btrfs: ignore incorrect btrfs_file_extent_item::ram_bytes

[HICCUP]
Kernels can create file extent items with incorrect ram_bytes like this:

	item 6 key (257 EXTENT_DATA 0) itemoff 15816 itemsize 53
		generation 7 type 1 (regular)
		extent data disk byte 13631488 nr 32768
		extent data offset 0 nr 4096 ram 4096
		extent compression 0 (none)

Thankfully kernel can handle them properly, as in that case ram_bytes is
not utilized at all.

[ENHANCEMENT]
Since the hiccup is not going to cause any data-loss and is only a minor
violation of on-disk format, here we only need to ignore the incorrect
ram_bytes value, and use the correct one from
btrfs_file_extent_item::disk_num_bytes.

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 2cc61c792ee68f157bd9e870a937566d760493b5..e815fefaffe1719e0f007a56bc49b127fc01c5a0 100644 (file)
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -1306,6 +1306,13 @@ void btrfs_extent_item_to_extent_map(struct btrfs_inode *inode,
                if (compress_type != BTRFS_COMPRESS_NONE) {
                        extent_map_set_compression(em, compress_type);
                } else {
+                       /*
+                        * Older kernels can create regular non-hole data
+                        * extents with ram_bytes smaller than disk_num_bytes.
+                        * Not a big deal, just always use disk_num_bytes
+                        * for ram_bytes.
+                        */
+                       em->ram_bytes = em->disk_num_bytes;
                        if (type == BTRFS_FILE_EXTENT_PREALLOC)
                                em->flags |= EXTENT_FLAG_PREALLOC;
                }