block/stream.c - third_party/qemu - Git at Google

 /*
  * Image streaming
  *
  * Copyright IBM, Corp. 2011
  *
  * Authors:
  *  Stefan Hajnoczi   <stefanha@linux.vnet.ibm.com>
  *
  * This work is licensed under the terms of the GNU LGPL, version 2 or later.
  * See the COPYING.LIB file in the top-level directory.
  *
  */

 #include "qemu/osdep.h"
 #include "trace.h"
 #include "block/block_int.h"
 #include "block/blockjob_int.h"
 #include "qapi/error.h"
 #include "qapi/qmp/qerror.h"
 #include "qemu/ratelimit.h"
 #include "sysemu/block-backend.h"

 enum {
     /*
      * Maximum chunk size to feed to copy-on-read.  This should be
      * large enough to process multiple clusters in a single call, so
      * that populating contiguous regions of the image is efficient.
      */
     STREAM_CHUNK = 512 * 1024, /* in bytes */
 };

 typedef struct StreamBlockJob {
     BlockJob common;
     BlockDriverState *bottom;
     BlockdevOnError on_error;
     char *backing_file_str;
     bool bs_read_only;
     bool chain_frozen;
 } StreamBlockJob;

 static int coroutine_fn stream_populate(BlockBackend *blk,
                                         int64_t offset, uint64_t bytes)
 {
     assert(bytes < SIZE_MAX);

     return blk_co_preadv(blk, offset, bytes, NULL,
                          BDRV_REQ_COPY_ON_READ | BDRV_REQ_PREFETCH);
 }

 static void stream_abort(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);

     if (s->chain_frozen) {
         BlockJob *bjob = &s->common;
         bdrv_unfreeze_backing_chain(blk_bs(bjob->blk), s->bottom);
     }
 }

 static int stream_prepare(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
     BlockJob *bjob = &s->common;
     BlockDriverState *bs = blk_bs(bjob->blk);
     BlockDriverState *base = backing_bs(s->bottom);
     Error *local_err = NULL;
     int ret = 0;

     bdrv_unfreeze_backing_chain(bs, s->bottom);
     s->chain_frozen = false;

     if (bs->backing) {
         const char *base_id = NULL, *base_fmt = NULL;
         if (base) {
             base_id = s->backing_file_str;
             if (base->drv) {
                 base_fmt = base->drv->format_name;
             }
         }
         bdrv_set_backing_hd(bs, base, &local_err);
         ret = bdrv_change_backing_file(bs, base_id, base_fmt);
         if (local_err) {
             error_report_err(local_err);
             return -EPERM;
         }
     }

     return ret;
 }

 static void stream_clean(Job *job)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
     BlockJob *bjob = &s->common;
     BlockDriverState *bs = blk_bs(bjob->blk);

     /* Reopen the image back in read-only mode if necessary */
     if (s->bs_read_only) {
         /* Give up write permissions before making it read-only */
         blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
         bdrv_reopen_set_read_only(bs, true, NULL);
     }

     g_free(s->backing_file_str);
 }

 static int coroutine_fn stream_run(Job *job, Error **errp)
 {
     StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
     BlockBackend *blk = s->common.blk;
     BlockDriverState *bs = blk_bs(blk);
     bool enable_cor = !backing_bs(s->bottom);
     int64_t len;
     int64_t offset = 0;
     uint64_t delay_ns = 0;
     int error = 0;
     int64_t n = 0; /* bytes */

     if (bs == s->bottom) {
         /* Nothing to stream */
         return 0;
     }

     len = bdrv_getlength(bs);
     if (len < 0) {
         return len;
     }
     job_progress_set_remaining(&s->common.job, len);

     /* Turn on copy-on-read for the whole block device so that guest read
      * requests help us make progress.  Only do this when copying the entire
      * backing chain since the copy-on-read operation does not take base into
      * account.
      */
     if (enable_cor) {
         bdrv_enable_copy_on_read(bs);
     }

     for ( ; offset < len; offset += n) {
         bool copy;
         int ret;

