First pass, fairly superficial, hope it helps anyway.
Dietmar Maurer <diet...@proxmox.com> writes:
> Function backup_job_create() creates a block job to backup a block device.
> The coroutine is started with backup_job_start().
>
> We call backup_do_cow() for each write during backup. That function
> reads the original data and pass it to 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 <diet...@proxmox.com>
> ---
> Makefile.objs | 1 +
> backup.c | 355
> ++++++++++++++++++++++++++++++++++++++++++++++
> backup.h | 30 ++++
> block.c | 71 +++++++++-
> include/block/block.h | 2 +
> include/block/blockjob.h | 10 ++
> 6 files changed, 463 insertions(+), 6 deletions(-)
> create mode 100644 backup.c
> create mode 100644 backup.h
>
> diff --git a/Makefile.objs b/Makefile.objs
> index a68cdac..df64f70 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -13,6 +13,7 @@ block-obj-$(CONFIG_POSIX) += aio-posix.o
> block-obj-$(CONFIG_WIN32) += aio-win32.o
> block-obj-y += block/
> block-obj-y += qapi-types.o qapi-visit.o
> +block-obj-y += backup.o
>
> block-obj-y += qemu-coroutine.o qemu-coroutine-lock.o qemu-coroutine-io.o
> block-obj-y += qemu-coroutine-sleep.o
> diff --git a/backup.c b/backup.c
> new file mode 100644
> index 0000000..8955e1a
> --- /dev/null
> +++ b/backup.c
> @@ -0,0 +1,355 @@
> +/*
> + * QEMU backup
> + *
> + * Copyright (C) 2013 Proxmox Server Solutions
> + *
> + * Authors:
> + * Dietmar Maurer (diet...@proxmox.com)
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#include <stdio.h>
> +#include <errno.h>
> +#include <unistd.h>
> +
> +#include "block/block.h"
> +#include "block/block_int.h"
> +#include "block/blockjob.h"
> +#include "qemu/ratelimit.h"
> +#include "backup.h"
> +
> +#define DEBUG_BACKUP 0
> +
> +#define USE_ALLOCATION_CHECK 0
What's this, and when would you want to enable it?
> +
> +#define DPRINTF(fmt, ...) \
> + do { if (DEBUG_BACKUP) { printf("backup: " fmt, ## __VA_ARGS__); } } \
> + while (0)
Have you considered tracepoints?
> +
> +
> +#define SLICE_TIME 100000000ULL /* ns */
> +
> +typedef struct BackupBlockJob {
> + BlockJob common;
> + RateLimit limit;
> + CoRwlock rwlock;
> + uint64_t sectors_read;
> + unsigned long *bitmap;
> + int bitmap_size;
> + BackupDumpFunc *backup_dump_cb;
> + BlockDriverCompletionFunc *backup_complete_cb;
> + void *opaque;
> +} BackupBlockJob;
> +
> +static bool backup_get_bitmap(BackupBlockJob *job, int64_t cluster_num)
> +{
> + assert(job);
> + assert(job->bitmap);
> +
> + unsigned long val, idx, bit;
> +
> + idx = cluster_num / BITS_PER_LONG;
> +
> + assert(job->bitmap_size > idx);
> +
> + bit = cluster_num % BITS_PER_LONG;
> + val = job->bitmap[idx];
> +
> + return !!(val & (1UL << bit));
> +}
Sure you can't use our bitmap helpers and need to roll your own? Have a
look at include/qemu/bitops.h and include/qemu/bitmap.h.
