btrfs: replace map_lookup->stripe_len by BTRFS_STRIPE_LEN

Currently btrfs doesn't support stripe lengths other than 64KiB.
This is already set in the tree-checker.

There is really no meaning to record that fixed value in map_lookup for
now, and can all be replaced with BTRFS_STRIPE_LEN.

Furthermore we can use the fix stripe length to do the following
optimization:

- Use BTRFS_STRIPE_LEN_SHIFT to replace some 64bit division
  Now we only need to do a right shift.

  And the value of BTRFS_STRIPE_LEN itself is already too large for bit
  shift, thus if we accidentally use BTRFS_STRIPE_LEN to do bit shift,
  a compiler warning would be triggered.

  Thus this bit shift optimization would be safe.

- Use BTRFS_STRIPE_LEN_MASK to calculate the offset inside a stripe

Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

5 files changed, 66 insertions, 60 deletions

diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c
index 5fc670c27f86..b27474731e7b 100644
--- a/fs/btrfs/block-group.c
+++ b/fs/btrfs/block-group.c
@@ -1977,12 +1977,12 @@ int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
 
 	map = em->map_lookup;
 	data_stripe_length = em->orig_block_len;
-	io_stripe_size = map->stripe_len;
+	io_stripe_size = BTRFS_STRIPE_LEN;
 	chunk_start = em->start;
 
 	/* For RAID5/6 adjust to a full IO stripe length */
 	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
-		io_stripe_size = map->stripe_len * nr_data_stripes(map);
+		io_stripe_size = nr_data_stripes(map) << BTRFS_STRIPE_LEN_SHIFT;
 
 	buf = kcalloc(map->num_stripes, sizeof(u64), GFP_NOFS);
 	if (!buf) {
@@ -2000,8 +2000,10 @@ int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,
 			      data_stripe_length))
 			continue;
 
-		stripe_nr = physical - map->stripes[i].physical;
-		stripe_nr = div64_u64_rem(stripe_nr, map->stripe_len, &offset);
+		stripe_nr = (physical - map->stripes[i].physical) >>
+			    BTRFS_STRIPE_LEN_SHIFT;
+		offset = (physical - map->stripes[i].physical) &
+			 BTRFS_STRIPE_LEN_MASK;
 
 		if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
 				 BTRFS_BLOCK_GROUP_RAID10)) {
diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c
index 69c93ae333f6..190536b90779 100644
--- a/fs/btrfs/scrub.c
+++ b/fs/btrfs/scrub.c
@@ -2722,7 +2722,7 @@ static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
 
 	if (flags & BTRFS_EXTENT_FLAG_DATA) {
 		if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
-			blocksize = map->stripe_len;
+			blocksize = BTRFS_STRIPE_LEN;
 		else
 			blocksize = sctx->fs_info->sectorsize;
 		spin_lock(&sctx->stat_lock);
@@ -2731,7 +2731,7 @@ static int scrub_extent(struct scrub_ctx *sctx, struct map_lookup *map,
 		spin_unlock(&sctx->stat_lock);
 	} else if (flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) {
 		if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
-			blocksize = map->stripe_len;
+			blocksize = BTRFS_STRIPE_LEN;
 		else
 			blocksize = sctx->fs_info->nodesize;
 		spin_lock(&sctx->stat_lock);
@@ -2920,9 +2920,9 @@ static int get_raid56_logic_offset(u64 physical, int num,
 
 	*offset = last_offset;
 	for (i = 0; i < data_stripes; i++) {
-		*offset = last_offset + i * map->stripe_len;
+		*offset = last_offset + (i << BTRFS_STRIPE_LEN_SHIFT);
 
-		stripe_nr = div64_u64(*offset, map->stripe_len);
+		stripe_nr = *offset >> BTRFS_STRIPE_LEN_SHIFT;
 		stripe_nr = div_u64(stripe_nr, data_stripes);
 
