ext4: cache extent hole in extent status tree for ext4_da_map_blocks()

Currently extent status tree doesn't cache extent hole when a write
looks up in extent tree to make sure whether a block has been allocated
or not.  In this case, we don't put extent hole in extent cache because
later this extent might be removed and a new delayed extent might be
added back.  But it will cause a defect when we do a lot of writes.  If
we don't put extent hole in extent cache, the following writes also need
to access extent tree to look at whether or not a block has been
allocated.  It brings a cache miss.  This commit fixes this defect.
Also if the inode doesn't have any extent, this extent hole will be
cached as well.

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

include/trace/events/ext4.h

@@ -43,8 +43,7 @@ struct extent_status;
 	{ EXT4_GET_BLOCKS_METADATA_NOFAIL,	"METADATA_NOFAIL" },	\
 	{ EXT4_GET_BLOCKS_NO_NORMALIZE,		"NO_NORMALIZE" },	\
 	{ EXT4_GET_BLOCKS_KEEP_SIZE,		"KEEP_SIZE" },		\
-	{ EXT4_GET_BLOCKS_NO_LOCK,		"NO_LOCK" },		\
-	{ EXT4_GET_BLOCKS_NO_PUT_HOLE,		"NO_PUT_HOLE" })
+	{ EXT4_GET_BLOCKS_NO_LOCK,		"NO_LOCK" })
 
 #define show_mflags(flags) __print_flags(flags, "",	\
 	{ EXT4_MAP_NEW,		"N" },			\