From: Naohiro Aota <naohiro.aota@wdc.com>
Date: Tue, 16 Sep 2025 02:46:11 +0000 (+0900)
Subject: btrfs: zoned: fix stripe width calculation
X-Git-Tag: v6.18-rc6~39^2~3
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=6a1ab50135ce829b834b448ce49867b5210a1641;p=thirdparty%2Flinux.git

btrfs: zoned: fix stripe width calculation

The stripe offset calculation in the zoned code for raid0 and raid10
wrongly uses map->stripe_size to calculate it. In fact, map->stripe_size is
the size of the device extent composing the block group, which always is
the zone_size on the zoned setup.

Fix it by using BTRFS_STRIPE_LEN and BTRFS_STRIPE_LEN_SHIFT. Also, optimize
the calculation a bit by doing the common calculation only once.

Fixes: c0d90a79e8e6 ("btrfs: zoned: fix alloc_offset calculation for partly conventional block groups")
CC: stable@vger.kernel.org # 6.17+
Signed-off-by: Naohiro Aota <naohiro.aota@wdc.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---

diff --git a/fs/btrfs/zoned.c b/fs/btrfs/zoned.c
index 8f006dff8893d..b622c73fe30f9 100644
--- a/fs/btrfs/zoned.c
+++ b/fs/btrfs/zoned.c
@@ -1523,6 +1523,8 @@ static int btrfs_load_block_group_raid0(struct btrfs_block_group *bg,
 					u64 last_alloc)
 {
 	struct btrfs_fs_info *fs_info = bg->fs_info;
+	u64 stripe_nr = 0, stripe_offset = 0;
+	u32 stripe_index = 0;
 
 	if ((map->type & BTRFS_BLOCK_GROUP_DATA) && !fs_info->stripe_root) {
 		btrfs_err(fs_info, "zoned: data %s needs raid-stripe-tree",
@@ -1530,28 +1532,26 @@ static int btrfs_load_block_group_raid0(struct btrfs_block_group *bg,
 		return -EINVAL;
 	}
 
+	if (last_alloc) {
+		u32 factor = map->num_stripes;
+
+		stripe_nr = last_alloc >> BTRFS_STRIPE_LEN_SHIFT;
+		stripe_offset = last_alloc & BTRFS_STRIPE_LEN_MASK;
+		stripe_nr = div_u64_rem(stripe_nr, factor, &stripe_index);
+	}
+
 	for (int i = 0; i < map->num_stripes; i++) {
 		if (zone_info[i].alloc_offset == WP_MISSING_DEV)
 			continue;
 
 		if (zone_info[i].alloc_offset == WP_CONVENTIONAL) {
-			u64 stripe_nr, full_stripe_nr;
-			u64 stripe_offset;
-			int stripe_index;
 
-			stripe_nr = div64_u64(last_alloc, map->stripe_size);
-			stripe_offset = stripe_nr * map->stripe_size;
-			full_stripe_nr = div_u64(stripe_nr, map->num_stripes);
-			div_u64_rem(stripe_nr, map->num_stripes, &stripe_index);
-
-			zone_info[i].alloc_offset =
-				full_stripe_nr * map->stripe_size;
+			zone_info[i].alloc_offset = btrfs_stripe_nr_to_offset(stripe_nr);
 
 			if (stripe_index > i)
-				zone_info[i].alloc_offset += map->stripe_size;
+				zone_info[i].alloc_offset += BTRFS_STRIPE_LEN;
 			else if (stripe_index == i)
-				zone_info[i].alloc_offset +=
-					(last_alloc - stripe_offset);
+				zone_info[i].alloc_offset += stripe_offset;
 		}
 
 		if (test_bit(0, active) != test_bit(i, active)) {
@@ -1575,6 +1575,8 @@ static int btrfs_load_block_group_raid10(struct btrfs_block_group *bg,
 					 u64 last_alloc)
 {
 	struct btrfs_fs_info *fs_info = bg->fs_info;
+	u64 stripe_nr = 0, stripe_offset = 0;
+	u32 stripe_index = 0;
 
 	if ((map->type & BTRFS_BLOCK_GROUP_DATA) && !fs_info->stripe_root) {
 		btrfs_err(fs_info, "zoned: data %s needs raid-stripe-tree",
@@ -1582,6 +1584,14 @@ static int btrfs_load_block_group_raid10(struct btrfs_block_group *bg,
 		return -EINVAL;
 	}
 
+	if (last_alloc) {
+		u32 factor = map->num_stripes / map->sub_stripes;
+
+		stripe_nr = last_alloc >> BTRFS_STRIPE_LEN_SHIFT;
+		stripe_offset = last_alloc & BTRFS_STRIPE_LEN_MASK;
+		stripe_nr = div_u64_rem(stripe_nr, factor, &stripe_index);
+	}
+
 	for (int i = 0; i < map->num_stripes; i++) {
 		if (zone_info[i].alloc_offset == WP_MISSING_DEV)
 			continue;
@@ -1595,26 +1605,12 @@ static int btrfs_load_block_group_raid10(struct btrfs_block_group *bg,
 		}
 
 		if (zone_info[i].alloc_offset == WP_CONVENTIONAL) {
-			u64 stripe_nr, full_stripe_nr;
-			u64 stripe_offset;
-			int stripe_index;
-
-			stripe_nr = div64_u64(last_alloc, map->stripe_size);
-			stripe_offset = stripe_nr * map->stripe_size;
-			full_stripe_nr = div_u64(stripe_nr,
-					 map->num_stripes / map->sub_stripes);
-			div_u64_rem(stripe_nr,
-				    (map->num_stripes / map->sub_stripes),
-				    &stripe_index);
-
-			zone_info[i].alloc_offset =
-				full_stripe_nr * map->stripe_size;
+			zone_info[i].alloc_offset = btrfs_stripe_nr_to_offset(stripe_nr);
 
 			if (stripe_index > (i / map->sub_stripes))
-				zone_info[i].alloc_offset += map->stripe_size;
+				zone_info[i].alloc_offset += BTRFS_STRIPE_LEN;
 			else if (stripe_index == (i / map->sub_stripes))
-				zone_info[i].alloc_offset +=
-					(last_alloc - stripe_offset);
+				zone_info[i].alloc_offset += stripe_offset;
 		}
 
 		if ((i % map->sub_stripes) == 0) {