udf: don't increment lenExtents while writing to a hole

Incrementing lenExtents even while writing to a hole is bad
for performance as calls to udf_discard_prealloc and
udf_truncate_tail_extent would not return from start if
isize != lenExtents
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ashish Sangwan <a.sangwan@samsung.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/udf/inode.c

@@ -601,6 +601,7 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 	struct udf_inode_info *iinfo = UDF_I(inode);
 	int goal = 0, pgoal = iinfo->i_location.logicalBlockNum;
 	int lastblock = 0;
+	bool isBeyondEOF;
 
 	*err = 0;
 	*new = 0;
@@ -680,7 +681,7 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 	/* Are we beyond EOF? */
 	if (etype == -1) {
 		int ret;
-
+		isBeyondEOF = 1;
 		if (count) {
 			if (c)
 				laarr[0] = laarr[1];
@@ -723,6 +724,7 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 		endnum = c + 1;
 		lastblock = 1;
 	} else {
+		isBeyondEOF = 0;
 		endnum = startnum = ((count > 2) ? 2 : count);
 
 		/* if the current extent is in position 0,
@@ -770,7 +772,8 @@ static sector_t inode_getblk(struct inode *inode, sector_t block,
 			*err = -ENOSPC;
 			return 0;
 		}
-		iinfo->i_lenExtents += inode->i_sb->s_blocksize;
+		if (isBeyondEOF)
+			iinfo->i_lenExtents += inode->i_sb->s_blocksize;
 	}
 
 	/* if the extent the requsted block is located in contains multiple