Re: [PATCH v4 03/11] mm/hugetlb: unify migration callbacks

From: Michal Hocko <mhocko@kernel.org>
To: js1304@gmail.com
Cc: Andrew Morton <akpm@linux-foundation.org>,
	linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	kernel-team@lge.com, Vlastimil Babka <vbabka@suse.cz>,
	Christoph Hellwig <hch@infradead.org>,
	Roman Gushchin <guro@fb.com>,
	Mike Kravetz <mike.kravetz@oracle.com>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>
Subject: Re: [PATCH v4 03/11] mm/hugetlb: unify migration callbacks
Date: Tue, 7 Jul 2020 13:19:13 +0200	[thread overview]
Message-ID: <20200707111913.GG5913@dhcp22.suse.cz> (raw)
In-Reply-To: <1594107889-32228-4-git-send-email-iamjoonsoo.kim@lge.com>

On Tue 07-07-20 16:44:41, Joonsoo Kim wrote:
> From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> 
> There is no difference between two migration callback functions,
> alloc_huge_page_node() and alloc_huge_page_nodemask(), except
> __GFP_THISNODE handling. It's redundant to have two almost similar
> functions in order to handle this flag. So, this patch tries to
> remove one by introducing a new argument, gfp_mask, to
> alloc_huge_page_nodemask().
> 
> After introducing gfp_mask argument, it's caller's job to provide correct
> gfp_mask. So, every callsites for alloc_huge_page_nodemask() are changed
> to provide gfp_mask.
> 
> Note that it's safe to remove a node id check in alloc_huge_page_node()
> since there is no caller passing NUMA_NO_NODE as a node id.
> 
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>

Thanks for doing it this way. This makes much more sense than the
prvevious gfp_mask as a modifier approach.

I hope there won't be any weird include dependency problems but 0day
will tell us soon about that.