         /* Note that even when no rate limit is applied we need to yield
          * with no pending I/O here so that bdrv_drain_all() returns.
          */
         job_sleep_ns(&s->common.job, delay_ns);
         if (job_is_cancelled(&s->common.job)) {
             break;
         }

         copy = false;

         ret = bdrv_is_allocated(bs, offset, STREAM_CHUNK, &n);
         if (ret == 1) {
             /* Allocated in the top, no need to copy.  */
         } else if (ret >= 0) {
             /* Copy if allocated in the intermediate images.  Limit to the
              * known-unallocated area [offset, offset+n*BDRV_SECTOR_SIZE).  */
             ret = bdrv_is_allocated_above(backing_bs(bs), s->bottom, true,
                                           offset, n, &n);
             /* Finish early if end of backing file has been reached */
             if (ret == 0 && n == 0) {
                 n = len - offset;
             }

             copy = (ret == 1);
         }
         trace_stream_one_iteration(s, offset, n, ret);
         if (copy) {
             ret = stream_populate(blk, offset, n);
         }
         if (ret < 0) {
             BlockErrorAction action =
                 block_job_error_action(&s->common, s->on_error, true, -ret);
             if (action == BLOCK_ERROR_ACTION_STOP) {
                 n = 0;
                 continue;
             }
             if (error == 0) {
                 error = ret;
             }
             if (action == BLOCK_ERROR_ACTION_REPORT) {
                 break;
             }
         }

         /* Publish progress */
         job_progress_update(&s->common.job, n);
         if (copy) {
             delay_ns = block_job_ratelimit_get_delay(&s->common, n);
         } else {
             delay_ns = 0;
         }
     }

     if (enable_cor) {
         bdrv_disable_copy_on_read(bs);
     }

     /* Do not remove the backing file if an error was there but ignored. */
     return error;
 }

 static const BlockJobDriver stream_job_driver = {
     .job_driver = {
         .instance_size = sizeof(StreamBlockJob),
         .job_type      = JOB_TYPE_STREAM,
         .free          = block_job_free,
         .run           = stream_run,
         .prepare       = stream_prepare,
         .abort         = stream_abort,
         .clean         = stream_clean,
         .user_resume   = block_job_user_resume,
     },
 };

 void stream_start(const char *job_id, BlockDriverState *bs,
                   BlockDriverState *base, const char *backing_file_str,
                   int creation_flags, int64_t speed,
                   BlockdevOnError on_error, Error **errp)
 {
     StreamBlockJob *s;
     BlockDriverState *iter;
     bool bs_read_only;
     int basic_flags = BLK_PERM_CONSISTENT_READ | BLK_PERM_WRITE_UNCHANGED;
     BlockDriverState *bottom = bdrv_find_overlay(bs, base);

     if (bdrv_freeze_backing_chain(bs, bottom, errp) < 0) {
         return;
     }

     /* Make sure that the image is opened in read-write mode */
     bs_read_only = bdrv_is_read_only(bs);
     if (bs_read_only) {
         if (bdrv_reopen_set_read_only(bs, false, errp) != 0) {
             bs_read_only = false;
             goto fail;
         }
     }

     /* Prevent concurrent jobs trying to modify the graph structure here, we
      * already have our own plans. Also don't allow resize as the image size is
      * queried only at the job start and then cached. */
     s = block_job_create(job_id, &stream_job_driver, NULL, bs,
                          basic_flags | BLK_PERM_GRAPH_MOD,
                          basic_flags | BLK_PERM_WRITE,
                          speed, creation_flags, NULL, NULL, errp);
     if (!s) {
         goto fail;
     }

     /* Block all intermediate nodes between bs and base, because they will
      * disappear from the chain after this operation. The streaming job reads
      * every block only once, assuming that it doesn't change, so forbid writes
      * and resizes. Reassign the base node pointer because the backing BS of the
      * bottom node might change after the call to bdrv_reopen_set_read_only()
      * due to parallel block jobs running.
      */
     base = backing_bs(bottom);
     for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) {
         block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
                            basic_flags, &error_abort);
     }

     s->bottom = bottom;
     s->backing_file_str = g_strdup(backing_file_str);
     s->bs_read_only = bs_read_only;
     s->chain_frozen = true;

     s->on_error = on_error;
     trace_stream_start(bs, base, s);
     job_start(&s->common.job);
     return;

 fail:
     if (bs_read_only) {
         bdrv_reopen_set_read_only(bs, true, NULL);
     }
     bdrv_unfreeze_backing_chain(bs, bottom);
 }
	/*
	* Image streaming
	*
	* Copyright IBM, Corp. 2011
	*
	* Authors:
	* Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
	*
	* This work is licensed under the terms of the GNU LGPL, version 2 or later.
	* See the COPYING.LIB file in the top-level directory.
	*
	*/

