Extend __kvmalloc_node_noprof() to handle non-blocking GFP flags (GFP_NOWAIT and GFP_ATOMIC). Previously such flags were rejected, returning NULL. With this change: - kvmalloc() can fall back to vmalloc() if non-blocking contexts; - for non-blocking allocations the VM_ALLOW_HUGE_VMAP option is disabled, since the huge mapping path still contains might_sleep(); - documentation update to reflect that GFP_NOWAIT and GFP_ATOMIC are now supported. Acked-by: Michal Hocko Reviewed-by: Baoquan He Signed-off-by: Uladzislau Rezki (Sony) --- mm/slub.c | 19 +++++++++++++------ 1 file changed, 13 insertions(+), 6 deletions(-) diff --git a/mm/slub.c b/mm/slub.c index 584a5ff1828b..3de0719e24e9 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -7018,7 +7018,7 @@ static gfp_t kmalloc_gfp_adjust(gfp_t flags, size_t size) * Uses kmalloc to get the memory but if the allocation fails then falls back * to the vmalloc allocator. Use kvfree for freeing the memory. * - * GFP_NOWAIT and GFP_ATOMIC are not supported, neither is the __GFP_NORETRY modifier. + * GFP_NOWAIT and GFP_ATOMIC are supported, the __GFP_NORETRY modifier is not. * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is * preferable to the vmalloc fallback, due to visible performance drawbacks. * @@ -7027,6 +7027,7 @@ static gfp_t kmalloc_gfp_adjust(gfp_t flags, size_t size) void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align, gfp_t flags, int node) { + bool allow_block; void *ret; /* @@ -7039,16 +7040,22 @@ void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align, if (ret || size <= PAGE_SIZE) return ret; - /* non-sleeping allocations are not supported by vmalloc */ - if (!gfpflags_allow_blocking(flags)) - return NULL; - /* Don't even allow crazy sizes */ if (unlikely(size > INT_MAX)) { WARN_ON_ONCE(!(flags & __GFP_NOWARN)); return NULL; } + /* + * For non-blocking the VM_ALLOW_HUGE_VMAP is not used + * because the huge-mapping path in vmalloc contains at + * least one might_sleep() call. + * + * TODO: Revise huge-mapping path to support non-blocking + * flags. + */ + allow_block = gfpflags_allow_blocking(flags); + /* * kvmalloc() can always use VM_ALLOW_HUGE_VMAP, * since the callers already cannot assume anything @@ -7056,7 +7063,7 @@ void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align, * protection games. */ return __vmalloc_node_range_noprof(size, align, VMALLOC_START, VMALLOC_END, - flags, PAGE_KERNEL, VM_ALLOW_HUGE_VMAP, + flags, PAGE_KERNEL, allow_block ? VM_ALLOW_HUGE_VMAP:0, node, __builtin_return_address(0)); } EXPORT_SYMBOL(__kvmalloc_node_noprof); -- 2.47.3