 		/* Work out the disk rotation on this stripe-set */
@@ -2935,7 +2935,7 @@ static int get_raid56_logic_offset(u64 physical, int num,
 		if (stripe_index < num)
 			j++;
 	}
-	*offset = last_offset + j * map->stripe_len;
+	*offset = last_offset + (j << BTRFS_STRIPE_LEN_SHIFT);
 	return 1;
 }
 
@@ -3205,7 +3205,7 @@ static int scrub_raid56_data_stripe_for_parity(struct scrub_ctx *sctx,
 	/* Path must not be populated */
 	ASSERT(!path->nodes[0]);
 
-	while (cur_logical < logical + map->stripe_len) {
+	while (cur_logical < logical + BTRFS_STRIPE_LEN) {
 		struct btrfs_io_context *bioc = NULL;
 		struct btrfs_device *extent_dev;
 		u64 extent_start;
@@ -3217,7 +3217,7 @@ static int scrub_raid56_data_stripe_for_parity(struct scrub_ctx *sctx,
 		u64 extent_mirror_num;
 
 		ret = find_first_extent_item(extent_root, path, cur_logical,
-					     logical + map->stripe_len - cur_logical);
+					     logical + BTRFS_STRIPE_LEN - cur_logical);
 		/* No more extent item in this data stripe */
 		if (ret > 0) {
 			ret = 0;
@@ -3231,7 +3231,7 @@ static int scrub_raid56_data_stripe_for_parity(struct scrub_ctx *sctx,
 		/* Metadata should not cross stripe boundaries */
 		if ((extent_flags & BTRFS_EXTENT_FLAG_TREE_BLOCK) &&
 		    does_range_cross_boundary(extent_start, extent_size,
-					      logical, map->stripe_len)) {
+					      logical, BTRFS_STRIPE_LEN)) {
 			btrfs_err(fs_info,
 	"scrub: tree block %llu spanning stripes, ignored. logical=%llu",
 				  extent_start, logical);
@@ -3247,7 +3247,7 @@ static int scrub_raid56_data_stripe_for_parity(struct scrub_ctx *sctx,
 
 		/* Truncate the range inside this data stripe */
 		extent_size = min(extent_start + extent_size,
-				  logical + map->stripe_len) - cur_logical;
+				  logical + BTRFS_STRIPE_LEN) - cur_logical;
 		extent_start = cur_logical;
 		ASSERT(extent_size <= U32_MAX);
 
@@ -3320,8 +3320,7 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
 	path->search_commit_root = 1;
 	path->skip_locking = 1;
 
-	ASSERT(map->stripe_len <= U32_MAX);
-	nsectors = map->stripe_len >> fs_info->sectorsize_bits;
+	nsectors = BTRFS_STRIPE_LEN >> fs_info->sectorsize_bits;
 	ASSERT(nsectors <= BITS_PER_LONG);
 	sparity = kzalloc(sizeof(struct scrub_parity), GFP_NOFS);
 	if (!sparity) {
@@ -3332,8 +3331,7 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
 		return -ENOMEM;
 	}
 
-	ASSERT(map->stripe_len <= U32_MAX);
-	sparity->stripe_len = map->stripe_len;
+	sparity->stripe_len = BTRFS_STRIPE_LEN;
 	sparity->nsectors = nsectors;
 	sparity->sctx = sctx;
 	sparity->scrub_dev = sdev;
@@ -3344,7 +3342,7 @@ static noinline_for_stack int scrub_raid56_parity(struct scrub_ctx *sctx,
 
 	ret = 0;
 	for (cur_logical = logic_start; cur_logical < logic_end;
-	     cur_logical += map->stripe_len) {
+	     cur_logical += BTRFS_STRIPE_LEN) {
 		ret = scrub_raid56_data_stripe_for_parity(sctx, sparity, map,
 							  sdev, path, cur_logical);
 		if (ret < 0)
@@ -3536,7 +3534,7 @@ static u64 simple_stripe_full_stripe_len(const struct map_lookup *map)
 	ASSERT(map->type & (BTRFS_BLOCK_GROUP_RAID0 |
 			    BTRFS_BLOCK_GROUP_RAID10));
 
