[PATCH 0/4] iov_iter: Adjust styling/location of new splice functions

[PATCH 0/4] iov_iter: Adjust styling/location of new splice functions

[David Howells]

Hi Jens, Al, Christoph,

Here are patches to make some changes that Christoph requested[1] to the
new generic file splice functions that I implemented[2].  Apart from one
functional change, they just altering the styling and move one of the
functions to a different file:

 (1) Rename the main functions:

	generic_file_buffered_splice_read() -> filemap_splice_read()
	generic_file_direct_splice_read()   -> direct_splice_read()

 (2) Abstract out the calculation of the location of the head pipe buffer
     into a helper function in linux/pipe_fs_i.h.

 (3) Use init_sync_kiocb() in filemap_splice_read().

     This is where the functional change is.  Some kiocb fields are then
     filled in where they were set to 0 before, including setting ki_flags
     from f_iocb_flags.  I've filtered out IOCB_NOWAIT as the function is
     supposed to be synchronous.

 (4) Move filemap_splice_read() to mm/filemap.c.  filemap_get_pages() can
     then be made static again.

I've pushed the patches here also:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-extract-3

I've also updated worked the changes into the commits on my iov-extract
branch if that would be preferable, though that means Jens would need to
update his for-6.3/iov-extract again.

David

Link: https://lore.kernel.org/r/Y+n0n2UE8BQa/OwW@infradead.org/ [1]
Link: https://lore.kernel.org/r/20230207171305.3716974-1-dhowells@redhat.com/ [2]

David Howells (4):
  splice: Rename new splice functions
  splice: Provide pipe_head_buf() helper
  splice: Use init_sync_kiocb() in filemap_splice_read()
  splice: Move filemap_read_splice() to mm/filemap.c

 fs/splice.c               | 146 ++------------------------------------
 include/linux/pagemap.h   |   2 -
 include/linux/pipe_fs_i.h |  20 ++++++
 include/linux/splice.h    |   4 ++
 mm/filemap.c              | 138 +++++++++++++++++++++++++++++++++--
 5 files changed, 163 insertions(+), 147 deletions(-)

[PATCH 1/4] splice: Rename new splice functions

[David Howells]

Rename generic_file_buffered_splice_read() to filemap_splice_read().

Rename generic_file_direct_splice_read() to direct_splice_read().

Requested-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
---
 fs/splice.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 2717078949a2..91b9e2cb9e03 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -287,9 +287,9 @@ void splice_shrink_spd(struct splice_pipe_desc *spd)
  * Splice data from an O_DIRECT file into pages and then add them to the output
  * pipe.
  */
-static ssize_t generic_file_direct_splice_read(struct file *in, loff_t *ppos,
-					       struct pipe_inode_info *pipe,
-					       size_t len, unsigned int flags)
+static ssize_t direct_splice_read(struct file *in, loff_t *ppos,
+				  struct pipe_inode_info *pipe,
+				  size_t len, unsigned int flags)
 {
 	struct iov_iter to;
 	struct bio_vec *bv;
@@ -417,10 +417,9 @@ static size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
  * Splice folios from the pagecache of a buffered (ie. non-O_DIRECT) file into
  * a pipe.
  */
-static ssize_t generic_file_buffered_splice_read(struct file *in, loff_t *ppos,
-						 struct pipe_inode_info *pipe,
-						 size_t len,
-						 unsigned int flags)
+static ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
+				   struct pipe_inode_info *pipe,
+				   size_t len, unsigned int flags)
 {
 	struct folio_batch fbatch;
 	size_t total_spliced = 0, used, npages;
@@ -529,8 +528,8 @@ ssize_t generic_file_splice_read(struct file *in, loff_t *ppos,
 	if (unlikely(!len))
 		return 0;
 	if (in->f_flags & O_DIRECT)
-		return generic_file_direct_splice_read(in, ppos, pipe, len, flags);
-	return generic_file_buffered_splice_read(in, ppos, pipe, len, flags);
+		return direct_splice_read(in, ppos, pipe, len, flags);
+	return filemap_splice_read(in, ppos, pipe, len, flags);
 }
 EXPORT_SYMBOL(generic_file_splice_read);
 

Re: [PATCH 1/4] splice: Rename new splice functions

[Christoph Hellwig]

Looks good:

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

[PATCH 2/4] splice: Provide pipe_head_buf() helper

[David Howells]

Provide a helper, pipe_head_buf(), to get the current head buffer from a
pipe.  Implement this as a wrapper around a more general function,
pipe_buf(), that gets a specified buffer.

