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Commit 784b4e29 authored by Chris Mason's avatar Chris Mason
Browse files

Btrfs: add migrate page for metadata inode 



Migrate page will directly call the btrfs btree writepage function,
which isn't actually allowed.

Our writepage assumes that you have locked the extent_buffer and
flagged the block as written.  Without doing these steps, we can
corrupt metadata blocks.

A later commit will remove the btree writepage function since
it is really only safely used internally by btrfs.  We
use writepages for everything else.

Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 6418c961

fs/btrfs/disk-io.c

+25 −2
Original line number Diff line number Diff line
@@ -28,6 +28,7 @@ 
#include <linux/freezer.h>

#include <linux/crc32c.h>

#include <linux/slab.h>

#include <linux/migrate.h>

#include "compat.h"

#include "ctree.h"

#include "disk-io.h"
@@ -355,6 +356,8 @@ static int csum_dirty_buffer(struct btrfs_root *root, struct page *page) 
	ret = btree_read_extent_buffer_pages(root, eb, start + PAGE_CACHE_SIZE,

					     btrfs_header_generation(eb));

	BUG_ON(ret);

	WARN_ON(!btrfs_header_flag(eb, BTRFS_HEADER_FLAG_WRITTEN));



	found_start = btrfs_header_bytenr(eb);

	if (found_start != start) {

		WARN_ON(1);
@@ -693,6 +696,26 @@ static int btree_submit_bio_hook(struct inode *inode, int rw, struct bio *bio, 
				   __btree_submit_bio_done);

}



static int btree_migratepage(struct address_space *mapping,

			struct page *newpage, struct page *page)

{

	/*

	 * we can't safely write a btree page from here,

	 * we haven't done the locking hook

	 */

	if (PageDirty(page))

		return -EAGAIN;

	/*

	 * Buffers may be managed in a filesystem specific way.

	 * We must have no buffers or drop them.

	 */

	if (page_has_private(page) &&

	    !try_to_release_page(page, GFP_KERNEL))

		return -EAGAIN;



	return migrate_page(mapping, newpage, page);

}



static int btree_writepage(struct page *page, struct writeback_control *wbc)

{

	struct extent_io_tree *tree;
@@ -707,8 +730,7 @@ static int btree_writepage(struct page *page, struct writeback_control *wbc) 
	}



	redirty_page_for_writepage(wbc, page);

	eb = btrfs_find_tree_block(root, page_offset(page),

				      PAGE_CACHE_SIZE);

	eb = btrfs_find_tree_block(root, page_offset(page), PAGE_CACHE_SIZE);

	WARN_ON(!eb);



	was_dirty = test_and_set_bit(EXTENT_BUFFER_DIRTY, &eb->bflags);
@@ -799,6 +821,7 @@ static const struct address_space_operations btree_aops = { 
	.releasepage	= btree_releasepage,

	.invalidatepage = btree_invalidatepage,

	.sync_page	= block_sync_page,

	.migratepage	= btree_migratepage,

};



int readahead_tree_block(struct btrfs_root *root, u64 bytenr, u32 blocksize,