[Cluster-devel] [PATCH v2 06/14] buffer: Make block_write_full_page() handle large folios correctly

[Matthew Wilcox (Oracle)]

Keep the interface as struct page, but work entirely on the folio
internally.  Removes several PAGE_SIZE assumptions and removes
some references to page->index and page->mapping.

Signed-off-by: Matthew Wilcox (Oracle) 
Tested-by: Bob Peterson 
Reviewed-by: Bob Peterson 
---
 fs/buffer.c | 22 ++
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 4d518df50fab..d8c2c000676b 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -2678,33 +2678,31 @@ int block_write_full_page(struct page *page, 
get_block_t *get_block,
struct writeback_control *wbc)
 {
struct folio *folio = page_folio(page);
-   struct inode * const inode = page->mapping->host;
+   struct inode * const inode = folio->mapping->host;
loff_t i_size = i_size_read(inode);
-   const pgoff_t end_index = i_size >> PAGE_SHIFT;
-   unsigned offset;
 
-   /* Is the page fully inside i_size? */
-   if (page->index < end_index)
+   /* Is the folio fully inside i_size? */
+   if (folio_pos(folio) + folio_size(folio) <= i_size)
return __block_write_full_folio(inode, folio, get_block, wbc,
   end_buffer_async_write);
 
-   /* Is the page fully outside i_size? (truncate in progress) */
-   offset = i_size & (PAGE_SIZE-1);
-   if (page->index >= end_index+1 || !offset) {
+   /* Is the folio fully outside i_size? (truncate in progress) */
+   if (folio_pos(folio) > i_size) {
folio_unlock(folio);
return 0; /* don't care */
}
 
/*
-* The page straddles i_size.  It must be zeroed out on each and every
+* The folio straddles i_size.  It must be zeroed out on each and every
 * writepage invocation because it may be mmapped.  "A file is mapped
 * in multiples of the page size.  For a file that is not a multiple of
-* the  page size, the remaining memory is zeroed when mapped, and
+* the page size, the remaining memory is zeroed when mapped, and
 * writes to that region are not written out to the file."
 */
-   zero_user_segment(page, offset, PAGE_SIZE);
+   folio_zero_segment(folio, offset_in_folio(folio, i_size),
+   folio_size(folio));
return __block_write_full_folio(inode, folio, get_block, wbc,
-   end_buffer_async_write);
+   end_buffer_async_write);
 }
 EXPORT_SYMBOL(block_write_full_page);
 
-- 
2.39.2

Re: [Cluster-devel] [PATCH v2 06/14] buffer: Make block_write_full_page() handle large folios correctly

[Andreas Grünbacher]

Am Mi., 7. Juni 2023 um 00:41 Uhr schrieb Matthew Wilcox (Oracle)
:
> Keep the interface as struct page, but work entirely on the folio
> internally.  Removes several PAGE_SIZE assumptions and removes
> some references to page->index and page->mapping.
>
> Signed-off-by: Matthew Wilcox (Oracle) 
> Tested-by: Bob Peterson 
> Reviewed-by: Bob Peterson 
> ---
>  fs/buffer.c | 22 ++
>  1 file changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 4d518df50fab..d8c2c000676b 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2678,33 +2678,31 @@ int block_write_full_page(struct page *page, 
> get_block_t *get_block,
> struct writeback_control *wbc)
>  {
> struct folio *folio = page_folio(page);
> -   struct inode * const inode = page->mapping->host;
> +   struct inode * const inode = folio->mapping->host;
> loff_t i_size = i_size_read(inode);
> -   const pgoff_t end_index = i_size >> PAGE_SHIFT;
> -   unsigned offset;
>
> -   /* Is the page fully inside i_size? */
> -   if (page->index < end_index)
> +   /* Is the folio fully inside i_size? */
> +   if (folio_pos(folio) + folio_size(folio) <= i_size)
> return __block_write_full_folio(inode, folio, get_block, wbc,
>end_buffer_async_write);
>
> -   /* Is the page fully outside i_size? (truncate in progress) */
> -   offset = i_size & (PAGE_SIZE-1);
> -   if (page->index >= end_index+1 || !offset) {
> +   /* Is the folio fully outside i_size? (truncate in progress) */
> +   if (folio_pos(folio) > i_size) {

The folio is also fully outside i_size if folio_pos(folio) == i_size.

> folio_unlock(folio);
> return 0; /* don't care */
> }
>
> /*
> -* The page straddles i_size.  It must be zeroed out on each and every
> +* The folio straddles i_size.  It must be zeroed out on each and 
> every
>  * writepage invocation because it may be mmapped.  "A file is mapped
>  * in multiples of the page size.  For a file that is not a multiple 
> of
> -* the  page size, the remaining memory is zeroed when mapped, and
> +* the page size, the remaining memory is zeroed when mapped, and
>  * writes to that region are not written out to the file."
>  */
> -   zero_user_segment(page, offset, PAGE_SIZE);
> +   folio_zero_segment(folio, offset_in_folio(folio, i_size),
> +   folio_size(folio));
> return __block_write_full_folio(inode, folio, get_block, wbc,
> -   
> end_buffer_async_write);
> +   end_buffer_async_write);
>  }
>  EXPORT_SYMBOL(block_write_full_page);
>
> --
> 2.39.2
>

Thanks,
Andreas