[pve-devel] [PATCH 2/4] add basic backup support to block driver
Dietmar Maurer
dietmar at proxmox.com
Tue Nov 13 14:07:10 CET 2012
Function bdrv_backup_init() creates a block job to backup a block device.
We call brdv_co_backup_cow() for each write during backup. That function
reads the original data and pass it backup_dump_cb().
The tracked_request infrastructure is used to serialize access.
Currently backup cluster size is hardcoded to 65536 bytes.
Signed-off-by: Dietmar Maurer <dietmar at proxmox.com>
---
Makefile.objs | 1 +
backup.c | 288 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
block.c | 59 +++++++++++-
block.h | 2 +
block_int.h | 32 +++++++
5 files changed, 379 insertions(+), 3 deletions(-)
create mode 100644 backup.c
diff --git a/Makefile.objs b/Makefile.objs
index 593a592..68998ac 100644
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -44,6 +44,7 @@ coroutine-obj-$(CONFIG_WIN32) += coroutine-win32.o
block-obj-y = iov.o cache-utils.o qemu-option.o module.o async.o
block-obj-y += nbd.o block.o blockjob.o aes.o qemu-config.o
block-obj-y += thread-pool.o qemu-progress.o qemu-sockets.o uri.o notify.o
+block-obj-y += backup.o
block-obj-y += $(coroutine-obj-y) $(qobject-obj-y) $(version-obj-y)
block-obj-$(CONFIG_POSIX) += event_notifier-posix.o aio-posix.o
block-obj-$(CONFIG_WIN32) += event_notifier-win32.o aio-win32.o
diff --git a/backup.c b/backup.c
new file mode 100644
index 0000000..d8a0191
--- /dev/null
+++ b/backup.c
@@ -0,0 +1,288 @@
+/*
+ * QEMU backup
+ *
+ * Copyright (C) Proxmox Server Solutions
+ *
+ * Authors:
+ * Dietmar Maurer (dietmar at proxmox.com)
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2. See
+ * the COPYING file in the top-level directory.
+ *
+ */
+
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+
+#include "block.h"
+#include "block_int.h"
+#include "blockjob.h"
+
+//#define DEBUG_BACKUP
+
+#ifdef DEBUG_BACKUP
+#define DPRINTF(fmt, ...) \
+ do { printf("backup: " fmt, ## __VA_ARGS__); } while (0)
+#else
+#define DPRINTF(fmt, ...) \
+ do { } while (0)
+#endif
+
+
+#define BITS_PER_LONG (sizeof(unsigned long) * 8)
+
+static int backup_get_bitmap(BlockDriverState *bs, int64_t cluster_num)
+{
+ assert(bs);
+ assert(bs->backup_info);
+ assert(bs->backup_info->bitmap);
+
+ unsigned long val, idx, bit;
+
+ idx = cluster_num / BITS_PER_LONG;
+
+ assert(bs->backup_info->bitmap_size > idx);
+
+ bit = cluster_num % BITS_PER_LONG;
+ val = bs->backup_info->bitmap[idx];
+
+ return !!(val & (1UL << bit));
+}
+
+static void backup_set_bitmap(BlockDriverState *bs, int64_t cluster_num,
+ int dirty)
+{
+ assert(bs);
+ assert(bs->backup_info);
+ assert(bs->backup_info->bitmap);
+
+ unsigned long val, idx, bit;
+
+ idx = cluster_num / BITS_PER_LONG;
+
+ assert(bs->backup_info->bitmap_size > idx);
+
+ bit = cluster_num % BITS_PER_LONG;
+ val = bs->backup_info->bitmap[idx];
+ if (dirty) {
+ if (!(val & (1UL << bit))) {
+ val |= 1UL << bit;
+ }
+ } else {
+ if (val & (1UL << bit)) {