Requested-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
---
 fs/splice.c               |  9 +++------
 include/linux/pipe_fs_i.h | 20 ++++++++++++++++++++
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 91b9e2cb9e03..7c0ff187f87a 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -295,7 +295,6 @@ static ssize_t direct_splice_read(struct file *in, loff_t *ppos,
 	struct bio_vec *bv;
 	struct kiocb kiocb;
 	struct page **pages;
-	unsigned int head;
 	ssize_t ret;
 	size_t used, npages, chunk, remain, reclaim;
 	int i;
@@ -358,9 +357,8 @@ static ssize_t direct_splice_read(struct file *in, loff_t *ppos,
 	}
 
 	/* Push the remaining pages into the pipe. */
-	head = pipe->head;
 	for (i = 0; i < npages; i++) {
-		struct pipe_buffer *buf = &pipe->bufs[head & (pipe->ring_size - 1)];
+		struct pipe_buffer *buf = pipe_head_buf(pipe);
 
 		chunk = min_t(size_t, remain, PAGE_SIZE);
 		*buf = (struct pipe_buffer) {
@@ -369,10 +367,9 @@ static ssize_t direct_splice_read(struct file *in, loff_t *ppos,
 			.offset	= 0,
 			.len	= chunk,
 		};
-		head++;
+		pipe->head++;
 		remain -= chunk;
 	}
-	pipe->head = head;
 
 	kfree(bv);
 	return ret;
@@ -394,7 +391,7 @@ static size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
 
 	while (spliced < size &&
 	       !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
-		struct pipe_buffer *buf = &pipe->bufs[pipe->head & (pipe->ring_size - 1)];
+		struct pipe_buffer *buf = pipe_head_buf(pipe);
 		size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);
 
 		*buf = (struct pipe_buffer) {
diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h
index 6cb65df3e3ba..d2c3f16cf6b1 100644
--- a/include/linux/pipe_fs_i.h
+++ b/include/linux/pipe_fs_i.h
@@ -156,6 +156,26 @@ static inline bool pipe_full(unsigned int head, unsigned int tail,
 	return pipe_occupancy(head, tail) >= limit;
 }
 
+/**
+ * pipe_buf - Return the pipe buffer for the specified slot in the pipe ring
+ * @pipe: The pipe to access
+ * @slot: The slot of interest
+ */
+static inline struct pipe_buffer *pipe_buf(const struct pipe_inode_info *pipe,
+					   unsigned int slot)
+{
+	return &pipe->bufs[slot & (pipe->ring_size - 1)];
+}
+
+/**
+ * pipe_head_buf - Return the pipe buffer at the head of the pipe ring
+ * @pipe: The pipe to access
+ */
+static inline struct pipe_buffer *pipe_head_buf(const struct pipe_inode_info *pipe)
+{
+	return pipe_buf(pipe, pipe->head);
+}
+
 /**
  * pipe_buf_get - get a reference to a pipe_buffer
  * @pipe:	the pipe that the buffer belongs to

Re: [PATCH 2/4] splice: Provide pipe_head_buf() helper

[Christoph Hellwig]

On Mon, Feb 13, 2023 at 01:46:17PM +0000, David Howells wrote:
> Provide a helper, pipe_head_buf(), to get the current head buffer from a
> pipe.  Implement this as a wrapper around a more general function,
> pipe_buf(), that gets a specified buffer.

Looks good:

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

There's also a bunch of spots in existing code that should use this
helper.

[PATCH 3/4] splice: Use init_sync_kiocb() in filemap_splice_read()

[David Howells]

Use init_sync_kiocb() in filemap_splice_read() rather than open coding it
and filter out IOCB_NOWAIT since the splice is synchronous.

