btrfs: don't split NOCOW extent_maps in btrfs_extract_ordered_extent

NOCOW writes just overwrite an existing extent map, which thus should
not be split in btrfs_extract_ordered_extent.  The NOCOW case can't
currently happen as btrfs_extract_ordered_extent is only used on zoned
devices that do not support NOCOW writes, but this will change soon.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Boris Burkov <boris@bur.io>
[ hch: split from a larger patch, wrote a commit log ]
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 357d1626df1aeb888b554a461f26e0dd09561d18..26aeb4f000f5946168c1955d36c3958374f73c99 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -2621,6 +2621,14 @@ int btrfs_extract_ordered_extent(struct btrfs_bio *bbio,
        ret = btrfs_split_ordered_extent(ordered, len);
        if (ret)
                return ret;
+
+       /*
+        * Don't split the extent_map for NOCOW extents, as we're writing into
+        * a pre-existing one.
+        */
+       if (test_bit(BTRFS_ORDERED_NOCOW, &ordered->flags))
+               return 0;
+
        return split_extent_map(inode, bbio->file_offset, ordered_len, len);
 }