For the patch, feel free to add
Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  include/linux/hugetlb.h | 26 ++++++++++++++++++--------
>  mm/hugetlb.c            | 35 ++---------------------------------
>  mm/mempolicy.c          | 10 ++++++----
>  mm/migrate.c            | 11 +++++++----
>  4 files changed, 33 insertions(+), 49 deletions(-)
> 
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index 50650d0..bb93e95 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -10,6 +10,7 @@
>  #include <linux/list.h>
>  #include <linux/kref.h>
>  #include <linux/pgtable.h>
> +#include <linux/gfp.h>
>  
>  struct ctl_table;
>  struct user_struct;
> @@ -504,9 +505,8 @@ struct huge_bootmem_page {
>  
>  struct page *alloc_huge_page(struct vm_area_struct *vma,
>  				unsigned long addr, int avoid_reserve);
> -struct page *alloc_huge_page_node(struct hstate *h, int nid);
>  struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
> -				nodemask_t *nmask);
> +				nodemask_t *nmask, gfp_t gfp_mask);
>  struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
>  				unsigned long address);
>  struct page *alloc_migrate_huge_page(struct hstate *h, gfp_t gfp_mask,
> @@ -692,6 +692,15 @@ static inline bool hugepage_movable_supported(struct hstate *h)
>  	return true;
>  }
>  
> +/* Movability of hugepages depends on migration support. */
> +static inline gfp_t htlb_alloc_mask(struct hstate *h)
> +{
> +	if (hugepage_movable_supported(h))
> +		return GFP_HIGHUSER_MOVABLE;
> +	else
> +		return GFP_HIGHUSER;
> +}
> +
>  static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
>  					   struct mm_struct *mm, pte_t *pte)
>  {
> @@ -759,13 +768,9 @@ static inline struct page *alloc_huge_page(struct vm_area_struct *vma,
>  	return NULL;
>  }
>  
> -static inline struct page *alloc_huge_page_node(struct hstate *h, int nid)
> -{
> -	return NULL;
> -}
> -
>  static inline struct page *
> -alloc_huge_page_nodemask(struct hstate *h, int preferred_nid, nodemask_t *nmask)
> +alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
> +			nodemask_t *nmask, gfp_t gfp_mask)
>  {
>  	return NULL;
>  }
> @@ -878,6 +883,11 @@ static inline bool hugepage_movable_supported(struct hstate *h)
>  	return false;
>  }
>  
> +static inline gfp_t htlb_alloc_mask(struct hstate *h)
> +{
> +	return 0;
> +}
> +
>  static inline spinlock_t *huge_pte_lockptr(struct hstate *h,
>  					   struct mm_struct *mm, pte_t *pte)
>  {
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 7e5ba5c0..3245aa0 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1089,15 +1089,6 @@ static struct page *dequeue_huge_page_nodemask(struct hstate *h, gfp_t gfp_mask,
>  	return NULL;
>  }
>  
> -/* Movability of hugepages depends on migration support. */
> -static inline gfp_t htlb_alloc_mask(struct hstate *h)
> -{
> -	if (hugepage_movable_supported(h))
> -		return GFP_HIGHUSER_MOVABLE;
> -	else
> -		return GFP_HIGHUSER;
> -}
> -
>  static struct page *dequeue_huge_page_vma(struct hstate *h,
>  				struct vm_area_struct *vma,
>  				unsigned long address, int avoid_reserve,
> @@ -1979,31 +1970,9 @@ struct page *alloc_buddy_huge_page_with_mpol(struct hstate *h,
>  }
>  
>  /* page migration callback function */
> -struct page *alloc_huge_page_node(struct hstate *h, int nid)
> -{
> -	gfp_t gfp_mask = htlb_alloc_mask(h);
> -	struct page *page = NULL;
> -
> -	if (nid != NUMA_NO_NODE)
> -		gfp_mask |= __GFP_THISNODE;
> -
> -	spin_lock(&hugetlb_lock);
> -	if (h->free_huge_pages - h->resv_huge_pages > 0)
> -		page = dequeue_huge_page_nodemask(h, gfp_mask, nid, NULL);
> -	spin_unlock(&hugetlb_lock);
> -
> -	if (!page)
> -		page = alloc_migrate_huge_page(h, gfp_mask, nid, NULL);
> -
> -	return page;
> -}
> -
> -/* page migration callback function */
>  struct page *alloc_huge_page_nodemask(struct hstate *h, int preferred_nid,
> -		nodemask_t *nmask)
> +		nodemask_t *nmask, gfp_t gfp_mask)
>  {
> -	gfp_t gfp_mask = htlb_alloc_mask(h);
> -
>  	spin_lock(&hugetlb_lock);
>  	if (h->free_huge_pages - h->resv_huge_pages > 0) {
>  		struct page *page;
> @@ -2031,7 +2000,7 @@ struct page *alloc_huge_page_vma(struct hstate *h, struct vm_area_struct *vma,
>  
>  	gfp_mask = htlb_alloc_mask(h);
>  	node = huge_node(vma, address, gfp_mask, &mpol, &nodemask);
> -	page = alloc_huge_page_nodemask(h, node, nodemask);
> +	page = alloc_huge_page_nodemask(h, node, nodemask, gfp_mask);
>  	mpol_cond_put(mpol);
>  
>  	return page;
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index dabcee8..9034a53 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1068,10 +1068,12 @@ static int migrate_page_add(struct page *page, struct list_head *pagelist,
>  /* page allocation callback for NUMA node migration */
>  struct page *alloc_new_node_page(struct page *page, unsigned long node)
>  {
> -	if (PageHuge(page))
> -		return alloc_huge_page_node(page_hstate(compound_head(page)),
> -					node);
> -	else if (PageTransHuge(page)) {
> +	if (PageHuge(page)) {
> +		struct hstate *h = page_hstate(compound_head(page));
> +		gfp_t gfp_mask = htlb_alloc_mask(h) | __GFP_THISNODE;
> +
> +		return alloc_huge_page_nodemask(h, node, NULL, gfp_mask);
> +	} else if (PageTransHuge(page)) {
>  		struct page *thp;
>  
>  		thp = alloc_pages_node(node,
> diff --git a/mm/migrate.c b/mm/migrate.c
> index 7370a66..3b3d918 100644
> --- a/mm/migrate.c
> +++ b/mm/migrate.c
> @@ -1538,10 +1538,13 @@ struct page *new_page_nodemask(struct page *page,
>  	unsigned int order = 0;
>  	struct page *new_page = NULL;
>  
> -	if (PageHuge(page))
> -		return alloc_huge_page_nodemask(
> -				page_hstate(compound_head(page)),
> -				preferred_nid, nodemask);
> +	if (PageHuge(page)) {
> +		struct hstate *h = page_hstate(compound_head(page));
> +
> +		gfp_mask = htlb_alloc_mask(h);
> +		return alloc_huge_page_nodemask(h, preferred_nid,
> +						nodemask, gfp_mask);
> +	}
>  
>  	if (PageTransHuge(page)) {
>  		gfp_mask |= GFP_TRANSHUGE;
> -- 
> 2.7.4
> 

-- 
Michal Hocko
SUSE Labs