[PATCH v4 0/3] ocfs2: add nowait aio support

[Gang He]

As you know, VFS layer has introduced non-block aio
flag IOCB_NOWAIT, which informs kernel to bail out
if an AIO request will block for reasons such as file
allocations, or a writeback triggered, or would block
while allocating requests while performing direct I/O.
Subsequent, pwritev2/preadv2 also can leverage this
part kernel code.
So far, ext4/xfs/btrfs have supported this feature,
I'd like to add the related code for ocfs2 file system.

Compare with v3, modify the check condition for nowait in
ocfs2_file_write_iter() function. second, add direct-io and 
nowait combination check in ocfs2_file_read_iter() function.
Compare with v2, do some modification in ocfs2_overwrite_io()
function for OCFS2_INLINE_DATA_FL case.
Compare with v1, some changes are as below,
use osb pointer in ocfs2_try_rw_lock() function,
modify ocfs2_overwrite_io() function to make all error
value can be returned to the upper code,
move invoking ocfs2_overwrite_io() function from
ocfs2_file_write_iter() to ocfs2_prepare_inode_for_write(),
this change can combine acquiring the related locks.

Gang He (3):
  ocfs2: add ocfs2_try_rw_lock and ocfs2_try_inode_lock
  ocfs2: add ocfs2_overwrite_io function
  ocfs2: nowait aio support

 fs/ocfs2/dir.c         |   2 +-
 fs/ocfs2/dlmglue.c     |  41 +++++++++++++++++---
 fs/ocfs2/dlmglue.h     |   6 ++-
 fs/ocfs2/extent_map.c  |  45 ++++++++++++++++++++++
 fs/ocfs2/extent_map.h  |   3 ++
 fs/ocfs2/file.c        | 101 +++++++++++++++++++++++++++++++++++++++----------
 fs/ocfs2/mmap.c        |   2 +-
 fs/ocfs2/ocfs2_trace.h |  10 +++--
 8 files changed, 177 insertions(+), 33 deletions(-)

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1.8.5.6