[PATCHv2 10/13] mm, thp, tmpfs: huge page support in shmem_fallocate

[Ning Qu]

Try to allocate huge page if the range fits, otherwise,
fall back to small pages.

Signed-off-by: Ning Qu <quning@xxxxxxxxx>
---
 mm/shmem.c | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 1764a29..48b1d84 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2156,8 +2156,11 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 	inode->i_private = &shmem_falloc;
 	spin_unlock(&inode->i_lock);
 
-	for (index = start; index < end; index++) {
+	i_split_down_read(inode);
+	index = start;
+	while (index < end) {
 		struct page *page;
+		int nr = 1;
 
 		/*
 		 * Good, the fallocate(2) manpage permits EINTR: we may have
@@ -2169,8 +2172,15 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 			error = -ENOMEM;
 		else {
 			gfp_t gfp = mapping_gfp_mask(inode->i_mapping);
+			int flags = 0;
+
+			if (mapping_can_have_hugepages(inode->i_mapping) &&
+			    ((index == (index & ~HPAGE_CACHE_INDEX_MASK)) &&
+			     (index != (end & ~HPAGE_CACHE_INDEX_MASK))))
+				flags |= AOP_FLAG_TRANSHUGE;
+
 			error = shmem_getpage(inode, index, &page, SGP_FALLOC,
-					      gfp, 0, NULL);
+					      gfp, flags, NULL);
 		}
 		if (error) {
 			/* Remove the !PageUptodate pages we added */
@@ -2180,13 +2190,16 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 			goto undone;
 		}
 
+		nr = hpagecache_nr_pages(page);
+		if (PageTransHugeCache(page))
+			index &= ~HPAGE_CACHE_INDEX_MASK;
 		/*
 		 * Inform shmem_writepage() how far we have reached.
 		 * No need for lock or barrier: we have the page lock.
 		 */
-		shmem_falloc.next++;
+		shmem_falloc.next += nr;
 		if (!PageUptodate(page))
-			shmem_falloc.nr_falloced++;
+			shmem_falloc.nr_falloced += nr;
 
 		/*
 		 * If !PageUptodate, leave it that way so that freeable pages
@@ -2199,6 +2212,7 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
 		unlock_page(page);
 		page_cache_release(page);
 		cond_resched();
+		index += nr;
 	}
 
 	if (!(mode & FALLOC_FL_KEEP_SIZE) && offset + len > inode->i_size)
@@ -2209,7 +2223,9 @@ undone:
 	inode->i_private = NULL;
 	spin_unlock(&inode->i_lock);
 out:
+	i_split_up_read(inode);
 	mutex_unlock(&inode->i_mutex);
+
 	return error;
 }
 
-- 
1.8.4

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