	#include "qemu/osdep.h"
	#include "trace.h"
	#include "block/block_int.h"
	#include "block/blockjob_int.h"
	#include "qapi/error.h"
	#include "qapi/qmp/qerror.h"
	#include "qemu/ratelimit.h"
	#include "sysemu/block-backend.h"

	enum {
	/*
	* Maximum chunk size to feed to copy-on-read. This should be
	* large enough to process multiple clusters in a single call, so
	* that populating contiguous regions of the image is efficient.
	*/
	STREAM_CHUNK = 512 * 1024, /* in bytes */
	};

	typedef struct StreamBlockJob {
	BlockJob common;
	BlockDriverState *bottom;
	BlockdevOnError on_error;
	char *backing_file_str;
	bool bs_read_only;
	bool chain_frozen;
	} StreamBlockJob;

	static int coroutine_fn stream_populate(BlockBackend *blk,
	int64_t offset, uint64_t bytes)
	{
	assert(bytes < SIZE_MAX);

	return blk_co_preadv(blk, offset, bytes, NULL,
	BDRV_REQ_COPY_ON_READ \| BDRV_REQ_PREFETCH);
	}

	static void stream_abort(Job *job)
	{
	StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);

	if (s->chain_frozen) {
	BlockJob *bjob = &s->common;
	bdrv_unfreeze_backing_chain(blk_bs(bjob->blk), s->bottom);
	}
	}

	static int stream_prepare(Job *job)
	{
	StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
	BlockJob *bjob = &s->common;
	BlockDriverState *bs = blk_bs(bjob->blk);
	BlockDriverState *base = backing_bs(s->bottom);
	Error *local_err = NULL;
	int ret = 0;

	bdrv_unfreeze_backing_chain(bs, s->bottom);
	s->chain_frozen = false;

	if (bs->backing) {
	const char base_id = NULL, base_fmt = NULL;
	if (base) {
	base_id = s->backing_file_str;
	if (base->drv) {
	base_fmt = base->drv->format_name;
	}
	}
	bdrv_set_backing_hd(bs, base, &local_err);
	ret = bdrv_change_backing_file(bs, base_id, base_fmt);
	if (local_err) {
	error_report_err(local_err);
	return -EPERM;
	}
	}

	return ret;
	}

	static void stream_clean(Job *job)
	{
	StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
	BlockJob *bjob = &s->common;
	BlockDriverState *bs = blk_bs(bjob->blk);

	/* Reopen the image back in read-only mode if necessary */
	if (s->bs_read_only) {
	/* Give up write permissions before making it read-only */
	blk_set_perm(bjob->blk, 0, BLK_PERM_ALL, &error_abort);
	bdrv_reopen_set_read_only(bs, true, NULL);
	}

	g_free(s->backing_file_str);
	}

	static int coroutine_fn stream_run(Job job, Error *errp)
	{
	StreamBlockJob *s = container_of(job, StreamBlockJob, common.job);
	BlockBackend *blk = s->common.blk;
	BlockDriverState *bs = blk_bs(blk);
	bool enable_cor = !backing_bs(s->bottom);
	int64_t len;
	int64_t offset = 0;
	uint64_t delay_ns = 0;
	int error = 0;
	int64_t n = 0; /* bytes */

	if (bs == s->bottom) {
	/* Nothing to stream */
	return 0;
	}

	len = bdrv_getlength(bs);
	if (len < 0) {
	return len;
	}
	job_progress_set_remaining(&s->common.job, len);

	/* Turn on copy-on-read for the whole block device so that guest read
	* requests help us make progress. Only do this when copying the entire
	* backing chain since the copy-on-read operation does not take base into
	* account.
	*/
	if (enable_cor) {
	bdrv_enable_copy_on_read(bs);
	}

	for ( ; offset < len; offset += n) {
	bool copy;
	int ret;

