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Index: lib/libc/sys/aio_fsync.2
===================================================================
--- lib/libc/sys/aio_fsync.2
+++ lib/libc/sys/aio_fsync.2
@@ -80,10 +80,10 @@
.Bl -tag -width Er
.It Bq Er EAGAIN
The request was not queued because of system resource limitations.
-.It Bq Er ENOSYS
-The
-.Fn aio_fsync
-system call is not supported.
+.It Bq Er EOPNOTSUPP
+The descriptor associated with
+.Fa iocb->aio_fildes
+is unsafe and asynchronous I/O operations on unsafe descriptors are disabled.
.It Bq Er EINVAL
A value of the
.Fa op
Index: lib/libc/sys/aio_mlock.2
===================================================================
--- lib/libc/sys/aio_mlock.2
+++ lib/libc/sys/aio_mlock.2
@@ -92,10 +92,6 @@
.Bl -tag -width Er
.It Bq Er EAGAIN
The request was not queued because of system resource limitations.
-.It Bq Er ENOSYS
-The
-.Fn aio_mlock
-system call is not supported.
.El
.Pp
If the request is successfully enqueued, but subsequently cancelled
Index: lib/libc/sys/aio_read.2
===================================================================
--- lib/libc/sys/aio_read.2
+++ lib/libc/sys/aio_read.2
@@ -115,10 +115,10 @@
.Bl -tag -width Er
.It Bq Er EAGAIN
The request was not queued because of system resource limitations.
-.It Bq Er ENOSYS
-The
-.Fn aio_read
-system call is not supported.
+.It Bq Er EOPNOTSUPP
+The descriptor associated with
+.Fa iocb->aio_fildes
+is unsafe and asynchronous I/O operations on unsafe descriptors are disabled.
.El
.Pp
The following conditions may be synchronously detected when the
Index: lib/libc/sys/aio_write.2
===================================================================
--- lib/libc/sys/aio_write.2
+++ lib/libc/sys/aio_write.2
@@ -119,10 +119,10 @@
.Bl -tag -width Er
.It Bq Er EAGAIN
The request was not queued because of system resource limitations.
-.It Bq Er ENOSYS
-The
-.Fn aio_write
-system call is not supported.
+.It Bq Er EOPNOTSUPP
+The descriptor associated with
+.Fa iocb->aio_fildes
+is unsafe and asynchronous I/O operations on unsafe descriptors are disabled.
.El
.Pp
The following conditions may be synchronously detected when the
Index: share/man/man4/aio.4
===================================================================
--- share/man/man4/aio.4
+++ share/man/man4/aio.4
@@ -37,17 +37,23 @@
The
.Nm
facility provides system calls for asynchronous I/O.
-However, asynchronous I/O operations are only enabled for certain file
-types by default.
-Asynchronous I/O operations for other file types may block an AIO daemon
-indefinitely resulting in process and/or system hangs.
-Asynchronous I/O operations can be enabled for all file types by setting
+Asynchronous I/O operations are not completed synchronously by the
+calling thread.
+Instead, the calling thread invokes one system call to request an
+asynchronous I/O operation.
+The status of a completed request is retrieved later via a separate
+system call.
+.Pp
+Asynchronous I/O operations on some file descriptor types may block an
+AIO daemon indefinitely resulting in process and/or system hangs.
+Operations on these file descriptor types are disabled by default, but
+can be enabled by setting
the
.Va vfs.aio.enable_unsafe
sysctl node to a non-zero value.
.Pp
Asynchronous I/O operations on sockets and raw disk devices do not block
-indefinitely and are enabled by default.
+indefinitely and are always enabled.
.Pp
The
.Nm
Index: sys/kern/vfs_aio.c
===================================================================
--- sys/kern/vfs_aio.c
+++ sys/kern/vfs_aio.c
@@ -53,6 +53,7 @@
#include <sys/syscall.h>
#include <sys/sysent.h>
#include <sys/sysctl.h>
+#include <sys/syslog.h>
#include <sys/sx.h>
#include <sys/taskqueue.h>
#include <sys/vnode.h>
@@ -110,6 +111,11 @@
SYSCTL_INT(_vfs_aio, OID_AUTO, enable_unsafe, CTLFLAG_RW, &enable_aio_unsafe, 0,
"Permit asynchronous IO on all file types, not just known-safe types");
+static unsigned int unsafe_warningcnt = 1;
+SYSCTL_UINT(_vfs_aio, OID_AUTO, unsafe_warningcnt, CTLFLAG_RW,
+ &unsafe_warningcnt, 0,
+ "Warnings that will be triggered upon failed IO requests on unsafe files");
+
static int max_aio_procs = MAX_AIO_PROCS;
SYSCTL_INT(_vfs_aio, OID_AUTO, max_aio_procs, CTLFLAG_RW, &max_aio_procs, 0,
"Maximum number of kernel processes to use for handling async IO ");
@@ -1685,8 +1691,16 @@
goto done;
#endif
queueit:
- if (!enable_aio_unsafe)
+ if (!enable_aio_unsafe) {
+ if (unsafe_warningcnt > 0) {
+ unsafe_warningcnt--;
+ log(LOG_INFO,
+ "pid %d (%s) is attempting to use unsafe AIO requests%s\n",
+ curproc->p_pid, curproc->p_comm,
+ unsafe_warningcnt ? "" : " - not logging anymore");
+ }
return (EOPNOTSUPP);
+ }
if (opcode == LIO_SYNC) {
AIO_LOCK(ki);

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