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| author |   Linus Walleij <linus.walleij@linaro.org> | 2025-05-09 09:25:09 +0200 |
|---|---|---|
| committer |   Andrew Morton <akpm@linux-foundation.org> | 2025-07-09 22:57:50 -0700 |
| commit | f7b0ff2bc91d8bb2ba9fdb182da39dd9733b1c50 (patch) | |
| tree | 248a0b457e55001d6d55972043c22272a33875fe /kernel/fork.c | |
| parent | fork: clean-up naming of vm_stack/vm_struct variables in vmap stacks code (diff) | |
| download | wireguard-linux-f7b0ff2bc91d8bb2ba9fdb182da39dd9733b1c50.tar.xz wireguard-linux-f7b0ff2bc91d8bb2ba9fdb182da39dd9733b1c50.zip | |
fork: define a local GFP_VMAP_STACK
The current allocation of VMAP stack memory is using (THREADINFO_GFP &
~__GFP_ACCOUNT) which is a complicated way of saying (GFP_KERNEL |
__GFP_ZERO):
<linux/thread_info.h>:
define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO)
<linux/gfp_types.h>:
define GFP_KERNEL_ACCOUNT (GFP_KERNEL | __GFP_ACCOUNT)
This is an unfortunate side-effect of independent changes blurring the
picture:
commit 19809c2da28aee5860ad9a2eff760730a0710df0 changed (THREADINFO_GFP |
__GFP_HIGHMEM) to just THREADINFO_GFP since highmem became implicit.
commit 9b6f7e163cd0f468d1b9696b785659d3c27c8667 then added stack caching
and rewrote the allocation to (THREADINFO_GFP & ~__GFP_ACCOUNT) as cached
stacks need to be accounted separately. However that code, when it
eventually accounts the memory does this:
ret = memcg_kmem_charge(vm->pages[i], GFP_KERNEL, 0)
so the memory is charged as a GFP_KERNEL allocation.
Define a unique GFP_VMAP_STACK to use
GFP_KERNEL | __GFP_ZERO and move the comment there.
Link: https://lkml.kernel.org/r/20250509-gfp-stack-v1-1-82f6f7efc210@linaro.org
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Reported-by: Mateusz Guzik <mjguzik@gmail.com>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Mike Rapoport (Microsoft) <rppt@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Diffstat (limited to 'kernel/fork.c')
| -rw-r--r-- | kernel/fork.c | 13 |
1 files changed, 7 insertions, 6 deletions
diff --git a/kernel/fork.c b/kernel/fork.c index 5fd893c907a5..6616d173307a 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -201,6 +201,12 @@ static inline void free_task_struct(struct task_struct *tsk) */ #define NR_CACHED_STACKS 2 static DEFINE_PER_CPU(struct vm_struct *, cached_stacks[NR_CACHED_STACKS]); +/* + * Allocated stacks are cached and later reused by new threads, so memcg + * accounting is performed by the code assigning/releasing stacks to tasks. + * We need a zeroed memory without __GFP_ACCOUNT. + */ +#define GFP_VMAP_STACK (GFP_KERNEL | __GFP_ZERO) struct vm_stack { struct rcu_head rcu; @@ -307,13 +313,8 @@ static int alloc_thread_stack_node(struct task_struct *tsk, int node) return 0; } - /* - * Allocated stacks are cached and later reused by new threads, - * so memcg accounting is performed manually on assigning/releasing - * stacks to tasks. Drop __GFP_ACCOUNT. - */ stack = __vmalloc_node(THREAD_SIZE, THREAD_ALIGN, - THREADINFO_GFP & ~__GFP_ACCOUNT, + GFP_VMAP_STACK, node, __builtin_return_address(0)); if (!stack) return -ENOMEM; |