Re: [PATCH] bcache: Use a folio

On Fri, Jun 13, 2025 at 08:19:39PM +0800, Matthew Wilcox (Oracle) wrote:
> Retrieve a folio from the page cache instead of a page.  Removes a
> hidden call to compound_head().  Then be sure to call folio_put()
> instead of put_page() to release it.  That doesn't save any calls
> to compound_head(), just moves them around.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <[email protected]>

Acked-back: Coly Li <[email protected]>

The patch looks fine and works well. If you want this patch to go upstream
by your path, please add my Acked-by.

Otherwise I can submit it to Jens with my Signed-off-by.

Thanks.

Coly Li


> ---
>  drivers/md/bcache/super.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
> index 1efb768b2890..83c786a5cc47 100644
> --- a/drivers/md/bcache/super.c
> +++ b/drivers/md/bcache/super.c
> @@ -168,14 +168,14 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
>  {
>  	const char *err;
>  	struct cache_sb_disk *s;
> -	struct page *page;
> +	struct folio *folio;
>  	unsigned int i;
>  
> -	page = read_cache_page_gfp(bdev->bd_mapping,
> -				   SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
> -	if (IS_ERR(page))
> +	folio = mapping_read_folio_gfp(bdev->bd_mapping,
> +			SB_OFFSET >> PAGE_SHIFT, GFP_KERNEL);
> +	if (IS_ERR(folio))
>  		return "IO error";
> -	s = page_address(page) + offset_in_page(SB_OFFSET);
> +	s = folio_address(folio) + offset_in_folio(folio, SB_OFFSET);
>  
>  	sb->offset		= le64_to_cpu(s->offset);
>  	sb->version		= le64_to_cpu(s->version);
> @@ -272,7 +272,7 @@ static const char *read_super(struct cache_sb *sb, struct block_device *bdev,
>  	*res = s;
>  	return NULL;
>  err:
> -	put_page(page);
> +	folio_put(folio);
>  	return err;
>  }
>  
> @@ -1366,7 +1366,7 @@ static CLOSURE_CALLBACK(cached_dev_free)
>  	mutex_unlock(&bch_register_lock);
>  
>  	if (dc->sb_disk)
> -		put_page(virt_to_page(dc->sb_disk));
> +		folio_put(virt_to_folio(dc->sb_disk));
>  
>  	if (dc->bdev_file)
>  		fput(dc->bdev_file);
> @@ -2215,7 +2215,7 @@ void bch_cache_release(struct kobject *kobj)
>  		free_fifo(&ca->free[i]);
>  
>  	if (ca->sb_disk)
> -		put_page(virt_to_page(ca->sb_disk));
> +		folio_put(virt_to_folio(ca->sb_disk));
>  
>  	if (ca->bdev_file)
>  		fput(ca->bdev_file);
> @@ -2592,7 +2592,7 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
>  	if (!holder) {
>  		ret = -ENOMEM;
>  		err = "cannot allocate memory";
> -		goto out_put_sb_page;
> +		goto out_put_sb_folio;
>  	}
>  
>  	/* Now reopen in exclusive mode with proper holder */
> @@ -2666,8 +2666,8 @@ static ssize_t register_bcache(struct kobject *k, struct kobj_attribute *attr,
>  
>  out_free_holder:
>  	kfree(holder);
> -out_put_sb_page:
> -	put_page(virt_to_page(sb_disk));
> +out_put_sb_folio:
> +	folio_put(virt_to_folio(sb_disk));
>  out_blkdev_put:
>  	if (bdev_file)
>  		fput(bdev_file);
> -- 
> 2.47.2
> 
>