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block/qcow2: Generalize preallocate()

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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: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170613202107.10125-10-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
This commit is contained in:
Max Reitz 2017-06-13 22:21:00 +02:00
parent 35d72602ec
commit 7bc45dc172
1 changed files with 12 additions and 5 deletions
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17
block/qcow2.c
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@ -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");