Re: [PATCH] cramfs: convert cramfs_blkdev_read() to use folios

[Nicolas Pitre]

On Mon, 12 Oct 2026, Tal Zussman wrote:

> On 9/6/26 7:45 PM, Tal Zussman wrote:
> > Read the block device pages through read_mapping_folio() and copy with
> > memcpy_from_folio() instead of going through a page.
> > 
> > Signed-off-by: Tal Zussman <tz2294@xxxxxxxxxxxx>
> > ---
> >  fs/cramfs/inode.c | 23 +++++++++++++----------
> >  1 file changed, 13 insertions(+), 10 deletions(-)
> > 
> 
> Following up on this - I don't see a cramfs tree, so could this go
> through vfs if everything looks ok? It gets us one step closer to
> removing read_mapping_page().
> 
> Thanks,
> Tal

Yes, please forward to the vfs tree.

Acked-by: Nicolas Pitre <nico@xxxxxxxxxxx>



> > diff --git a/fs/cramfs/inode.c b/fs/cramfs/inode.c
> > index d4cd03f4f60d..b55eb3bd29c1 100644
> > --- a/fs/cramfs/inode.c
> > +++ b/fs/cramfs/inode.c
> > @@ -194,7 +194,7 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
> >  {
> >  	struct address_space *mapping = sb->s_bdev->bd_mapping;
> >  	struct file_ra_state ra = {};
> > -	struct page *pages[BLKS_PER_BUF];
> > +	struct folio *folios[BLKS_PER_BUF];
> >  	unsigned i, blocknr, buffer;
> >  	unsigned long devsize;
> >  	char *data;
> > @@ -227,15 +227,15 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
> >  	page_cache_sync_readahead(mapping, &ra, NULL, blocknr, BLKS_PER_BUF);
> >  
> >  	for (i = 0; i < BLKS_PER_BUF; i++) {
> > -		struct page *page = NULL;
> > +		struct folio *folio = NULL;
> >  
> >  		if (blocknr + i < devsize) {
> > -			page = read_mapping_page(mapping, blocknr + i, NULL);
> > +			folio = read_mapping_folio(mapping, blocknr + i, NULL);
> >  			/* synchronous error? */
> > -			if (IS_ERR(page))
> > -				page = NULL;
> > +			if (IS_ERR(folio))
> > +				folio = NULL;
> >  		}
> > -		pages[i] = page;
> > +		folios[i] = folio;
> >  	}
> >  
> >  	buffer = next_buffer;
> > @@ -245,11 +245,14 @@ static void *cramfs_blkdev_read(struct super_block *sb, unsigned int offset,
> >  
> >  	data = read_buffers[buffer];
> >  	for (i = 0; i < BLKS_PER_BUF; i++) {
> > -		struct page *page = pages[i];
> > +		struct folio *folio = folios[i];
> >  
> > -		if (page) {
> > -			memcpy_from_page(data, page, 0, PAGE_SIZE);
> > -			put_page(page);
> > +		if (folio) {
> > +			size_t offset = offset_in_folio(folio,
> > +					(loff_t)(blocknr + i) << PAGE_SHIFT);
> > +
> > +			memcpy_from_folio(data, folio, offset, PAGE_SIZE);
> > +			folio_put(folio);
> >  		} else
> >  			memset(data, 0, PAGE_SIZE);
> >  		data += PAGE_SIZE;
> > 
> > ---
> > base-commit: df2908090cda368b01ff43709f51890076c56157
> > change-id: 20260906-cramfs-blkdev-read-folio-16fecf6908ac
> > 
> > Best regards,
> > --  
> > Tal Zussman <tz2294@xxxxxxxxxxxx>
> 
>