Requested-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
---
 fs/splice.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 7c0ff187f87a..8b2a9d963bc4 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -419,15 +419,15 @@ static ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
 				   size_t len, unsigned int flags)
 {
 	struct folio_batch fbatch;
+	struct kiocb iocb;
 	size_t total_spliced = 0, used, npages;
 	loff_t isize, end_offset;
 	bool writably_mapped;
 	int i, error = 0;
 
-	struct kiocb iocb = {
-		.ki_filp	= in,
-		.ki_pos		= *ppos,
-	};
+	init_sync_kiocb(&iocb, in);
+	iocb.ki_pos = *ppos;
+	iocb.ki_flags &= IOCB_NOWAIT;
 
 	/* Work out how much data we can actually add into the pipe */
 	used = pipe_occupancy(pipe->head, pipe->tail);

Re: [PATCH 3/4] splice: Use init_sync_kiocb() in filemap_splice_read()

[Christoph Hellwig]

On Mon, Feb 13, 2023 at 01:46:18PM +0000, David Howells wrote:
> +	init_sync_kiocb(&iocb, in);
> +	iocb.ki_pos = *ppos;
> +	iocb.ki_flags &= IOCB_NOWAIT;

This clears everything but IOCB_NOWAIT.  But even IOCB_NOWAIT should
not be cleared here as far as I can tell.

Re: [PATCH 3/4] splice: Use init_sync_kiocb() in filemap_splice_read()

[Matthew Wilcox]

On Mon, Feb 13, 2023 at 01:46:18PM +0000, David Howells wrote:
> Use init_sync_kiocb() in filemap_splice_read() rather than open coding it
> and filter out IOCB_NOWAIT since the splice is synchronous.

If the user has asked for NOWAIT and the splice is going to be
synchronous, shouldn't we rather return -EWOULDBLOCK here?  Or
does this not block?

IOW, this either does the wrong thing, or it does something that's
irrelevant.

[PATCH 4/4] splice: Move filemap_read_splice() to mm/filemap.c

[David Howells]

Move filemap_read_splice() to mm/filemap.c and make filemap_get_pages()
static again.

Requested-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
---
 fs/splice.c             | 128 -------------------------------------
 include/linux/pagemap.h |   2 -
 include/linux/splice.h  |   4 ++
 mm/filemap.c            | 138 ++++++++++++++++++++++++++++++++++++++--
 4 files changed, 136 insertions(+), 136 deletions(-)

diff --git a/fs/splice.c b/fs/splice.c
index 8b2a9d963bc4..341cd8fb47a8 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -375,134 +375,6 @@ static ssize_t direct_splice_read(struct file *in, loff_t *ppos,
 	return ret;
 }
 
