diff mbox series

[02/13] iomap: Read page from srcmap for IOMAP_COW

Message ID 20190802220048.16142-3-rgoldwyn@suse.de (mailing list archive)
State New, archived
Headers show
Series Btrfs iomap | expand

Commit Message

Goldwyn Rodrigues Aug. 2, 2019, 10 p.m. UTC 
From: Goldwyn Rodrigues <rgoldwyn@suse.com>

In case of a IOMAP_COW, read a page from the srcmap before
performing a write on the page.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
---
 fs/iomap/buffered-io.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

Comments

Darrick J. Wong Aug. 3, 2019, 12:23 a.m. UTC | #1 
On Fri, Aug 02, 2019 at 05:00:37PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> In case of a IOMAP_COW, read a page from the srcmap before
> performing a write on the page.

Looks ok, I think...
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>

--D

> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
>  fs/iomap/buffered-io.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index f27756c0b31c..a96cc26eec92 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -581,7 +581,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
>  
>  static int
>  iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> -		struct page **pagep, struct iomap *iomap)
> +		struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
>  {
>  	const struct iomap_page_ops *page_ops = iomap->page_ops;
>  	pgoff_t index = pos >> PAGE_SHIFT;
> @@ -607,6 +607,8 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
>  
>  	if (iomap->type == IOMAP_INLINE)
>  		iomap_read_inline_data(inode, page, iomap);
> +	else if (iomap->type == IOMAP_COW)
> +		status = __iomap_write_begin(inode, pos, len, page, srcmap);
>  	else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
>  		status = __block_write_begin_int(page, pos, len, NULL, iomap);
>  	else
> @@ -772,7 +774,7 @@ iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>  		}
>  
>  		status = iomap_write_begin(inode, pos, bytes, flags, &page,
> -				iomap);
> +				iomap, srcmap);
>  		if (unlikely(status))
>  			break;
>  
> @@ -871,7 +873,7 @@ iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
>  			return PTR_ERR(rpage);
>  
>  		status = iomap_write_begin(inode, pos, bytes,
> -					   AOP_FLAG_NOFS, &page, iomap);
> +					   AOP_FLAG_NOFS, &page, iomap, srcmap);
>  		put_page(rpage);
>  		if (unlikely(status))
>  			return status;
> @@ -917,13 +919,13 @@ iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
>  EXPORT_SYMBOL_GPL(iomap_file_dirty);
>  
>  static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
> -		unsigned bytes, struct iomap *iomap)
> +		unsigned bytes, struct iomap *iomap, struct iomap *srcmap)
>  {
>  	struct page *page;
>  	int status;
>  
>  	status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page,
> -				   iomap);
> +				   iomap, srcmap);
>  	if (status)
>  		return status;
>  
> @@ -961,7 +963,7 @@ iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
>  		if (IS_DAX(inode))
>  			status = iomap_dax_zero(pos, offset, bytes, iomap);
>  		else
> -			status = iomap_zero(inode, pos, offset, bytes, iomap);
> +			status = iomap_zero(inode, pos, offset, bytes, iomap, srcmap);
>  		if (status < 0)
>  			return status;
>  
> -- 
> 2.16.4
>
Dave Chinner Aug. 4, 2019, 11:52 p.m. UTC | #2 
On Fri, Aug 02, 2019 at 05:00:37PM -0500, Goldwyn Rodrigues wrote:
> From: Goldwyn Rodrigues <rgoldwyn@suse.com>
> 
> In case of a IOMAP_COW, read a page from the srcmap before
> performing a write on the page.
> 
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
> ---
>  fs/iomap/buffered-io.c | 14 ++++++++------
>  1 file changed, 8 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index f27756c0b31c..a96cc26eec92 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -581,7 +581,7 @@ __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
>  
>  static int
>  iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
> -		struct page **pagep, struct iomap *iomap)
> +		struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
>  {
>  	const struct iomap_page_ops *page_ops = iomap->page_ops;
>  	pgoff_t index = pos >> PAGE_SHIFT;
> @@ -607,6 +607,8 @@ iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
>  
>  	if (iomap->type == IOMAP_INLINE)
>  		iomap_read_inline_data(inode, page, iomap);
> +	else if (iomap->type == IOMAP_COW)
> +		status = __iomap_write_begin(inode, pos, len, page, srcmap);
>  	else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
>  		status = __block_write_begin_int(page, pos, len, NULL, iomap);
>  	else

