Re: [PATCH v7 4/4] hugetlb: allow to free gigantic pages regardless of the configuration

christophe leroy <christophe.leroy@xxxxxx> · Sun, 17 Mar 2019 19:31:13 +0100

Le 17/03/2019 à 17:28, Alexandre Ghiti a écrit :
On systems without CONTIG_ALLOC activated but that support gigantic pages,
boottime reserved gigantic pages can not be freed at all. This patch
simply enables the possibility to hand back those pages to memory
allocator.

Signed-off-by: Alexandre Ghiti <alex@xxxxxxxx>
Acked-by: David S. Miller <davem@xxxxxxxxxxxxx> [sparc]
---
  arch/arm64/Kconfig                           |  2 +-
  arch/arm64/include/asm/hugetlb.h             |  4 --
  arch/powerpc/include/asm/book3s/64/hugetlb.h |  7 ---
  arch/powerpc/platforms/Kconfig.cputype       |  2 +-
  arch/s390/Kconfig                            |  2 +-
  arch/s390/include/asm/hugetlb.h              |  3 --
  arch/sh/Kconfig                              |  2 +-
  arch/sparc/Kconfig                           |  2 +-
  arch/x86/Kconfig                             |  2 +-
  arch/x86/include/asm/hugetlb.h               |  4 --
  include/asm-generic/hugetlb.h                | 14 +++++
  include/linux/gfp.h                          |  2 +-
  mm/hugetlb.c                                 | 54 ++++++++++++++------
  mm/page_alloc.c                              |  4 +-
  14 files changed, 61 insertions(+), 43 deletions(-)


[...]

diff --git a/include/asm-generic/hugetlb.h b/include/asm-generic/hugetlb.h
index 71d7b77eea50..aaf14974ee5f 100644
--- a/include/asm-generic/hugetlb.h
+++ b/include/asm-generic/hugetlb.h
@@ -126,4 +126,18 @@ static inline pte_t huge_ptep_get(pte_t *ptep)
  }
  #endif
  
+#ifndef __HAVE_ARCH_GIGANTIC_PAGE_RUNTIME_SUPPORTED
+#ifdef CONFIG_ARCH_HAS_GIGANTIC_PAGE
+static inline bool gigantic_page_runtime_supported(void)
+{
+	return true;
+}
+#else
+static inline bool gigantic_page_runtime_supported(void)
+{
+	return false;
+}
+#endif /* CONFIG_ARCH_HAS_GIGANTIC_PAGE */

What about the following instead:

static inline bool gigantic_page_runtime_supported(void)
{
	return IS_ENABLED(CONFIG_ARCH_HAS_GIGANTIC_PAGE);
}


+#endif /* __HAVE_ARCH_GIGANTIC_PAGE_RUNTIME_SUPPORTED */
+
  #endif /* _ASM_GENERIC_HUGETLB_H */
diff --git a/include/linux/gfp.h b/include/linux/gfp.h
index 1f1ad9aeebb9..58ea44bf75de 100644
--- a/include/linux/gfp.h
+++ b/include/linux/gfp.h
@@ -589,8 +589,8 @@ static inline bool pm_suspended_storage(void)
  /* The below functions must be run on a range from a single zone. */
  extern int alloc_contig_range(unsigned long start, unsigned long end,
  			      unsigned migratetype, gfp_t gfp_mask);
-extern void free_contig_range(unsigned long pfn, unsigned nr_pages);
  #endif
+extern void free_contig_range(unsigned long pfn, unsigned int nr_pages);

'extern' is unneeded and should be avoided (iaw checkpatch)

Christophe

  
  #ifdef CONFIG_CMA
  /* CMA stuff */
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index afef61656c1e..4e55aa38704f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -1058,6 +1058,7 @@ static void free_gigantic_page(struct page *page, unsigned int order)
  	free_contig_range(page_to_pfn(page), 1 << order);
  }
  
+#ifdef CONFIG_CONTIG_ALLOC
  static int __alloc_gigantic_page(unsigned long start_pfn,
  				unsigned long nr_pages, gfp_t gfp_mask)
  {
@@ -1142,11 +1143,20 @@ static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
  
  static void prep_new_huge_page(struct hstate *h, struct page *page, int nid);
  static void prep_compound_gigantic_page(struct page *page, unsigned int order);
+#else /* !CONFIG_CONTIG_ALLOC */
+static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
+					int nid, nodemask_t *nodemask)
+{
+	return NULL;
+}
+#endif /* CONFIG_CONTIG_ALLOC */
  