> +
> +static void backup_set_bitmap(BackupBlockJob *job, int64_t cluster_num,
> + bool dirty)
> +{
> + assert(job);
> + assert(job->bitmap);
> +
> + unsigned long val, idx, bit;
> +
> + idx = cluster_num / BITS_PER_LONG;
> +
> + assert(job->bitmap_size > idx);
> +
> + bit = cluster_num % BITS_PER_LONG;
> + val = job->bitmap[idx];
> + if (dirty) {
> + val |= 1UL << bit;
> + } else {
> + val &= ~(1UL << bit);
> + }
> + job->bitmap[idx] = val;
> +}
> +
> +static int coroutine_fn backup_do_cow(BlockDriverState *bs,
> + int64_t sector_num, int nb_sectors)
> +{
> + assert(bs);
> + BackupBlockJob *job = (BackupBlockJob *)bs->job;
> + assert(job);
> +
> + BlockDriver *drv = bs->drv;
> + struct iovec iov;
> + QEMUIOVector bounce_qiov;
> + void *bounce_buffer = NULL;
> + int ret = 0;
> +
> + qemu_co_rwlock_rdlock(&job->rwlock);
> +
> + 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;
Looks similar to round_to_job_clusters().
> +
> + DPRINTF("brdv_co_backup_cow enter %s C%" PRId64 " %" PRId64 " %d\n",
> + bdrv_get_device_name(bs), start, sector_num, nb_sectors);
> +
> + for (; start < end; start++) {
> + bool zero = 0;
> +
> + if (backup_get_bitmap(job, start)) {
> + DPRINTF("brdv_co_backup_cow skip C%" PRId64 "\n", start);
> + continue; /* already copied */
> + }
> +
> + /* immediately set bitmap (avoid coroutine race) */
> + backup_set_bitmap(job, start, 1);
> +
> + DPRINTF("brdv_co_backup_cow C%" PRId64 "\n", start);
> +
> + if (!bounce_buffer) {
> + iov.iov_len = BACKUP_CLUSTER_SIZE;
> + iov.iov_base = bounce_buffer = qemu_blockalign(bs, iov.iov_len);
Naive question: why must bounce_buffer be aligned?
> + qemu_iovec_init_external(&bounce_qiov, &iov, 1);
> + }
> +
> +#if USE_ALLOCATION_CHECK
> + int n = 0;
> + ret = bdrv_co_is_allocated_above(bs, NULL,
> + start * BACKUP_BLOCKS_PER_CLUSTER,
> + BACKUP_BLOCKS_PER_CLUSTER, &n);
> + if (ret < 0) {
> + DPRINTF("brdv_co_backup_cow is_allocated C%" PRId64 " failed\n",
> + start);
> + goto out;
> + }
> +
> + zero = (ret == 0) && (n == BACKUP_BLOCKS_PER_CLUSTER);
> +
> + if (!zero) {
> +#endif
> + 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%" PRId64 " failed\n",
> + start);
> + goto out;
> + }
> +#if USE_ALLOCATION_CHECK
> + }
> +#endif
> + job->sectors_read += BACKUP_BLOCKS_PER_CLUSTER;
> +
> + ret = job->backup_dump_cb(job->opaque, bs, start,
> + zero ? NULL : bounce_buffer);
> + if (ret < 0) {
> + DPRINTF("brdv_co_backup_cow dump_cluster_cb C%" PRId64 "
> failed\n",
> + start);
> + goto out;
> + }
> +
> + DPRINTF("brdv_co_backup_cow done C%" PRId64 "\n", start);
> + }
> +
> +out:
> + if (bounce_buffer) {
> + qemu_vfree(bounce_buffer);
> + }
> +
> + qemu_co_rwlock_unlock(&job->rwlock);
> +
> + return ret;
> +}
> +
> +static int coroutine_fn backup_before_read(BlockDriverState *bs,
> + int64_t sector_num,
> + int nb_sectors, QEMUIOVector
> *qiov)
> +{
> + return backup_do_cow(bs, sector_num, nb_sectors);
> +}
> +
> +static int coroutine_fn backup_before_write(BlockDriverState *bs,
> + int64_t sector_num,
> + int nb_sectors, QEMUIOVector
> *qiov)
> +{
> + return backup_do_cow(bs, sector_num, nb_sectors);
> +}
> +
> +static void backup_set_speed(BlockJob *job, int64_t speed, Error **errp)
> +{
> + BackupBlockJob *s = container_of(job, BackupBlockJob, common);
> +
> + if (speed < 0) {
> + error_set(errp, QERR_INVALID_PARAMETER, "speed");
> + return;
> + }
> + ratelimit_set_speed(&s->limit, speed / BDRV_SECTOR_SIZE, SLICE_TIME);
> +}
> +
> +static BlockJobType backup_job_type = {
