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 | 89 +++++++++++++++++++++++++++++++++++++++--------
2 files changed, 85 insertions(+), 14 deletions(-)
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index bd07fc1..5a7dda9 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -271,6 +271,16 @@ 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_thp_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags);
+#else
+static inline struct page *grab_thp_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 7b4736c..bcb679c 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2290,16 +2290,17 @@ out:
EXPORT_SYMBOL(generic_file_direct_write);
/*
- * Find or create a page at the given pagecache position. Return the locked
- * page. This function is specifically for buffered writes.
+ * Returns true if the page was found in page cache and
+ * false if it had to allocate a new page.
*/
-struct page *grab_cache_page_write_begin(struct address_space *mapping,
- pgoff_t index, unsigned flags)
+static bool __grab_cache_page_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags, unsigned int order,
+ struct page **page)
{
int status;
gfp_t gfp_mask;
- struct page *page;
gfp_t gfp_notmask = 0;
+ int found = true;
gfp_mask = mapping_gfp_mask(mapping);
if (mapping_cap_account_dirty(mapping))
@@ -2307,27 +2308,87 @@ struct page *grab_cache_page_write_begin(struct address_space *mapping,
if (flags & AOP_FLAG_NOFS)
gfp_notmask = __GFP_FS;
repeat:
- page = find_lock_page(mapping, index);
- if (page)
+ *page = find_lock_page(mapping, index);
+ if (*page)
goto found;
- page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
- if (!page)
- return NULL;
- status = add_to_page_cache_lru(page, mapping, index,
+ found = false;
+ if (order)
+ *page = alloc_pages(gfp_mask & ~gfp_notmask, order);
+ else
+ *page = __page_cache_alloc(gfp_mask & ~gfp_notmask);
+ if (!*page)
+ return false;
+ status = add_to_page_cache_lru(*page, mapping, index,
GFP_KERNEL & ~gfp_notmask);
if (unlikely(status)) {
- page_cache_release(page);
+ page_cache_release(*page);
if (status == -EEXIST)
goto repeat;
- return NULL;
+ *page = NULL;
+ return false;
}
found:
- wait_for_stable_page(page);
+ wait_for_stable_page(*page);
+ return found;
+}
+
+/*
+ * Find or create a page at the given pagecache position. Return the locked
+ * page. This function is specifically for buffered writes.
+ */
+struct page *grab_cache_page_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags)
+{
+ struct page *page;
+ __grab_cache_page_write_begin(mapping, index, flags, 0, &page);
return page;
}
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_thp_write_begin(struct address_space *mapping,
+ pgoff_t index, unsigned flags)
+{
+ gfp_t gfp_mask;
+ struct page *page;
+ bool found;
+
+ BUG_ON(index & HPAGE_CACHE_INDEX_MASK);
+ gfp_mask = mapping_gfp_mask(mapping);
+ BUG_ON(!(gfp_mask & __GFP_COMP));
+
+ found = __grab_cache_page_write_begin(mapping, index, flags,
+ HPAGE_PMD_ORDER, &page);
+ if (!page) {
+ if (!found)
+ count_vm_event(THP_WRITE_ALLOC_FAILED);
+ return NULL;
+ }
+
+ if (!found)
+ count_vm_event(THP_WRITE_ALLOC);
+
+ if (!PageTransHuge(page)) {
+ unlock_page(page);
+ page_cache_release(page);
+ return NULL;
+ }
+
+ 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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