direct-io: Implement generic deferred AIO completions

Add support to the core direct-io code to defer AIO completions to user
context using a workqueue.  This replaces opencoded and less efficient
code in XFS and ext4 (we save a memory allocation for each direct IO)
and will be needed to properly support O_(D)SYNC for AIO.

The communication between the filesystem and the direct I/O code requires
a new buffer head flag, which is a bit ugly but not avoidable until the
direct I/O code stops abusing the buffer_head structure for communicating
with the filesystems.

Currently this creates a per-superblock unbound workqueue for these
completions, which is taken from an earlier patch by Jan Kara.  I'm
not really convinced about this use and would prefer a "normal" global
workqueue with a high concurrency limit, but this needs further discussion.

JK: Fixed ext4 part, dynamic allocation of the workqueue.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

1 files changed, 1 insertions, 7 deletions

diff --git a/fs/ocfs2/aops.c b/fs/ocfs2/aops.c
index 2abf97b2a592..94417a85ce6e 100644
--- a/fs/ocfs2/aops.c
+++ b/fs/ocfs2/aops.c
@@ -565,9 +565,7 @@ bail:
 static void ocfs2_dio_end_io(struct kiocb *iocb,
                              loff_t offset,
                              ssize_t bytes,
-                             void *private,
-                             int ret,
-                             bool is_async)
+                             void *private)
 {
         struct inode *inode = file_inode(iocb->ki_filp);
         int level;
@@ -592,10 +590,6 @@ static void ocfs2_dio_end_io(struct kiocb *iocb,
 
         level = ocfs2_iocb_rw_locked_level(iocb);
         ocfs2_rw_unlock(inode, level);
-
-        inode_dio_done(inode);
-        if (is_async)
-                aio_complete(iocb, ret, 0);
 }
 
 /*