block/qcow2-cache.c - qemu - Git at Google

 /*
  * L2/refcount table cache for the QCOW2 format
  *
  * Copyright (c) 2010 Kevin Wolf <kwolf@redhat.com>
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */

 #include "block/block_int.h"
 #include "qemu-common.h"
 #include "qcow2.h"
 #include "trace.h"

 typedef struct Qcow2CachedTable {
     int64_t  offset;
     bool     dirty;
     uint64_t lru_counter;
     int      ref;
 } Qcow2CachedTable;

 struct Qcow2Cache {
     Qcow2CachedTable       *entries;
     struct Qcow2Cache      *depends;
     int                     size;
     bool                    depends_on_flush;
     void                   *table_array;
     uint64_t                lru_counter;
 };

 static inline void *qcow2_cache_get_table_addr(BlockDriverState *bs,
                     Qcow2Cache *c, int table)
 {
     BDRVQcowState *s = bs->opaque;
     return (uint8_t *) c->table_array + (size_t) table * s->cluster_size;
 }

 static inline int qcow2_cache_get_table_idx(BlockDriverState *bs,
                   Qcow2Cache *c, void *table)
 {
     BDRVQcowState *s = bs->opaque;
     ptrdiff_t table_offset = (uint8_t *) table - (uint8_t *) c->table_array;
     int idx = table_offset / s->cluster_size;
     assert(idx >= 0 && idx < c->size && table_offset % s->cluster_size == 0);
     return idx;
 }

 Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables)
 {
     BDRVQcowState *s = bs->opaque;
     Qcow2Cache *c;

     c = g_new0(Qcow2Cache, 1);
     c->size = num_tables;
     c->entries = g_try_new0(Qcow2CachedTable, num_tables);
     c->table_array = qemu_try_blockalign(bs->file,
                                          (size_t) num_tables * s->cluster_size);

     if (!c->entries || !c->table_array) {
         qemu_vfree(c->table_array);
         g_free(c->entries);
         g_free(c);
         c = NULL;
     }

     return c;
 }

 int qcow2_cache_destroy(BlockDriverState *bs, Qcow2Cache *c)
 {
     int i;

     for (i = 0; i < c->size; i++) {
         assert(c->entries[i].ref == 0);
     }

     qemu_vfree(c->table_array);
     g_free(c->entries);
     g_free(c);

     return 0;
 }

 static int qcow2_cache_flush_dependency(BlockDriverState *bs, Qcow2Cache *c)
 {
     int ret;

     ret = qcow2_cache_flush(bs, c->depends);
     if (ret < 0) {
         return ret;
     }

     c->depends = NULL;
     c->depends_on_flush = false;

     return 0;
 }

 static int qcow2_cache_entry_flush(BlockDriverState *bs, Qcow2Cache *c, int i)
 {
     BDRVQcowState *s = bs->opaque;
     int ret = 0;

     if (!c->entries[i].dirty || !c->entries[i].offset) {
         return 0;
     }

     trace_qcow2_cache_entry_flush(qemu_coroutine_self(),
                                   c == s->l2_table_cache, i);

     if (c->depends) {
         ret = qcow2_cache_flush_dependency(bs, c);
     } else if (c->depends_on_flush) {
         ret = bdrv_flush(bs->file);
         if (ret >= 0) {
             c->depends_on_flush = false;
         }
     }

     if (ret < 0) {
         return ret;
     }

     if (c == s->refcount_block_cache) {
         ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_REFCOUNT_BLOCK,
                 c->entries[i].offset, s->cluster_size);
     } else if (c == s->l2_table_cache) {
         ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L2,
                 c->entries[i].offset, s->cluster_size);
     } else {
         ret = qcow2_pre_write_overlap_check(bs, 0,
                 c->entries[i].offset, s->cluster_size);
     }

     if (ret < 0) {
         return ret;
     }

     if (c == s->refcount_block_cache) {
         BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE_PART);
     } else if (c == s->l2_table_cache) {
         BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE);
     }

     ret = bdrv_pwrite(bs->file, c->entries[i].offset,
                       qcow2_cache_get_table_addr(bs, c, i), s->cluster_size);
     if (ret < 0) {
         return ret;
     }

     c->entries[i].dirty = false;

     return 0;
 }

 int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c)
 {
     BDRVQcowState *s = bs->opaque;
     int result = 0;
     int ret;
     int i;

     trace_qcow2_cache_flush(qemu_coroutine_self(), c == s->l2_table_cache);

     for (i = 0; i < c->size; i++) {
         ret = qcow2_cache_entry_flush(bs, c, i);
         if (ret < 0 && result != -ENOSPC) {
             result = ret;
         }
     }

