tree ed246651aebcb8dae57de8c58dc20983064ee017
parent c7064ef13b2181a489836349f9baf87df0dab28f
author Jiaying Zhang <jiayingz@google.com> 1267737242 -0500
committer Theodore Ts'o <tytso@mit.edu> 1267737242 -0500

ext4: use ext4_get_block_write in buffer write

Allocate uninitialized extent before ext4 buffer write and
convert the extent to initialized after io completes.
The purpose is to make sure an extent can only be marked
initialized after it has been written with new data so
we can safely drop the i_mutex lock in ext4 DIO read without
exposing stale data. This helps to improve multi-thread DIO
read performance on high-speed disks.

Skip the nobh and data=journal mount cases to make things simple for now.

Signed-off-by: Jiaying Zhang <jiayingz@google.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>