# HG changeset patch
# User Keir Fraser <keir.fraser@xxxxxxxxxx>
# Date 1264755327 0
# Node ID b0ffb4912c46ca78a799ec2fe1f4709b05248cfe
# Parent 218026df8d5faee84080e5c104d732a5d99689ca
blktap2: Prefer AIO eventfd support on kernels >= 2.6.22
Mainline kernel support for eventfd(2) in linux aio was added between
2.6.21 and 2.6.22. Libaio after 0.3.107 has the header file, but
presently few systems support it. Neither do we rely on an up-to-date
libc6.
Instead, this patch adds a header which defines custom iocb_common
struct, and works around a potentially missing sys/eventfd.h.
Signed-off-by: Daniel Stodden <daniel.stodden@xxxxxxxxxx>
---
tools/blktap2/drivers/block-aio.c | 1
tools/blktap2/drivers/libaio-compat.h | 92 +++++++++++++++++
tools/blktap2/drivers/tapdisk-queue.c | 180 ++++++++++++++++++++++++++++------
tools/blktap2/drivers/tapdisk-utils.c | 32 ++++++
tools/blktap2/drivers/tapdisk-utils.h | 1
5 files changed, 274 insertions(+), 32 deletions(-)
diff -r 218026df8d5f -r b0ffb4912c46 tools/blktap2/drivers/block-aio.c
--- a/tools/blktap2/drivers/block-aio.c Fri Jan 29 08:54:51 2010 +0000
+++ b/tools/blktap2/drivers/block-aio.c Fri Jan 29 08:55:27 2010 +0000
@@ -28,7 +28,6 @@
#include <errno.h>
-#include <libaio.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
diff -r 218026df8d5f -r b0ffb4912c46 tools/blktap2/drivers/libaio-compat.h
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/tools/blktap2/drivers/libaio-compat.h Fri Jan 29 08:55:27 2010 +0000
@@ -0,0 +1,92 @@
+/*
+ * Copyright (c) 2010, XenSource Inc.
+ * All rights reserved.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public License
+ * as published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA
+ */
+
+/*
+ * kernel 2.6.21 added eventfd(2) support, kernel 2.6.22 eventfds for
+ * aio. libaio 0.3.107 updated the header file, but few systems have
+ * it. define a custom iocb_common struct instead, and work around a
+ * potentially missing sys/eventfd.h. this header should vanish over
+ * time.
+ */
+
+#ifndef __LIBAIO_COMPAT
+#define __LIBAIO_COMPAT
+
+#include <libaio.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+
+struct __compat_io_iocb_common {
+ char __pad_buf[8];
+ char __pad_nbytes[8];
+ long long offset;
+ long long __pad3;
+ unsigned flags;
+ unsigned resfd;
+};
+
+static inline void __io_set_eventfd(struct iocb *iocb, int eventfd)
+{
+ struct __compat_io_iocb_common *c;
+ c = (struct __compat_io_iocb_common*)&iocb->u.c;
+ c->flags |= (1 << 0);
+ c->resfd = eventfd;
+}
+
+#ifndef SYS_eventfd
+#ifndef __NR_eventfd
+# if defined(__alpha__)
+# define __NR_eventfd 478
+# elif defined(__arm__)
+# define __NR_eventfd (__NR_SYSCALL_BASE+351)
+# elif defined(__ia64__)
+# define __NR_eventfd 1309
+# elif defined(__i386__)
+# define __NR_eventfd 323
+# elif defined(__m68k__)
+# define __NR_eventfd 319
+# elif 0 && defined(__mips__)
+# error __NR_eventfd?
+# define __NR_eventfd (__NR_Linux + 319)
+# define __NR_eventfd (__NR_Linux + 278)
+# define __NR_eventfd (__NR_Linux + 282)
+# elif defined(__hppa__)
+# define __NR_eventfd (__NR_Linux + 304)
+# elif defined(__PPC__) || defined(__powerpc64__)
+# define __NR_eventfd 307
+# elif defined(__s390__) || defined(__s390x__)
+# define __NR_eventfd 318
+# elif defined(__sparc__)
+# define __NR_eventfd 313
+# elif defined(__x86_64__)
+# define __NR_eventfd 284
+# endif
+#else
+# error __NR_eventfd?
