On Mon, Jan 25, 2021 at 02:07:01PM +0100, Michal Hocko wrote:

On Thu 21-01-21 09:54:59, Minchan Kim wrote:

...

The upcoming patch will introduce __GFP_NORETRY semantic in alloc_contig_range which is a failfast mode of the API. Instead of adding a additional parameter for gfp, replace no_warn with gfp flag.

To keep old behaviors, it follows the rule below.

no_warn gfp_flags

false GFP_KERNEL true GFP_KERNEL|__GFP_NOWARN gfp & __GFP_NOWARN GFP_KERNEL | (gfp & __GFP_NOWARN)

Reviewed-by: Suren Baghdasaryan surenb@google.com Signed-off-by: Minchan Kim minchan@kernel.org

[...]

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diff --git a/mm/cma.c b/mm/cma.c index 0ba69cd16aeb..d50627686fec 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -419,13 +419,13 @@ static inline void cma_debug_show_areas(struct cma *cma) { }

• @cma: Contiguous memory region for which the allocation is performed.
• @count: Requested number of pages.
• @align: Requested alignment of pages (in PAGE_SIZE order).

• • @no_warn: Avoid printing message about failed allocation

• • @gfp_mask: GFP mask to use during the cma allocation.

Call out supported gfp flags explicitly. Have a look at kvmalloc_node for a guidance.

How about this?

diff --git a/mm/cma.c b/mm/cma.c index d50627686fec..b94727b694d6 100644 --- a/mm/cma.c +++ b/mm/cma.c @@ -423,6 +423,10 @@ static inline void cma_debug_show_areas(struct cma *cma) { } * * This function allocates part of contiguous memory on specific * contiguous memory area. + * + * For gfp_mask, GFP_KERNEL and __GFP_NORETRY are supported. __GFP_NORETRY + * will avoid costly functions(e.g., waiting on page_writeback and locking) + * at current implementaion during the page migration. */ struct page *cma_alloc(struct cma *cma, size_t count, unsigned int align, gfp_t gfp_mask)