-/*
- * Splice subpages from a folio into a pipe.
- */
-static size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
-				     struct folio *folio,
-				     loff_t fpos, size_t size)
-{
-	struct page *page;
-	size_t spliced = 0, offset = offset_in_folio(folio, fpos);
-
-	page = folio_page(folio, offset / PAGE_SIZE);
-	size = min(size, folio_size(folio) - offset);
-	offset %= PAGE_SIZE;
-
-	while (spliced < size &&
-	       !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
-		struct pipe_buffer *buf = pipe_head_buf(pipe);
-		size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);
-
-		*buf = (struct pipe_buffer) {
-			.ops	= &page_cache_pipe_buf_ops,
-			.page	= page,
-			.offset	= offset,
-			.len	= part,
-		};
-		folio_get(folio);
-		pipe->head++;
-		page++;
-		spliced += part;
-		offset = 0;
-	}
-
-	return spliced;
-}
-
-/*
- * Splice folios from the pagecache of a buffered (ie. non-O_DIRECT) file into
- * a pipe.
- */
-static ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
-				   struct pipe_inode_info *pipe,
-				   size_t len, unsigned int flags)
-{
-	struct folio_batch fbatch;
-	struct kiocb iocb;
-	size_t total_spliced = 0, used, npages;
-	loff_t isize, end_offset;
-	bool writably_mapped;
-	int i, error = 0;
-
-	init_sync_kiocb(&iocb, in);
-	iocb.ki_pos = *ppos;
-	iocb.ki_flags &= IOCB_NOWAIT;
-
-	/* Work out how much data we can actually add into the pipe */
-	used = pipe_occupancy(pipe->head, pipe->tail);
-	npages = max_t(ssize_t, pipe->max_usage - used, 0);
-	len = min_t(size_t, len, npages * PAGE_SIZE);
-
-	folio_batch_init(&fbatch);
-
-	do {
-		cond_resched();
-
-		if (*ppos >= i_size_read(file_inode(in)))
-			break;
-
-		iocb.ki_pos = *ppos;
-		error = filemap_get_pages(&iocb, len, &fbatch, true);
-		if (error < 0)
-			break;
-
-		/*
-		 * i_size must be checked after we know the pages are Uptodate.
-		 *
-		 * Checking i_size after the check allows us to calculate
-		 * the correct value for "nr", which means the zero-filled
-		 * part of the page is not copied back to userspace (unless
-		 * another truncate extends the file - this is desired though).
-		 */
-		isize = i_size_read(file_inode(in));
-		if (unlikely(*ppos >= isize))
-			break;
-		end_offset = min_t(loff_t, isize, *ppos + len);
-
-		/*
-		 * Once we start copying data, we don't want to be touching any
-		 * cachelines that might be contended:
-		 */
-		writably_mapped = mapping_writably_mapped(in->f_mapping);
-
-		for (i = 0; i < folio_batch_count(&fbatch); i++) {
-			struct folio *folio = fbatch.folios[i];
-			size_t n;
-
-			if (folio_pos(folio) >= end_offset)
-				goto out;
-			folio_mark_accessed(folio);
-
-			/*
-			 * If users can be writing to this folio using arbitrary
-			 * virtual addresses, take care of potential aliasing
-			 * before reading the folio on the kernel side.
-			 */
-			if (writably_mapped)
-				flush_dcache_folio(folio);
-
-			n = splice_folio_into_pipe(pipe, folio, *ppos, len);
-			if (!n)
-				goto out;
-			len -= n;
-			total_spliced += n;
-			*ppos += n;
-			in->f_ra.prev_pos = *ppos;
-			if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
-				goto out;
-		}
-
-		folio_batch_release(&fbatch);
-	} while (len);
-
-out:
-	folio_batch_release(&fbatch);
-	file_accessed(in);
-
-	return total_spliced ? total_spliced : error;
-}
-
 /**
  * generic_file_splice_read - splice data from file to a pipe
  * @in:		file to splice from
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 3a7bdb35acff..29e1f9e76eb6 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -748,8 +748,6 @@ struct page *read_cache_page(struct address_space *, pgoff_t index,
 		filler_t *filler, struct file *file);
 extern struct page * read_cache_page_gfp(struct address_space *mapping,
 				pgoff_t index, gfp_t gfp_mask);
-int filemap_get_pages(struct kiocb *iocb, size_t count,
-		      struct folio_batch *fbatch, bool need_uptodate);
 
 static inline struct page *read_mapping_page(struct address_space *mapping,
 				pgoff_t index, struct file *file)
diff --git a/include/linux/splice.h b/include/linux/splice.h
index a55179fd60fc..691c44ef5c0b 100644
--- a/include/linux/splice.h
+++ b/include/linux/splice.h
@@ -67,6 +67,10 @@ typedef int (splice_actor)(struct pipe_inode_info *, struct pipe_buffer *,
 typedef int (splice_direct_actor)(struct pipe_inode_info *,
 				  struct splice_desc *);
 
+ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
+			    struct pipe_inode_info *pipe,
+			    size_t len, unsigned int flags);
+
 extern ssize_t splice_from_pipe(struct pipe_inode_info *, struct file *,
 				loff_t *, size_t, unsigned int,
 				splice_actor *);
diff --git a/mm/filemap.c b/mm/filemap.c
index 6970be64a3e0..963602671fee 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -42,6 +42,8 @@
 #include <linux/ramfs.h>
 #include <linux/page_idle.h>
 #include <linux/migrate.h>
+#include <linux/pipe_fs_i.h>
+#include <linux/splice.h>
 #include <asm/pgalloc.h>
 #include <asm/tlbflush.h>
 #include "internal.h"
@@ -2576,12 +2578,8 @@ static int filemap_readahead(struct kiocb *iocb, struct file *file,
 	return 0;
 }
 
-/*
- * Extract some folios from the pagecache of a file, reading those pages from
- * the backing store if necessary and waiting for them.
- */
-int filemap_get_pages(struct kiocb *iocb, size_t count,
-		      struct folio_batch *fbatch, bool need_uptodate)
+static int filemap_get_pages(struct kiocb *iocb, size_t count,
+		struct folio_batch *fbatch, bool need_uptodate)
 {
 	struct file *filp = iocb->ki_filp;
 	struct address_space *mapping = filp->f_mapping;
@@ -2845,6 +2843,134 @@ generic_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 }
 EXPORT_SYMBOL(generic_file_read_iter);
 