+ val &= ~(1UL << bit);
+ }
+ }
+ bs->backup_info->bitmap[idx] = val;
+}
+
+int coroutine_fn brdv_co_backup_cow(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors)
+{
+ assert(bs);
+
+ BackupInfo *info = bs->backup_info;
+ BlockDriver *drv = bs->drv;
+ struct iovec iov;
+ QEMUIOVector bounce_qiov;
+ void *bounce_buffer = NULL;
+ int ret = 0;
+
+ assert(info);
+
+ int64_t start, end;
+
+ start = sector_num / BACKUP_BLOCKS_PER_CLUSTER;
+ end = (sector_num + nb_sectors + BACKUP_BLOCKS_PER_CLUSTER - 1) /
+ BACKUP_BLOCKS_PER_CLUSTER;
+
+ DPRINTF("brdv_co_backup_cow enter %s C%zd %zd %d\n", bdrv_get_device_name(bs),
+ start, sector_num, nb_sectors);
+
+ for (; start < end; start++) {
+ if (backup_get_bitmap(bs, start)) {
+ DPRINTF("brdv_co_backup_cow skip C%zd\n", start);
+ continue; // already copied
+ }
+ /* immediately set bitmap (avoid coroutine race) */
+ backup_set_bitmap(bs, start, 1);
+
+ DPRINTF("brdv_co_backup_cow C%zd\n", start);
+
+ if (!bounce_buffer) {
+ iov.iov_len = BACKUP_CLUSTER_SIZE;
+ iov.iov_base = bounce_buffer = qemu_blockalign(bs, iov.iov_len);
+ qemu_iovec_init_external(&bounce_qiov, &iov, 1);
+ }
+
+ ret = drv->bdrv_co_readv(bs, start * BACKUP_BLOCKS_PER_CLUSTER,
+ BACKUP_BLOCKS_PER_CLUSTER,
+ &bounce_qiov);
+ if (ret < 0) {
+ DPRINTF("brdv_co_backup_cow bdrv_read C%zd failed\n", start);
+ goto out;
+ }
+
+ ret = info->backup_dump_cb(info->opaque, bs, start, bounce_buffer);
+ if (ret < 0) {
+ DPRINTF("brdv_co_backup_cow dump_cluster_cb C%zd failed\n", start);
+ goto out;
+ }
+
+ DPRINTF("brdv_co_backup_cow done C%zd\n", start);
+ }
+
+out:
+ if (bounce_buffer)
+ qemu_vfree(bounce_buffer);
+ return ret;
+}
+
+void bdrv_backup_deinit(BlockDriverState *bs)
+{
+ BackupInfo *info = bs->backup_info;
+
+ if (!info)
+ return;
+
+ DPRINTF("backup_deinit %s\n", bdrv_get_device_name(bs));
+
+ g_free(info->bitmap);
+
+ bs->backup_info = NULL;
+}
+
+typedef struct BackupBlockJob {
+ BlockJob common;
+} BackupBlockJob;
+
+static BlockJobType backup_job_type = {
+ .instance_size = sizeof(BackupBlockJob),
+ .job_type = "backup",
+};
+
+static void coroutine_fn backup_run(void *opaque)
+{
+ BackupBlockJob *job = opaque;
+ BlockDriverState *bs = job->common.bs;
+ assert(bs);
+ assert(bs->backup_info);
+
+ QEMUIOVector qiov;
+ void *buffer = qemu_blockalign(bs, BDRV_SECTOR_SIZE);
+ struct iovec iov = {
+ .iov_base = buffer,
+ .iov_len = BDRV_SECTOR_SIZE,
+ };
+
+ int64_t start, end;
+
+ qemu_iovec_init_external(&qiov, &iov, 1);
+
+ start = 0;
+ end = (bs->total_sectors + BACKUP_BLOCKS_PER_CLUSTER - 1) /
+ BACKUP_BLOCKS_PER_CLUSTER;
+
+ DPRINTF("backup_run start %s %zd %zd\n", bdrv_get_device_name(bs),
+ start, end);
+
+ int ret = 0;
+
+ for (; start < end; start++) {
+ if (block_job_is_cancelled(&job->common)) {
+ ret = -1;
+ break;
+ }
+
+ if (backup_get_bitmap(bs, start))
+ continue; // already copied
+
+ /* we need to yield so that qemu_aio_flush() returns.
+ * (without, VM does not reboot)
+ * todo: can we avoid that?
