Btrfs: fix divide error upon chunk's stripe_len

The struct 'map_lookup' uses type int for @stripe_len, while
btrfs_chunk_stripe_len() can return a u64 value, and it may end up with
@stripe_len being undefined value and it can lead to 'divide error' in
 __btrfs_map_block().

This changes 'map_lookup' to use type u64 for stripe_len, also right now
we only use BTRFS_STRIPE_LEN for stripe_len, so this adds a valid checker for
BTRFS_STRIPE_LEN.
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Reported-by: Quentin Casasnovas <quentin.casasnovas@oracle.com>
Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
[ folded division fix to scrub_raid56_parity ]
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/scrub.c

@@ -2860,7 +2860,7 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
 	int extent_mirror_num;
 	int stop_loop = 0;
 
-	nsectors = map->stripe_len / root->sectorsize;
+	nsectors = div_u64(map->stripe_len, root->sectorsize);
 	bitmap_len = scrub_calc_parity_bitmap_len(nsectors);
 	sparity = kzalloc(sizeof(struct scrub_parity) + 2 * bitmap_len,
 			  GFP_NOFS);

fs/btrfs/volumes.c

@@ -6254,7 +6254,7 @@ static int read_one_chunk(struct btrfs_root *root, struct btrfs_key *key,
 			"invalid chunk length %llu", length);
 		return -EIO;
 	}
-	if (!is_power_of_2(stripe_len)) {
+	if (!is_power_of_2(stripe_len) || stripe_len != BTRFS_STRIPE_LEN) {
 		btrfs_err(root->fs_info, "invalid chunk stripe length: %llu",
 			  stripe_len);
 		return -EIO;

fs/btrfs/volumes.h

@@ -347,7 +347,7 @@ struct map_lookup {
 	u64 type;
 	int io_align;
 	int io_width;
-	int stripe_len;
+	u64 stripe_len;
 	int sector_size;
 	int num_stripes;
 	int sub_stripes;