Commit 67af674e authored by Kevin Wolf's avatar Kevin Wolf Committed by Stefan Hajnoczi
Browse files

qcow2: Options to enable discard for freed clusters 



Deleted snapshots are discarded in the image file by default, discard
requests take their default from the -drive discard=... option and other
places that free clusters must always be enabled explicitly.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Signed-off-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 6cfcb9b8

block/qcow2-refcount.c

+5 −0
Original line number Diff line number Diff line
@@ -488,6 +488,11 @@ static int QEMU_WARN_UNUSED_RESULT update_refcount(BlockDriverState *bs, 
            s->free_cluster_index = cluster_index;

        }

        refcount_block[block_index] = cpu_to_be16(refcount);

        if (refcount == 0 && s->discard_passthrough[type]) {

            /* Try discarding, ignore errors */

            /* FIXME Doing this cluster by cluster will be painfully slow */

            bdrv_discard(bs->file, cluster_offset, 1);

        }

    }



    ret = 0;

block/qcow2.c

+26 −0
Original line number Diff line number Diff line
@@ -295,6 +295,22 @@ static QemuOptsList qcow2_runtime_opts = { 
            .type = QEMU_OPT_BOOL,

            .help = "Postpone refcount updates",

        },

        {

            .name = QCOW2_OPT_DISCARD_REQUEST,

            .type = QEMU_OPT_BOOL,

            .help = "Pass guest discard requests to the layer below",

        },

        {

            .name = QCOW2_OPT_DISCARD_SNAPSHOT,

            .type = QEMU_OPT_BOOL,

            .help = "Generate discard requests when snapshot related space "

                    "is freed",

        },

        {

            .name = QCOW2_OPT_DISCARD_OTHER,

            .type = QEMU_OPT_BOOL,

            .help = "Generate discard requests when other clusters are freed",

        },

        { /* end of list */ }

    },

};
@@ -532,6 +548,16 @@ static int qcow2_open(BlockDriverState *bs, QDict *options, int flags) 
    s->use_lazy_refcounts = qemu_opt_get_bool(opts, QCOW2_OPT_LAZY_REFCOUNTS,

        (s->compatible_features & QCOW2_COMPAT_LAZY_REFCOUNTS));



    s->discard_passthrough[QCOW2_DISCARD_NEVER] = false;

    s->discard_passthrough[QCOW2_DISCARD_ALWAYS] = true;

    s->discard_passthrough[QCOW2_DISCARD_REQUEST] =

        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_REQUEST,

                          flags & BDRV_O_UNMAP);

    s->discard_passthrough[QCOW2_DISCARD_SNAPSHOT] =

        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_SNAPSHOT, true);

    s->discard_passthrough[QCOW2_DISCARD_OTHER] =

        qemu_opt_get_bool(opts, QCOW2_OPT_DISCARD_OTHER, false);



    qemu_opts_del(opts);



    if (s->use_lazy_refcounts && s->qcow_version < 3) {

block/qcow2.h

+5 −0
Original line number Diff line number Diff line
@@ -60,6 +60,9 @@ 




#define QCOW2_OPT_LAZY_REFCOUNTS "lazy_refcounts"

#define QCOW2_OPT_DISCARD_REQUEST "pass_discard_request"

#define QCOW2_OPT_DISCARD_SNAPSHOT "pass_discard_snapshot"

#define QCOW2_OPT_DISCARD_OTHER "pass_discard_other"



typedef struct QCowHeader {

    uint32_t magic;
@@ -187,6 +190,8 @@ typedef struct BDRVQcowState { 
    int qcow_version;

    bool use_lazy_refcounts;



    bool discard_passthrough[QCOW2_DISCARD_MAX];



    uint64_t incompatible_features;

    uint64_t compatible_features;

    uint64_t autoclear_features;