[PATCH v17 02/14] splice: Make do_splice_to() generic and export it

[PATCH v17 02/14] splice: Make do_splice_to() generic and export it

[David Howells]

Rename do_splice_to() to vfs_splice_read() and export it so that it can be
used as a helper when calling down to a lower layer filesystem as it
performs all the necessary checks[1].

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Miklos Szeredi <miklos@szeredi.hu>
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-unionfs@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/CAJfpeguGksS3sCigmRi9hJdUec8qtM9f+_9jC1rJhsXT+dV01w@mail.gmail.com/ [1]
---
 fs/splice.c            | 27 ++++++++++++++++++++-------
 include/linux/splice.h |  3 +++
 2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index abd21a455a2b..90ccd3666dca 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -851,12 +851,24 @@ static long do_splice_from(struct pipe_inode_info *pipe, struct file *out,
 	return out->f_op->splice_write(pipe, out, ppos, len, flags);
 }
 
-/*
- * Attempt to initiate a splice from a file to a pipe.
+/**
+ * vfs_splice_read - Read data from a file and splice it into a pipe
+ * @in:		File to splice from
+ * @ppos:	Input file offset
+ * @pipe:	Pipe to splice to
+ * @len:	Number of bytes to splice
+ * @flags:	Splice modifier flags (SPLICE_F_*)
+ *
+ * Splice the requested amount of data from the input file to the pipe.  This
+ * is synchronous as the caller must hold the pipe lock across the entire
+ * operation.
+ *
+ * If successful, it returns the amount of data spliced, 0 if it hit the EOF or
+ * a hole and a negative error code otherwise.
  */
-static long do_splice_to(struct file *in, loff_t *ppos,
-			 struct pipe_inode_info *pipe, size_t len,
-			 unsigned int flags)
+long 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;
@@ -879,6 +891,7 @@ static long do_splice_to(struct file *in, loff_t *ppos,
 		return warn_unsupported(in, "read");
 	return in->f_op->splice_read(in, ppos, pipe, len, flags);
 }
+EXPORT_SYMBOL_GPL(vfs_splice_read);
 
 /**
  * splice_direct_to_actor - splices data directly between two non-pipes
@@ -949,7 +962,7 @@ ssize_t splice_direct_to_actor(struct file *in, struct splice_desc *sd,
 		size_t read_len;
 		loff_t pos = sd->pos, prev_pos = pos;
 
-		ret = do_splice_to(in, &pos, pipe, len, flags);
+		ret = vfs_splice_read(in, &pos, pipe, len, flags);
 		if (unlikely(ret <= 0))
 			goto out_release;
 
@@ -1097,7 +1110,7 @@ long splice_file_to_pipe(struct file *in,
 	pipe_lock(opipe);
 	ret = wait_for_space(opipe, flags);
 	if (!ret)
-		ret = do_splice_to(in, offset, opipe, len, flags);
+		ret = vfs_splice_read(in, offset, opipe, len, flags);
 	pipe_unlock(opipe);
 	if (ret > 0)
 		wakeup_pipe_readers(opipe);
diff --git a/include/linux/splice.h b/include/linux/splice.h
index a55179fd60fc..8f052c3dae95 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -76,6 +76,9 @@ 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);
 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,

Re: [PATCH v17 02/14] splice: Make do_splice_to() generic and export it

[Christoph Hellwig]

> -static long do_splice_to(struct file *in, loff_t *ppos,
> -			 struct pipe_inode_info *pipe, size_t len,
> -			 unsigned int flags)
> +long vfs_splice_read(struct file *in, loff_t *ppos,

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.

Otherwise looks good:

Reviewed-by: Christoph Hellwig <hch@lst.de>

Re: [PATCH v17 02/14] splice: Make do_splice_to() generic and export it

[David Howells]

Christoph Hellwig <hch@infradead.org> wrote:

> > -static long do_splice_to(struct file *in, loff_t *ppos,
> > -			 struct pipe_inode_info *pipe, size_t len,
> > -			 unsigned int flags)
> > +long vfs_splice_read(struct file *in, loff_t *ppos,
> 
> 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.

