[PATCH v3 19/21] btrfs: Avoid truncate tailing page if fallocate range doesn't exceed inode size

[Qu Wenruo <quwenruo@cn.fujitsu.com>]

Current code will always truncate tailing page if its alloc_start is
smaller than inode size.

This behavior will cause a lot of unneeded COW page size extent.

This patch will avoid such problem.

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
---
v2:
  Newly introduced
v3:
  None
---
 fs/btrfs/file.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 35bfabf..e59b123 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -2640,7 +2640,7 @@ static long btrfs_fallocate(struct file *file, int mode,
 					alloc_start);
 		if (ret)
 			goto out;
-	} else {
+	} else if (offset + len > inode->i_size) {
 		/*
 		 * If we are fallocating from the end of the file onward we
 		 * need to zero out the end of the page if i_size lands in the
-- 
2.6.1