From: "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx>
The function is grab_cache_page_write_begin() twin but it tries to
allocate huge page at given position aligned to HPAGE_CACHE_NR.
If, for some reason, it's not possible allocate a huge page at this
possition, it returns NULL. Caller should take care of fallback to
small pages.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
---
include/linux/pagemap.h | 10 ++++++++
mm/filemap.c | 58 +++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 68 insertions(+)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index 408c4e3..c87ed7c 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -270,6 +270,16 @@ unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
struct page *grab_cache_page_write_begin(struct address_space *mapping,
pgoff_t index, unsigned flags);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+struct page *grab_cache_huge_page_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags);
+#else
+static inline struct page *grab_cache_huge_page_write_begin(
+ struct address_space *mapping, pgoff_t index, unsigned flags)
+{
+ return NULL;
+}
+#endif
/*
* Returns locked page at given index in given cache, creating it if needed.
diff --git a/mm/filemap.c b/mm/filemap.c
index 38fdc92..bdedb1b 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2332,6 +2332,64 @@ found:
}
EXPORT_SYMBOL(grab_cache_page_write_begin);
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+/*
+ * Find or create a huge page at the given pagecache position, aligned to
+ * HPAGE_CACHE_NR. Return the locked huge page.
+ *
+ * If, for some reason, it's not possible allocate a huge page at this
+ * possition, it returns NULL. Caller should take care of fallback to small
+ * pages.
+ *
+ * This function is specifically for buffered writes.
+ */
+struct page *grab_cache_huge_page_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags)
+{
+ int status;
+ gfp_t gfp_mask;
+ struct page *page;
+ gfp_t gfp_notmask = 0;
+
+ BUG_ON(index & HPAGE_CACHE_INDEX_MASK);
+ gfp_mask = mapping_gfp_mask(mapping);
+ BUG_ON(!(gfp_mask & __GFP_COMP));
+ if (mapping_cap_account_dirty(mapping))
+ gfp_mask |= __GFP_WRITE;
+ if (flags & AOP_FLAG_NOFS)
+ gfp_notmask = __GFP_FS;
+repeat:
+ page = find_lock_page(mapping, index);
+ if (page) {
+ if (!PageTransHuge(page)) {
+ unlock_page(page);
+ page_cache_release(page);
+ return NULL;
+ }
+ goto found;
+ }
+
+ page = alloc_pages(gfp_mask & ~gfp_notmask, HPAGE_PMD_ORDER);
+ if (!page) {
+ count_vm_event(THP_WRITE_FAILED);
+ return NULL;
+ }
+
+ count_vm_event(THP_WRITE_ALLOC);
+ status = add_to_page_cache_lru(page, mapping, index,
+ GFP_KERNEL & ~gfp_notmask);
+ if (unlikely(status)) {
+ page_cache_release(page);
+ if (status == -EEXIST)
+ goto repeat;
+ return NULL;
+ }
+found:
+ wait_on_page_writeback(page);
+ return page;
+}
+#endif
+
static ssize_t generic_perform_write(struct file *file,
struct iov_iter *i, loff_t pos)
{
--
1.7.10.4
--
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