raw-posix: add Linux native AIO support

Now that do have a nicer interface to work against we can add Linux native
AIO support.  It's an extremly thing layer just setting up an iocb for
the io_submit system call in the submission path, and registering an
eventfd with the qemu poll handler to do complete the iocbs directly
from there.

This started out based on Anthony's earlier AIO patch, but after
estimated 42,000 rewrites and just as many build system changes
there's not much left of it.

To enable native kernel aio use the aio=native sub-command on the
drive command line.  I have also added an option to qemu-io to
test the aio support without needing a guest.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

1 files changed, 6 insertions, 1 deletions

diff --git a/qemu-io.c b/qemu-io.c
index a68f195c11..f96a4de6b4 100644
--- a/qemu-io.c
+++ b/qemu-io.c
@@ -1401,6 +1401,7 @@ static void usage(const char *name)
 "  -n, --nocache        disable host cache\n"
 "  -g, --growable       allow file to grow (only applies to protocols)\n"
 "  -m, --misalign       misalign allocations for O_DIRECT\n"
+"  -k, --native-aio     use kernel AIO implementation (on Linux only)\n"
 "  -h, --help           display this help and exit\n"
 "  -V, --version        output version information and exit\n"
 "\n",
@@ -1412,7 +1413,7 @@ int main(int argc, char **argv)
 {
 	int readonly = 0;
 	int growable = 0;
-	const char *sopt = "hVc:Crsnmg";
+	const char *sopt = "hVc:Crsnmgk";
 	struct option lopt[] = {
 		{ "help", 0, NULL, 'h' },
 		{ "version", 0, NULL, 'V' },
@@ -1424,6 +1425,7 @@ int main(int argc, char **argv)
 		{ "nocache", 0, NULL, 'n' },
 		{ "misalign", 0, NULL, 'm' },
 		{ "growable", 0, NULL, 'g' },
+		{ "native-aio", 0, NULL, 'k' },
 		{ NULL, 0, NULL, 0 }
 	};
 	int c;
@@ -1455,6 +1457,9 @@ int main(int argc, char **argv)
 		case 'g':
 			growable = 1;
 			break;
+		case 'k':
+			flags |= BDRV_O_NATIVE_AIO;
+			break;
 		case 'V':
 			printf("%s version %s\n", progname, VERSION);
 			exit(0);