Commit 6af4e9ea authored by Paolo Bonzini's avatar Paolo Bonzini Committed by Kevin Wolf
Browse files

qcow2: always operate caches in writeback mode 



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: default avatarPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 7cdd481c

block/qcow2-cache.c

+2 −23
Original line number Diff line number Diff line
@@ -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);
@@ -307,13 +304,8 @@ found: 
    *table = NULL;



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



    if (c->writethrough) {

        return qcow2_cache_entry_flush(bs, c, i);

    } else {

    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;

}

block/qcow2-refcount.c

+0 −12
Original line number Diff line number Diff line
@@ -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++)

block/qcow2.c

+2 −5
Original line number Diff line number Diff line
@@ -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 */

block/qcow2.h

+1 −4
Original line number Diff line number Diff line
@@ -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);