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fork: optimize memcg_charge_kernel_stack() a bit

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Since commit f1c1a9ee00e4 ("fork: Move memcg_charge_kernel_stack()
into CONFIG_VMAP_STACK"), memcg_charge_kernel_stack() has been moved
into CONFIG_VMAP_STACK block, so the CONFIG_VMAP_STACK check can be
removed.

Furthermore, memcg_charge_kernel_stack() is only invoked by
alloc_thread_stack_node() instead of dup_task_struct(). If
memcg_kmem_charge_page() fails, the uncharge process is handled in
memcg_charge_kernel_stack() itself instead of free_thread_stack(),
so remove the incorrect comments.

If memcg_charge_kernel_stack() fails to charge pages used by kernel
stack, only charged pages need to be uncharged. It's unnecessary to
uncharge those pages which memory cgroup pointer is NULL.

[akpm@linux-foundation.org: remove assertion that PAGE_SIZE is a multiple of 1k]
Link: https://lkml.kernel.org/r/20230508064458.32855-1-haifeng.xu@shopee.com
Signed-off-by: Haifeng Xu <haifeng.xu@shopee.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Haifeng Xu 2023-05-08 06:44:58 +00:00 committed by Andrew Morton
parent 3db55767da
commit 4e2f6342cc
1 changed files with 3 additions and 7 deletions
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10
kernel/fork.c
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@ -252,23 +252,19 @@ static int memcg_charge_kernel_stack(struct vm_struct *vm)
{
int i;
int ret;
int nr_charged = 0;
BUILD_BUG_ON(IS_ENABLED(CONFIG_VMAP_STACK) && PAGE_SIZE % 1024 != 0);
BUG_ON(vm->nr_pages != THREAD_SIZE / PAGE_SIZE);
for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++) {
ret = memcg_kmem_charge_page(vm->pages[i], GFP_KERNEL, 0);
if (ret)
goto err;
nr_charged++;
}
return 0;
err:
/*
* If memcg_kmem_charge_page() fails, page's memory cgroup pointer is
* NULL, and memcg_kmem_uncharge_page() in free_thread_stack() will
* ignore this page.
*/
for (i = 0; i < THREAD_SIZE / PAGE_SIZE; i++)
for (i = 0; i < nr_charged; i++)
memcg_kmem_uncharge_page(vm->pages[i], 0);
return ret;
}