> + .instance_size = sizeof(BackupBlockJob),
> + .before_read = backup_before_read,
> + .before_write = backup_before_write,
> + .job_type = "backup",
> + .set_speed = backup_set_speed,
> +};
> +
> +static void coroutine_fn backup_run(void *opaque)
> +{
> + BackupBlockJob *job = opaque;
> + BlockDriverState *bs = job->common.bs;
> + assert(bs);
> +
> + int64_t start, end;
> +
> + start = 0;
> + end = (bs->total_sectors + BACKUP_BLOCKS_PER_CLUSTER - 1) /
> + BACKUP_BLOCKS_PER_CLUSTER;
> +
> + DPRINTF("backup_run start %s %" PRId64 " %" PRId64 "\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;
> + }
> +
> + /* we need to yield so that qemu_aio_flush() returns.
> + * (without, VM does not reboot)
> + * Note: use 1000 instead of 0 (0 prioritize this task too much)
> + */
> + if (job->common.speed) {
> + uint64_t delay_ns = ratelimit_calculate_delay(
> + &job->limit, job->sectors_read);
> + job->sectors_read = 0;
> + block_job_sleep_ns(&job->common, rt_clock, delay_ns);
> + } else {
> + block_job_sleep_ns(&job->common, rt_clock, 1000);
> + }
Magic number 1000. How did you arrive at that value?
> +
> + if (block_job_is_cancelled(&job->common)) {
> + ret = -1;
> + break;
> + }
> +
> + if (backup_get_bitmap(job, start)) {
> + continue; /* already copied */
> + }
> +
> + DPRINTF("backup_run loop C%" PRId64 "\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;
> + }
> +
> + /* wait until pending backup_do_cow()calls have completed */
> + qemu_co_rwlock_wrlock(&job->rwlock);
> + qemu_co_rwlock_unlock(&job->rwlock);
> +
> + 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;
> + assert(bs);
> + BackupBlockJob *job = (BackupBlockJob *)bs->job;
> + assert(job);
> +
> + DPRINTF("backup_job_cleanup_cb start %d\n", ret);
> +
> + job->backup_complete_cb(job->opaque, ret);
> +
> + DPRINTF("backup_job_cleanup_cb end\n");
> +
> + g_free(job->bitmap);
> +}
> +
> +void
> +backup_job_start(BlockDriverState *bs, bool cancel)
> +{
> + assert(bs);
> + assert(bs->job);
> + assert(bs->job->co == NULL);
> +
> + if (cancel) {
> + block_job_cancel(bs->job); /* set cancel flag */
> + }
> +
> + bs->job->co = qemu_coroutine_create(backup_run);
> + qemu_coroutine_enter(bs->job->co, bs->job);
> +}
> +
> +int
> +backup_job_create(BlockDriverState *bs, BackupDumpFunc *backup_dump_cb,
> + BlockDriverCompletionFunc *backup_complete_cb,
> + void *opaque, int64_t speed)
> +{
> + assert(bs);
> + assert(backup_dump_cb);
> + assert(backup_complete_cb);
> +
> + if (bs->job) {
> + DPRINTF("bdrv_backup_init failed - running job on %s\n",
> + bdrv_get_device_name(bs));
> + return -1;
> + }
> +
> + int64_t bitmap_size;
> + const char *devname = bdrv_get_device_name(bs);
> +
> + if (!devname || !devname[0]) {
> + return -1;
> + }
> +
> + DPRINTF("bdrv_backup_init %s\n", bdrv_get_device_name(bs));
> +
> + Error *errp;
> + BackupBlockJob *job = block_job_create(&backup_job_type, bs, speed,
> + backup_job_cleanup_cb, bs, &errp);
> +
> + qemu_co_rwlock_init(&job->rwlock);
> +
> + job->common.cluster_size = BACKUP_CLUSTER_SIZE;
> +
> + bitmap_size = bs->total_sectors +
> + BACKUP_BLOCKS_PER_CLUSTER * BITS_PER_LONG - 1;
> + bitmap_size /= BACKUP_BLOCKS_PER_CLUSTER * BITS_PER_LONG;
> +
> + job->backup_dump_cb = backup_dump_cb;
> + job->backup_complete_cb = backup_complete_cb;
> + job->opaque = opaque;
> + job->bitmap_size = bitmap_size;
> + job->bitmap = g_new0(unsigned long, bitmap_size);
> +
> + job->common.len = bs->total_sectors*BDRV_SECTOR_SIZE;
Spaces around * please.
