[1/5] fs: Export generic_file_buffered_read()

Commit Message

Goldwyn Rodrigues Nov. 26, 2019, 3:14 a.m. UTC

From: Goldwyn Rodrigues <[e-mail]>

Export generic_file_buffered_read() to be used to
supplement incomplete direct reads.

While we are at it, correct the comments and variable names.

Signed-off-by: Goldwyn Rodrigues <[e-mail]>
---
 include/linux/fs.h |  2 ++
 mm/filemap.c       | 13 +++++++------
 2 files changed, 9 insertions(+), 6 deletions(-)

Comments

Matthew Wilcox Nov. 26, 2019, 3:43 a.m. UTC | #1

On Mon, Nov 25, 2019 at 09:14:52PM -0600, Goldwyn Rodrigues wrote:
> @@ -2003,11 +2003,11 @@ static void shrink_readahead_size_eio(struct file *filp,
>   * of the logic when it comes to error handling etc.
>   *
>   * Return:
> - * * total number of bytes copied, including those the were already @written
> + * * total number of bytes copied, including those the were @copied

"those that were"

Johannes Thumshirn Nov. 26, 2019, 10:10 a.m. UTC | #2

Apart from Willy's comment
Reviewed-by: Johannes Thumshirn <[e-mail]>

Johannes Thumshirn Nov. 26, 2019, 10:43 a.m. UTC | #3

On 26/11/2019 11:10, Johannes Thumshirn wrote:
> Apart from Willy's comment
> Reviewed-by: Johannes Thumshirn <[e-mail]>

On the other hand, you could as well do:

static ssize_t btrfs_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
+{
+	ssize_t ret = 0;
+	if (iocb->ki_flags & IOCB_DIRECT)
+		ret = btrfs_dio_read(iocb, to);
+	if (ret < 0)
+		return ret;
+
+	return generic_file_read_iter(iocb, ret);
+}

In patch 3/5, if IOCB_DIRECT is set we're branching into
btrfs_dio_read() above and if not generic_file_read_iter() will then
directly call generic_file_buffered_read()

Patch

diff --git a/include/linux/fs.h b/include/linux/fs.h
index e0d909d35763..5bc75cff3536 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -3095,6 +3095,8 @@  extern int generic_file_rw_checks(struct file *file_in, struct file *file_out);
 extern int generic_copy_file_checks(struct file *file_in, loff_t pos_in,
 				    struct file *file_out, loff_t pos_out,
 				    size_t *count, unsigned int flags);
+extern ssize_t generic_file_buffered_read(struct kiocb *iocb,
+		struct iov_iter *to, ssize_t already_read);
 extern ssize_t generic_file_read_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t __generic_file_write_iter(struct kiocb *, struct iov_iter *);
 extern ssize_t generic_file_write_iter(struct kiocb *, struct iov_iter *);
diff --git a/mm/filemap.c b/mm/filemap.c
index 85b7d087eb45..6a1be2fcdfe7 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1994,7 +1994,7 @@  static void shrink_readahead_size_eio(struct file *filp,
  * generic_file_buffered_read - generic file read routine
  * @iocb:	the iocb to read
  * @iter:	data destination
- * @written:	already copied
+ * @copied:	already copied
  *
  * This is a generic file read routine, and uses the
  * mapping->a_ops->readpage() function for the actual low-level stuff.
@@ -2003,11 +2003,11 @@  static void shrink_readahead_size_eio(struct file *filp,
  * of the logic when it comes to error handling etc.
  *
  * Return:
- * * total number of bytes copied, including those the were already @written
+ * * total number of bytes copied, including those the were @copied
  * * negative error code if nothing was copied
  */
-static ssize_t generic_file_buffered_read(struct kiocb *iocb,
-		struct iov_iter *iter, ssize_t written)
+ssize_t generic_file_buffered_read(struct kiocb *iocb,
+		struct iov_iter *iter, ssize_t copied)
 {
 	struct file *filp = iocb->ki_filp;
 	struct address_space *mapping = filp->f_mapping;
@@ -2148,7 +2148,7 @@  static ssize_t generic_file_buffered_read(struct kiocb *iocb,
 		prev_offset = offset;
 
 		put_page(page);
-		written += ret;
+		copied += ret;
 		if (!iov_iter_count(iter))
 			goto out;
 		if (ret < nr) {
@@ -2256,8 +2256,9 @@  static ssize_t generic_file_buffered_read(struct kiocb *iocb,
 
 	*ppos = ((loff_t)index << PAGE_SHIFT) + offset;
 	file_accessed(filp);
-	return written ? written : error;
+	return copied ? copied : error;
 }
+EXPORT_SYMBOL_GPL(generic_file_buffered_read);
 
 /**
  * generic_file_read_iter - generic filesystem read routine