+ */
+ co_sleep_ns(rt_clock, 0);
+ if (block_job_is_cancelled(&job->common)) {
+ ret = -1;
+ break;
+ }
+ DPRINTF("backup_run loop C%zd\n", start);
+
+ /**
+ * This triggers a cluster copy
+ * Note: avoid direct call to brdv_co_backup_cow, because
+ * this does not call tracked_request_begin()
+ */
+ ret = bdrv_co_backup(bs, start*BACKUP_BLOCKS_PER_CLUSTER, 1);
+ if (ret < 0) {
+ break;
+ }
+ /* Publish progress */
+ job->common.offset += BACKUP_CLUSTER_SIZE;
+ }
+
+ qemu_vfree(buffer);
+ DPRINTF("backup_run complete %d\n", ret);
+ block_job_completed(&job->common, ret);
+}
+
+static void backup_job_cleanup_cb(void *opaque, int ret)
+{
+ BlockDriverState *bs = opaque;
+
+ DPRINTF("backup_job_cleanup_cb start %d\n", ret);
+
+ bs->backup_info->backup_complete_cb(bs->backup_info->opaque, ret);
+
+ DPRINTF("backup_job_cleanup_cb end\n");
+
+ bdrv_backup_deinit(bs);
+}
+
+BackupInfo *
+bdrv_backup_init(BlockDriverState *bs, BackupDumpFunc *backup_dump_cb,
+ BlockDriverCompletionFunc *backup_complete_cb,
+ void *opaque)
+{
+ assert(bs);
+ assert(backup_dump_cb);
+ assert(backup_complete_cb);
+
+ if (bs->backup_info) {
+ DPRINTF("bdrv_backup_init already initialized %s\n",
+ bdrv_get_device_name(bs));
+ return NULL;
+ }
+
+ BackupInfo *info = g_malloc0(sizeof(BackupInfo));
+ int64_t bitmap_size;
+ const char *devname = bdrv_get_device_name(bs);
+
+ if (!devname || !devname[0])
+ return NULL;
+
+ DPRINTF("bdrv_backup_init %s\n", bdrv_get_device_name(bs));
+
+ bitmap_size = bs->total_sectors +
+ BACKUP_BLOCKS_PER_CLUSTER * BITS_PER_LONG - 1;
+ bitmap_size /= BACKUP_BLOCKS_PER_CLUSTER * BITS_PER_LONG;
+
+ info->backup_dump_cb = backup_dump_cb;
+ info->backup_complete_cb = backup_complete_cb;
+ info->opaque = opaque;
+ info->bitmap_size = bitmap_size;
+ info->bitmap = g_new0(unsigned long, bitmap_size);
+
+ Error *errp;
+ BackupBlockJob *job = block_job_create(&backup_job_type, bs, 0,
+ backup_job_cleanup_cb, bs, &errp);
+
+ bs->backup_info = info;
+
+ job->common.len = bs->total_sectors*BDRV_SECTOR_SIZE;
+ job->common.co = qemu_coroutine_create(backup_run);
+ qemu_coroutine_enter(job->common.co, job);
+
+ return info;
+}
diff --git a/block.c b/block.c
index da1fdca..94fec48 100644
--- a/block.c
+++ b/block.c
@@ -54,6 +54,7 @@
typedef enum {
BDRV_REQ_COPY_ON_READ = 0x1,
BDRV_REQ_ZERO_WRITE = 0x2,
+ BDRV_REQ_BACKUP_ONLY = 0x4,
} BdrvRequestFlags;
static void bdrv_dev_change_media_cb(BlockDriverState *bs, bool load);
@@ -1132,6 +1133,11 @@ void bdrv_close(BlockDriverState *bs)
block_job_cancel_sync(bs->job);
}
bdrv_drain_all();
+
+ if (bs->backup_info) {
+ bdrv_backup_deinit(bs);
+ }
+
notifier_list_notify(&bs->close_notifiers, bs);
if (bs->drv) {
@@ -1541,7 +1547,7 @@ int bdrv_commit(BlockDriverState *bs)
if (!drv)
return -ENOMEDIUM;
-
+
if (!bs->backing_hd) {
return -ENOTSUP;
}
@@ -1678,6 +1684,20 @@ static void round_to_clusters(BlockDriverState *bs,
}
}
+/**
+ * Round a region to backup cluster boundaries
+ */
+static void round_to_backup_clusters(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors,
+ int64_t *cluster_sector_num,
+ int *cluster_nb_sectors)
+{
+ int64_t c = BACKUP_BLOCKS_PER_CLUSTER;
+ *cluster_sector_num = QEMU_ALIGN_DOWN(sector_num, c);
+ *cluster_nb_sectors = QEMU_ALIGN_UP(sector_num - *cluster_sector_num +
+ nb_sectors, c);
+}
+
static bool tracked_request_overlaps(BdrvTrackedRequest *req,
int64_t sector_num, int nb_sectors) {
/* aaaa bbbb */
@@ -1708,6 +1728,11 @@ static void coroutine_fn wait_for_overlapping_requests(BlockDriverState *bs,
round_to_clusters(bs, sector_num, nb_sectors,
&cluster_sector_num, &cluster_nb_sectors);
+ if (bs->backup_info) {
+ round_to_backup_clusters(bs, sector_num, nb_sectors,
