ext4: add a new nolock flag in ext4_map_blocks
EXT4_GET_BLOCKS_NO_LOCK flag is added to indicate that we don't need
to acquire i_data_sem lock in ext4_map_blocks. Meanwhile, it changes
ext4_get_block() to not start a new journal because when we do a
overwrite dio, there is no any metadata that needs to be modified.
We define a new function called ext4_get_block_write_nolock, which is
used in dio overwrite nolock. In this function, it doesn't try to
acquire i_data_sem lock and doesn't start a new journal as it does a
lookup.
CC: Tao Ma <tm@tao.ma>
CC: Eric Sandeen <sandeen@redhat.com>
CC: Robin Dong <hao.bigrat@gmail.com>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 01434f2..4a49f82 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -571,6 +571,8 @@
#define EXT4_GET_BLOCKS_NO_NORMALIZE 0x0040
/* Request will not result in inode size update (user for fallocate) */
#define EXT4_GET_BLOCKS_KEEP_SIZE 0x0080
+ /* Do not take i_data_sem locking in ext4_map_blocks */
+#define EXT4_GET_BLOCKS_NO_LOCK 0x0100
/*
* Flags used by ext4_free_blocks