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qcow2: Let vmstate call qcow2_co_preadv/pwrite directly 

We don't really want to go through the block layer in order to read from
or write to the vmstate in a qcow2 image. Doing so required a few ugly
hacks like saving and restoring the old image size (because writing to
vmstate offsets would increase the image size) or disabling the "reads
after EOF = zeroes" logic. When calling the right functions directly,
these hacks aren't necessary any more.

Note that .bdrv_vmstate_load/save() return 0 instead of the number of
bytes in case of success now.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Kevin Wolf 2016-06-01 17:07:24 +02:00
parent 1a8ae82217
commit 734a77584a
1 changed files with 4 additions and 20 deletions
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24
block/qcow2.c
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@ -2909,36 +2909,20 @@ static int qcow2_save_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t pos) int64_t pos)
{ {
BDRVQcow2State *s = bs->opaque; BDRVQcow2State *s = bs->opaque;
int64_t total_sectors = bs->total_sectors;
bool zero_beyond_eof = bs->zero_beyond_eof;
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE); BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_SAVE);
bs->zero_beyond_eof = false; return bs->drv->bdrv_co_pwritev(bs, qcow2_vm_state_offset(s) + pos,
ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov); qiov->size, qiov, 0);
bs->zero_beyond_eof = zero_beyond_eof;
/* bdrv_co_do_writev will have increased the total_sectors value to include
* the VM state - the VM state is however not an actual part of the block
* device, therefore, we need to restore the old value. */
bs->total_sectors = total_sectors;
return ret;
} }
static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov, static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
int64_t pos) int64_t pos)
{ {
BDRVQcow2State *s = bs->opaque; BDRVQcow2State *s = bs->opaque;
bool zero_beyond_eof = bs->zero_beyond_eof;
int ret;
BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD); BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD);
bs->zero_beyond_eof = false; return bs->drv->bdrv_co_preadv(bs, qcow2_vm_state_offset(s) + pos,
ret = bdrv_preadv(bs, qcow2_vm_state_offset(s) + pos, qiov); qiov->size, qiov, 0);
bs->zero_beyond_eof = zero_beyond_eof;
return ret;
} }
/* /*