info *pipe,
-			    struct pipe_buffer *buf, struct splice_desc *sd)
+static ssize_t pipe_to_sendpage(struct pipe_inode_info *pipe,
+				struct pipe_buffer *buf, struct splice_desc *sd)
 {
 	struct file *file = sd->u.file;
 	loff_t pos = sd->pos;
@@ -468,7 +469,7 @@ static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_des
 	unsigned int head = pipe->head;
 	unsigned int tail = pipe->tail;
 	unsigned int mask = pipe->ring_size - 1;
-	int ret;
+	ssize_t ret;
 
 	while (!pipe_empty(head, tail)) {
 		struct pipe_buffer *buf = &pipe->bufs[tail & mask];
@@ -621,7 +622,7 @@ static void splice_from_pipe_end(struct pipe_inode_info *pipe, struct splice_des
 ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 			   splice_actor *actor)
 {
-	int ret;
+	ssize_t ret;
 
 	splice_from_pipe_begin(sd);
 	do {
@@ -827,8 +828,8 @@ static int warn_unsupported(struct file *file, const char *op)
 /*
  * Attempt to initiate a splice from pipe to file.
  */
-static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
-			   loff_t *ppos, size_t len, unsigned int flags)
+static ssize_t do_splice_from(struct pipe_inode_info *pipe, struct file *out,
+			      loff_t *ppos, size_t len, unsigned int flags)
 {
 	if (unlikely(!out->f_op->splice_write))
 		return warn_unsupported(out, "write");
@@ -850,12 +851,12 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
  * If successful, it returns the amount of data spliced, 0 if it hit the EOF or
  * a hole and a negative error code otherwise.
  */
-long vfs_splice_read(struct file *in, loff_t *ppos,
-		     struct pipe_inode_info *pipe, size_t len,
-		     unsigned int flags)
+ssize_t vfs_splice_read(struct file *in, loff_t *ppos,
+			struct pipe_inode_info *pipe, size_t len,
+			unsigned int flags)
 {
 	unsigned int p_space;
-	int ret;
+	ssize_t ret;
 
 	if (unlikely(!(in->f_mode & FMODE_READ)))
 		return -EBADF;
@@ -894,7 +895,7 @@ 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;
+	ssize_t ret, bytes;
 	size_t len;
 	int i, flags, more;
 
@@ -1007,7 +1008,7 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 }
 EXPORT_SYMBOL(splice_direct_to_actor);
 
-static int direct_splice_actor(struct pipe_inode_info *pipe,
+static ssize_t direct_splice_actor(struct pipe_inode_info *pipe,
 			       struct splice_desc *sd)
 {
 	struct file *file = sd->u.file;
@@ -1032,8 +1033,8 @@ static int direct_splice_actor(struct pipe_inode_info *pipe,
  *    can splice directly through a process-private pipe.
  *
  */
-long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
-		      loff_t *opos, size_t len, unsigned int flags)
+ssize_t do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
+			 loff_t *opos, size_t len, unsigned int flags)
 {
 	struct splice_desc sd = {
 		.len		= len,
@@ -1043,7 +1044,7 @@ long do_splice_direct(struct file *in, loff_t *ppos, struct file *out,
 		.u.file		= out,
 		.opos		= opos,
 	};
-	long ret;
+	ssize_t ret;
 
 	if (unlikely(!(out->f_mode & FMODE_WRITE)))
 		return -EBADF;
@@ -1080,16 +1081,16 @@ static int wait_for_space(struct pipe_inode_info *pipe, unsigned flags)
 	}
 }
 
-static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
-			       struct pipe_inode_info *opipe,
-			       size_t len, unsigned int flags);
+static ssize_t splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
+				   struct pipe_inode_info *opipe,
+				   size_t len, unsigned int flags);
 
-long splice_file_to_pipe(struct file *in,
-			 struct pipe_inode_info *opipe,
-			 loff_t *offset,
-			 size_t len, unsigned int flags)
+ssize_t splice_file_to_pipe(struct file *in,
+			    struct pipe_inode_info *opipe,
+			    loff_t *offset,
+			    size_t len, unsigned int flags)
 {
-	long ret;
+	ssize_t ret;
 
 	pipe_lock(opipe);
 	ret = wait_for_space(opipe, flags);
@@ -1104,13 +1105,13 @@ long splice_file_to_pipe(struct file *in,
 /*
  * Determine where to splice to/from.
  */
-long do_splice(struct file *in, loff_t *off_in, struct file *out,
-	       loff_t *off_out, size_t len, unsigned int flags)
+ssize_t do_splice(struct file *in, loff_t *off_in, struct file *out,
+		  loff_t *off_out, size_t len, unsigned int flags)
 {
 	struct pipe_inode_info *ipipe;
 	struct pipe_inode_info *opipe;
 	loff_t offset;
-	long ret;
+	ssize_t ret;
 
 	if (unlikely(!(in->f_mode & FMODE_READ) ||
 		     !(out->f_mode & FMODE_WRITE)))
@@ -1192,14 +1193,14 @@ long do_splice(struct file *in, loff_t *off_in, struct file *out,
 	return -EINVAL;
 }
 
