linux-kernel - Re: [PATCH V2 2/2] mm/highmem: Lift memcpy_[to|from]

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Message-ID: <20201207232649.GD7338@casper.infradead.org>
Date:   Mon, 7 Dec 2020 23:26:49 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     ira.weiny@...el.com
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Christoph Hellwig <hch@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Al Viro <viro@...iv.linux.org.uk>,
        Eric Biggers <ebiggers@...nel.org>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH V2 2/2] mm/highmem: Lift memcpy_[to|from]_page to core

On Mon, Dec 07, 2020 at 02:57:03PM -0800, ira.weiny@...el.com wrote:
> +static inline void memcpy_page(struct page *dst_page, size_t dst_off,
> +			       struct page *src_page, size_t src_off,
> +			       size_t len)
> +{
> +	char *dst = kmap_local_page(dst_page);
> +	char *src = kmap_local_page(src_page);

I appreciate you've only moved these, but please add:

	BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);

> +	memcpy(dst + dst_off, src + src_off, len);
> +	kunmap_local(src);
> +	kunmap_local(dst);
> +}
> +
> +static inline void memmove_page(struct page *dst_page, size_t dst_off,
> +			       struct page *src_page, size_t src_off,
> +			       size_t len)
> +{
> +	char *dst = kmap_local_page(dst_page);
> +	char *src = kmap_local_page(src_page);

	BUG_ON(dst_off + len > PAGE_SIZE || src_off + len > PAGE_SIZE);

> +	memmove(dst + dst_off, src + src_off, len);
> +	kunmap_local(src);
> +	kunmap_local(dst);
> +}
> +
> +static inline void memcpy_from_page(char *to, struct page *page, size_t offset, size_t len)
> +{
> +	char *from = kmap_local_page(page);

	BUG_ON(offset + len > PAGE_SIZE);

> +	memcpy(to, from + offset, len);
> +	kunmap_local(from);
> +}
> +
> +static inline void memcpy_to_page(struct page *page, size_t offset, const char *from, size_t len)
> +{
> +	char *to = kmap_local_page(page);

	BUG_ON(offset + len > PAGE_SIZE);

> +	memcpy(to + offset, from, len);
> +	kunmap_local(to);
> +}
> +
> +static inline void memset_page(struct page *page, size_t offset, int val, size_t len)
> +{
> +	char *addr = kmap_local_page(page);

	BUG_ON(offset + len > PAGE_SIZE);

> +	memset(addr + offset, val, len);
> +	kunmap_local(addr);
> +}
> +
>  #endif /* _LINUX_PAGEMAP_H */