netdev - [PATCH bpf-next 1/2] vmalloc: expose vmap_allow_huge via get_vmap_allow

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Date:   Wed, 9 Feb 2022 22:41:07 -0800
From:   Song Liu <song@...nel.org>
To:     <linux-mm@...ck.org>, <bpf@...r.kernel.org>,
        <netdev@...r.kernel.org>
CC:     <ast@...nel.org>, <daniel@...earbox.net>, <andrii@...nel.org>,
        <kernel-team@...com>, <akpm@...ux-foundation.org>,
        <eric.dumazet@...il.com>, Song Liu <song@...nel.org>
Subject: [PATCH bpf-next 1/2] vmalloc: expose vmap_allow_huge via get_vmap_allow_huge()

Users can use get_vmap_allow_huge() to predict the behavior of vmalloc (or
its variations). Specifically, if get_vmap_allow_huge() == false, vmalloc
will never return huge pages.

Signed-off-by: Song Liu <song@...nel.org>
---
 include/linux/vmalloc.h | 1 +
 mm/vmalloc.c            | 5 +++++
 2 files changed, 6 insertions(+)

diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h
index 880227b9f044..22acfcd2d0d1 100644
--- a/include/linux/vmalloc.h
+++ b/include/linux/vmalloc.h
@@ -256,6 +256,7 @@ extern long vread(char *buf, char *addr, unsigned long count);
 extern struct list_head vmap_area_list;
 extern __init void vm_area_add_early(struct vm_struct *vm);
 extern __init void vm_area_register_early(struct vm_struct *vm, size_t align);
+extern bool get_vmap_allow_huge(void);
 
 #ifdef CONFIG_SMP
 # ifdef CONFIG_MMU
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 4165304d3547..895ac81b6bb4 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -72,6 +72,11 @@ early_param("nohugevmalloc", set_nohugevmalloc);
 static const bool vmap_allow_huge = false;
 #endif	/* CONFIG_HAVE_ARCH_HUGE_VMALLOC */
 
+bool get_vmap_allow_huge(void)
+{
+	return vmap_allow_huge;
+}
+
 bool is_vmalloc_addr(const void *x)
 {
 	unsigned long addr = (unsigned long)x;
-- 
2.30.2