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Subject[PATCH 06/23] thp, mm: rewrite add_to_page_cache_locked() to support huge pages
Date
From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>

For huge page we add to radix tree HPAGE_CACHE_NR pages at once: head
page for the specified index and HPAGE_CACHE_NR-1 tail pages for
following indexes.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
---
include/linux/huge_mm.h | 24 ++++++++++++++++++++++
include/linux/page-flags.h | 33 ++++++++++++++++++++++++++++++
mm/filemap.c | 50 +++++++++++++++++++++++++++++++++++-----------
3 files changed, 95 insertions(+), 12 deletions(-)

diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index 1534e1e..4dc66c9 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -230,6 +230,20 @@ static inline int do_huge_pmd_numa_page(struct mm_struct *mm, struct vm_area_str

#endif /* CONFIG_TRANSPARENT_HUGEPAGE */

+#ifdef CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE
+
+#define HPAGE_CACHE_ORDER (HPAGE_SHIFT - PAGE_CACHE_SHIFT)
+#define HPAGE_CACHE_NR (1L << HPAGE_CACHE_ORDER)
+#define HPAGE_CACHE_INDEX_MASK (HPAGE_CACHE_NR - 1)
+
+#else
+
+#define HPAGE_CACHE_ORDER ({ BUILD_BUG(); 0; })
+#define HPAGE_CACHE_NR ({ BUILD_BUG(); 0; })
+#define HPAGE_CACHE_INDEX_MASK ({ BUILD_BUG(); 0; })
+
+#endif
+
static inline bool transparent_hugepage_pagecache(void)
{
if (!IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE))
@@ -238,4 +252,14 @@ static inline bool transparent_hugepage_pagecache(void)
return false;
return transparent_hugepage_flags & (1<<TRANSPARENT_HUGEPAGE_PAGECACHE);
}
+
+static inline int hpagecache_nr_pages(struct page *page)
+{
+ if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE))
+ return hpage_nr_pages(page);
+
+ BUG_ON(PageTransHuge(page));
+ return 1;
+}
+
#endif /* _LINUX_HUGE_MM_H */
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index f1a5b59..7657de0 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -452,6 +452,39 @@ static inline int PageTransTail(struct page *page)
}
#endif

+#ifdef CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE
+static inline int PageTransHugeCache(struct page *page)
+{
+ return PageTransHuge(page);
+}
+
+static inline int PageTransCompoundCache(struct page *page)
+{
+ return PageTransCompound(page);
+}
+
+static inline int PageTransTailCache(struct page *page)
+{
+ return PageTransTail(page);
+}
+#else
+
+static inline int PageTransHugeCache(struct page *page)
+{
+ return 0;
+}
+
+static inline int PageTransCompoundCache(struct page *page)
+{
+ return 0;
+}
+
+static inline int PageTransTailCache(struct page *page)
+{
+ return 0;
+}
+#endif
+
/*
* If network-based swap is enabled, sl*b must keep track of whether pages
* were allocated from pfmemalloc reserves.
diff --git a/mm/filemap.c b/mm/filemap.c
index ae5cc01..619e6cb 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -460,38 +460,64 @@ int add_to_page_cache_locked(struct page *page, struct address_space *mapping,
pgoff_t offset, gfp_t gfp_mask)
{
int error;
+ int i, nr;

VM_BUG_ON(!PageLocked(page));
VM_BUG_ON(PageSwapBacked(page));

+ /* memory cgroup controller handles thp pages on its side */
error = mem_cgroup_cache_charge(page, current->mm,
gfp_mask & GFP_RECLAIM_MASK);
if (error)
return error;

- error = radix_tree_maybe_preload(gfp_mask & ~__GFP_HIGHMEM);
+ if (PageTransHugeCache(page))
+ BUILD_BUG_ON(HPAGE_CACHE_NR > RADIX_TREE_PRELOAD_NR);
+
+ nr = hpagecache_nr_pages(page);
+
+ error = radix_tree_maybe_preload_contig(nr, gfp_mask & ~__GFP_HIGHMEM);
if (error) {
mem_cgroup_uncharge_cache_page(page);
return error;
}

- page_cache_get(page);
- page->mapping = mapping;
- page->index = offset;
-
spin_lock_irq(&mapping->tree_lock);
- error = radix_tree_insert(&mapping->page_tree, offset, page);
+ page_cache_get(page);
+ for (i = 0; i < nr; i++) {
+ error = radix_tree_insert(&mapping->page_tree,
+ offset + i, page + i);
+ /*
+ * In the midle of THP we can collide with small page which was
+ * established before THP page cache is enabled or by other VMA
+ * with bad alignement (most likely MAP_FIXED).
+ */
+ if (error)
+ goto err_insert;
+ page[i].index = offset + i;
+ page[i].mapping = mapping;
+ }
radix_tree_preload_end();
- if (unlikely(error))
- goto err_insert;
- mapping->nrpages++;
- __inc_zone_page_state(page, NR_FILE_PAGES);
+ mapping->nrpages += nr;
+ __mod_zone_page_state(page_zone(page), NR_FILE_PAGES, nr);
+ if (PageTransHuge(page))
+ __inc_zone_page_state(page, NR_FILE_TRANSPARENT_HUGEPAGES);
spin_unlock_irq(&mapping->tree_lock);
trace_mm_filemap_add_to_page_cache(page);
return 0;
err_insert:
- page->mapping = NULL;
- /* Leave page->index set: truncation relies upon it */
+ radix_tree_preload_end();
+ if (i != 0)
+ error = -ENOSPC; /* no space for a huge page */
+
+ /* page[i] was not inserted to tree, skip it */
+ i--;
+
+ for (; i >= 0; i--) {
+ /* Leave page->index set: truncation relies upon it */
+ page[i].mapping = NULL;
+ radix_tree_delete(&mapping->page_tree, offset + i);
+ }
spin_unlock_irq(&mapping->tree_lock);
mem_cgroup_uncharge_cache_page(page);
page_cache_release(page);
--
1.8.3.2


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