  #else /* !CONFIG_ARCH_HAS_GIGANTIC_PAGE */
-static inline bool gigantic_page_supported(void) { return false; }
  static struct page *alloc_gigantic_page(struct hstate *h, gfp_t gfp_mask,
-		int nid, nodemask_t *nodemask) { return NULL; }
+					int nid, nodemask_t *nodemask)
+{
+	return NULL;
+}
  static inline void free_gigantic_page(struct page *page, unsigned int order) { }
  static inline void destroy_compound_gigantic_page(struct page *page,
  						unsigned int order) { }
@@ -1156,7 +1166,7 @@ static void update_and_free_page(struct hstate *h, struct page *page)
  {
  	int i;
  
-	if (hstate_is_gigantic(h) && !gigantic_page_supported())
+	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported())
  		return;
  
  	h->nr_huge_pages--;
@@ -2276,13 +2286,27 @@ static int adjust_pool_surplus(struct hstate *h, nodemask_t *nodes_allowed,
  }
  
  #define persistent_huge_pages(h) (h->nr_huge_pages - h->surplus_huge_pages)
-static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
-						nodemask_t *nodes_allowed)
+static int set_max_huge_pages(struct hstate *h, unsigned long count,
+			      nodemask_t *nodes_allowed)
  {
  	unsigned long min_count, ret;
  
-	if (hstate_is_gigantic(h) && !gigantic_page_supported())
-		return h->max_huge_pages;
+	spin_lock(&hugetlb_lock);
+
+	/*
+	 * Gigantic pages runtime allocation depend on the capability for large
+	 * page range allocation.
+	 * If the system does not provide this feature, return an error when
+	 * the user tries to allocate gigantic pages but let the user free the
+	 * boottime allocated gigantic pages.
+	 */
+	if (hstate_is_gigantic(h) && !IS_ENABLED(CONFIG_CONTIG_ALLOC)) {
+		if (count > persistent_huge_pages(h)) {
+			spin_unlock(&hugetlb_lock);
+			return -EINVAL;
+		}
+		/* Fall through to decrease pool */
+	}
  
  	/*
  	 * Increase the pool size
@@ -2295,7 +2319,6 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
  	 * pool might be one hugepage larger than it needs to be, but
  	 * within all the constraints specified by the sysctls.
  	 */
-	spin_lock(&hugetlb_lock);
  	while (h->surplus_huge_pages && count > persistent_huge_pages(h)) {
  		if (!adjust_pool_surplus(h, nodes_allowed, -1))
  			break;
@@ -2350,9 +2373,10 @@ static unsigned long set_max_huge_pages(struct hstate *h, unsigned long count,
  			break;
  	}
  out:
-	ret = persistent_huge_pages(h);
+	h->max_huge_pages = persistent_huge_pages(h);
  	spin_unlock(&hugetlb_lock);
-	return ret;
+
+	return 0;
  }
  
  #define HSTATE_ATTR_RO(_name) \
@@ -2404,7 +2428,7 @@ static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
  	int err;
  	NODEMASK_ALLOC(nodemask_t, nodes_allowed, GFP_KERNEL | __GFP_NORETRY);
  
-	if (hstate_is_gigantic(h) && !gigantic_page_supported()) {
+	if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) {
  		err = -EINVAL;
  		goto out;
  	}
@@ -2428,15 +2452,13 @@ static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
  	} else
  		nodes_allowed = &node_states[N_MEMORY];
  
-	h->max_huge_pages = set_max_huge_pages(h, count, nodes_allowed);
+	err = set_max_huge_pages(h, count, nodes_allowed);
  
+out:
  	if (nodes_allowed != &node_states[N_MEMORY])
  		NODEMASK_FREE(nodes_allowed);
  
-	return len;
-out:
-	NODEMASK_FREE(nodes_allowed);
-	return err;
+	return err ? err : len;
  }
  
  static ssize_t nr_hugepages_store_common(bool obey_mempolicy,
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index ac9c45ffb344..a4547d90fa7a 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -8234,8 +8234,9 @@ int alloc_contig_range(unsigned long start, unsigned long end,
  				pfn_max_align_up(end), migratetype);
  	return ret;
  }
+#endif /* CONFIG_CONTIG_ALLOC */
  
-void free_contig_range(unsigned long pfn, unsigned nr_pages)
+void free_contig_range(unsigned long pfn, unsigned int nr_pages)
  {
  	unsigned int count = 0;
  
@@ -8247,7 +8248,6 @@ void free_contig_range(unsigned long pfn, unsigned nr_pages)
  	}
  	WARN(count != 0, "%d pages are still in use!\n", count);
  }
-#endif
  
  #ifdef CONFIG_MEMORY_HOTPLUG
  /*


---
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