on 8/16/2024 3:57 PM, Ojaswin Mujoo wrote:
> Although we have checks to make sure s_stripe is a multiple of cluster
> size, in case we accidentally end up with a scenario where this is not
> the case, use EXT4_NUM_B2C() so that we don't end up with unexpected
> cases where EXT4_B2C(stripe) becomes 0.
>
> Also make the is_stripe_aligned check in regular_allocator a bit more
> robust while we are at it. This should ideally have no functional change
> unless we have a bug somewhere causing (stripe % cluster_size != 0)
>
> Signed-off-by: Ojaswin Mujoo <ojaswin@xxxxxxxxxxxxx>> ---
> fs/ext4/mballoc.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 9dda9cd68ab2..b2e836a4bd18 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -2553,7 +2553,7 @@ void ext4_mb_scan_aligned(struct ext4_allocation_context *ac,
> do_div(a, sbi->s_stripe);
> i = (a * sbi->s_stripe) - first_group_block;
>
> - stripe = EXT4_B2C(sbi, sbi->s_stripe);
> + stripe = EXT4_NUM_B2C(sbi, sbi->s_stripe);
> i = EXT4_B2C(sbi, i);
> while (i < EXT4_CLUSTERS_PER_GROUP(sb)) {
> if (!mb_test_bit(i, bitmap)) {
> @@ -2929,8 +2929,9 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
> ext4_mb_simple_scan_group(ac, &e4b);
> else {
> bool is_stripe_aligned = sbi->s_stripe &&
> + sbi->s_stripe >= sbi->s_cluster_ratio &&
sbi->s_cluster_ratio is >= 1, so sbi->s_stripe >= sbi->s_cluster_ratio could
cover the case that sbi->s_stripe is non-zero. Non-zero check of sbi->s_stripe
seems not needed.
> !(ac->ac_g_ex.fe_len %
> - EXT4_B2C(sbi, sbi->s_stripe));
> + EXT4_NUM_B2C(sbi, sbi->s_stripe));
>
> if ((cr == CR_GOAL_LEN_FAST ||
> cr == CR_BEST_AVAIL_LEN) &&
> @@ -3707,7 +3708,7 @@ int ext4_mb_init(struct super_block *sb)
> */
> if (sbi->s_stripe > 1) {
> sbi->s_mb_group_prealloc = roundup(
> - sbi->s_mb_group_prealloc, EXT4_B2C(sbi, sbi->s_stripe));
> + sbi->s_mb_group_prealloc, EXT4_NUM_B2C(sbi, sbi->s_stripe));
> }
>
> sbi->s_locality_groups = alloc_percpu(struct ext4_locality_group);
>