-	return map->num_stripes / map->sub_stripes * map->stripe_len;
+	return (map->num_stripes / map->sub_stripes) << BTRFS_STRIPE_LEN_SHIFT;
 }
 
 /* Get the logical bytenr for the stripe */
@@ -3552,7 +3550,8 @@ static u64 simple_stripe_get_logical(struct map_lookup *map,
 	 * (stripe_index / sub_stripes) gives how many data stripes we need to
 	 * skip.
 	 */
-	return (stripe_index / map->sub_stripes) * map->stripe_len + bg->start;
+	return ((stripe_index / map->sub_stripes) << BTRFS_STRIPE_LEN_SHIFT) +
+	       bg->start;
 }
 
 /* Get the mirror number for the stripe */
@@ -3589,14 +3588,14 @@ static int scrub_simple_stripe(struct scrub_ctx *sctx,
 		 * this stripe.
 		 */
 		ret = scrub_simple_mirror(sctx, extent_root, csum_root, bg, map,
-					  cur_logical, map->stripe_len, device,
+					  cur_logical, BTRFS_STRIPE_LEN, device,
 					  cur_physical, mirror_num);
 		if (ret)
 			return ret;
 		/* Skip to next stripe which belongs to the target device */
 		cur_logical += logical_increment;
 		/* For physical offset, we just go to next stripe */
-		cur_physical += map->stripe_len;
+		cur_physical += BTRFS_STRIPE_LEN;
 	}
 	return ret;
 }
@@ -3690,7 +3689,7 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 	if (profile & (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID10)) {
 		ret = scrub_simple_stripe(sctx, root, csum_root, bg, map,
 					  scrub_dev, stripe_index);
-		offset = map->stripe_len * (stripe_index / map->sub_stripes);
+		offset = (stripe_index / map->sub_stripes) << BTRFS_STRIPE_LEN_SHIFT;
 		goto out;
 	}
 
@@ -3705,7 +3704,7 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 
 	/* Initialize @offset in case we need to go to out: label */
 	get_raid56_logic_offset(physical, stripe_index, map, &offset, NULL);
-	increment = map->stripe_len * nr_data_stripes(map);
+	increment = nr_data_stripes(map) << BTRFS_STRIPE_LEN_SHIFT;
 
 	/*
 	 * Due to the rotation, for RAID56 it's better to iterate each stripe
@@ -3736,13 +3735,13 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
 		 * is still based on @mirror_num.
 		 */
 		ret = scrub_simple_mirror(sctx, root, csum_root, bg, map,
-					  logical, map->stripe_len,
+					  logical, BTRFS_STRIPE_LEN,
 					  scrub_dev, physical, 1);
 		if (ret < 0)
 			goto out;
 next:
 		logical += increment;
-		physical += map->stripe_len;
+		physical += BTRFS_STRIPE_LEN;
 		spin_lock(&sctx->stat_lock);
 		if (stop_loop)
 			sctx->stat.last_physical =
diff --git a/fs/btrfs/tests/extent-map-tests.c b/fs/btrfs/tests/extent-map-tests.c
index f2f2e11dac4c..ed0f36ae5346 100644
--- a/fs/btrfs/tests/extent-map-tests.c
+++ b/fs/btrfs/tests/extent-map-tests.c
@@ -486,7 +486,6 @@ static int test_rmap_block(struct btrfs_fs_info *fs_info,
 	em->map_lookup = map;
 
 	map->num_stripes = test->num_stripes;
-	map->stripe_len = BTRFS_STRIPE_LEN;
 	map->type = test->raid_type;
 
 	for (i = 0; i < map->num_stripes; i++) {
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index c6d592870400..d2b8b8a8bd89 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -5125,7 +5125,7 @@ static void init_alloc_chunk_ctl_policy_regular(
 	/* We don't want a chunk larger than 10% of writable space */
 	ctl->max_chunk_size = min(mult_perc(fs_devices->total_rw_bytes, 10),
 				  ctl->max_chunk_size);
-	ctl->dev_extent_min = BTRFS_STRIPE_LEN * ctl->dev_stripes;
+	ctl->dev_extent_min = ctl->dev_stripes << BTRFS_STRIPE_LEN_SHIFT;
 }
 