> +
> + return 0;
> +}
> diff --git a/backup.h b/backup.h
> new file mode 100644
> index 0000000..9b1ea1c
> --- /dev/null
> +++ b/backup.h
> @@ -0,0 +1,30 @@
> +/*
> + * QEMU backup related definitions
> + *
> + * Copyright (C) 2013 Proxmox Server Solutions
> + *
> + * Authors:
> + * Dietmar Maurer (diet...@proxmox.com)
> + *
> + * This work is licensed under the terms of the GNU GPL, version 2 or later.
> + * See the COPYING file in the top-level directory.
> + *
> + */
> +
> +#ifndef QEMU_BACKUP_H
> +#define QEMU_BACKUP_H
> +
> +#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);
> +
> +void backup_job_start(BlockDriverState *bs, bool cancel);
> +
> +int backup_job_create(BlockDriverState *bs, BackupDumpFunc *backup_dump_cb,
> + BlockDriverCompletionFunc *backup_complete_cb,
> + void *opaque, int64_t speed);
> +
> +#endif /* QEMU_BACKUP_H */
> diff --git a/block.c b/block.c
> index 50dab8e..6e6d08f 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);
> @@ -1554,7 +1555,7 @@ int bdrv_commit(BlockDriverState *bs)
>
> if (!drv)
> return -ENOMEDIUM;
> -
> +
> if (!bs->backing_hd) {
> return -ENOTSUP;
> }
Unrelated whitespace cleanup. Separate patch or drop.
> @@ -1691,6 +1692,22 @@ void bdrv_round_to_clusters(BlockDriverState *bs,
> }
> }
>
> +/**
> + * Round a region to job cluster boundaries
> + */
> +static void round_to_job_clusters(BlockDriverState *bs,
> + int64_t sector_num, int nb_sectors,
> + int job_cluster_size,
> + int64_t *cluster_sector_num,
> + int *cluster_nb_sectors)
> +{
> + int64_t c = job_cluster_size/BDRV_SECTOR_SIZE;
> +
> + *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 */
> @@ -1705,7 +1722,9 @@ static bool tracked_request_overlaps(BdrvTrackedRequest
> *req,
> }
>
> static void coroutine_fn wait_for_overlapping_requests(BlockDriverState *bs,
> - int64_t sector_num, int nb_sectors)
> + int64_t sector_num,
> + int nb_sectors,
> + int job_cluster_size)
> {
> BdrvTrackedRequest *req;
> int64_t cluster_sector_num;
Just add your parameter, no need to reformat the argument list.