This looks busted w.r.t. IOMAP_F_BUFFER_HEAD.  i.e. What's to stop
someone returning iomap->type == IOMAP_COW, iomap->flags &
IOMAP_F_BUFFER_HEAD?

In which case we can't call __iomap_write_begin(), right?

I'm with Darrick on CONFIG_IOMAP_DEBUG here - we need to start
locking down invalid behaviour and invalid combinations with asserts
that tell developers they've broken something.

Cheers,

Dave.
diff mbox series

Patch

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index f27756c0b31c..a96cc26eec92 100644
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -581,7 +581,7 @@  __iomap_write_begin(struct inode *inode, loff_t pos, unsigned len,
 
 static int
 iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
-		struct page **pagep, struct iomap *iomap)
+		struct page **pagep, struct iomap *iomap, struct iomap *srcmap)
 {
 	const struct iomap_page_ops *page_ops = iomap->page_ops;
 	pgoff_t index = pos >> PAGE_SHIFT;
@@ -607,6 +607,8 @@  iomap_write_begin(struct inode *inode, loff_t pos, unsigned len, unsigned flags,
 
 	if (iomap->type == IOMAP_INLINE)
 		iomap_read_inline_data(inode, page, iomap);
+	else if (iomap->type == IOMAP_COW)
+		status = __iomap_write_begin(inode, pos, len, page, srcmap);
 	else if (iomap->flags & IOMAP_F_BUFFER_HEAD)
 		status = __block_write_begin_int(page, pos, len, NULL, iomap);
 	else
@@ -772,7 +774,7 @@  iomap_write_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 		}
 
 		status = iomap_write_begin(inode, pos, bytes, flags, &page,
-				iomap);
+				iomap, srcmap);
 		if (unlikely(status))
 			break;
 
@@ -871,7 +873,7 @@  iomap_dirty_actor(struct inode *inode, loff_t pos, loff_t length, void *data,
 			return PTR_ERR(rpage);
 
 		status = iomap_write_begin(inode, pos, bytes,
-					   AOP_FLAG_NOFS, &page, iomap);
+					   AOP_FLAG_NOFS, &page, iomap, srcmap);
 		put_page(rpage);
 		if (unlikely(status))
 			return status;
@@ -917,13 +919,13 @@  iomap_file_dirty(struct inode *inode, loff_t pos, loff_t len,
 EXPORT_SYMBOL_GPL(iomap_file_dirty);
 
 static int iomap_zero(struct inode *inode, loff_t pos, unsigned offset,
-		unsigned bytes, struct iomap *iomap)
+		unsigned bytes, struct iomap *iomap, struct iomap *srcmap)
 {
 	struct page *page;
 	int status;
 
 	status = iomap_write_begin(inode, pos, bytes, AOP_FLAG_NOFS, &page,
-				   iomap);
+				   iomap, srcmap);
 	if (status)
 		return status;
 
@@ -961,7 +963,7 @@  iomap_zero_range_actor(struct inode *inode, loff_t pos, loff_t count,
 		if (IS_DAX(inode))
 			status = iomap_dax_zero(pos, offset, bytes, iomap);
 		else
-			status = iomap_zero(inode, pos, offset, bytes, iomap);
+			status = iomap_zero(inode, pos, offset, bytes, iomap, srcmap);
 		if (status < 0)
 			return status;