block/backup-top.c - qemu - Git at Google

 /*
  * backup-top filter driver
  *
  * The driver performs Copy-Before-Write (CBW) operation: it is injected above
  * some node, and before each write it copies _old_ data to the target node.
  *
  * Copyright (c) 2018-2019 Virtuozzo International GmbH.
  *
  * Author:
  *  Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program 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 General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program. If not, see <http://www.gnu.org/licenses/>.
  */

 #include "qemu/osdep.h"

 #include "sysemu/block-backend.h"
 #include "qemu/cutils.h"
 #include "qapi/error.h"
 #include "block/block_int.h"
 #include "block/qdict.h"
 #include "block/block-copy.h"

 #include "block/backup-top.h"

 typedef struct BDRVBackupTopState {
     BlockCopyState *bcs;
     BdrvChild *target;
     bool active;
     int64_t cluster_size;
 } BDRVBackupTopState;

 static coroutine_fn int backup_top_co_preadv(
         BlockDriverState *bs, uint64_t offset, uint64_t bytes,
         QEMUIOVector *qiov, int flags)
 {
     return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
 }

 static coroutine_fn int backup_top_cbw(BlockDriverState *bs, uint64_t offset,
                                        uint64_t bytes, BdrvRequestFlags flags)
 {
     BDRVBackupTopState *s = bs->opaque;
     uint64_t off, end;

     if (flags & BDRV_REQ_WRITE_UNCHANGED) {
         return 0;
     }

     off = QEMU_ALIGN_DOWN(offset, s->cluster_size);
     end = QEMU_ALIGN_UP(offset + bytes, s->cluster_size);

     return block_copy(s->bcs, off, end - off, NULL);
 }

 static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs,
                                                int64_t offset, int bytes)
 {
     int ret = backup_top_cbw(bs, offset, bytes, 0);
     if (ret < 0) {
         return ret;
     }

     return bdrv_co_pdiscard(bs->backing, offset, bytes);
 }

 static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs,
         int64_t offset, int bytes, BdrvRequestFlags flags)
 {
     int ret = backup_top_cbw(bs, offset, bytes, flags);
     if (ret < 0) {
         return ret;
     }

     return bdrv_co_pwrite_zeroes(bs->backing, offset, bytes, flags);
 }

 static coroutine_fn int backup_top_co_pwritev(BlockDriverState *bs,
                                               uint64_t offset,
                                               uint64_t bytes,
                                               QEMUIOVector *qiov, int flags)
 {
     int ret = backup_top_cbw(bs, offset, bytes, flags);
     if (ret < 0) {
         return ret;
     }

     return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
 }

 static int coroutine_fn backup_top_co_flush(BlockDriverState *bs)
 {
     if (!bs->backing) {
         return 0;
     }

     return bdrv_co_flush(bs->backing->bs);
 }

 static void backup_top_refresh_filename(BlockDriverState *bs)
 {
     if (bs->backing == NULL) {
         /*
          * we can be here after failed bdrv_attach_child in
          * bdrv_set_backing_hd
          */
         return;
     }
     pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
             bs->backing->bs->filename);
 }

 static void backup_top_child_perm(BlockDriverState *bs, BdrvChild *c,
                                   const BdrvChildClass *child_class,
                                   BdrvChildRole role,
                                   BlockReopenQueue *reopen_queue,
                                   uint64_t perm, uint64_t shared,
                                   uint64_t *nperm, uint64_t *nshared)
 {
     BDRVBackupTopState *s = bs->opaque;

     if (!s->active) {
         /*
          * The filter node may be in process of bdrv_append(), which firstly do
          * bdrv_set_backing_hd() and then bdrv_replace_node(). This means that
          * we can't unshare BLK_PERM_WRITE during bdrv_append() operation. So,
          * let's require nothing during bdrv_append() and refresh permissions
          * after it (see bdrv_backup_top_append()).
          */
         *nperm = 0;
         *nshared = BLK_PERM_ALL;
         return;
     }

     if (!(role & BDRV_CHILD_FILTERED)) {
         /*
          * Target child
          *
          * Share write to target (child_file), to not interfere
          * with guest writes to its disk which may be in target backing chain.
          * Can't resize during a backup block job because we check the size
          * only upfront.
          */
         *nshared = BLK_PERM_ALL & ~BLK_PERM_RESIZE;
         *nperm = BLK_PERM_WRITE;
     } else {
         /* Source child */
         bdrv_filter_default_perms(bs, c, child_class, role, reopen_queue,
                                   perm, shared, nperm, nshared);

         if (perm & BLK_PERM_WRITE) {
             *nperm = *nperm | BLK_PERM_CONSISTENT_READ;
         }
         *nshared &= ~(BLK_PERM_WRITE | BLK_PERM_RESIZE);
     }
 }