+ &cluster_sector_num, &cluster_nb_sectors);
+ }
+
do {
retry = false;
QLIST_FOREACH(req, &bs->tracked_requests, list) {
@@ -2277,12 +2302,22 @@ static int coroutine_fn bdrv_co_do_readv(BlockDriverState *bs,
bs->copy_on_read_in_flight++;
}
- if (bs->copy_on_read_in_flight) {
+ if (bs->copy_on_read_in_flight || bs->backup_info) {
wait_for_overlapping_requests(bs, sector_num, nb_sectors);
}
tracked_request_begin(&req, bs, sector_num, nb_sectors, false);
+ if (flags & BDRV_REQ_BACKUP_ONLY) {
+ // Note: We do not return any data to the caller
+ if (bs->backup_info) {
+ ret = brdv_co_backup_cow(bs, sector_num, nb_sectors);
+ } else {
+ ret = -1;
+ }
+ goto out;
+ }
+
if (flags & BDRV_REQ_COPY_ON_READ) {
int pnum;
@@ -2326,6 +2361,16 @@ int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
BDRV_REQ_COPY_ON_READ);
}
+int coroutine_fn bdrv_co_backup(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors)
+{
+ if (!bs->backup_info)
+ return -ENOTSUP;
+
+ return bdrv_co_do_readv(bs, sector_num, nb_sectors, NULL,
+ BDRV_REQ_BACKUP_ONLY);
+}
+
static int coroutine_fn bdrv_co_do_write_zeroes(BlockDriverState *bs,
int64_t sector_num, int nb_sectors)
{
@@ -2383,12 +2428,19 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
bdrv_io_limits_intercept(bs, true, nb_sectors);
}
- if (bs->copy_on_read_in_flight) {
+ if (bs->copy_on_read_in_flight || bs->backup_info) {
wait_for_overlapping_requests(bs, sector_num, nb_sectors);
}
tracked_request_begin(&req, bs, sector_num, nb_sectors, true);
+ if (bs->backup_info) {
+ ret = brdv_co_backup_cow(bs, sector_num, nb_sectors);
+ if (ret < 0) {
+ goto out;
+ }
+ }
+
if (flags & BDRV_REQ_ZERO_WRITE) {
ret = bdrv_co_do_write_zeroes(bs, sector_num, nb_sectors);
} else {
@@ -2407,6 +2459,7 @@ static int coroutine_fn bdrv_co_do_writev(BlockDriverState *bs,
bs->wr_highest_sector = sector_num + nb_sectors - 1;
}
+out:
tracked_request_end(&req);
return ret;
diff --git a/block.h b/block.h
index 722c620..94e5903 100644
--- a/block.h
+++ b/block.h
@@ -172,6 +172,8 @@ int coroutine_fn bdrv_co_readv(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov);
int coroutine_fn bdrv_co_copy_on_readv(BlockDriverState *bs,
int64_t sector_num, int nb_sectors, QEMUIOVector *qiov);
+int coroutine_fn bdrv_co_backup(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors);
int coroutine_fn bdrv_co_writev(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov);
/*
diff --git a/block_int.h b/block_int.h
index 9deedb8..3320888 100644
--- a/block_int.h
+++ b/block_int.h
@@ -68,6 +68,36 @@ typedef struct BlockIOBaseValue {
uint64_t ios[2];
} BlockIOBaseValue;
+/**
+ * Backup related definitions
+ */
+
+#define BACKUP_CLUSTER_BITS 16
+#define BACKUP_CLUSTER_SIZE (1<<BACKUP_CLUSTER_BITS)
+#define BACKUP_BLOCKS_PER_CLUSTER (BACKUP_CLUSTER_SIZE/BDRV_SECTOR_SIZE)
+
+typedef int BackupDumpFunc(void *opaque, BlockDriverState *bs,
+ int64_t cluster_num, unsigned char *buf);
+
+typedef struct BackupInfo {
+ unsigned long *bitmap;
+ int bitmap_size;
+ BackupDumpFunc *backup_dump_cb;
+ BlockDriverCompletionFunc *backup_complete_cb;
+ void *opaque;
+} BackupInfo;
+
+BackupInfo *bdrv_backup_init(BlockDriverState *bs,
+ BackupDumpFunc *backup_dump_cb,
+ BlockDriverCompletionFunc *backup_complete_cb,
+ void *opaque);
+
+void bdrv_backup_deinit(BlockDriverState *bs);
+
+int coroutine_fn brdv_co_backup_cow(BlockDriverState *bs,
+ int64_t sector_num, int nb_sectors);
+
+
struct BlockDriver {
const char *format_name;
int instance_size;
@@ -276,6 +306,8 @@ struct BlockDriverState {
QLIST_HEAD(, BdrvTrackedRequest) tracked_requests;
+ BackupInfo *backup_info;
+
/* long-running background operation */
BlockJob *job;
--
1.7.2.5
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