     if (result == 0) {
         ret = bdrv_flush(bs->file);
         if (ret < 0) {
             result = ret;
         }
     }

     return result;
 }

 int qcow2_cache_set_dependency(BlockDriverState *bs, Qcow2Cache *c,
     Qcow2Cache *dependency)
 {
     int ret;

     if (dependency->depends) {
         ret = qcow2_cache_flush_dependency(bs, dependency);
         if (ret < 0) {
             return ret;
         }
     }

     if (c->depends && (c->depends != dependency)) {
         ret = qcow2_cache_flush_dependency(bs, c);
         if (ret < 0) {
             return ret;
         }
     }

     c->depends = dependency;
     return 0;
 }

 void qcow2_cache_depends_on_flush(Qcow2Cache *c)
 {
     c->depends_on_flush = true;
 }

 int qcow2_cache_empty(BlockDriverState *bs, Qcow2Cache *c)
 {
     int ret, i;

     ret = qcow2_cache_flush(bs, c);
     if (ret < 0) {
         return ret;
     }

     for (i = 0; i < c->size; i++) {
         assert(c->entries[i].ref == 0);
         c->entries[i].offset = 0;
         c->entries[i].lru_counter = 0;
     }

     c->lru_counter = 0;

     return 0;
 }

 static int qcow2_cache_do_get(BlockDriverState *bs, Qcow2Cache *c,
     uint64_t offset, void **table, bool read_from_disk)
 {
     BDRVQcowState *s = bs->opaque;
     int i;
     int ret;
     int lookup_index;
     uint64_t min_lru_counter = UINT64_MAX;
     int min_lru_index = -1;

     trace_qcow2_cache_get(qemu_coroutine_self(), c == s->l2_table_cache,
                           offset, read_from_disk);

     /* Check if the table is already cached */
     i = lookup_index = (offset / s->cluster_size * 4) % c->size;
     do {
         const Qcow2CachedTable *t = &c->entries[i];
         if (t->offset == offset) {
             goto found;
         }
         if (t->ref == 0 && t->lru_counter < min_lru_counter) {
             min_lru_counter = t->lru_counter;
             min_lru_index = i;
         }
         if (++i == c->size) {
             i = 0;
         }
     } while (i != lookup_index);

     if (min_lru_index == -1) {
         /* This can't happen in current synchronous code, but leave the check
          * here as a reminder for whoever starts using AIO with the cache */
         abort();
     }

     /* Cache miss: write a table back and replace it */
     i = min_lru_index;
     trace_qcow2_cache_get_replace_entry(qemu_coroutine_self(),
                                         c == s->l2_table_cache, i);

     ret = qcow2_cache_entry_flush(bs, c, i);
     if (ret < 0) {
         return ret;
     }

     trace_qcow2_cache_get_read(qemu_coroutine_self(),
                                c == s->l2_table_cache, i);
     c->entries[i].offset = 0;
     if (read_from_disk) {
         if (c == s->l2_table_cache) {
             BLKDBG_EVENT(bs->file, BLKDBG_L2_LOAD);
         }

         ret = bdrv_pread(bs->file, offset, qcow2_cache_get_table_addr(bs, c, i),
                          s->cluster_size);
         if (ret < 0) {
             return ret;
         }
     }

     c->entries[i].offset = offset;

     /* And return the right table */
 found:
     c->entries[i].ref++;
     *table = qcow2_cache_get_table_addr(bs, c, i);

     trace_qcow2_cache_get_done(qemu_coroutine_self(),
                                c == s->l2_table_cache, i);

     return 0;
 }

 int qcow2_cache_get(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
     void **table)
 {
     return qcow2_cache_do_get(bs, c, offset, table, true);
 }

 int qcow2_cache_get_empty(BlockDriverState *bs, Qcow2Cache *c, uint64_t offset,
     void **table)
 {
     return qcow2_cache_do_get(bs, c, offset, table, false);
 }

 void qcow2_cache_put(BlockDriverState *bs, Qcow2Cache *c, void **table)
 {
     int i = qcow2_cache_get_table_idx(bs, c, *table);

     c->entries[i].ref--;
     *table = NULL;

     if (c->entries[i].ref == 0) {
         c->entries[i].lru_counter = ++c->lru_counter;
     }

     assert(c->entries[i].ref >= 0);
 }

 void qcow2_cache_entry_mark_dirty(BlockDriverState *bs, Qcow2Cache *c,
      void *table)
 {
     int i = qcow2_cache_get_table_idx(bs, c, table);
     assert(c->entries[i].offset != 0);
     c->entries[i].dirty = true;
 }
	/*
	* L2/refcount table cache for the QCOW2 format
	*
	* Copyright (c) 2010 Kevin Wolf <kwolf@redhat.com>
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to deal
	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/