 BlockDriver bdrv_backup_top_filter = {
     .format_name = "backup-top",
     .instance_size = sizeof(BDRVBackupTopState),

     .bdrv_co_preadv             = backup_top_co_preadv,
     .bdrv_co_pwritev            = backup_top_co_pwritev,
     .bdrv_co_pwrite_zeroes      = backup_top_co_pwrite_zeroes,
     .bdrv_co_pdiscard           = backup_top_co_pdiscard,
     .bdrv_co_flush              = backup_top_co_flush,

     .bdrv_co_block_status       = bdrv_co_block_status_from_backing,

     .bdrv_refresh_filename      = backup_top_refresh_filename,

     .bdrv_child_perm            = backup_top_child_perm,

     .is_filter = true,
 };

 BlockDriverState *bdrv_backup_top_append(BlockDriverState *source,
                                          BlockDriverState *target,
                                          const char *filter_node_name,
                                          uint64_t cluster_size,
                                          BdrvRequestFlags write_flags,
                                          BlockCopyState **bcs,
                                          Error **errp)
 {
     Error *local_err = NULL;
     BDRVBackupTopState *state;
     BlockDriverState *top;
     bool appended = false;

     assert(source->total_sectors == target->total_sectors);

     top = bdrv_new_open_driver(&bdrv_backup_top_filter, filter_node_name,
                                BDRV_O_RDWR, errp);
     if (!top) {
         return NULL;
     }

     state = top->opaque;
     top->total_sectors = source->total_sectors;
     top->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED |
             (BDRV_REQ_FUA & source->supported_write_flags);
     top->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED |
             ((BDRV_REQ_FUA | BDRV_REQ_MAY_UNMAP | BDRV_REQ_NO_FALLBACK) &
              source->supported_zero_flags);

     bdrv_ref(target);
     state->target = bdrv_attach_child(top, target, "target", &child_file, 0,
                                       errp);
     if (!state->target) {
         bdrv_unref(target);
         bdrv_unref(top);
         return NULL;
     }

     bdrv_drained_begin(source);

     bdrv_ref(top);
     bdrv_append(top, source, &local_err);
     if (local_err) {
         error_prepend(&local_err, "Cannot append backup-top filter: ");
         goto fail;
     }
     appended = true;

     /*
      * bdrv_append() finished successfully, now we can require permissions
      * we want.
      */
     state->active = true;
     bdrv_child_refresh_perms(top, top->backing, &local_err);
     if (local_err) {
         error_prepend(&local_err,
                       "Cannot set permissions for backup-top filter: ");
         goto fail;
     }

     state->cluster_size = cluster_size;
     state->bcs = block_copy_state_new(top->backing, state->target,
                                       cluster_size, write_flags, &local_err);
     if (local_err) {
         error_prepend(&local_err, "Cannot create block-copy-state: ");
         goto fail;
     }
     *bcs = state->bcs;

     bdrv_drained_end(source);

     return top;

 fail:
     if (appended) {
         state->active = false;
         bdrv_backup_top_drop(top);
     } else {
         bdrv_unref(top);
     }

     bdrv_drained_end(source);
     error_propagate(errp, local_err);

     return NULL;
 }

 void bdrv_backup_top_drop(BlockDriverState *bs)
 {
     BDRVBackupTopState *s = bs->opaque;

     bdrv_drained_begin(bs);

     block_copy_state_free(s->bcs);

     s->active = false;
     bdrv_child_refresh_perms(bs, bs->backing, &error_abort);
     bdrv_replace_node(bs, backing_bs(bs), &error_abort);
     bdrv_set_backing_hd(bs, NULL, &error_abort);

     bdrv_drained_end(bs);

     bdrv_unref(bs);
 }
	/*
	* backup-top filter driver
	*
	* The driver performs Copy-Before-Write (CBW) operation: it is injected above
	* some node, and before each write it copies _old_ data to the target node.
	*
	* Copyright (c) 2018-2019 Virtuozzo International GmbH.
	*
	* Author:
	* Sementsov-Ogievskiy Vladimir <vsementsov@virtuozzo.com>
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program 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 General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program. If not, see <http://www.gnu.org/licenses/>.
	*/