+#endif
+#define SYS_eventfd __NR_eventfd
+#endif
+
+static inline int tapdisk_sys_eventfd(int initval)
+{
+ return syscall(SYS_eventfd, initval, 0);
+}
+
+#endif /* __LIBAIO_COMPAT */
diff -r 218026df8d5f -r b0ffb4912c46 tools/blktap2/drivers/tapdisk-queue.c
--- a/tools/blktap2/drivers/tapdisk-queue.c Fri Jan 29 08:54:51 2010 +0000
+++ b/tools/blktap2/drivers/tapdisk-queue.c Fri Jan 29 08:55:27 2010 +0000
@@ -30,12 +30,18 @@
#include <stdlib.h>
#include <unistd.h>
#include <libaio.h>
+#ifdef __linux__
+#include <linux/version.h>
+#endif
#include "tapdisk.h"
#include "tapdisk-log.h"
#include "tapdisk-queue.h"
#include "tapdisk-filter.h"
#include "tapdisk-server.h"
+#include "tapdisk-utils.h"
+
+#include "libaio-compat.h"
#include "atomicio.h"
#define WARN(_f, _a...) tlog_write(TLOG_WARN, _f, ##_a)
@@ -270,9 +276,121 @@ struct lio {
io_context_t aio_ctx;
struct io_event *aio_events;
- int poll_fd;
+ int event_fd;
int event_id;
+
+ int flags;
};
+
+#define LIO_FLAG_EVENTFD (1<<0)
+
+static int
+tapdisk_lio_check_resfd(void)
+{
+ return tapdisk_linux_version() >= KERNEL_VERSION(2, 6, 22);
+}
+
+static void
+tapdisk_lio_destroy_aio(struct tqueue *queue)
+{
+ struct lio *lio = queue->tio_data;
+
+ if (lio->event_fd >= 0) {
+ close(lio->event_fd);
+ lio->event_fd = -1;
+ }
+
+ if (lio->aio_ctx) {
+ io_destroy(lio->aio_ctx);
+ lio->aio_ctx = 0;
+ }
+}
+
+static int
+__lio_setup_aio_poll(struct tqueue *queue, int qlen)
+{
+ struct lio *lio = queue->tio_data;
+ int err, fd;
+
+ lio->aio_ctx = REQUEST_ASYNC_FD;
+
+ fd = io_setup(qlen, &lio->aio_ctx);
+ if (fd < 0) {
+ lio->aio_ctx = 0;
+ err = -errno;
+
+ if (err == -EINVAL)
+ goto fail_fd;
+
+ goto fail;
+ }
+
+ lio->event_fd = fd;
+
+ return 0;
+
+fail_fd:
+ DPRINTF("Couldn't get fd for AIO poll support. This is probably "
+ "because your kernel does not have the aio-poll patch "
+ "applied.\n");
+fail:
+ return err;
+}
+
+static int
+__lio_setup_aio_eventfd(struct tqueue *queue, int qlen)
+{
+ struct lio *lio = queue->tio_data;
+ int err;
+
+ err = io_setup(qlen, &lio->aio_ctx);
+ if (err < 0) {
+ lio->aio_ctx = 0;
+ return err;
+ }
+
+ lio->event_fd = tapdisk_sys_eventfd(0);
+ if (lio->event_fd < 0)
+ return -errno;
+
+ lio->flags |= LIO_FLAG_EVENTFD;
+
+ return 0;
+}
+
+static int
+tapdisk_lio_setup_aio(struct tqueue *queue, int qlen)
+{
+ struct lio *lio = queue->tio_data;
+ int err;
+
+ lio->aio_ctx = 0;
+ lio->event_fd = -1;
+
+ /*
+ * prefer the mainline eventfd(2) api, if available.
+ * if not, fall back to the poll fd patch.
+ */
+
+ err = !tapdisk_lio_check_resfd();
+ if (!err)
+ err = __lio_setup_aio_eventfd(queue, qlen);
+ if (err)
+ err = __lio_setup_aio_poll(queue, qlen);
+
+ if (err == -EAGAIN)
+ goto fail_rsv;
+fail:
+ return err;
+
+fail_rsv:
+ DPRINTF("Couldn't setup AIO context. If you are trying to "
+ "concurrently use a large number of blktap-based disks, you may
"
+ "need to increase the system-wide aio request limit. "
+ "(e.g. 'echo 1048576 > /proc/sys/fs/aio-max-nr')\n");
+ goto fail;
+}
+
static void
tapdisk_lio_destroy(struct tqueue *queue)
@@ -287,15 +405,33 @@ tapdisk_lio_destroy(struct tqueue *queue
lio->event_id = -1;
}
- if (lio->aio_ctx) {
- io_destroy(lio->aio_ctx);
- lio->aio_ctx = NULL;
- }
+ tapdisk_lio_destroy_aio(queue);
if (lio->aio_events) {
free(lio->aio_events);
lio->aio_events = NULL;
}
+}
+
+static void
+tapdisk_lio_set_eventfd(struct tqueue *queue, int n, struct iocb **iocbs)
+{
+ struct lio *lio = queue->tio_data;
