Commit 7bc45dc1 authored by Max Reitz's avatar Max Reitz
Browse files

block/qcow2: Generalize preallocate() 



This patch adds two new parameters to the preallocate() function so we
will be able to use it not just for preallocating a new image but also
for preallocated image growth.

The offset parameter allows the caller to specify a virtual offset from
which to start preallocating. For newly created images this is always 0,
but for preallocating growth this will be the old image length.

The new_length parameter specifies the supposed new length of the image
(basically the "end offset" for preallocation). During image truncation,
bdrv_getlength() will return the old image length so we cannot rely on
its return value then.

Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
Reviewed-by: default avatarEric Blake <eblake@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170613202107.10125-10-mreitz@redhat.com
Signed-off-by: default avatarMax Reitz <mreitz@redhat.com>
parent 35d72602

block/qcow2.c

+12 −5
Original line number Diff line number Diff line
@@ -2476,17 +2476,24 @@ static int qcow2_set_up_encryption(BlockDriverState *bs, const char *encryptfmt, 
}





static int preallocate(BlockDriverState *bs)

/**

 * Preallocates metadata structures for data clusters between @offset (in the

 * guest disk) and @new_length (which is thus generally the new guest disk

 * size).

 *

 * Returns: 0 on success, -errno on failure.

 */

static int preallocate(BlockDriverState *bs,

                       uint64_t offset, uint64_t new_length)

{

    uint64_t bytes;

    uint64_t offset;

    uint64_t host_offset = 0;

    unsigned int cur_bytes;

    int ret;

    QCowL2Meta *meta;



    bytes = bdrv_getlength(bs);

    offset = 0;

    assert(offset <= new_length);

    bytes = new_length - offset;



    while (bytes) {

        cur_bytes = MIN(bytes, INT_MAX);
@@ -2830,7 +2837,7 @@ static int qcow2_create2(const char *filename, int64_t total_size, 
    if (prealloc != PREALLOC_MODE_OFF) {

        BDRVQcow2State *s = blk_bs(blk)->opaque;

        qemu_co_mutex_lock(&s->lock);

        ret = preallocate(blk_bs(blk));

        ret = preallocate(blk_bs(blk), 0, total_size);

        qemu_co_mutex_unlock(&s->lock);

        if (ret < 0) {

            error_setg_errno(errp, -ret, "Could not preallocate metadata");