1 files changed, 12 insertions, 6 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 45cf03ee1bc2..2e25d698bab0 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4156,11 +4156,6 @@ static ssize_t btrfs_direct_IO(int rw, struct kiocb *iocb,
         return -EINVAL;
 }
 
-static sector_t btrfs_bmap(struct address_space *mapping, sector_t iblock)
-{
-        return extent_bmap(mapping, iblock, btrfs_get_extent);
-}
-
 int btrfs_readpage(struct file *file, struct page *page)
 {
         struct extent_io_tree *tree;
@@ -4985,13 +4980,24 @@ static struct extent_io_ops btrfs_extent_io_ops = {
         .clear_bit_hook = btrfs_clear_bit_hook,
 };
 
+/*
+ * btrfs doesn't support the bmap operation because swapfiles
+ * use bmap to make a mapping of extents in the file.  They assume
+ * these extents won't change over the life of the file and they
+ * use the bmap result to do IO directly to the drive.
+ *
+ * the btrfs bmap call would return logical addresses that aren't
+ * suitable for IO and they also will change frequently as COW
+ * operations happen.  So, swapfile + btrfs == corruption.
+ *
+ * For now we're avoiding this by dropping bmap.
+ */
 static struct address_space_operations btrfs_aops = {
         .readpage       = btrfs_readpage,
         .writepage      = btrfs_writepage,
         .writepages     = btrfs_writepages,
         .readpages      = btrfs_readpages,
         .sync_page      = block_sync_page,
-        .bmap           = btrfs_bmap,
         .direct_IO      = btrfs_direct_IO,
         .invalidatepage = btrfs_invalidatepage,
         .releasepage    = btrfs_releasepage,