[PATCH v5 3/5] fat: skip cluster allocation on fallocated region

[Namjae Jeon <namjae.jeon@samsung.com>]

Skip new cluster allocation after checking i_disksize in _fat_get_block.
because the blocks are already allocated in fallocated region.

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
---
 fs/fat/inode.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index b6a2da2..ecd455c 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -120,6 +120,14 @@ static int fat_add_cluster(struct inode *inode)
 	return err;
 }
 
+static inline int check_fallocated_region(struct inode *inode, sector_t iblock)
+{
+	struct super_block *sb = inode->i_sb;
+	sector_t last_disk_block = MSDOS_I(inode)->i_disksize >>
+		sb->s_blocksize_bits;
+	return iblock < last_disk_block;
+}
+
 static inline int __fat_get_block(struct inode *inode, sector_t iblock,
 				  unsigned long *max_blocks,
 				  struct buffer_head *bh_result, int create)
@@ -148,7 +156,7 @@ static inline int __fat_get_block(struct inode *inode, sector_t iblock,
 	}
 
 	offset = (unsigned long)iblock & (sbi->sec_per_clus - 1);
-	if (!offset) {
+	if (!offset && !check_fallocated_region(inode, iblock)) {
 		/* TODO: multiple cluster allocation would be desirable. */
 		err = fat_add_cluster(inode);
 		if (err)
-- 
1.7.11-rc0