There's a while lot of places in splice.c that use long rather than ssize_t.
I can produce a separate patch that changes them all, but that should perhaps
be separate to this.

David

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

[David Howells]

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

[PATCH v17 04/14] overlayfs: Implement splice-read

[David Howells]

Implement splice-read for overlayfs by passing the request down a layer
rather than going through generic_file_splice_read() which is going to be
changed to assume that ->read_folio() is present on buffered files.

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: Miklos Szeredi <miklos@szeredi.hu>
cc: linux-unionfs@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---

Notes:
    ver #17)
     - Use vfs_splice_read() helper rather than open-coding checks.
    
    ver #15)
     - Remove redundant FMODE_CAN_ODIRECT check on real file.
     - Do rw_verify_area() on the real file, not the overlay file.
     - Fix a file leak.

 fs/overlayfs/file.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/fs/overlayfs/file.c b/fs/overlayfs/file.c
index 7c04f033aadd..86197882ff35 100644
--- a/fs/overlayfs/file.c
+++ b/fs/overlayfs/file.c
@@ -419,6 +419,27 @@ static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 	return ret;
 }
 
+static ssize_t ovl_splice_read(struct file *in, loff_t *ppos,
+			       struct pipe_inode_info *pipe, size_t len,
+			       unsigned int flags)
+{
+	const struct cred *old_cred;
+	struct fd real;
+	ssize_t ret;
+
+	ret = ovl_real_fdget(in, &real);
+	if (ret)
+		return ret;
+
+	old_cred = ovl_override_creds(file_inode(in)->i_sb);
+	ret = vfs_splice_read(real.file, ppos, pipe, len, flags);
+	revert_creds(old_cred);
+	ovl_file_accessed(in);
+
+	fdput(real);
+	return ret;
+}
+
 /*
  * Calling iter_file_splice_write() directly from overlay's f_op may deadlock
  * due to lock order inversion between pipe->mutex in iter_file_splice_write()
@@ -695,7 +716,7 @@ const struct file_operations ovl_file_operations = {
 	.fallocate	= ovl_fallocate,
 	.fadvise	= ovl_fadvise,
 	.flush		= ovl_flush,
-	.splice_read    = generic_file_splice_read,
+	.splice_read    = ovl_splice_read,
 	.splice_write   = ovl_splice_write,
 
 	.copy_file_range	= ovl_copy_file_range,

[PATCH v17 05/14] coda: Implement splice-read

[David Howells]

Implement splice-read for coda by passing the request down a layer rather
than going through generic_file_splice_read() which is going to be changed
to assume that ->read_folio() is present on buffered files.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jan Harkes <jaharkes@cs.cmu.edu>
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: coda@cs.cmu.edu
cc: codalist@coda.cs.cmu.edu
cc: linux-unionfs@vger.kernel.org
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---

Notes:
    ver #17)
     - Use vfs_splice_read() helper rather than open-coding checks.

 fs/coda/file.c | 29 ++++++++++++++++++++++++++++-
 1 file changed, 28 insertions(+), 1 deletion(-)

diff --git a/fs/coda/file.c b/fs/coda/file.c
index 3f3c81e6b1ab..12b26bd13564 100644
--- a/fs/coda/file.c
+++ b/fs/coda/file.c
@@ -23,6 +23,7 @@
 #include <linux/slab.h>
 #include <linux/uaccess.h>
 #include <linux/uio.h>
+#include <linux/splice.h>
 
 #include <linux/coda.h>
 #include "coda_psdev.h"
@@ -94,6 +95,32 @@ coda_file_write_iter(struct kiocb *iocb, struct iov_iter *to)
 	return ret;
 }
 