 static void init_alloc_chunk_ctl_policy_zoned(
@@ -5407,7 +5407,6 @@ static struct btrfs_block_group *create_chunk(struct btrfs_trans_handle *trans,
 						   j * ctl->stripe_size;
 		}
 	}
-	map->stripe_len = BTRFS_STRIPE_LEN;
 	map->io_align = BTRFS_STRIPE_LEN;
 	map->io_width = BTRFS_STRIPE_LEN;
 	map->type = type;
@@ -5615,11 +5614,11 @@ int btrfs_chunk_alloc_add_chunk_item(struct btrfs_trans_handle *trans,
 
 	btrfs_set_stack_chunk_length(chunk, bg->length);
 	btrfs_set_stack_chunk_owner(chunk, BTRFS_EXTENT_TREE_OBJECTID);
-	btrfs_set_stack_chunk_stripe_len(chunk, map->stripe_len);
+	btrfs_set_stack_chunk_stripe_len(chunk, BTRFS_STRIPE_LEN);
 	btrfs_set_stack_chunk_type(chunk, map->type);
 	btrfs_set_stack_chunk_num_stripes(chunk, map->num_stripes);
-	btrfs_set_stack_chunk_io_align(chunk, map->stripe_len);
-	btrfs_set_stack_chunk_io_width(chunk, map->stripe_len);
+	btrfs_set_stack_chunk_io_align(chunk, BTRFS_STRIPE_LEN);
+	btrfs_set_stack_chunk_io_width(chunk, BTRFS_STRIPE_LEN);
 	btrfs_set_stack_chunk_sector_size(chunk, fs_info->sectorsize);
 	btrfs_set_stack_chunk_sub_stripes(chunk, map->sub_stripes);
 
@@ -5809,7 +5808,7 @@ unsigned long btrfs_full_stripe_len(struct btrfs_fs_info *fs_info,
 	if (!WARN_ON(IS_ERR(em))) {
 		map = em->map_lookup;
 		if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK)
-			len = map->stripe_len * nr_data_stripes(map);
+			len = nr_data_stripes(map) << BTRFS_STRIPE_LEN_SHIFT;
 		free_extent_map(em);
 	}
 	return len;
@@ -5975,7 +5974,6 @@ struct btrfs_discard_stripe *btrfs_map_discard(struct btrfs_fs_info *fs_info,
 	u64 stripe_nr_end;
 	u64 stripe_end_offset;
 	u64 stripe_cnt;
-	u64 stripe_len;
 	u64 stripe_offset;
 	u32 stripe_index;
 	u32 factor = 0;
@@ -5996,26 +5994,25 @@ struct btrfs_discard_stripe *btrfs_map_discard(struct btrfs_fs_info *fs_info,
 	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
 		ret = -EOPNOTSUPP;
 		goto out_free_map;
-}
+	}
 
 	offset = logical - em->start;
 	length = min_t(u64, em->start + em->len - logical, length);
 	*length_ret = length;
 
-	stripe_len = map->stripe_len;
 	/*
 	 * stripe_nr counts the total number of stripes we have to stride
 	 * to get to this block
 	 */
-	stripe_nr = div64_u64(offset, stripe_len);
+	stripe_nr = offset >> BTRFS_STRIPE_LEN_SHIFT;
 
 	/* stripe_offset is the offset of this block in its stripe */
-	stripe_offset = offset - stripe_nr * stripe_len;
+	stripe_offset = offset - (stripe_nr << BTRFS_STRIPE_LEN_SHIFT);
 
