Commit 86c4a946 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Andrew Morton
Browse files

mm: split out a writeout helper from pageout 

Patch series "stop passing a writeback_control to swap/shmem writeout",
v3.

This series was intended to remove the last remaining users of
AOP_WRITEPAGE_ACTIVATE after my other pending patches removed the rest,
but spectacularly failed at that.

But instead it nicely improves the code, and removes two pointers from
struct writeback_control.


This patch (of 6):

Move the code to write back swap / shmem folios into a self-contained
helper to keep prepare for refactoring it.

Link: https://lkml.kernel.org/r/20250610054959.2057526-1-hch@lst.de
Link: https://lkml.kernel.org/r/20250610054959.2057526-2-hch@lst.de


Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarBaolin Wang <baolin.wang@linux.aibaba.com>
Cc: Chengming Zhou <chengming.zhou@linux.dev>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 453742ba

mm/vmscan.c

+48 −46
Original line number Diff line number Diff line
@@ -652,14 +652,55 @@ typedef enum { 
	PAGE_CLEAN,

} pageout_t;



static pageout_t writeout(struct folio *folio, struct address_space *mapping,

		struct swap_iocb **plug, struct list_head *folio_list)

{

	struct writeback_control wbc = {

		.sync_mode = WB_SYNC_NONE,

		.nr_to_write = SWAP_CLUSTER_MAX,

		.range_start = 0,

		.range_end = LLONG_MAX,

		.for_reclaim = 1,

		.swap_plug = plug,

	};

	int res;



	folio_set_reclaim(folio);



	/*

	 * The large shmem folio can be split if CONFIG_THP_SWAP is not enabled

	 * or we failed to allocate contiguous swap entries.

	 */

	if (shmem_mapping(mapping)) {

		if (folio_test_large(folio))

			wbc.list = folio_list;

		res = shmem_writeout(folio, &wbc);

	} else {

		res = swap_writeout(folio, &wbc);

	}



	if (res < 0)

		handle_write_error(mapping, folio, res);

	if (res == AOP_WRITEPAGE_ACTIVATE) {

		folio_clear_reclaim(folio);

		return PAGE_ACTIVATE;

	}



	/* synchronous write? */

	if (!folio_test_writeback(folio))

		folio_clear_reclaim(folio);



	trace_mm_vmscan_write_folio(folio);

	node_stat_add_folio(folio, NR_VMSCAN_WRITE);

	return PAGE_SUCCESS;

}



/*

 * pageout is called by shrink_folio_list() for each dirty folio.

 */

static pageout_t pageout(struct folio *folio, struct address_space *mapping,

			 struct swap_iocb **plug, struct list_head *folio_list)

{

	int (*writeout)(struct folio *, struct writeback_control *);



	/*

	 * We no longer attempt to writeback filesystem folios here, other

	 * than tmpfs/shmem.  That's taken care of in page-writeback.
@@ -690,51 +731,12 @@ static pageout_t pageout(struct folio *folio, struct address_space *mapping, 
		}

		return PAGE_KEEP;

	}

	if (shmem_mapping(mapping))

		writeout = shmem_writeout;

	else if (folio_test_anon(folio))

		writeout = swap_writeout;

	else

		return PAGE_ACTIVATE;



	if (folio_clear_dirty_for_io(folio)) {

		int res;

		struct writeback_control wbc = {

			.sync_mode = WB_SYNC_NONE,

			.nr_to_write = SWAP_CLUSTER_MAX,

			.range_start = 0,

			.range_end = LLONG_MAX,

			.for_reclaim = 1,

			.swap_plug = plug,

		};



		/*

		 * The large shmem folio can be split if CONFIG_THP_SWAP is

		 * not enabled or contiguous swap entries are failed to

		 * allocate.

		 */

		if (shmem_mapping(mapping) && folio_test_large(folio))

			wbc.list = folio_list;



		folio_set_reclaim(folio);

		res = writeout(folio, &wbc);

		if (res < 0)

			handle_write_error(mapping, folio, res);

		if (res == AOP_WRITEPAGE_ACTIVATE) {

			folio_clear_reclaim(folio);

	if (!shmem_mapping(mapping) && !folio_test_anon(folio))

		return PAGE_ACTIVATE;

		}



		if (!folio_test_writeback(folio)) {

			/* synchronous write? */

			folio_clear_reclaim(folio);

		}

		trace_mm_vmscan_write_folio(folio);

		node_stat_add_folio(folio, NR_VMSCAN_WRITE);

		return PAGE_SUCCESS;

	}



	if (!folio_clear_dirty_for_io(folio))

		return PAGE_CLEAN;

	return writeout(folio, mapping, plug, folio_list);

}



/*