Move backend-specific fields of kaiocb into a union.

This reduces the size of kaiocb slightly. I've also added some generic
fields that other backends can use in place of the BIO-specific fields.

Change the socket and Chelsio DDP backends to use 'backend3' instead of
abusing _aiocb_private.status directly. This confines the use of
_aiocb_private to the AIO internals in vfs_aio.c.

Reviewed by:	kib (earlier version)
Approved by:	re (gjb)
Sponsored by:	Chelsio Communications
Differential Revision:	https://reviews.freebsd.org/D6547

1 files changed, 17 insertions, 5 deletions

diff --git a/sys/sys/aio.h b/sys/sys/aio.h
index 3c6ed54..134914e 100644
--- a/sys/sys/aio.h
+++ b/sys/sys/aio.h
@@ -121,10 +121,6 @@ struct kaiocb {
 	int	jobflags;		/* (a) job flags */
 	int	inputcharge;		/* (*) input blocks */
 	int	outputcharge;		/* (*) output blocks */
-	struct	bio *bp;		/* (*) BIO backend BIO pointer */
-	struct	buf *pbuf;		/* (*) BIO backend buffer pointer */
-	struct	vm_page *pages[btoc(MAXPHYS)+1]; /* BIO backend pages */
-	int	npages;			/* BIO backend number of pages */
 	struct	proc *userproc;		/* (*) user process */
 	struct	ucred *cred;		/* (*) active credential when created */
 	struct	file *fd_file;		/* (*) pointer to file structure */
@@ -134,9 +130,25 @@ struct kaiocb {
 	struct	aiocb uaiocb;		/* (*) copy of user I/O control block */
 	ksiginfo_t ksi;			/* (a) realtime signal info */
 	uint64_t seqno;			/* (*) job number */
-	int	pending;		/* (a) number of pending I/O, aio_fsync only */
 	aio_cancel_fn_t *cancel_fn;	/* (a) backend cancel function */
 	aio_handle_fn_t *handle_fn;	/* (c) backend handle function */
+	union {				/* Backend-specific data fields */
+		struct {		/* BIO backend */
+			struct bio *bp;	/* (*) BIO pointer */
+			struct buf *pbuf; /* (*) buffer pointer */
+			struct vm_page *pages[btoc(MAXPHYS)+1]; /* (*) */
+			int	npages;	/* (*) number of pages */
+		};
+		struct {		/* fsync() requests */
+			int	pending; /* (a) number of pending I/O */
+		};
+		struct {
+			void	*backend1;
+			void	*backend2;
+			long	backend3;
+			int	backend4;
+		};
+	};
 };
 
 struct socket;