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mm: kvmalloc: add non-blocking support for vmalloc

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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.

Link: https://lkml.kernel.org/r/20251007122035.56347-11-urezki@gmail.com
Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Baoquan He <bhe@redhat.com>
Cc: Alexander Potapenko <glider@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Cc: Marco Elver <elver@google.com>
Cc: Michal Hocko <mhocko@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Uladzislau Rezki (Sony) 2025-10-07 14:20:35 +02:00 committed by Andrew Morton
parent 0667b209e9
commit c6307674ed
1 changed files with 13 additions and 6 deletions
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19
mm/slub.c
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@ -7090,7 +7090,7 @@ 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 * Uses kmalloc to get the memory but if the allocation fails then falls back
* to the vmalloc allocator. Use kvfree for freeing the memory. * 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 * __GFP_RETRY_MAYFAIL is supported, and it should be used only if kmalloc is
* preferable to the vmalloc fallback, due to visible performance drawbacks. * preferable to the vmalloc fallback, due to visible performance drawbacks.
* *
@ -7099,6 +7099,7 @@ static gfp_t kmalloc_gfp_adjust(gfp_t flags, size_t size)
void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align, void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align,
gfp_t flags, int node) gfp_t flags, int node)
{ {
bool allow_block;
void *ret; void *ret;
/* /*
@ -7111,16 +7112,22 @@ void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align,
if (ret || size <= PAGE_SIZE) if (ret || size <= PAGE_SIZE)
return ret; return ret;
/* non-sleeping allocations are not supported by vmalloc */
if (!gfpflags_allow_blocking(flags))
return NULL;
/* Don't even allow crazy sizes */ /* Don't even allow crazy sizes */
if (unlikely(size > INT_MAX)) { if (unlikely(size > INT_MAX)) {
WARN_ON_ONCE(!(flags & __GFP_NOWARN)); WARN_ON_ONCE(!(flags & __GFP_NOWARN));
return NULL; 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, * kvmalloc() can always use VM_ALLOW_HUGE_VMAP,
* since the callers already cannot assume anything * since the callers already cannot assume anything
@ -7128,7 +7135,7 @@ void *__kvmalloc_node_noprof(DECL_BUCKET_PARAMS(size, b), unsigned long align,
* protection games. * protection games.
*/ */
return __vmalloc_node_range_noprof(size, align, VMALLOC_START, VMALLOC_END, 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)); node, __builtin_return_address(0));
} }
EXPORT_SYMBOL(__kvmalloc_node_noprof); EXPORT_SYMBOL(__kvmalloc_node_noprof);