	/* Note that even when no rate limit is applied we need to yield
	* with no pending I/O here so that bdrv_drain_all() returns.
	*/
	job_sleep_ns(&s->common.job, delay_ns);
	if (job_is_cancelled(&s->common.job)) {
	break;
	}

	copy = false;

	ret = bdrv_is_allocated(bs, offset, STREAM_CHUNK, &n);
	if (ret == 1) {
	/* Allocated in the top, no need to copy. */
	} else if (ret >= 0) {
	/* Copy if allocated in the intermediate images. Limit to the
	* known-unallocated area [offset, offset+nBDRV_SECTOR_SIZE). /
	ret = bdrv_is_allocated_above(backing_bs(bs), s->bottom, true,
	offset, n, &n);
	/* Finish early if end of backing file has been reached */
	if (ret == 0 && n == 0) {
	n = len - offset;
	}

	copy = (ret == 1);
	}
	trace_stream_one_iteration(s, offset, n, ret);
	if (copy) {
	ret = stream_populate(blk, offset, n);
	}
	if (ret < 0) {
	BlockErrorAction action =
	block_job_error_action(&s->common, s->on_error, true, -ret);
	if (action == BLOCK_ERROR_ACTION_STOP) {
	n = 0;
	continue;
	}
	if (error == 0) {
	error = ret;
	}
	if (action == BLOCK_ERROR_ACTION_REPORT) {
	break;
	}
	}

	/* Publish progress */
	job_progress_update(&s->common.job, n);
	if (copy) {
	delay_ns = block_job_ratelimit_get_delay(&s->common, n);
	} else {
	delay_ns = 0;
	}
	}

	if (enable_cor) {
	bdrv_disable_copy_on_read(bs);
	}

	/* Do not remove the backing file if an error was there but ignored. */
	return error;
	}

	static const BlockJobDriver stream_job_driver = {
	.job_driver = {
	.instance_size = sizeof(StreamBlockJob),
	.job_type = JOB_TYPE_STREAM,
	.free = block_job_free,
	.run = stream_run,
	.prepare = stream_prepare,
	.abort = stream_abort,
	.clean = stream_clean,
	.user_resume = block_job_user_resume,
	},
	};

	void stream_start(const char job_id, BlockDriverState bs,
	BlockDriverState base, const char backing_file_str,
	int creation_flags, int64_t speed,
	BlockdevOnError on_error, Error **errp)
	{
	StreamBlockJob *s;
	BlockDriverState *iter;
	bool bs_read_only;
	int basic_flags = BLK_PERM_CONSISTENT_READ \| BLK_PERM_WRITE_UNCHANGED;
	BlockDriverState *bottom = bdrv_find_overlay(bs, base);

	if (bdrv_freeze_backing_chain(bs, bottom, errp) < 0) {
	return;
	}

	/* Make sure that the image is opened in read-write mode */
	bs_read_only = bdrv_is_read_only(bs);
	if (bs_read_only) {
	if (bdrv_reopen_set_read_only(bs, false, errp) != 0) {
	bs_read_only = false;
	goto fail;
	}
	}

	/* Prevent concurrent jobs trying to modify the graph structure here, we
	* already have our own plans. Also don't allow resize as the image size is
	* queried only at the job start and then cached. */
	s = block_job_create(job_id, &stream_job_driver, NULL, bs,
	basic_flags \| BLK_PERM_GRAPH_MOD,
	basic_flags \| BLK_PERM_WRITE,
	speed, creation_flags, NULL, NULL, errp);
	if (!s) {
	goto fail;
	}

	/* Block all intermediate nodes between bs and base, because they will
	* disappear from the chain after this operation. The streaming job reads
	* every block only once, assuming that it doesn't change, so forbid writes
	* and resizes. Reassign the base node pointer because the backing BS of the
	* bottom node might change after the call to bdrv_reopen_set_read_only()
	* due to parallel block jobs running.
	*/
	base = backing_bs(bottom);
	for (iter = backing_bs(bs); iter && iter != base; iter = backing_bs(iter)) {
	block_job_add_bdrv(&s->common, "intermediate node", iter, 0,
	basic_flags, &error_abort);
	}

	s->bottom = bottom;
	s->backing_file_str = g_strdup(backing_file_str);
	s->bs_read_only = bs_read_only;
	s->chain_frozen = true;

	s->on_error = on_error;
	trace_stream_start(bs, base, s);
	job_start(&s->common.job);
	return;

	fail:
	if (bs_read_only) {
	bdrv_reopen_set_read_only(bs, true, NULL);
	}
	bdrv_unfreeze_backing_chain(bs, bottom);
	}