Re: [PATCH 1/4] staging: zsmalloc: add gfp flags to zs_create_pool

Minchan Kim
2013-01-28T03:39:47Z

Hi Seth,

On Fri, Jan 25, 2013 at 11:46:15AM -0600, Seth Jennings wrote:
> zs_create_pool() currently takes a gfp flags argument
> that is used when growing the memory pool. However
> it is not used in allocating the metadata for the pool
> itself. That is currently hardcoded to GFP_KERNEL.
>
> zswap calls zs_create_pool() at swapon time which is done
> in atomic context, resulting in a "might sleep" warning.
>
> This patch changes the meaning of the flags argument in
> zs_create_pool() to mean the flags for the metadata allocation,
> and adds a flags argument to zs_malloc that will be used for
> memory pool growth if required.

As I mentioned, I'm not strongly against with this patch but it
should be last resort in case of not being able to address
frontswap's init routine's dependency with swap_lock.

I sent a patch and am waiting reply of Konrand or Dan.
If we can fix frontswap, it would be better rather than
changing zsmalloc.

>
> Acked-by: Nitin Gupta <ngupta@vflare.org>
> Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
> ---
> drivers/staging/zram/zram_drv.c | 4 ++--
> drivers/staging/zsmalloc/zsmalloc-main.c | 9 +++------
> drivers/staging/zsmalloc/zsmalloc.h | 2 +-
> 3 files changed, 6 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c
> index 6762b99..836dccf 100644
> --- a/drivers/staging/zram/zram_drv.c
> +++ b/drivers/staging/zram/zram_drv.c
> @@ -325,7 +325,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> clen = PAGE_SIZE;
> }
>
> - handle = zs_malloc(zram->mem_pool, clen);
> + handle = zs_malloc(zram->mem_pool, clen, GFP_NOIO | __GFP_HIGHMEM);
> if (!handle) {
> pr_info("Error allocating memory for compressed "
> "page: %u, size=%zu\n", index, clen);
> @@ -565,7 +565,7 @@ int zram_init_device(struct zram *zram)
> /* zram devices sort of resembles non-rotational disks */
> queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
>
> - zram->mem_pool = zs_create_pool("zram", GFP_NOIO | __GFP_HIGHMEM);
> + zram->mem_pool = zs_create_pool("zram", GFP_KERNEL);
> if (!zram->mem_pool) {
> pr_err("Error creating memory pool\n");
> ret = -ENOMEM;
> diff --git a/drivers/staging/zsmalloc/zsmalloc-main.c b/drivers/staging/zsmalloc/zsmalloc-main.c
> index eb00772..f29f170 100644
> --- a/drivers/staging/zsmalloc/zsmalloc-main.c
> +++ b/drivers/staging/zsmalloc/zsmalloc-main.c
> @@ -205,8 +205,6 @@ struct link_free {
>
> struct zs_pool {
> struct size_class size_class[ZS_SIZE_CLASSES];
> -
> - gfp_t flags; /* allocation flags used when growing pool */
> const char *name;
> };
>
> @@ -818,7 +816,7 @@ struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
> return NULL;
>
> ovhd_size = roundup(sizeof(*pool), PAGE_SIZE);
> - pool = kzalloc(ovhd_size, GFP_KERNEL);
> + pool = kzalloc(ovhd_size, flags);
> if (!pool)
> return NULL;
>
> @@ -838,7 +836,6 @@ struct zs_pool *zs_create_pool(const char *name, gfp_t flags)
>
> }
>
> - pool->flags = flags;
> pool->name = name;
>
> return pool;
> @@ -874,7 +871,7 @@ EXPORT_SYMBOL_GPL(zs_destroy_pool);
> * otherwise 0.
> * Allocation requests with size > ZS_MAX_ALLOC_SIZE will fail.
> */
> -unsigned long zs_malloc(struct zs_pool *pool, size_t size)
> +unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t flags)
> {
> unsigned long obj;
> struct link_free *link;
> @@ -896,7 +893,7 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
>
> if (!first_page) {
> spin_unlock(&class->lock);
> - first_page = alloc_zspage(class, pool->flags);
> + first_page = alloc_zspage(class, flags);
> if (unlikely(!first_page))
> return 0;
>
> diff --git a/drivers/staging/zsmalloc/zsmalloc.h b/drivers/staging/zsmalloc/zsmalloc.h
> index de2e8bf..907ff03 100644
> --- a/drivers/staging/zsmalloc/zsmalloc.h
> +++ b/drivers/staging/zsmalloc/zsmalloc.h
> @@ -31,7 +31,7 @@ struct zs_pool;
> struct zs_pool *zs_create_pool(const char *name, gfp_t flags);
> void zs_destroy_pool(struct zs_pool *pool);
>
> -unsigned long zs_malloc(struct zs_pool *pool, size_t size);
> +unsigned long zs_malloc(struct zs_pool *pool, size_t size, gfp_t flags);
> void zs_free(struct zs_pool *pool, unsigned long obj);
>
> void *zs_map_object(struct zs_pool *pool, unsigned long handle,
> --
> 1.7.9.5
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: email@kvack.org

--
Kind regards,
Minchan Kim