Re: [PATCH v5 2/2] mm: add a field to store names for private anonymous memory

From: Matthew Wilcox <willy@infradead.org>
To: Sumit Semwal <sumit.semwal@linaro.org>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	"Alexey Dobriyan" <adobriyan@gmail.com>,
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Subject: Re: [PATCH v5 2/2] mm: add a field to store names for private anonymous memory
Date: Wed, 19 Aug 2020 16:02:51 +0100	[thread overview]
Message-ID: <20200819150251.GD17456@casper.infradead.org> (raw)
In-Reply-To: <20200819141650.7462-3-sumit.semwal@linaro.org>

On Wed, Aug 19, 2020 at 07:46:50PM +0530, Sumit Semwal wrote:
> +++ b/include/linux/mm_types.h
> @@ -336,10 +336,18 @@ struct vm_area_struct {
>  	/*
>  	 * For areas with an address space and backing store,
>  	 * linkage into the address_space->i_mmap interval tree.
> +	 *
> +	 * For private anonymous mappings, a pointer to a null terminated string
> +	 * in the user process containing the name given to the vma, or NULL
> +	 * if unnamed.
>  	 */
> -	struct {
> -		struct rb_node rb;
> -		unsigned long rb_subtree_last;
> +
> +	union {
> +		struct {
> +			struct rb_node rb;
> +			unsigned long rb_subtree_last;
> +		} interval;
> +		const char __user *anon_name;
>  	} shared;

You can significantly reduce the size of this patch by doing this instead:

	union {
		struct {
			struct rb_node rb;
			unsigned long rb_subtree_last;
		} shared;
		const char __user *anon_name;
	};