ocfs2: add ocfs2_try_rw_lock() and ocfs2_try_inode_lock()

ocfs2: add ocfs2_try_rw_lock() and ocfs2_try_inode_lock()

Patch series "ocfs2: add nowait aio support", v4.

VFS layer has introduced the non-blocking aio flag IOCB_NOWAIT, which
tells the kernel to bail out if an AIO request will block for reasons
such as file allocations, or writeback triggering, or would block while
allocating requests while performing direct I/O.

Subsequently, pwritev2/preadv2 also can leverage this part of kernel
code.  So far, ext4/xfs/btrfs have supported this feature.  Add the
related code for the ocfs2 file system.

This patch (of 3):

Add ocfs2_try_rw_lock and ocfs2_try_inode_lock functions, which will be
used in non-blocking IO scenarios.

[[email protected]: v2]
Link: http://lkml.kernel.org/r/[email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Gang He <[email protected]>
Reviewed-by: Jun Piao <[email protected]>
Acked-by: alex chen <[email protected]>
Cc: Mark Fasheh <[email protected]>
Cc: Joel Becker <[email protected]>
Cc: Junxiao Bi <[email protected]>
Cc: Joseph Qi <[email protected]>
Cc: Changwei Ge <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>