+ int i;
+
+ if (lio->flags & LIO_FLAG_EVENTFD)
+ for (i = 0; i < n; ++i)
+ __io_set_eventfd(iocbs[i], lio->event_fd);
+}
+
+static void
+tapdisk_lio_ack_event(struct tqueue *queue)
+{
+ struct lio *lio = queue->tio_data;
+ uint64_t val;
+
+ if (lio->flags & LIO_FLAG_EVENTFD)
+ read(lio->event_fd, &val, sizeof(val));
}
static void
@@ -308,6 +444,8 @@ tapdisk_lio_event(event_id_t id, char mo
struct tiocb *tiocb;
struct io_event *ep;
+ tapdisk_lio_ack_event(queue);
+
lio = queue->tio_data;
ret = io_getevents(lio->aio_ctx, 0,
queue->size, lio->aio_events, NULL);
@@ -336,22 +474,14 @@ tapdisk_lio_setup(struct tqueue *queue,
int err;
lio->event_id = -1;
- lio->aio_ctx = REQUEST_ASYNC_FD;
-
- lio->poll_fd = io_setup(qlen, &lio->aio_ctx);
- err = lio->poll_fd;
- if (err < 0) {
- lio->aio_ctx = NULL;
-
- if (err == -EAGAIN)
- goto fail_rsv;
-
- goto fail_fd;
- }
+
+ err = tapdisk_lio_setup_aio(queue, qlen);
+ if (err)
+ goto fail;
lio->event_id =
tapdisk_server_register_event(SCHEDULER_POLL_READ_FD,
- lio->poll_fd, 0,
+ lio->event_fd, 0,
tapdisk_lio_event,
queue);
err = lio->event_id;
@@ -369,19 +499,6 @@ fail:
fail:
tapdisk_lio_destroy(queue);
return err;
-
-fail_rsv:
- DPRINTF("Couldn't setup AIO context. If you are trying to "
- "concurrently use a large number of blktap-based disks, you may
"
- "need to increase the system-wide aio request limit. "
- "(e.g. 'echo 1048576 > /proc/sys/fs/aio-max-nr')\n");
- goto fail;
-
-fail_fd:
- DPRINTF("Couldn't get fd for AIO poll support. This is probably "
- "because your kernel does not have the aio-poll patch "
- "applied.\n");
- goto fail;
}
static int
@@ -395,6 +512,7 @@ tapdisk_lio_submit(struct tqueue *queue)
tapdisk_filter_iocbs(queue->filter, queue->iocbs, queue->queued);
merged = io_merge(&queue->opioctx, queue->iocbs, queue->queued);
+ tapdisk_lio_set_eventfd(queue, merged, queue->iocbs);
submitted = io_submit(lio->aio_ctx, merged, queue->iocbs);
DBG("queued: %d, merged: %d, submitted: %d\n",
diff -r 218026df8d5f -r b0ffb4912c46 tools/blktap2/drivers/tapdisk-utils.c
--- a/tools/blktap2/drivers/tapdisk-utils.c Fri Jan 29 08:54:51 2010 +0000
+++ b/tools/blktap2/drivers/tapdisk-utils.c Fri Jan 29 08:55:27 2010 +0000
@@ -33,6 +33,10 @@
#include <sys/mman.h>
#include <sys/ioctl.h>
#include <sys/resource.h>
+#include <sys/utsname.h>
+#ifdef __linux__
+#include <linux/version.h>
+#endif
#include "blk.h"
#include "tapdisk.h"
@@ -183,3 +187,31 @@ tapdisk_get_image_size(int fd, uint64_t
return 0;
}
+
+#ifdef __linux__
+
+int tapdisk_linux_version(void)
+{
+ struct utsname uts;
+ unsigned int version, patchlevel, sublevel;
+ int n, err;
+
+ err = uname(&uts);
+ if (err)
+ return -errno;
+
+ n = sscanf(uts.release, "%u.%u.%u", &version, &patchlevel, &sublevel);
+ if (n != 3)
+ return -ENOSYS;
+
+ return KERNEL_VERSION(version, patchlevel, sublevel);
+}
+
+#else
+
+int tapdisk_linux_version(void)
+{
+ return -ENOSYS;
+}
+
+#endif
diff -r 218026df8d5f -r b0ffb4912c46 tools/blktap2/drivers/tapdisk-utils.h
--- a/tools/blktap2/drivers/tapdisk-utils.h Fri Jan 29 08:54:51 2010 +0000
+++ b/tools/blktap2/drivers/tapdisk-utils.h Fri Jan 29 08:55:27 2010 +0000
@@ -38,5 +38,6 @@ int tapdisk_namedup(char **, const char
int tapdisk_namedup(char **, const char *);
int tapdisk_parse_disk_type(const char *, char **, int *);
int tapdisk_get_image_size(int, uint64_t *, uint32_t *);
+int tapdisk_linux_version(void);
#endif
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