	#include "block/block_int.h"
	#include "qemu-common.h"
	#include "qcow2.h"
	#include "trace.h"

	typedef struct Qcow2CachedTable {
	int64_t offset;
	bool dirty;
	uint64_t lru_counter;
	int ref;
	} Qcow2CachedTable;

	struct Qcow2Cache {
	Qcow2CachedTable *entries;
	struct Qcow2Cache *depends;
	int size;
	bool depends_on_flush;
	void *table_array;
	uint64_t lru_counter;
	};

	static inline void qcow2_cache_get_table_addr(BlockDriverState bs,
	Qcow2Cache *c, int table)
	{
	BDRVQcowState *s = bs->opaque;
	return (uint8_t ) c->table_array + (size_t) table s->cluster_size;
	}

	static inline int qcow2_cache_get_table_idx(BlockDriverState *bs,
	Qcow2Cache c, void table)
	{
	BDRVQcowState *s = bs->opaque;
	ptrdiff_t table_offset = (uint8_t ) table - (uint8_t ) c->table_array;
	int idx = table_offset / s->cluster_size;
	assert(idx >= 0 && idx < c->size && table_offset % s->cluster_size == 0);
	return idx;
	}

	Qcow2Cache qcow2_cache_create(BlockDriverState bs, int num_tables)
	{
	BDRVQcowState *s = bs->opaque;
	Qcow2Cache *c;

	c = g_new0(Qcow2Cache, 1);
	c->size = num_tables;
	c->entries = g_try_new0(Qcow2CachedTable, num_tables);
	c->table_array = qemu_try_blockalign(bs->file,
	(size_t) num_tables * s->cluster_size);

	if (!c->entries \|\| !c->table_array) {
	qemu_vfree(c->table_array);
	g_free(c->entries);
	g_free(c);
	c = NULL;
	}

	return c;
	}

	int qcow2_cache_destroy(BlockDriverState bs, Qcow2Cache c)
	{
	int i;

	for (i = 0; i < c->size; i++) {
	assert(c->entries[i].ref == 0);
	}

	qemu_vfree(c->table_array);
	g_free(c->entries);
	g_free(c);

	return 0;
	}

	static int qcow2_cache_flush_dependency(BlockDriverState bs, Qcow2Cache c)
	{
	int ret;

	ret = qcow2_cache_flush(bs, c->depends);
	if (ret < 0) {
	return ret;
	}

	c->depends = NULL;
	c->depends_on_flush = false;

	return 0;
	}

	static int qcow2_cache_entry_flush(BlockDriverState bs, Qcow2Cache c, int i)
	{
	BDRVQcowState *s = bs->opaque;
	int ret = 0;

	if (!c->entries[i].dirty \|\| !c->entries[i].offset) {
	return 0;
	}

	trace_qcow2_cache_entry_flush(qemu_coroutine_self(),
	c == s->l2_table_cache, i);

	if (c->depends) {
	ret = qcow2_cache_flush_dependency(bs, c);
	} else if (c->depends_on_flush) {
	ret = bdrv_flush(bs->file);
	if (ret >= 0) {
	c->depends_on_flush = false;
	}
	}

	if (ret < 0) {
	return ret;
	}

	if (c == s->refcount_block_cache) {
	ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_REFCOUNT_BLOCK,
	c->entries[i].offset, s->cluster_size);
	} else if (c == s->l2_table_cache) {
	ret = qcow2_pre_write_overlap_check(bs, QCOW2_OL_ACTIVE_L2,
	c->entries[i].offset, s->cluster_size);
	} else {
	ret = qcow2_pre_write_overlap_check(bs, 0,
	c->entries[i].offset, s->cluster_size);
	}

	if (ret < 0) {
	return ret;
	}

	if (c == s->refcount_block_cache) {
	BLKDBG_EVENT(bs->file, BLKDBG_REFBLOCK_UPDATE_PART);
	} else if (c == s->l2_table_cache) {
	BLKDBG_EVENT(bs->file, BLKDBG_L2_UPDATE);
	}

	ret = bdrv_pwrite(bs->file, c->entries[i].offset,
	qcow2_cache_get_table_addr(bs, c, i), s->cluster_size);
	if (ret < 0) {
	return ret;
	}

	c->entries[i].dirty = false;

	return 0;
	}

	int qcow2_cache_flush(BlockDriverState bs, Qcow2Cache c)
	{
	BDRVQcowState *s = bs->opaque;
	int result = 0;
	int ret;
	int i;

	trace_qcow2_cache_flush(qemu_coroutine_self(), c == s->l2_table_cache);

	for (i = 0; i < c->size; i++) {
	ret = qcow2_cache_entry_flush(bs, c, i);
	if (ret < 0 && result != -ENOSPC) {
	result = ret;
	}
	}