	#include "qemu/osdep.h"

	#include "sysemu/block-backend.h"
	#include "qemu/cutils.h"
	#include "qapi/error.h"
	#include "block/block_int.h"
	#include "block/qdict.h"
	#include "block/block-copy.h"

	#include "block/backup-top.h"

	typedef struct BDRVBackupTopState {
	BlockCopyState *bcs;
	BdrvChild *target;
	bool active;
	int64_t cluster_size;
	} BDRVBackupTopState;

	static coroutine_fn int backup_top_co_preadv(
	BlockDriverState *bs, uint64_t offset, uint64_t bytes,
	QEMUIOVector *qiov, int flags)
	{
	return bdrv_co_preadv(bs->backing, offset, bytes, qiov, flags);
	}

	static coroutine_fn int backup_top_cbw(BlockDriverState *bs, uint64_t offset,
	uint64_t bytes, BdrvRequestFlags flags)
	{
	BDRVBackupTopState *s = bs->opaque;
	uint64_t off, end;

	if (flags & BDRV_REQ_WRITE_UNCHANGED) {
	return 0;
	}

	off = QEMU_ALIGN_DOWN(offset, s->cluster_size);
	end = QEMU_ALIGN_UP(offset + bytes, s->cluster_size);

	return block_copy(s->bcs, off, end - off, NULL);
	}

	static int coroutine_fn backup_top_co_pdiscard(BlockDriverState *bs,
	int64_t offset, int bytes)
	{
	int ret = backup_top_cbw(bs, offset, bytes, 0);
	if (ret < 0) {
	return ret;
	}

	return bdrv_co_pdiscard(bs->backing, offset, bytes);
	}

	static int coroutine_fn backup_top_co_pwrite_zeroes(BlockDriverState *bs,
	int64_t offset, int bytes, BdrvRequestFlags flags)
	{
	int ret = backup_top_cbw(bs, offset, bytes, flags);
	if (ret < 0) {
	return ret;
	}

	return bdrv_co_pwrite_zeroes(bs->backing, offset, bytes, flags);
	}

	static coroutine_fn int backup_top_co_pwritev(BlockDriverState *bs,
	uint64_t offset,
	uint64_t bytes,
	QEMUIOVector *qiov, int flags)
	{
	int ret = backup_top_cbw(bs, offset, bytes, flags);
	if (ret < 0) {
	return ret;
	}

	return bdrv_co_pwritev(bs->backing, offset, bytes, qiov, flags);
	}

	static int coroutine_fn backup_top_co_flush(BlockDriverState *bs)
	{
	if (!bs->backing) {
	return 0;
	}

	return bdrv_co_flush(bs->backing->bs);
	}

	static void backup_top_refresh_filename(BlockDriverState *bs)
	{
	if (bs->backing == NULL) {
	/*
	* we can be here after failed bdrv_attach_child in
	* bdrv_set_backing_hd
	*/
	return;
	}
	pstrcpy(bs->exact_filename, sizeof(bs->exact_filename),
	bs->backing->bs->filename);
	}

	static void backup_top_child_perm(BlockDriverState bs, BdrvChild c,
	const BdrvChildClass *child_class,
	BdrvChildRole role,
	BlockReopenQueue *reopen_queue,
	uint64_t perm, uint64_t shared,
	uint64_t nperm, uint64_t nshared)
	{
	BDRVBackupTopState *s = bs->opaque;

	if (!s->active) {
	/*
	* The filter node may be in process of bdrv_append(), which firstly do
	* bdrv_set_backing_hd() and then bdrv_replace_node(). This means that
	* we can't unshare BLK_PERM_WRITE during bdrv_append() operation. So,
	* let's require nothing during bdrv_append() and refresh permissions
	* after it (see bdrv_backup_top_append()).
	*/
	*nperm = 0;
	*nshared = BLK_PERM_ALL;
	return;
	}

	if (!(role & BDRV_CHILD_FILTERED)) {
	/*
	* Target child
	*
	* Share write to target (child_file), to not interfere
	* with guest writes to its disk which may be in target backing chain.
	* Can't resize during a backup block job because we check the size
	* only upfront.
	*/
	*nshared = BLK_PERM_ALL & ~BLK_PERM_RESIZE;
	*nperm = BLK_PERM_WRITE;
	} else {
	/* Source child */
	bdrv_filter_default_perms(bs, c, child_class, role, reopen_queue,
	perm, shared, nperm, nshared);

	if (perm & BLK_PERM_WRITE) {
	nperm = nperm \| BLK_PERM_CONSISTENT_READ;
	}
	*nshared &= ~(BLK_PERM_WRITE \| BLK_PERM_RESIZE);
	}
	}