+/*
+ * Splice subpages from a folio into a pipe.
+ */
+static size_t splice_folio_into_pipe(struct pipe_inode_info *pipe,
+				     struct folio *folio,
+				     loff_t fpos, size_t size)
+{
+	struct page *page;
+	size_t spliced = 0, offset = offset_in_folio(folio, fpos);
+
+	page = folio_page(folio, offset / PAGE_SIZE);
+	size = min(size, folio_size(folio) - offset);
+	offset %= PAGE_SIZE;
+
+	while (spliced < size &&
+	       !pipe_full(pipe->head, pipe->tail, pipe->max_usage)) {
+		struct pipe_buffer *buf = pipe_head_buf(pipe);
+		size_t part = min_t(size_t, PAGE_SIZE - offset, size - spliced);
+
+		*buf = (struct pipe_buffer) {
+			.ops	= &page_cache_pipe_buf_ops,
+			.page	= page,
+			.offset	= offset,
+			.len	= part,
+		};
+		folio_get(folio);
+		pipe->head++;
+		page++;
+		spliced += part;
+		offset = 0;
+	}
+
+	return spliced;
+}
+
+/*
+ * Splice folios from the pagecache of a buffered (ie. non-O_DIRECT) file into
+ * a pipe.
+ */
+ssize_t filemap_splice_read(struct file *in, loff_t *ppos,
+			    struct pipe_inode_info *pipe,
+			    size_t len, unsigned int flags)
+{
+	struct folio_batch fbatch;
+	struct kiocb iocb;
+	size_t total_spliced = 0, used, npages;
+	loff_t isize, end_offset;
+	bool writably_mapped;
+	int i, error = 0;
+
+	init_sync_kiocb(&iocb, in);
+	iocb.ki_pos = *ppos;
+	iocb.ki_flags &= IOCB_NOWAIT;
+
+	/* Work out how much data we can actually add into the pipe */
+	used = pipe_occupancy(pipe->head, pipe->tail);
+	npages = max_t(ssize_t, pipe->max_usage - used, 0);
+	len = min_t(size_t, len, npages * PAGE_SIZE);
+
+	folio_batch_init(&fbatch);
+
+	do {
+		cond_resched();
+
+		if (*ppos >= i_size_read(file_inode(in)))
+			break;
+
+		iocb.ki_pos = *ppos;
+		error = filemap_get_pages(&iocb, len, &fbatch, true);
+		if (error < 0)
+			break;
+
+		/*
+		 * i_size must be checked after we know the pages are Uptodate.
+		 *
+		 * Checking i_size after the check allows us to calculate
+		 * the correct value for "nr", which means the zero-filled
+		 * part of the page is not copied back to userspace (unless
+		 * another truncate extends the file - this is desired though).
+		 */
+		isize = i_size_read(file_inode(in));
+		if (unlikely(*ppos >= isize))
+			break;
+		end_offset = min_t(loff_t, isize, *ppos + len);
+
+		/*
+		 * Once we start copying data, we don't want to be touching any
+		 * cachelines that might be contended:
+		 */
+		writably_mapped = mapping_writably_mapped(in->f_mapping);
+
+		for (i = 0; i < folio_batch_count(&fbatch); i++) {
+			struct folio *folio = fbatch.folios[i];
+			size_t n;
+
+			if (folio_pos(folio) >= end_offset)
+				goto out;
+			folio_mark_accessed(folio);
+
+			/*
+			 * If users can be writing to this folio using arbitrary
+			 * virtual addresses, take care of potential aliasing
+			 * before reading the folio on the kernel side.
+			 */
+			if (writably_mapped)
+				flush_dcache_folio(folio);
+
+			n = splice_folio_into_pipe(pipe, folio, *ppos, len);
+			if (!n)
+				goto out;
+			len -= n;
+			total_spliced += n;
+			*ppos += n;
+			in->f_ra.prev_pos = *ppos;
+			if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
+				goto out;
+		}
+
+		folio_batch_release(&fbatch);
+	} while (len);
+
+out:
+	folio_batch_release(&fbatch);
+	file_accessed(in);
+
+	return total_spliced ? total_spliced : error;
+}
+
 static inline loff_t folio_seek_hole_data(struct xa_state *xas,
 		struct address_space *mapping, struct folio *folio,
 		loff_t start, loff_t end, bool seek_data)

Re: [PATCH 4/4] splice: Move filemap_read_splice() to mm/filemap.c

[Christoph Hellwig]

Looks good:

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