Commit fffca572 authored by Jan Kara's avatar Jan Kara
Browse files

mpage: Provide variant of mpage_writepages() with own optional folio handler 



Some filesystems need to treat some folios specially (for example for
inodes with inline data). Doing the handling in their .writepages method
in a race-free manner results in duplicating some of the writeback
internals. So provide generalized version of mpage_writepages() that
allows filesystem to provide a handler called for each folio which can
handle the folio in a special way.

Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>
Link: https://patch.msgid.link/20260326140635.15895-3-jack@suse.cz


Signed-off-by: default avatarJan Kara <jack@suse.cz>
parent c3692998

fs/mpage.c

+24 −6
Original line number Diff line number Diff line
@@ -646,17 +646,24 @@ static int mpage_write_folio(struct writeback_control *wbc, struct folio *folio, 
}



/**

 * mpage_writepages - walk the list of dirty pages of the given address space & writepage() all of them

 * __mpage_writepages - walk the list of dirty pages of the given address space

 * 			& writepage() all of them

 * @mapping: address space structure to write

 * @wbc: subtract the number of written pages from *@wbc->nr_to_write

 * @get_block: the filesystem's block mapper function.

 * @write_folio: handler to call for each folio before calling

 *		 mpage_write_folio()

 *

 * This is a library function, which implements the writepages()

 * address_space_operation.

 * address_space_operation. It calls @write_folio handler for each folio. If

 * the handler returns value > 0, it calls mpage_write_folio() to do the

 * folio writeback.

 */

int

mpage_writepages(struct address_space *mapping,

		struct writeback_control *wbc, get_block_t get_block)

__mpage_writepages(struct address_space *mapping,

		   struct writeback_control *wbc, get_block_t get_block,

		   int (*write_folio)(struct folio *folio,

				      struct writeback_control *wbc))

{

	struct mpage_data mpd = {

		.get_block	= get_block,
@@ -666,11 +673,22 @@ mpage_writepages(struct address_space *mapping, 
	int error;



	blk_start_plug(&plug);

	while ((folio = writeback_iter(mapping, wbc, folio, &error)))

	while ((folio = writeback_iter(mapping, wbc, folio, &error))) {

		if (write_folio) {

			error = write_folio(folio, wbc);

			/*

			 * == 0 means folio is handled, < 0 means error. In

			 * both cases hand back control to writeback_iter()

			 */

			if (error <= 0)

				continue;

			/* Let mpage_write_folio() handle the folio. */

		}

		error = mpage_write_folio(wbc, folio, &mpd);

	}

	if (mpd.bio)

		mpage_bio_submit_write(mpd.bio);

	blk_finish_plug(&plug);

	return error;

}

EXPORT_SYMBOL(mpage_writepages);
 
EXPORT_SYMBOL(__mpage_writepages);

include/linux/mpage.h

+9 −2
Original line number Diff line number Diff line
@@ -17,7 +17,14 @@ struct readahead_control; 


void mpage_readahead(struct readahead_control *, get_block_t get_block);

int mpage_read_folio(struct folio *folio, get_block_t get_block);

int mpage_writepages(struct address_space *mapping,

		struct writeback_control *wbc, get_block_t get_block);

int __mpage_writepages(struct address_space *mapping,

		struct writeback_control *wbc, get_block_t get_block,

		int (*write_folio)(struct folio *folio,

				   struct writeback_control *wbc));

static inline int mpage_writepages(struct address_space *mapping,

		struct writeback_control *wbc, get_block_t get_block)

{

	return __mpage_writepages(mapping, wbc, get_block, NULL);

}



#endif