On 7/2/26 6:48 AM, Matthew Auld wrote:
> On 29/06/2026 08:43, Arunpravin Paneer Selvam wrote:
>> The try_harder contiguous fallback could return a range whose start
>> offset did not match the caller's min_block_size. When a candidate's
>> start is misaligned, realign it: free the misaligned run and reallocate
>> exactly @size at the next lower min_block_size boundary. This keeps the
>> returned size unchanged with no surplus to trim, and rejects the request
>> only when no aligned candidate fits.
>>
>> v2: align misaligned candidates down to min_block_size instead of
>> bailing out, for both the RHS and LHS paths (Matthew).
>>
>> Suggested-by: Christian König <[email protected]>
>> Fixes: 0a1844bf0b53 ("drm/buddy: Improve contiguous memory allocation")
>> Cc: Matthew Auld <[email protected]>
>> Cc: Christian König <[email protected]>
>> Cc: Timur Kristóf <[email protected]>
>> Cc: John Olender <[email protected]>
>> Cc: [email protected]
>> Signed-off-by: Arunpravin Paneer Selvam <[email protected]>
>
> Reviewed-by: Matthew Auld <[email protected]>
>
I haven't hit any issues with this revision during testing.
Thanks,
John
>> ---
>> drivers/gpu/buddy.c | 63 +++++++++++++++++++++++++++++++--------------
>> 1 file changed, 44 insertions(+), 19 deletions(-)
>>
>> diff --git a/drivers/gpu/buddy.c b/drivers/gpu/buddy.c
>> index dc81fe0301ce..3c73ae87f3c5 100644
>> --- a/drivers/gpu/buddy.c
>> +++ b/drivers/gpu/buddy.c
>> @@ -1118,22 +1118,30 @@ static int __gpu_buddy_alloc_range(struct gpu_buddy
>> *mm,
>> blocks, total_allocated_on_err);
>> }
>> +static int __alloc_contig_aligned_retry(struct gpu_buddy *mm,
>> + u64 unaligned_offset,
>> + u64 size,
>> + u64 min_block_size,
>> + struct list_head *blocks)
>> +{
>> + u64 aligned_offset = round_down(unaligned_offset, min_block_size);
>> +
>> + return __gpu_buddy_alloc_range(mm, aligned_offset, size, NULL, blocks);
>> +}
>> +
>> static int __alloc_contig_try_harder(struct gpu_buddy *mm,
>> u64 size,
>> u64 min_block_size,
>> struct list_head *blocks)
>> {
>> - u64 rhs_offset, lhs_offset, lhs_size, filled;
>> + u64 rhs_offset, lhs_offset, filled;
>> struct gpu_buddy_block *block;
>> unsigned int tree, order;
>> - LIST_HEAD(blocks_lhs);
>> - unsigned long pages;
>> u64 modify_size;
>> int err;
>> modify_size = rounddown_pow_of_two(size);
>> - pages = modify_size >> ilog2(mm->chunk_size);
>> - order = fls(pages) - 1;
>> + order = ilog2(modify_size) - ilog2(mm->chunk_size);
>> if (order == 0)
>> return -ENOSPC;
>> @@ -1149,31 +1157,48 @@ static int __alloc_contig_try_harder(struct
>> gpu_buddy *mm,
>> while (iter) {
>> block = rbtree_get_free_block(iter);
>> - /* Allocate blocks traversing RHS */
>> rhs_offset = gpu_buddy_block_offset(block);
>> +
>> + /* Allocate blocks traversing RHS */
>> err = __gpu_buddy_alloc_range(mm, rhs_offset, size,
>> &filled, blocks);
>> - if (!err || err != -ENOSPC)
>> + if (err && err != -ENOSPC)
>> return err;
>> + if (!err && IS_ALIGNED(rhs_offset, min_block_size))
>> + return 0;
>> + if (!err) {
>> + /* Allocate the unaligned RHS offset using round_down */
>> + gpu_buddy_free_list_internal(mm, blocks);
>> + err = __alloc_contig_aligned_retry(mm, rhs_offset,
>> + size,
>> + min_block_size,
>> + blocks);
>> + if (!err)
>> + return 0;
>> + if (err != -ENOSPC) {
>> + gpu_buddy_free_list_internal(mm, blocks);
>> + return err;
>> + }
>> + goto next;
>> + }
>> - lhs_size = max((size - filled), min_block_size);
>> - if (!IS_ALIGNED(lhs_size, min_block_size))
>> - lhs_size = round_up(lhs_size, min_block_size);
>> + if (size - filled > rhs_offset)
>> + goto next;
>> - /* Allocate blocks traversing LHS */
>> - lhs_offset = gpu_buddy_block_offset(block) - lhs_size;
>> - err = __gpu_buddy_alloc_range(mm, lhs_offset, lhs_size,
>> - NULL, &blocks_lhs);
>> - if (!err) {
>> - list_splice(&blocks_lhs, blocks);
>> + lhs_offset = rhs_offset - (size - filled);
>> +
>> + /* Allocate the unaligned LHS offset using round_down */
>> + gpu_buddy_free_list_internal(mm, blocks);
>> + err = __alloc_contig_aligned_retry(mm, lhs_offset, size,
>> + min_block_size, blocks);
>> + if (!err)
>> return 0;
>> - } else if (err != -ENOSPC) {
>> + if (err != -ENOSPC) {
>> gpu_buddy_free_list_internal(mm, blocks);
>> return err;
>> }
>> - /* Free blocks for the next iteration */
>> +next:
>> gpu_buddy_free_list_internal(mm, blocks);
>> -
>> iter = rb_prev(iter);
>> }
>> }
>>
>> base-commit: 6648301c5bb2ef23f0fb15bcb01d21ff66f36799
>
