linux-kernel - Re: [PATCH] staging: zcache: fix highmem crash on 32-bit

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Date:	Tue, 23 Aug 2011 12:05:11 -0500
From:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
To:	Greg Kroah-Hartman <gregkh@...e.de>
CC:	cascardo@...oscopio.com, dan.magenheimer@...cle.com,
	rdunlap@...otime.net, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH] staging: zcache: fix highmem crash on 32-bit

Please disregard, I sent this one out before on 8/10 :-/

Sorry for the noise.

I couldn't find the original post in the LKML archives, 
so I thought I had never sent it.  Turns out that I only 
sent it to the driver project list.

On 08/23/2011 11:06 AM, Seth Jennings wrote:
> After commit 966b9016a1, zcache_put_page() was modified to pass
> page_address(page) instead of the actual page pointer. In
> combination with the function signature changes to tmem_put()
> and zcache_pampd_create(), zcache_pampd_create() tries to (re)derive
> the page structure from the virtual address.  However, if the
> original page is a high memory page (or any unmapped page),
> this virt_to_page() fails because the page_address() in
> zcache_put_page() returned NULL.
> 
> This patch changes zcache_put_page() and zcache_get_page() to pass
> the page structure instead of the page's virtual address, which
> may or may not exist.
> 
> Signed-off-by: Seth Jennings <sjenning@...ux.vnet.ibm.com>
> ---
>  drivers/staging/zcache/zcache-main.c |    8 ++++----
>  1 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
> index 855a5bb..a3f5162 100644
> --- a/drivers/staging/zcache/zcache-main.c
> +++ b/drivers/staging/zcache/zcache-main.c
> @@ -1158,7 +1158,7 @@ static void *zcache_pampd_create(char *data, size_t size, bool raw, int eph,
>  	size_t clen;
>  	int ret;
>  	unsigned long count;
> -	struct page *page = virt_to_page(data);
> +	struct page *page = (struct page *)(data);
>  	struct zcache_client *cli = pool->client;
>  	uint16_t client_id = get_client_id_from_client(cli);
>  	unsigned long zv_mean_zsize;
> @@ -1227,7 +1227,7 @@ static int zcache_pampd_get_data(char *data, size_t *bufsize, bool raw,
>  	int ret = 0;
> 
>  	BUG_ON(is_ephemeral(pool));
> -	zv_decompress(virt_to_page(data), pampd);
> +	zv_decompress((struct page *)(data), pampd);
>  	return ret;
>  }
> 
> @@ -1539,7 +1539,7 @@ static int zcache_put_page(int cli_id, int pool_id, struct tmem_oid *oidp,
>  		goto out;
>  	if (!zcache_freeze && zcache_do_preload(pool) == 0) {
>  		/* preload does preempt_disable on success */
> -		ret = tmem_put(pool, oidp, index, page_address(page),
> +		ret = tmem_put(pool, oidp, index, (char *)(page),
>  				PAGE_SIZE, 0, is_ephemeral(pool));
>  		if (ret < 0) {
>  			if (is_ephemeral(pool))
> @@ -1572,7 +1572,7 @@ static int zcache_get_page(int cli_id, int pool_id, struct tmem_oid *oidp,
>  	pool = zcache_get_pool_by_id(cli_id, pool_id);
>  	if (likely(pool != NULL)) {
>  		if (atomic_read(&pool->obj_count) > 0)
> -			ret = tmem_get(pool, oidp, index, page_address(page),
> +			ret = tmem_get(pool, oidp, index, (char *)(page),
>  					&size, 0, is_ephemeral(pool));
>  		zcache_put_pool(pool);
>  	}

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