> @@ -1721,6 +1740,11 @@ static void coroutine_fn
> wait_for_overlapping_requests(BlockDriverState *bs,
> bdrv_round_to_clusters(bs, sector_num, nb_sectors,
> &cluster_sector_num, &cluster_nb_sectors);
>
> + if (job_cluster_size) {
> + round_to_job_clusters(bs, sector_num, nb_sectors, job_cluster_size,
> + &cluster_sector_num, &cluster_nb_sectors);
> + }
> +
> do {
> retry = false;
> QLIST_FOREACH(req, &bs->tracked_requests, list) {
> @@ -2260,12 +2284,24 @@ static int coroutine_fn
> bdrv_co_do_readv(BlockDriverState *bs,
> bs->copy_on_read_in_flight++;
> }
>
> - if (bs->copy_on_read_in_flight) {
> - wait_for_overlapping_requests(bs, sector_num, nb_sectors);
> + int job_cluster_size = bs->job && bs->job->cluster_size ?
> + bs->job->cluster_size : 0;
> +
> + if (bs->copy_on_read_in_flight || job_cluster_size) {
> + wait_for_overlapping_requests(bs, sector_num, nb_sectors,
> + job_cluster_size);
> }
>
> tracked_request_begin(&req, bs, sector_num, nb_sectors, false);
>
> + if (bs->job && bs->job->job_type->before_read) {
> + ret = bs->job->job_type->before_read(bs, sector_num, nb_sectors,
> qiov);
> + if ((ret < 0) || (flags & BDRV_REQ_BACKUP_ONLY)) {
> + /* Note: We do not return any data to the caller */
> + goto out;
> + }
> + }
> +
> if (flags & BDRV_REQ_COPY_ON_READ) {
> int pnum;
>
> @@ -2309,6 +2345,17 @@ 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->job) {
> + 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)
> {
> @@ -2366,12 +2413,23 @@ 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) {
> - wait_for_overlapping_requests(bs, sector_num, nb_sectors);
> + int job_cluster_size = bs->job && bs->job->cluster_size ?
> + bs->job->cluster_size : 0;
Declaration not at beginning of block.
> +
> + if (bs->copy_on_read_in_flight || job_cluster_size) {
> + wait_for_overlapping_requests(bs, sector_num, nb_sectors,
> + job_cluster_size);
> }
>
> tracked_request_begin(&req, bs, sector_num, nb_sectors, true);
>
> + if (bs->job && bs->job->job_type->before_write) {
> + ret = bs->job->job_type->before_write(bs, sector_num, nb_sectors,
> qiov);
> + if (ret < 0) {
> + goto out;
> + }
> + }
> +
> if (flags & BDRV_REQ_ZERO_WRITE) {
> ret = bdrv_co_do_write_zeroes(bs, sector_num, nb_sectors);
> } else {
> @@ -2390,6 +2448,7 @@ 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/include/block/block.h b/include/block/block.h
> index 5c3b911..b6144be 100644
> --- a/include/block/block.h
> +++ b/include/block/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/include/block/blockjob.h b/include/block/blockjob.h
> index c290d07..6f42495 100644
> --- a/include/block/blockjob.h
> +++ b/include/block/blockjob.h
> @@ -50,6 +50,13 @@ typedef struct BlockJobType {
> * manually.
> */
> void (*complete)(BlockJob *job, Error **errp);
> +
> + /** tracked requests */
> + int coroutine_fn (*before_read)(BlockDriverState *bs, int64_t sector_num,
> + int nb_sectors, QEMUIOVector *qiov);
> + int coroutine_fn (*before_write)(BlockDriverState *bs, int64_t
> sector_num,
> + int nb_sectors, QEMUIOVector *qiov);
> +
Comment should explain meaning of the callbacks.
> } BlockJobType;
>
> /**
> @@ -103,6 +110,9 @@ struct BlockJob {
> /** Speed that was set with @block_job_set_speed. */
> int64_t speed;
>
> + /** tracked requests */
> + int cluster_size;
> +
Comment should explain what the variable does.
> /** The completion function that will be called when the job completes.
> */
> BlockDriverCompletionFunc *cb;