-	stripe_nr_end = round_up(offset + length, map->stripe_len);
-	stripe_nr_end = div64_u64(stripe_nr_end, map->stripe_len);
+	stripe_nr_end = round_up(offset + length, BTRFS_STRIPE_LEN) >>
+			BTRFS_STRIPE_LEN_SHIFT;
 	stripe_cnt = stripe_nr_end - stripe_nr;
-	stripe_end_offset = stripe_nr_end * map->stripe_len -
+	stripe_end_offset = (stripe_nr_end << BTRFS_STRIPE_LEN_SHIFT) -
 			    (offset + length);
 	/*
 	 * after this, stripe_nr is the number of stripes on this
@@ -6057,15 +6054,15 @@ struct btrfs_discard_stripe *btrfs_map_discard(struct btrfs_fs_info *fs_info,
 	for (i = 0; i < *num_stripes; i++) {
 		stripes[i].physical =
 			map->stripes[stripe_index].physical +
-			stripe_offset + stripe_nr * map->stripe_len;
+			stripe_offset + (stripe_nr << BTRFS_STRIPE_LEN_SHIFT);
 		stripes[i].dev = map->stripes[stripe_index].dev;
 
 		if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
 				 BTRFS_BLOCK_GROUP_RAID10)) {
-			stripes[i].length = stripes_per_dev * map->stripe_len;
+			stripes[i].length = stripes_per_dev << BTRFS_STRIPE_LEN_SHIFT;
 
 			if (i / sub_stripes < remaining_stripes)
-				stripes[i].length += map->stripe_len;
+				stripes[i].length += BTRFS_STRIPE_LEN;
 
 			/*
 			 * Special for the first stripe and
@@ -6304,22 +6301,32 @@ static u64 btrfs_max_io_len(struct map_lookup *map, enum btrfs_map_op op,
 			    u64 offset, u64 *stripe_nr, u64 *stripe_offset,
 			    u64 *full_stripe_start)
 {
-	u32 stripe_len = map->stripe_len;
-
 	ASSERT(op != BTRFS_MAP_DISCARD);
 
 	/*
 	 * Stripe_nr is the stripe where this block falls.  stripe_offset is
 	 * the offset of this block in its stripe.
 	 */
-	*stripe_nr = div64_u64_rem(offset, stripe_len, stripe_offset);
+	*stripe_offset = offset & BTRFS_STRIPE_LEN_MASK;
+	*stripe_nr = offset >> BTRFS_STRIPE_LEN_SHIFT;
 	ASSERT(*stripe_offset < U32_MAX);
 
 	if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
-		unsigned long full_stripe_len = stripe_len * nr_data_stripes(map);
+		unsigned long full_stripe_len = nr_data_stripes(map) <<
+						BTRFS_STRIPE_LEN_SHIFT;
 
+		/*
+		 * For full stripe start, we use previously calculated
+		 * @stripe_nr. Align it to nr_data_stripes, then multiply with
+		 * STRIPE_LEN.
+		 *
+		 * By this we can avoid u64 division completely.  And we have
+		 * to go rounddown(), not round_down(), as nr_data_stripes is
+		 * not ensured to be power of 2.
+		 */
 		*full_stripe_start =
-			div64_u64(offset, full_stripe_len) * full_stripe_len;
+			rounddown(*stripe_nr, nr_data_stripes(map)) <<
+			BTRFS_STRIPE_LEN_SHIFT;
 
 		/*
 		 * For writes to RAID56, allow to write a full stripe set, but
@@ -6334,7 +6341,7 @@ static u64 btrfs_max_io_len(struct map_lookup *map, enum btrfs_map_op op,
 	 * a single disk).
 	 */
 	if (map->type & BTRFS_BLOCK_GROUP_STRIPE_MASK)
-		return stripe_len - *stripe_offset;
+		return BTRFS_STRIPE_LEN - *stripe_offset;
 	return U64_MAX;
 }
 
