linux-kernel - Re: [RESEND PATCH 2/3] mm/vmap: add DEBUG_AUGMENT_PROPAGATE

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Message-ID: <20190403211540.GJ6778@tower.DHCP.thefacebook.com>
Date:   Wed, 3 Apr 2019 21:15:44 +0000
From:   Roman Gushchin <guro@...com>
To:     "Uladzislau Rezki (Sony)" <urezki@...il.com>
CC:     Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Garnier <thgarnie@...gle.com>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joelaf@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...e.hu>, Tejun Heo <tj@...nel.org>
Subject: Re: [RESEND PATCH 2/3] mm/vmap: add DEBUG_AUGMENT_PROPAGATE_CHECK
 macro

On Tue, Apr 02, 2019 at 06:25:30PM +0200, Uladzislau Rezki (Sony) wrote:
> This macro adds some debug code to check that the augment tree
> is maintained correctly, meaning that every node contains valid
> subtree_max_size value.
> 
> By default this option is set to 0 and not active. It requires
> recompilation of the kernel to activate it. Set to 1, compile
> the kernel.
> 
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
> ---
>  mm/vmalloc.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 53 insertions(+)
> 
> diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> index 3adbad3fb6c1..1449a8c43aa2 100644
> --- a/mm/vmalloc.c
> +++ b/mm/vmalloc.c
> @@ -322,6 +322,8 @@ unsigned long vmalloc_to_pfn(const void *vmalloc_addr)
>  EXPORT_SYMBOL(vmalloc_to_pfn);
>  
>  /*** Global kva allocator ***/
> +#define DEBUG_AUGMENT_PROPAGATE_CHECK 0
> +
>  #define VM_LAZY_FREE	0x02
>  #define VM_VM_AREA	0x04
>  
> @@ -544,6 +546,53 @@ __unlink_va(struct vmap_area *va, struct rb_root *root)
>  	}
>  }
>  
> +#if DEBUG_AUGMENT_PROPAGATE_CHECK
> +static void
> +augment_tree_propagate_do_check(struct rb_node *n)
> +{
> +	struct vmap_area *va;
> +	struct rb_node *node;
> +	unsigned long size;
> +	bool found = false;
> +
> +	if (n == NULL)
> +		return;
> +
> +	va = rb_entry(n, struct vmap_area, rb_node);
> +	size = va->subtree_max_size;
> +	node = n;
> +
> +	while (node) {
> +		va = rb_entry(node, struct vmap_area, rb_node);
> +
> +		if (get_subtree_max_size(node->rb_left) == size) {
> +			node = node->rb_left;
> +		} else {
> +			if (__va_size(va) == size) {
> +				found = true;
> +				break;
> +			}
> +
> +			node = node->rb_right;
> +		}
> +	}
> +
> +	if (!found) {
> +		va = rb_entry(n, struct vmap_area, rb_node);
> +		pr_emerg("tree is corrupted: %lu, %lu\n",
> +			__va_size(va), va->subtree_max_size);
> +	}
> +
> +	augment_tree_propagate_do_check(n->rb_left);
> +	augment_tree_propagate_do_check(n->rb_right);
> +}
> +
> +static void augment_tree_propagate_from_check(void)

Why do you need this intermediate function?

Other than that looks good to me, please free to use
Reviewed-by: Roman Gushchin <guro@...com>

Thank you!