[PATCH v21 05/30] splice: Make do_splice_to() generic and export it

[PATCH v21 05/30] 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>
Reviewed-by: Christoph Hellwig <hch@lst.de>
cc: Miklos Szeredi <miklos@szeredi.hu>
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 f9a9be797b0c..d815a69f6589 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -867,12 +867,24 @@ 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;
@@ -895,6 +907,7 @@ 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
@@ -964,7 +977,7 @@ 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;
 
@@ -1112,7 +1125,7 @@ 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 v21 05/30] splice: Make do_splice_to() generic and export it

[Christian Brauner]

On Sat, May 20, 2023 at 01:00:24AM +0100, David Howells wrote:
> 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>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> cc: Miklos Szeredi <miklos@szeredi.hu>
> 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]
> ---

Reviewed-by: Christian Brauner <brauner@kernel.org>

[PATCH v21 10/30] 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,

Re: [PATCH v21 10/30] overlayfs: Implement splice-read

[Christian Brauner]

[Cc Amir as well]

On Sat, May 20, 2023 at 01:00:29AM +0100, David Howells wrote:
> 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
> ---

Acked-by: Christian Brauner <brauner@kernel.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 v21 11/30] 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>
Acked-by: 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,
 };