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: Chris Mason <chris.mason@oracle.com>
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index b40dfe4..a67b98d 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -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 @@
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 @@
__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 @@
}
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 @@
.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,