Re: [PATCH 1/7] mm/page_alloc: Move gfp_allowed_mask enforcement to prepare_alloc_pages
On Fri, Mar 19, 2021 at 05:11:39PM +0100, Vlastimil Babka wrote: > On 3/12/21 4:43 PM, Mel Gorman wrote: > > __alloc_pages updates GFP flags to enforce what flags are allowed > > during a global context such as booting or suspend. This patch moves the > > enforcement from __alloc_pages to prepare_alloc_pages so the code can be > > shared between the single page allocator and a new bulk page allocator. > > > > When moving, it is obvious that __alloc_pages() and __alloc_pages > > use different names for the same variable. This is an unnecessary > > complication so rename gfp_mask to gfp in prepare_alloc_pages() so the > > name is consistent. > > > > No functional change. > > Hm, I have some doubts. > And you were right, I'll drop the patch and apply the same mask to the bulk allocator. -- Mel Gorman SUSE Labs
Re: [PATCH 1/7] mm/page_alloc: Move gfp_allowed_mask enforcement to prepare_alloc_pages
On 3/12/21 4:43 PM, Mel Gorman wrote:
> __alloc_pages updates GFP flags to enforce what flags are allowed
> during a global context such as booting or suspend. This patch moves the
> enforcement from __alloc_pages to prepare_alloc_pages so the code can be
> shared between the single page allocator and a new bulk page allocator.
>
> When moving, it is obvious that __alloc_pages() and __alloc_pages
> use different names for the same variable. This is an unnecessary
> complication so rename gfp_mask to gfp in prepare_alloc_pages() so the
> name is consistent.
>
> No functional change.
Hm, I have some doubts.
> Signed-off-by: Mel Gorman
> ---
> mm/page_alloc.c | 25 +
> 1 file changed, 13 insertions(+), 12 deletions(-)
>
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> index 00b67c47ad87..f0c1d74ead6f 100644
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -4914,15 +4914,18 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int
> order,
> return page;
> }
>
> -static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
> +static inline bool prepare_alloc_pages(gfp_t gfp, unsigned int order,
> int preferred_nid, nodemask_t *nodemask,
> struct alloc_context *ac, gfp_t *alloc_gfp,
> unsigned int *alloc_flags)
> {
> - ac->highest_zoneidx = gfp_zone(gfp_mask);
> - ac->zonelist = node_zonelist(preferred_nid, gfp_mask);
> + gfp &= gfp_allowed_mask;
> + *alloc_gfp = gfp;
> +
...
> @@ -4980,8 +4983,6 @@ struct page *__alloc_pages(gfp_t gfp, unsigned int
> order, int preferred_nid,
> return NULL;
> }
>
> - gfp &= gfp_allowed_mask;
> - alloc_gfp = gfp;
> if (!prepare_alloc_pages(gfp, order, preferred_nid, nodemask, ,
> _gfp, _flags))
> return NULL;
As a result, "gfp" doesn't have the restrictions by gfp_allowed_mask applied,
only alloc_gfp does. But in case we go to slowpath, before
going there we throw away the current alloc_gfp:
alloc_gfp = current_gfp_context(gfp);
...
page = __alloc_pages_slowpath(alloc_gfp, ...);
So we lost the gfp_allowed_mask restrictions here?
[PATCH 1/7] mm/page_alloc: Move gfp_allowed_mask enforcement to prepare_alloc_pages
__alloc_pages updates GFP flags to enforce what flags are allowed
during a global context such as booting or suspend. This patch moves the
enforcement from __alloc_pages to prepare_alloc_pages so the code can be
shared between the single page allocator and a new bulk page allocator.
When moving, it is obvious that __alloc_pages() and __alloc_pages
use different names for the same variable. This is an unnecessary
complication so rename gfp_mask to gfp in prepare_alloc_pages() so the
name is consistent.
No functional change.
Signed-off-by: Mel Gorman
---
mm/page_alloc.c | 25 +
1 file changed, 13 insertions(+), 12 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 00b67c47ad87..f0c1d74ead6f 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4914,15 +4914,18 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int
order,
return page;
}
-static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,
+static inline bool prepare_alloc_pages(gfp_t gfp, unsigned int order,
int preferred_nid, nodemask_t *nodemask,
struct alloc_context *ac, gfp_t *alloc_gfp,
unsigned int *alloc_flags)
{
- ac->highest_zoneidx = gfp_zone(gfp_mask);
- ac->zonelist = node_zonelist(preferred_nid, gfp_mask);
+ gfp &= gfp_allowed_mask;
+ *alloc_gfp = gfp;
+
+ ac->highest_zoneidx = gfp_zone(gfp);
+ ac->zonelist = node_zonelist(preferred_nid, gfp);
ac->nodemask = nodemask;
- ac->migratetype = gfp_migratetype(gfp_mask);
+ ac->migratetype = gfp_migratetype(gfp);
if (cpusets_enabled()) {
*alloc_gfp |= __GFP_HARDWALL;
@@ -4936,18 +4939,18 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask,
unsigned int order,
*alloc_flags |= ALLOC_CPUSET;
}
- fs_reclaim_acquire(gfp_mask);
- fs_reclaim_release(gfp_mask);
+ fs_reclaim_acquire(gfp);
+ fs_reclaim_release(gfp);
- might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM);
+ might_sleep_if(gfp & __GFP_DIRECT_RECLAIM);
- if (should_fail_alloc_page(gfp_mask, order))
+ if (should_fail_alloc_page(gfp, order))
return false;
- *alloc_flags = current_alloc_flags(gfp_mask, *alloc_flags);
+ *alloc_flags = current_alloc_flags(gfp, *alloc_flags);
/* Dirty zone balancing only done in the fast path */
- ac->spread_dirty_pages = (gfp_mask & __GFP_WRITE);
+ ac->spread_dirty_pages = (gfp & __GFP_WRITE);
/*
* The preferred zone is used for statistics but crucially it is
@@ -4980,8 +4983,6 @@ struct page *__alloc_pages(gfp_t gfp, unsigned int order,
int preferred_nid,
return NULL;
}
- gfp &= gfp_allowed_mask;
- alloc_gfp = gfp;
if (!prepare_alloc_pages(gfp, order, preferred_nid, nodemask, ,
_gfp, _flags))
return NULL;
--
2.26.2