@@ -6343,7 +6350,7 @@ static void set_io_stripe(struct btrfs_io_stripe *dst, const struct map_lookup *
 {
 	dst->dev = map->stripes[stripe_index].dev;
 	dst->physical = map->stripes[stripe_index].physical +
-			stripe_offset + stripe_nr * map->stripe_len;
+			stripe_offset + (stripe_nr << BTRFS_STRIPE_LEN_SHIFT);
 }
 
 int __btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
@@ -6357,7 +6364,6 @@ int __btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 	u64 map_offset;
 	u64 stripe_offset;
 	u64 stripe_nr;
-	u64 stripe_len;
 	u32 stripe_index;
 	int data_stripes;
 	int i;
@@ -6384,7 +6390,6 @@ int __btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 
 	map = em->map_lookup;
 	data_stripes = nr_data_stripes(map);
-	stripe_len = map->stripe_len;
 
 	map_offset = logical - em->start;
 	max_len = btrfs_max_io_len(map, op, map_offset, &stripe_nr,
@@ -6460,11 +6465,10 @@ int __btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 		}
 
 	} else if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {
-		ASSERT(map->stripe_len == BTRFS_STRIPE_LEN);
 		if (need_raid_map && (need_full_stripe(op) || mirror_num > 1)) {
 			/* push stripe_nr back to the start of the full stripe */
 			stripe_nr = div64_u64(raid56_full_stripe_start,
-					stripe_len * data_stripes);
+					      data_stripes << BTRFS_STRIPE_LEN_SHIFT);
 
 			/* RAID[56] write or recovery. Return all stripes */
 			num_stripes = map->num_stripes;
@@ -6473,7 +6477,7 @@ int __btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 			/* Return the length to the full stripe end */
 			*length = min(logical + *length,
 				      raid56_full_stripe_start + em->start +
-				      data_stripes * stripe_len) - logical;
+				      (data_stripes << BTRFS_STRIPE_LEN_SHIFT)) - logical;
 			stripe_index = 0;
 			stripe_offset = 0;
 		} else {
@@ -6568,7 +6572,7 @@ int __btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,
 		tmp = stripe_nr * data_stripes;
 		for (i = 0; i < data_stripes; i++)
 			bioc->raid_map[(i + rot) % num_stripes] =
-				em->start + (tmp + i) * map->stripe_len;
+				em->start + ((tmp + i) << BTRFS_STRIPE_LEN_SHIFT);
 
 		bioc->raid_map[(i + rot) % map->num_stripes] = RAID5_P_STRIPE;
 		if (map->type & BTRFS_BLOCK_GROUP_RAID6)
@@ -6941,7 +6945,6 @@ static int read_one_chunk(struct btrfs_key *key, struct extent_buffer *leaf,
 	map->num_stripes = num_stripes;
 	map->io_width = btrfs_chunk_io_width(leaf, chunk);
 	map->io_align = btrfs_chunk_io_align(leaf, chunk);
-	map->stripe_len = btrfs_chunk_stripe_len(leaf, chunk);
 	map->type = type;
 	/*
 	 * We can't use the sub_stripes value, as for profiles other than
diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
index 7e51f2238f72..9f397b4c1b4f 100644
--- a/fs/btrfs/volumes.h
+++ b/fs/btrfs/volumes.h
@@ -17,7 +17,11 @@
 
 extern struct mutex uuid_mutex;
 
-#define BTRFS_STRIPE_LEN	SZ_64K
+#define BTRFS_STRIPE_LEN		SZ_64K
+#define BTRFS_STRIPE_LEN_SHIFT		(16)
+#define BTRFS_STRIPE_LEN_MASK		(BTRFS_STRIPE_LEN - 1)
+
+static_assert(const_ilog2(BTRFS_STRIPE_LEN) == BTRFS_STRIPE_LEN_SHIFT);
 
 /* Used by sanity check for btrfs_raid_types. */
 #define const_ffs(n) (__builtin_ctzll(n) + 1)
@@ -446,7 +450,6 @@ struct map_lookup {
 	u64 type;
 	int io_align;
 	int io_width;
-	u32 stripe_len;
 	int num_stripes;
 	int sub_stripes;
 	int verified_stripes; /* For mount time dev extent verification */