Commit f8e66081 authored by Roman Gushchin's avatar Roman Gushchin Committed by David Sterba
Browse files

btrfs: implement migratepage callback for data pages 



Currently btrfs doesn't provide a migratepage callback for data pages.
It means that fallback_migrate_page() is used to migrate btrfs pages.

fallback_migrate_page() cannot move dirty pages, instead it tries to
flush them (in sync mode) or just fails (in async mode).

In the sync mode pages which are scheduled to be processed by
btrfs_writepage_fixup_worker() can't be effectively flushed by the
migration code, because there is no established way to wait for the
completion of the delayed work.

It all leads to page migration failures.

To fix it the patch implements a btrs-specific migratepage callback,
which is similar to iomap_migrate_page() used by some other fs, except
it does take care of the PagePrivate2 flag which is used for data
ordering purposes.

Reviewed-by: default avatarChris Mason <clm@fb.com>
Signed-off-by: default avatarRoman Gushchin <guro@fb.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 0078a9f9

fs/btrfs/inode.c

+37 −0
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <linux/magic.h>

#include <linux/iversion.h>

#include <linux/swap.h>

#include <linux/migrate.h>

#include <linux/sched/mm.h>

#include <asm/unaligned.h>

#include "misc.h"
@@ -8327,6 +8328,39 @@ static int btrfs_releasepage(struct page *page, gfp_t gfp_flags) 
	return __btrfs_releasepage(page, gfp_flags);

}



#ifdef CONFIG_MIGRATION

static int btrfs_migratepage(struct address_space *mapping,

			     struct page *newpage, struct page *page,

			     enum migrate_mode mode)

{

	int ret;



	ret = migrate_page_move_mapping(mapping, newpage, page, 0);

	if (ret != MIGRATEPAGE_SUCCESS)

		return ret;



	if (page_has_private(page)) {

		ClearPagePrivate(page);

		get_page(newpage);

		set_page_private(newpage, page_private(page));

		set_page_private(page, 0);

		put_page(page);

		SetPagePrivate(newpage);

	}



	if (PagePrivate2(page)) {

		ClearPagePrivate2(page);

		SetPagePrivate2(newpage);

	}



	if (mode != MIGRATE_SYNC_NO_COPY)

		migrate_page_copy(newpage, page);

	else

		migrate_page_states(newpage, page);

	return MIGRATEPAGE_SUCCESS;

}

#endif



static void btrfs_invalidatepage(struct page *page, unsigned int offset,

				 unsigned int length)

{
@@ -10532,6 +10566,9 @@ static const struct address_space_operations btrfs_aops = { 
	.direct_IO	= btrfs_direct_IO,

	.invalidatepage = btrfs_invalidatepage,

	.releasepage	= btrfs_releasepage,

#ifdef CONFIG_MIGRATION

	.migratepage	= btrfs_migratepage,

#endif

	.set_page_dirty	= btrfs_set_page_dirty,

	.error_remove_page = generic_error_remove_page,

	.swap_activate	= btrfs_swap_activate,

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