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qcow2: always operate caches in writeback mode

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Writethrough does not need special-casing anymore in the qcow2 caches.
The block layer adds flushes after every guest-initiated data write,
and these will also flush the qcow2 caches to the OS.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Paolo Bonzini 2012-06-06 00:04:55 +02:00 committed by Kevin Wolf
parent 7cdd481cdf
commit 6af4e9ead4
4 changed files with 5 additions and 44 deletions
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25
block/qcow2-cache.c
View File

@ -40,11 +40,9 @@ struct Qcow2Cache {
struct Qcow2Cache* depends;
int size;
bool depends_on_flush;
bool writethrough;
};
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables,
bool writethrough)
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables)
{
BDRVQcowState *s = bs->opaque;
Qcow2Cache *c;
@ -53,7 +51,6 @@ Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables,
c = g_malloc0(sizeof(*c));
c->size = num_tables;
c->entries = g_malloc0(sizeof(*c->entries) * num_tables);
c->writethrough = writethrough;
for (i = 0; i < c->size; i++) {
c->entries[i].table = qemu_blockalign(bs, s->cluster_size);
@ -307,12 +304,7 @@ found:
*table = NULL;
assert(c->entries[i].ref >= 0);
if (c->writethrough) {
return qcow2_cache_entry_flush(bs, c, i);
} else {
return 0;
}
return 0;
}
void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table)
@ -329,16 +321,3 @@ void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table)
found:
c->entries[i].dirty = true;
}
bool qcow2_cache_set_writethrough(BlockDriverState *bs, Qcow2Cache *c,
bool enable)
{
bool old = c->writethrough;
if (!old && enable) {
qcow2_cache_flush(bs, c);
}
c->writethrough = enable;
return old;
}

12
block/qcow2-refcount.c
View File

@ -726,13 +726,6 @@ int qcow2_update_snapshot_refcount(BlockDriverState *bs,
int64_t old_offset, old_l2_offset;
int i, j, l1_modified = 0, nb_csectors, refcount;
int ret;
bool old_l2_writethrough, old_refcount_writethrough;
/* Switch caches to writeback mode during update */
old_l2_writethrough =
qcow2_cache_set_writethrough(bs, s->l2_table_cache, false);
old_refcount_writethrough =
qcow2_cache_set_writethrough(bs, s->refcount_block_cache, false);
l2_table = NULL;
l1_table = NULL;
@ -856,11 +849,6 @@ fail:
qcow2_cache_put(bs, s->l2_table_cache, (void**) &l2_table);
}
/* Enable writethrough cache mode again */
qcow2_cache_set_writethrough(bs, s->l2_table_cache, old_l2_writethrough);
qcow2_cache_set_writethrough(bs, s->refcount_block_cache,
old_refcount_writethrough);
/* Update L1 only if it isn't deleted anyway (addend = -1) */
if (addend >= 0 && l1_modified) {
for(i = 0; i < l1_size; i++)

7
block/qcow2.c
View File

@ -220,7 +220,6 @@ static int qcow2_open(BlockDriverState *bs, int flags)
int len, i, ret = 0;
QCowHeader header;
uint64_t ext_end;
bool writethrough;
ret = bdrv_pread(bs->file, 0, &header, sizeof(header));
if (ret < 0) {
@ -367,10 +366,8 @@ static int qcow2_open(BlockDriverState *bs, int flags)
}
/* alloc L2 table/refcount block cache */
writethrough = ((flags & BDRV_O_CACHE_WB) == 0);
s->l2_table_cache = qcow2_cache_create(bs, L2_CACHE_SIZE, writethrough);
s->refcount_block_cache = qcow2_cache_create(bs, REFCOUNT_CACHE_SIZE,
writethrough);
s->l2_table_cache = qcow2_cache_create(bs, L2_CACHE_SIZE);
s->refcount_block_cache = qcow2_cache_create(bs, REFCOUNT_CACHE_SIZE);
s->cluster_cache = g_malloc(s->cluster_size);
/* one more sector for decompressed data alignment */

5
block/qcow2.h
View File

@ -297,11 +297,8 @@ void qcow2_free_snapshots(BlockDriverState *bs);
int qcow2_read_snapshots(BlockDriverState *bs);
/* qcow2-cache.c functions */
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables,
bool writethrough);
Qcow2Cache *qcow2_cache_create(BlockDriverState *bs, int num_tables);
int qcow2_cache_destroy(BlockDriverState* bs, Qcow2Cache *c);
bool qcow2_cache_set_writethrough(BlockDriverState *bs, Qcow2Cache *c,
bool enable);
void qcow2_cache_entry_mark_dirty(Qcow2Cache *c, void *table);
int qcow2_cache_flush(BlockDriverState *bs, Qcow2Cache *c);