Revert commit f1549cb5ab2b ("mm/z3fold.c: allow __GFP_HIGHMEM in
z3fold_alloc").
z3fold can't support GFP_HIGHMEM page now. page_address is used
directly at all places. Moreover, z3fold_header is on per cpu
unbuddied list which could be access anytime. So we should rid
the support of GFP_HIGHMEM allocation for z3fold.
Signed-off-by: Miaohe Lin <[email protected]>
---
mm/z3fold.c | 8 +++-----
1 file changed, 3 insertions(+), 5 deletions(-)
diff --git a/mm/z3fold.c b/mm/z3fold.c
index b3b4e65c107f..5f5d5f1556be 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -212,10 +212,8 @@ static int size_to_chunks(size_t size)
static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
gfp_t gfp)
{
- struct z3fold_buddy_slots *slots;
-
- slots = kmem_cache_zalloc(pool->c_handle,
- (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
+ struct z3fold_buddy_slots *slots = kmem_cache_zalloc(pool->c_handle,
+ gfp);
if (slots) {
/* It will be freed separately in free_handle(). */
@@ -1075,7 +1073,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
enum buddy bud;
bool can_sleep = gfpflags_allow_blocking(gfp);
- if (!size)
+ if (!size || (gfp & __GFP_HIGHMEM))
return -EINVAL;
if (size > PAGE_SIZE)
--
2.23.0
On 2022/5/19 15:12, Vitaly Wool wrote:
> On Fri, Apr 29, 2022 at 8:41 AM Miaohe Lin <[email protected]> wrote:
>>
>> Revert commit f1549cb5ab2b ("mm/z3fold.c: allow __GFP_HIGHMEM in
>> z3fold_alloc").
>>
>> z3fold can't support GFP_HIGHMEM page now. page_address is used
>> directly at all places. Moreover, z3fold_header is on per cpu
>> unbuddied list which could be access anytime. So we should rid
>> the support of GFP_HIGHMEM allocation for z3fold.
>
> Could you please clarify how kmem_cache is affected here?
With this code changes, kmem_cache should be unaffected. HIGHMEM is still not supported for
kmem_cache just like before but caller ensures __GFP_HIGHMEM is not passed in now. The issue
I want to fix here is that if z3fold page is allocated from highmem, page_address can't be
used directly. Did I answer your question? Or don't I get your point?
Thanks!
>
> Thanks,
> Vitaly
Many thanks for your time! :)
>
>> Signed-off-by: Miaohe Lin <[email protected]>
>> ---
>> mm/z3fold.c | 8 +++-----
>> 1 file changed, 3 insertions(+), 5 deletions(-)
>>
>> diff --git a/mm/z3fold.c b/mm/z3fold.c
>> index b3b4e65c107f..5f5d5f1556be 100644
>> --- a/mm/z3fold.c
>> +++ b/mm/z3fold.c
>> @@ -212,10 +212,8 @@ static int size_to_chunks(size_t size)
>> static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
>> gfp_t gfp)
>> {
>> - struct z3fold_buddy_slots *slots;
>> -
>> - slots = kmem_cache_zalloc(pool->c_handle,
>> - (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
>> + struct z3fold_buddy_slots *slots = kmem_cache_zalloc(pool->c_handle,
>> + gfp);
>>
>> if (slots) {
>> /* It will be freed separately in free_handle(). */
>> @@ -1075,7 +1073,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
>> enum buddy bud;
>> bool can_sleep = gfpflags_allow_blocking(gfp);
>>
>> - if (!size)
>> + if (!size || (gfp & __GFP_HIGHMEM))
>> return -EINVAL;
>>
>> if (size > PAGE_SIZE)
>> --
>> 2.23.0
>>
> .
>
On Fri, Apr 29, 2022 at 8:41 AM Miaohe Lin <[email protected]> wrote:
>
> Revert commit f1549cb5ab2b ("mm/z3fold.c: allow __GFP_HIGHMEM in
> z3fold_alloc").
>
> z3fold can't support GFP_HIGHMEM page now. page_address is used
> directly at all places. Moreover, z3fold_header is on per cpu
> unbuddied list which could be access anytime. So we should rid
> the support of GFP_HIGHMEM allocation for z3fold.
Could you please clarify how kmem_cache is affected here?
Thanks,
Vitaly
> Signed-off-by: Miaohe Lin <[email protected]>
> ---
> mm/z3fold.c | 8 +++-----
> 1 file changed, 3 insertions(+), 5 deletions(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index b3b4e65c107f..5f5d5f1556be 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -212,10 +212,8 @@ static int size_to_chunks(size_t size)
> static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
> gfp_t gfp)
> {
> - struct z3fold_buddy_slots *slots;
> -
> - slots = kmem_cache_zalloc(pool->c_handle,
> - (gfp & ~(__GFP_HIGHMEM | __GFP_MOVABLE)));
> + struct z3fold_buddy_slots *slots = kmem_cache_zalloc(pool->c_handle,
> + gfp);
>
> if (slots) {
> /* It will be freed separately in free_handle(). */
> @@ -1075,7 +1073,7 @@ static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
> enum buddy bud;
> bool can_sleep = gfpflags_allow_blocking(gfp);
>
> - if (!size)
> + if (!size || (gfp & __GFP_HIGHMEM))
> return -EINVAL;
>
> if (size > PAGE_SIZE)
> --
> 2.23.0
>
On Thu, 19 May 2022 19:34:01 +0800 Miaohe Lin <[email protected]> wrote:
> On 2022/5/19 15:12, Vitaly Wool wrote:
> > On Fri, Apr 29, 2022 at 8:41 AM Miaohe Lin <[email protected]> wrote:
> >>
> >> Revert commit f1549cb5ab2b ("mm/z3fold.c: allow __GFP_HIGHMEM in
> >> z3fold_alloc").
> >>
> >> z3fold can't support GFP_HIGHMEM page now. page_address is used
> >> directly at all places. Moreover, z3fold_header is on per cpu
> >> unbuddied list which could be access anytime. So we should rid
> >> the support of GFP_HIGHMEM allocation for z3fold.
> >
> > Could you please clarify how kmem_cache is affected here?
>
> With this code changes, kmem_cache should be unaffected. HIGHMEM is still not supported for
> kmem_cache just like before but caller ensures __GFP_HIGHMEM is not passed in now. The issue
> I want to fix here is that if z3fold page is allocated from highmem, page_address can't be
> used directly. Did I answer your question? Or don't I get your point?
>
Yes, page_address() against a highmem page only works if that page has
been mapped into pagetables with kmap() or kmap_atomic(), and z3fold
doesn't appear to do that.
Given that other zpool_driver implementations do appear to support
highmem pages, I expect that z3fold should be taught likewise.
I didn't look very hard, but this particular patch is a bit worrisome.
As I understand it, zswap can enable highmem:
if (zpool_malloc_support_movable(entry->pool->zpool))
gfp |= __GFP_HIGHMEM | __GFP_MOVABLE;
and z3fold will silently ignore the __GFP_HIGHMEM, which is OK. But
with this patch, z3fold will now return -EINVAL, so existing setups
will start failing?