Vlastimil Babka said that kmalloc will return a power-of-two-aligned buffer if it was called with a power-of-two size. So, we can use kmalloc instead of our own slab cache in dm-bufio. Note that the code for the slab cache was not removed because dm-bufio supports non-power-of-two buffer sizes. Link: https://lore.kernel.org/linux-mm/e7fca292-7c79-4f97-a90c-d68178d8ca59@xxxxxxx/ [1] Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx> --- drivers/md/dm-bufio.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) Index: linux-2.6/drivers/md/dm-bufio.c =================================================================== --- linux-2.6.orig/drivers/md/dm-bufio.c 2024-11-13 15:24:33.000000000 +0100 +++ linux-2.6/drivers/md/dm-bufio.c 2024-11-13 15:46:58.000000000 +0100 @@ -318,9 +318,10 @@ static struct lru_entry *lru_evict(struc */ enum data_mode { DATA_MODE_SLAB = 0, - DATA_MODE_GET_FREE_PAGES = 1, - DATA_MODE_VMALLOC = 2, - DATA_MODE_LIMIT = 3 + DATA_MODE_KMALLOC = 1, + DATA_MODE_GET_FREE_PAGES = 2, + DATA_MODE_VMALLOC = 3, + DATA_MODE_LIMIT = 4 }; struct dm_buffer { @@ -1062,6 +1063,7 @@ static unsigned long dm_bufio_retain_byt static unsigned long dm_bufio_peak_allocated; static unsigned long dm_bufio_allocated_kmem_cache; +static unsigned long dm_bufio_allocated_kmalloc; static unsigned long dm_bufio_allocated_get_free_pages; static unsigned long dm_bufio_allocated_vmalloc; static unsigned long dm_bufio_current_allocated; @@ -1104,6 +1106,7 @@ static void adjust_total_allocated(struc static unsigned long * const class_ptr[DATA_MODE_LIMIT] = { &dm_bufio_allocated_kmem_cache, + &dm_bufio_allocated_kmalloc, &dm_bufio_allocated_get_free_pages, &dm_bufio_allocated_vmalloc, }; @@ -1181,6 +1184,11 @@ static void *alloc_buffer_data(struct dm return kmem_cache_alloc(c->slab_cache, gfp_mask); } + if (unlikely(c->block_size < PAGE_SIZE)) { + *data_mode = DATA_MODE_KMALLOC; + return kmalloc(c->block_size, gfp_mask | __GFP_RECLAIMABLE); + } + if (c->block_size <= KMALLOC_MAX_SIZE && gfp_mask & __GFP_NORETRY) { *data_mode = DATA_MODE_GET_FREE_PAGES; @@ -1204,6 +1212,10 @@ static void free_buffer_data(struct dm_b kmem_cache_free(c->slab_cache, data); break; + case DATA_MODE_KMALLOC: + kfree(data); + break; + case DATA_MODE_GET_FREE_PAGES: free_pages((unsigned long)data, c->sectors_per_block_bits - (PAGE_SHIFT - SECTOR_SHIFT)); @@ -2519,8 +2531,7 @@ struct dm_bufio_client *dm_bufio_client_ goto bad_dm_io; } - if (block_size <= KMALLOC_MAX_SIZE && - (block_size < PAGE_SIZE || !is_power_of_2(block_size))) { + if (block_size <= KMALLOC_MAX_SIZE && !is_power_of_2(block_size)) { unsigned int align = min(1U << __ffs(block_size), (unsigned int)PAGE_SIZE); snprintf(slab_name, sizeof(slab_name), "dm_bufio_cache-%u-%u", @@ -2902,6 +2913,7 @@ static int __init dm_bufio_init(void) __u64 mem; dm_bufio_allocated_kmem_cache = 0; + dm_bufio_allocated_kmalloc = 0; dm_bufio_allocated_get_free_pages = 0; dm_bufio_allocated_vmalloc = 0; dm_bufio_current_allocated = 0; @@ -2990,6 +3002,9 @@ MODULE_PARM_DESC(peak_allocated_bytes, " module_param_named(allocated_kmem_cache_bytes, dm_bufio_allocated_kmem_cache, ulong, 0444); MODULE_PARM_DESC(allocated_kmem_cache_bytes, "Memory allocated with kmem_cache_alloc"); +module_param_named(allocated_kmalloc_bytes, dm_bufio_allocated_kmalloc, ulong, 0444); +MODULE_PARM_DESC(allocated_kmalloc_bytes, "Memory allocated with kmalloc_alloc"); + module_param_named(allocated_get_free_pages_bytes, dm_bufio_allocated_get_free_pages, ulong, 0444); MODULE_PARM_DESC(allocated_get_free_pages_bytes, "Memory allocated with get_free_pages");