	BlockDriver bdrv_backup_top_filter = {
	.format_name = "backup-top",
	.instance_size = sizeof(BDRVBackupTopState),

	.bdrv_co_preadv = backup_top_co_preadv,
	.bdrv_co_pwritev = backup_top_co_pwritev,
	.bdrv_co_pwrite_zeroes = backup_top_co_pwrite_zeroes,
	.bdrv_co_pdiscard = backup_top_co_pdiscard,
	.bdrv_co_flush = backup_top_co_flush,

	.bdrv_co_block_status = bdrv_co_block_status_from_backing,

	.bdrv_refresh_filename = backup_top_refresh_filename,

	.bdrv_child_perm = backup_top_child_perm,

	.is_filter = true,
	};

	BlockDriverState bdrv_backup_top_append(BlockDriverState source,
	BlockDriverState *target,
	const char *filter_node_name,
	uint64_t cluster_size,
	BdrvRequestFlags write_flags,
	BlockCopyState **bcs,
	Error **errp)
	{
	Error *local_err = NULL;
	BDRVBackupTopState *state;
	BlockDriverState *top;
	bool appended = false;

	assert(source->total_sectors == target->total_sectors);

	top = bdrv_new_open_driver(&bdrv_backup_top_filter, filter_node_name,
	BDRV_O_RDWR, errp);
	if (!top) {
	return NULL;
	}

	state = top->opaque;
	top->total_sectors = source->total_sectors;
	top->supported_write_flags = BDRV_REQ_WRITE_UNCHANGED \|
	(BDRV_REQ_FUA & source->supported_write_flags);
	top->supported_zero_flags = BDRV_REQ_WRITE_UNCHANGED \|
	((BDRV_REQ_FUA \| BDRV_REQ_MAY_UNMAP \| BDRV_REQ_NO_FALLBACK) &
	source->supported_zero_flags);

	bdrv_ref(target);
	state->target = bdrv_attach_child(top, target, "target", &child_file, 0,
	errp);
	if (!state->target) {
	bdrv_unref(target);
	bdrv_unref(top);
	return NULL;
	}

	bdrv_drained_begin(source);

	bdrv_ref(top);
	bdrv_append(top, source, &local_err);
	if (local_err) {
	error_prepend(&local_err, "Cannot append backup-top filter: ");
	goto fail;
	}
	appended = true;

	/*
	* bdrv_append() finished successfully, now we can require permissions
	* we want.
	*/
	state->active = true;
	bdrv_child_refresh_perms(top, top->backing, &local_err);
	if (local_err) {
	error_prepend(&local_err,
	"Cannot set permissions for backup-top filter: ");
	goto fail;
	}

	state->cluster_size = cluster_size;
	state->bcs = block_copy_state_new(top->backing, state->target,
	cluster_size, write_flags, &local_err);
	if (local_err) {
	error_prepend(&local_err, "Cannot create block-copy-state: ");
	goto fail;
	}
	*bcs = state->bcs;

	bdrv_drained_end(source);

	return top;

	fail:
	if (appended) {
	state->active = false;
	bdrv_backup_top_drop(top);
	} else {
	bdrv_unref(top);
	}

	bdrv_drained_end(source);
	error_propagate(errp, local_err);

	return NULL;
	}

	void bdrv_backup_top_drop(BlockDriverState *bs)
	{
	BDRVBackupTopState *s = bs->opaque;

	bdrv_drained_begin(bs);

	block_copy_state_free(s->bcs);

	s->active = false;
	bdrv_child_refresh_perms(bs, bs->backing, &error_abort);
	bdrv_replace_node(bs, backing_bs(bs), &error_abort);
	bdrv_set_backing_hd(bs, NULL, &error_abort);

	bdrv_drained_end(bs);

	bdrv_unref(bs);
	}