-static long __do_splice(struct file *in, loff_t __user *off_in,
-			struct file *out, loff_t __user *off_out,
-			size_t len, unsigned int flags)
+static ssize_t __do_splice(struct file *in, loff_t __user *off_in,
+			   struct file *out, loff_t __user *off_out,
+			   size_t len, unsigned int flags)
 {
 	struct pipe_inode_info *ipipe;
 	struct pipe_inode_info *opipe;
 	loff_t offset, *__off_in = NULL, *__off_out = NULL;
-	long ret;
+	ssize_t ret;
 
 	ipipe = get_pipe_info(in, true);
 	opipe = get_pipe_info(out, true);
@@ -1232,16 +1233,16 @@ static long __do_splice(struct file *in, loff_t __user *off_in,
 	return ret;
 }
 
-static int iter_to_pipe(struct iov_iter *from,
-			struct pipe_inode_info *pipe,
-			unsigned flags)
+static ssize_t iter_to_pipe(struct iov_iter *from,
+			    struct pipe_inode_info *pipe,
+			    unsigned flags)
 {
 	struct pipe_buffer buf = {
 		.ops = &user_page_pipe_buf_ops,
 		.flags = flags
 	};
 	size_t total = 0;
-	int ret = 0;
+	ssize_t ret = 0;
 
 	while (iov_iter_count(from)) {
 		struct page *pages[16];
@@ -1257,7 +1258,7 @@ static int iter_to_pipe(struct iov_iter *from,
 
 		n = DIV_ROUND_UP(left + start, PAGE_SIZE);
 		for (i = 0; i < n; i++) {
-			int size = min_t(int, left, PAGE_SIZE - start);
+			size_t size = min_t(int, left, PAGE_SIZE - start);
 
 			buf.page = pages[i];
 			buf.offset = start;
@@ -1279,10 +1280,10 @@ static int iter_to_pipe(struct iov_iter *from,
 	return total ? total : ret;
 }
 
-static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
-			struct splice_desc *sd)
+static ssize_t pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
+			    struct splice_desc *sd)
 {
-	int n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
+	size_t n = copy_page_to_iter(buf->page, buf->offset, sd->len, sd->u.data);
 	return n == sd->len ? n : -EFAULT;
 }
 
@@ -1290,8 +1291,8 @@ static int pipe_to_user(struct pipe_inode_info *pipe, struct pipe_buffer *buf,
  * For lack of a better implementation, implement vmsplice() to userspace
  * as a simple copy of the pipes pages to the user iov.
  */
-static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
-			     unsigned int flags)
+static ssize_t vmsplice_to_user(struct file *file, struct iov_iter *iter,
+				unsigned int flags)
 {
 	struct pipe_inode_info *pipe = get_pipe_info(file, true);
 	struct splice_desc sd = {
@@ -1299,7 +1300,7 @@ static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
 		.flags = flags,
 		.u.data = iter
 	};
-	long ret = 0;
+	ssize_t ret = 0;
 
 	if (!pipe)
 		return -EBADF;
@@ -1318,12 +1319,12 @@ static long vmsplice_to_user(struct file *file, struct iov_iter *iter,
  * as splice-from-memory, where the regular splice is splice-from-file (or
  * to file). In both cases the output is a pipe, naturally.
  */
-static long vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
-			     unsigned int flags)
+static ssize_t vmsplice_to_pipe(struct file *file, struct iov_iter *iter,
+				unsigned int flags)
 {
 	struct pipe_inode_info *pipe;
-	long ret = 0;
-	unsigned buf_flag = 0;
+	ssize_t ret = 0;
+	unsigned int buf_flag = 0;
 
 	if (flags & SPLICE_F_GIFT)
 		buf_flag = PIPE_BUF_FLAG_GIFT;
@@ -1414,7 +1415,7 @@ SYSCALL_DEFINE6(splice, int, fd_in, loff_t __user *, off_in,
 		size_t, len, unsigned int, flags)
 {
 	struct fd in, out;
-	long error;
+	ssize_t error;
 
 	if (unlikely(!len))
 		return 0;
@@ -1514,15 +1515,15 @@ static int opipe_prep(struct pipe_inode_info *pipe, unsigned int flags)
 /*
  * Splice contents of ipipe to opipe.
  */
-static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
-			       struct pipe_inode_info *opipe,
-			       size_t len, unsigned int flags)
+static ssize_t splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
+				   struct pipe_inode_info *opipe,
+				   size_t len, unsigned int flags)
 {
 	struct pipe_buffer *ibuf, *obuf;
 	unsigned int i_head, o_head;
 	unsigned int i_tail, o_tail;
 	unsigned int i_mask, o_mask;
-	int ret = 0;
+	ssize_t ret = 0;
 	bool input_wakeup = false;
 
