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SubjectRe: [PATCH v2] staging: zcache: support multiple clients, prep for KVM and RAMster
On 08/10/2011 10:08 AM, Dan Magenheimer wrote:
>> From: Seth Jennings [mailto:sjenning@linux.vnet.ibm.com]
>> Subject: Re: [PATCH v2] staging: zcache: support multiple clients, prep for KVM and RAMster
>>
>>> This crash is hit every time a high memory page is swapped out.
>>>
>>> I have no solution right now other that to revert this patch and
>>> restore the original signatures.
>
> Hi Seth --
>
> Thanks for your testing. I haven't done much testing on 32-bit.
>
>> Sorry for the noise, but I noticed right after I sent this that
>> the tmem layer doesn't DO anything with the data parameter. So
>> a possible solution is to just pass the page pointer instead of
>> the virtual address. After all, pointers are pointers.
>
> Yes, this looks like a good patch.
>
>> --- a/drivers/staging/zcache/zcache.c
>> +++ b/drivers/staging/zcache/zcache.c
>> @@ -1153,7 +1153,7 @@ static void *zcache_pampd_create(char *data, size_t size,
>> 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;
>> @@ -1220,7 +1220,7 @@ static int zcache_pampd_get_data(char *data, size_t *bufsi
>> int ret = 0;
>>
>> BUG_ON(is_ephemeral(pool));
>> - zv_decompress(virt_to_page(data), pampd);
>> + zv_decompress((struct page *)(data), pampd);
>> return ret;
>> }
>>
>> @@ -1532,7 +1532,7 @@ static int zcache_put_page(int cli_id, int pool_id, struct
>> 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))
>> @@ -1565,7 +1565,7 @@ static int zcache_get_page(int cli_id, int pool_id, struct
>> 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);
>> }
>>
>> I tested this and it works.
>>
>> Dan, does this mess anything else up?
>
> Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
>
>>> What was the rationale for the signature changes?
>>> Seth
>
> The change on the tmem side allows tmem to handle pre-compressed pages,
> which is useful to RAMster and possibly for KVM. The new "raw"
> parameter identifies that case, but for zcache "raw" is always zero so
> your solution looks fine.
>
> Seth, could you submit an "official" patch (i.e. proper subject field,
> signed-off-by) and I will ack that and ask GregKH to queue it up for
> a 3.1-rc?

Will do. I'm actually about to send out a set of 3 patches for zcache.
There is a Makefile issue, and a 32-bit link-time issue I have found
as well. Hopefully, I'll send it out today.

>
> Subject something like: staging: zcache: fix highmem crash on 32-bit
>
> Thanks,
> Dan
>
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