	if (result == 0) {
	ret = bdrv_flush(bs->file);
	if (ret < 0) {
	result = ret;
	}
	}

	return result;
	}

	int qcow2_cache_set_dependency(BlockDriverState bs, Qcow2Cache c,
	Qcow2Cache *dependency)
	{
	int ret;

	if (dependency->depends) {
	ret = qcow2_cache_flush_dependency(bs, dependency);
	if (ret < 0) {
	return ret;
	}
	}

	if (c->depends && (c->depends != dependency)) {
	ret = qcow2_cache_flush_dependency(bs, c);
	if (ret < 0) {
	return ret;
	}
	}

	c->depends = dependency;
	return 0;
	}

	void qcow2_cache_depends_on_flush(Qcow2Cache *c)
	{
	c->depends_on_flush = true;
	}

	int qcow2_cache_empty(BlockDriverState bs, Qcow2Cache c)
	{
	int ret, i;

	ret = qcow2_cache_flush(bs, c);
	if (ret < 0) {
	return ret;
	}

	for (i = 0; i < c->size; i++) {
	assert(c->entries[i].ref == 0);
	c->entries[i].offset = 0;
	c->entries[i].lru_counter = 0;
	}

	c->lru_counter = 0;

	return 0;
	}

	static int qcow2_cache_do_get(BlockDriverState bs, Qcow2Cache c,
	uint64_t offset, void **table, bool read_from_disk)
	{
	BDRVQcowState *s = bs->opaque;
	int i;
	int ret;
	int lookup_index;
	uint64_t min_lru_counter = UINT64_MAX;
	int min_lru_index = -1;

	trace_qcow2_cache_get(qemu_coroutine_self(), c == s->l2_table_cache,
	offset, read_from_disk);

	/* Check if the table is already cached */
	i = lookup_index = (offset / s->cluster_size * 4) % c->size;
	do {
	const Qcow2CachedTable *t = &c->entries[i];
	if (t->offset == offset) {
	goto found;
	}
	if (t->ref == 0 && t->lru_counter < min_lru_counter) {
	min_lru_counter = t->lru_counter;
	min_lru_index = i;
	}
	if (++i == c->size) {
	i = 0;
	}
	} while (i != lookup_index);

	if (min_lru_index == -1) {
	/* This can't happen in current synchronous code, but leave the check
	* here as a reminder for whoever starts using AIO with the cache */
	abort();
	}

	/* Cache miss: write a table back and replace it */
	i = min_lru_index;
	trace_qcow2_cache_get_replace_entry(qemu_coroutine_self(),
	c == s->l2_table_cache, i);

	ret = qcow2_cache_entry_flush(bs, c, i);
	if (ret < 0) {
	return ret;
	}

	trace_qcow2_cache_get_read(qemu_coroutine_self(),
	c == s->l2_table_cache, i);
	c->entries[i].offset = 0;
	if (read_from_disk) {
	if (c == s->l2_table_cache) {
	BLKDBG_EVENT(bs->file, BLKDBG_L2_LOAD);
	}

	ret = bdrv_pread(bs->file, offset, qcow2_cache_get_table_addr(bs, c, i),
	s->cluster_size);
	if (ret < 0) {
	return ret;
	}
	}

	c->entries[i].offset = offset;

	/* And return the right table */
	found:
	c->entries[i].ref++;
	*table = qcow2_cache_get_table_addr(bs, c, i);

	trace_qcow2_cache_get_done(qemu_coroutine_self(),
	c == s->l2_table_cache, i);

	return 0;
	}

	int qcow2_cache_get(BlockDriverState bs, Qcow2Cache c, uint64_t offset,
	void **table)
	{
	return qcow2_cache_do_get(bs, c, offset, table, true);
	}

	int qcow2_cache_get_empty(BlockDriverState bs, Qcow2Cache c, uint64_t offset,
	void **table)
	{
	return qcow2_cache_do_get(bs, c, offset, table, false);
	}

	void qcow2_cache_put(BlockDriverState bs, Qcow2Cache c, void **table)
	{
	int i = qcow2_cache_get_table_idx(bs, c, *table);

	c->entries[i].ref--;
	*table = NULL;

	if (c->entries[i].ref == 0) {
	c->entries[i].lru_counter = ++c->lru_counter;
	}

	assert(c->entries[i].ref >= 0);
	}

	void qcow2_cache_entry_mark_dirty(BlockDriverState bs, Qcow2Cache c,
	void *table)
	{
	int i = qcow2_cache_get_table_idx(bs, c, table);
	assert(c->entries[i].offset != 0);
	c->entries[i].dirty = true;
	}