 
@@ -1651,15 +1652,15 @@ static int splice_pipe_to_pipe(struct pipe_inode_info *ipipe,
 /*
  * Link contents of ipipe to opipe.
  */
-static int link_pipe(struct pipe_inode_info *ipipe,
-		     struct pipe_inode_info *opipe,
-		     size_t len, unsigned int flags)
+static ssize_t link_pipe(struct pipe_inode_info *ipipe,
+			 struct pipe_inode_info *opipe,
+			 size_t len, unsigned int flags)
 {
 	struct pipe_buffer *ibuf, *obuf;
 	unsigned int i_head, o_head;
 	unsigned int i_tail, o_tail;
 	unsigned int i_mask, o_mask;
-	int ret = 0;
+	ssize_t ret = 0;
 
 	/*
 	 * Potential ABBA deadlock, work around it by ordering lock
@@ -1742,11 +1743,11 @@ static int link_pipe(struct pipe_inode_info *ipipe,
  * The 'flags' used are the SPLICE_F_* variants, currently the only
  * applicable one is SPLICE_F_NONBLOCK.
  */
-long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
+ssize_t do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
 {
 	struct pipe_inode_info *ipipe = get_pipe_info(in, true);
 	struct pipe_inode_info *opipe = get_pipe_info(out, true);
-	int ret = -EINVAL;
+	ssize_t ret = -EINVAL;
 
 	if (unlikely(!(in->f_mode & FMODE_READ) ||
 		     !(out->f_mode & FMODE_WRITE)))
@@ -1778,7 +1779,7 @@ long do_tee(struct file *in, struct file *out, size_t len, unsigned int flags)
 SYSCALL_DEFINE4(tee, int, fdin, int, fdout, size_t, len, unsigned int, flags)
 {
 	struct fd in, out;
-	int error;
+	ssize_t error;
 
 	if (unlikely(flags & ~SPLICE_F_ALL))
 		return -EINVAL;
diff --git a/include/linux/splice.h b/include/linux/splice.h
index 8f052c3dae95..6af5e197ccd0 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -62,10 +62,10 @@ struct splice_pipe_desc {
 	void (*spd_release)(struct splice_pipe_desc *, unsigned int);
 };
 
-typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
-			   struct splice_desc *);
-typedef int (splice_direct_actor)(struct pipe_inode_info *,
-				  struct splice_desc *);
+typedef ssize_t (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
+			       struct splice_desc *);
+typedef ssize_t (splice_direct_actor)(struct pipe_inode_info *,
+				      struct splice_desc *);
 
 extern ssize_t splice_from_pipe(struct pipe_inode_info *, struct file *,
 				loff_t *, size_t, unsigned int,
@@ -76,17 +76,17 @@ extern ssize_t splice_to_pipe(struct pipe_inode_info *,
 			      struct splice_pipe_desc *);
 extern ssize_t add_to_pipe(struct pipe_inode_info *,
 			      struct pipe_buffer *);
-long vfs_splice_read(struct file *in, loff_t *ppos,
-		     struct pipe_inode_info *pipe, size_t len,
-		     unsigned int flags);
+ssize_t vfs_splice_read(struct file *in, loff_t *ppos,
+			struct pipe_inode_info *pipe, size_t len,
+			unsigned int flags);
 extern ssize_t splice_direct_to_actor(struct file *, struct splice_desc *,
 				      splice_direct_actor *);
-extern long do_splice(struct file *in, loff_t *off_in,
-		      struct file *out, loff_t *off_out,
-		      size_t len, unsigned int flags);
+extern ssize_t do_splice(struct file *in, loff_t *off_in,
+			 struct file *out, loff_t *off_out,
+			 size_t len, unsigned int flags);
 
-extern long do_tee(struct file *in, struct file *out, size_t len,
-		   unsigned int flags);
+extern ssize_t do_tee(struct file *in, struct file *out, size_t len,
+		      unsigned int flags);
 
 /*
  * for dynamic pipe sizing