+static ssize_t
+coda_file_splice_read(struct file *coda_file, loff_t *ppos,
+		      struct pipe_inode_info *pipe,
+		      size_t len, unsigned int flags)
+{
+	struct inode *coda_inode = file_inode(coda_file);
+	struct coda_file_info *cfi = coda_ftoc(coda_file);
+	struct file *in = cfi->cfi_container;
+	loff_t ki_pos = *ppos;
+	ssize_t ret;
+
+	ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
+				  &cfi->cfi_access_intent,
+				  len, ki_pos, CODA_ACCESS_TYPE_READ);
+	if (ret)
+		goto finish_read;
+
+	ret = vfs_splice_read(in, ppos, pipe, len, flags);
+
+finish_read:
+	venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
+			    &cfi->cfi_access_intent,
+			    len, ki_pos, CODA_ACCESS_TYPE_READ_FINISH);
+	return ret;
+}
+
 static void
 coda_vm_open(struct vm_area_struct *vma)
 {
@@ -302,5 +329,5 @@ const struct file_operations coda_file_operations = {
 	.open		= coda_open,
 	.release	= coda_release,
 	.fsync		= coda_fsync,
-	.splice_read	= generic_file_splice_read,
+	.splice_read	= coda_file_splice_read,
 };

Re: [PATCH v17 05/14] coda: Implement splice-read

[Jan Harkes]

That actually looks better than the original code because this brings
in the experimental read intent hinting which allows userspace to
mediate access to partially cached files.

Jan


On Wed, Mar 08, 2023 at 11:53:19AM -0500, David Howells wrote:
> Implement splice-read for coda by passing the request down a layer rather
> than going through generic_file_splice_read() which is going to be changed
> to assume that ->read_folio() is present on buffered files.
> 
> Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Jan Harkes <jaharkes@cs.cmu.edu>

> cc: Jan Harkes <jaharkes@cs.cmu.edu>
> 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: coda@cs.cmu.edu
> cc: codalist@coda.cs.cmu.edu
> cc: linux-unionfs@vger.kernel.org
> cc: linux-block@vger.kernel.org
> cc: linux-fsdevel@vger.kernel.org
> cc: linux-mm@kvack.org
> ---
> 
> Notes:
>     ver #17)
>      - Use vfs_splice_read() helper rather than open-coding checks.
> 
>  fs/coda/file.c | 29 ++++++++++++++++++++++++++++-
>  1 file changed, 28 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/coda/file.c b/fs/coda/file.c
> index 3f3c81e6b1ab..12b26bd13564 100644
> --- a/fs/coda/file.c
> +++ b/fs/coda/file.c
> @@ -23,6 +23,7 @@
>  #include <linux/slab.h>
>  #include <linux/uaccess.h>
>  #include <linux/uio.h>
> +#include <linux/splice.h>
>  
>  #include <linux/coda.h>
>  #include "coda_psdev.h"
> @@ -94,6 +95,32 @@ coda_file_write_iter(struct kiocb *iocb, struct iov_iter *to)
>  	return ret;
>  }
>  
> +static ssize_t
> +coda_file_splice_read(struct file *coda_file, loff_t *ppos,
> +		      struct pipe_inode_info *pipe,
> +		      size_t len, unsigned int flags)
> +{
> +	struct inode *coda_inode = file_inode(coda_file);
> +	struct coda_file_info *cfi = coda_ftoc(coda_file);
> +	struct file *in = cfi->cfi_container;
> +	loff_t ki_pos = *ppos;
> +	ssize_t ret;
> +
> +	ret = venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
> +				  &cfi->cfi_access_intent,
> +				  len, ki_pos, CODA_ACCESS_TYPE_READ);
> +	if (ret)
> +		goto finish_read;
> +
> +	ret = vfs_splice_read(in, ppos, pipe, len, flags);
> +
> +finish_read:
> +	venus_access_intent(coda_inode->i_sb, coda_i2f(coda_inode),
> +			    &cfi->cfi_access_intent,
> +			    len, ki_pos, CODA_ACCESS_TYPE_READ_FINISH);
> +	return ret;
> +}
> +
>  static void
>  coda_vm_open(struct vm_area_struct *vma)
>  {
> @@ -302,5 +329,5 @@ const struct file_operations coda_file_operations = {
>  	.open		= coda_open,
>  	.release	= coda_release,
>  	.fsync		= coda_fsync,
> -	.splice_read	= generic_file_splice_read,
> +	.splice_read	= coda_file_splice_read,
>  };
> 
>