Change the way support for asynchronous I/O is indicated to applications

to conform to 1003.1-2001.  Make it possible for applications to actually
tell whether or not asynchronous I/O is supported.

Since FreeBSD's aio implementation works on all descriptor types, don't
call down into file or vnode ops when [f]pathconf() is asked about
_PC_ASYNC_IO; this avoids the need for every file and vnode op to know about
it.

5 files changed, 40 insertions, 3 deletions

diff --git a/sys/kern/kern_descrip.c b/sys/kern/kern_descrip.c
index 6c9ca9d..13b339b 100644
--- a/sys/kern/kern_descrip.c
+++ b/sys/kern/kern_descrip.c
@@ -969,6 +969,12 @@ fpathconf(td, uap)
 
 	if ((error = fget(td, uap->fd, &fp)) != 0)
 		return (error);
+
+	/* If asynchronous I/O is available, it works for all descriptors. */
+	if (uap->name == _PC_ASYNC_IO) {
+		td->td_retval[0] = async_io_version;
+		goto out;
+	}
 	switch (fp->f_type) {
 	case DTYPE_PIPE:
 	case DTYPE_SOCKET:
@@ -990,6 +996,7 @@ fpathconf(td, uap)
 		error = EOPNOTSUPP;
 		break;
 	}
+out:
 	fdrop(fp, td);
 	return (error);
 }
diff --git a/sys/kern/posix4_mib.c b/sys/kern/posix4_mib.c
index d368593..6f1fe46 100644
--- a/sys/kern/posix4_mib.c
+++ b/sys/kern/posix4_mib.c
@@ -36,6 +36,7 @@
 #include <sys/kernel.h>
 #include <sys/queue.h>
 #include <sys/sysctl.h>
+#include <sys/vnode.h>
 #include <posix4/posix4.h>
 
 static int facility[CTL_P1003_1B_MAXID - 1];
@@ -64,7 +65,8 @@ SYSCTL_NODE(_kern, OID_AUTO, p1003_1b, CTLFLAG_RW, 0, "P1003.1B");
 
 #endif
 
-P1B_SYSCTL(CTL_P1003_1B_ASYNCHRONOUS_IO, asynchronous_io);
+SYSCTL_INT(_p1003_1b, CTL_P1003_1B_ASYNCHRONOUS_IO, \
+	asynchronous_io, CTLFLAG_RD, &async_io_version, 0, "");
 P1B_SYSCTL(CTL_P1003_1B_MAPPED_FILES, mapped_files);
 P1B_SYSCTL(CTL_P1003_1B_MEMLOCK, memlock);
 P1B_SYSCTL(CTL_P1003_1B_MEMLOCK_RANGE, memlock_range);
diff --git a/sys/kern/vfs_aio.c b/sys/kern/vfs_aio.c
index e105cbd..556f37c 100644
--- a/sys/kern/vfs_aio.c
+++ b/sys/kern/vfs_aio.c
@@ -348,6 +348,7 @@ aio_onceonly(void)
 	aiod_timeout = AIOD_TIMEOUT_DEFAULT;
 	aiod_lifetime = AIOD_LIFETIME_DEFAULT;
 	jobrefid = 1;
+	async_io_version = _POSIX_VERSION;
 }
 
 /*
@@ -365,6 +366,7 @@ aio_unload(void)
 	if (!unloadable)
 		return (EOPNOTSUPP);
 
+	async_io_version = 0;
 	aio_swake = NULL;
 	rm_at_exit(aio_proc_rundown);
 	rm_at_exec(aio_proc_rundown);
diff --git a/sys/kern/vfs_extattr.c b/sys/kern/vfs_extattr.c
index 6e2aa6b..55aea6e 100644
--- a/sys/kern/vfs_extattr.c
+++ b/sys/kern/vfs_extattr.c
@@ -93,6 +93,14 @@ int (*union_dircheckp)(struct thread *td, struct vnode **, struct file *);
 int (*softdep_fsync_hook)(struct vnode *);
 
 /*
+ * The module initialization routine for POSIX asynchronous I/O will
+ * set this to the version of AIO that it implements.  (Zero means
+ * that it is not implemented.)  This value is used here by pathconf()
+ * and in kern_descrip.c by fpathconf().
+ */
+int async_io_version;
+
+/*
  * Sync each mounted filesystem.
  */
 #ifndef _SYS_SYSPROTO_H_
@@ -1823,7 +1831,12 @@ pathconf(td, uap)
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
-	error = VOP_PATHCONF(nd.ni_vp, SCARG(uap, name), td->td_retval);
+
+	/* If asynchronous I/O is available, it works for all files. */
+	if (uap->name == _PC_ASYNC_IO)
+		td->td_retval[0] = async_io_version;
+	else
+		error = VOP_PATHCONF(nd.ni_vp, uap->name, td->td_retval);
 	vput(nd.ni_vp);
 	return (error);
 }
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 6e2aa6b..55aea6e 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -93,6 +93,14 @@ int (*union_dircheckp)(struct thread *td, struct vnode **, struct file *);
 int (*softdep_fsync_hook)(struct vnode *);
 
 /*
+ * The module initialization routine for POSIX asynchronous I/O will
+ * set this to the version of AIO that it implements.  (Zero means
+ * that it is not implemented.)  This value is used here by pathconf()
+ * and in kern_descrip.c by fpathconf().
+ */
+int async_io_version;
+
+/*
  * Sync each mounted filesystem.
  */
 #ifndef _SYS_SYSPROTO_H_
@@ -1823,7 +1831,12 @@ pathconf(td, uap)
 	if ((error = namei(&nd)) != 0)
 		return (error);
 	NDFREE(&nd, NDF_ONLY_PNBUF);
-	error = VOP_PATHCONF(nd.ni_vp, SCARG(uap, name), td->td_retval);
+
+	/* If asynchronous I/O is available, it works for all files. */
+	if (uap->name == _PC_ASYNC_IO)
+		td->td_retval[0] = async_io_version;
+	else
+		error = VOP_PATHCONF(nd.ni_vp, uap->name, td->td_retval);
 	vput(nd.ni_vp);
 	return (error);
 }