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Re: [Qemu-devel] [PATCH 5/6] qcow2: Let vmstate call qcow2_co_preadv/pwr
From: |
Eric Blake |
Subject: |
Re: [Qemu-devel] [PATCH 5/6] qcow2: Let vmstate call qcow2_co_preadv/pwrite directly |
Date: |
Fri, 10 Jun 2016 16:39:29 -0600 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 |
On 06/10/2016 10:05 AM, Kevin Wolf wrote:
> 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 <address@hidden>
> ---
> block/qcow2.c | 24 ++++--------------------
> 1 file changed, 4 insertions(+), 20 deletions(-)
>
> +++ b/block/qcow2.c
> @@ -2903,36 +2903,20 @@ static int qcow2_save_vmstate(BlockDriverState *bs,
> QEMUIOVector *qiov,
> int64_t pos)
> {
> 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);
> - bs->zero_beyond_eof = false;
> - ret = bdrv_pwritev(bs, qcow2_vm_state_offset(s) + pos, qiov);
> - 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;
> + return bs->drv->bdrv_co_pwritev(bs, qcow2_vm_state_offset(s) + pos,
> + qiov->size, qiov, 0);
> }
bs->drv->bdrv_co_pwritev() is an optional interface; not all the drivers
have it yet. Should you be asserting that it exists, and/or returning
an error if it does not?
>
> static int qcow2_load_vmstate(BlockDriverState *bs, QEMUIOVector *qiov,
> int64_t pos)
> {
> BDRVQcow2State *s = bs->opaque;
> - bool zero_beyond_eof = bs->zero_beyond_eof;
> - int ret;
>
> BLKDBG_EVENT(bs->file, BLKDBG_VMSTATE_LOAD);
> - bs->zero_beyond_eof = false;
> - ret = bdrv_preadv(bs, qcow2_vm_state_offset(s) + pos, qiov);
> - bs->zero_beyond_eof = zero_beyond_eof;
> -
> - return ret;
> + return bs->drv->bdrv_co_preadv(bs, qcow2_vm_state_offset(s) + pos,
> + qiov->size, qiov, 0);
Ditto.
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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- [Qemu-devel] [PATCH 3/6] block: Allow .bdrv_load/save_vmstate() to return 0/-errno, (continued)
- [Qemu-devel] [PATCH 3/6] block: Allow .bdrv_load/save_vmstate() to return 0/-errno, Kevin Wolf, 2016/06/10
- [Qemu-devel] [PATCH 1/6] block: Introduce bdrv_preadv(), Kevin Wolf, 2016/06/10
- [Qemu-devel] [PATCH 4/6] block: Make bdrv_load/save_vmstate coroutine_fns, Kevin Wolf, 2016/06/10
- [Qemu-devel] [PATCH 2/6] block: Make .bdrv_load_vmstate() vectored, Kevin Wolf, 2016/06/10
- [Qemu-devel] [PATCH 5/6] qcow2: Let vmstate call qcow2_co_preadv/pwrite directly, Kevin Wolf, 2016/06/10
- Re: [Qemu-devel] [PATCH 5/6] qcow2: Let vmstate call qcow2_co_preadv/pwrite directly,
Eric Blake <=
- [Qemu-devel] [PATCH 6/6] block: Remove bs->zero_beyond_eof, Kevin Wolf, 2016/06/10
- Re: [Qemu-devel] [PATCH 0/6] block: bdrv_load/save_vmstate() cleanups, Fam Zheng, 2016/06/11
- Re: [Qemu-devel] [Qemu-block] [PATCH 0/6] block: bdrv_load/save_vmstate() cleanups, Stefan Hajnoczi, 2016/06/16
- Re: [Qemu-devel] [PATCH 0/6] block: bdrv_load/save_vmstate() cleanups, Kevin Wolf, 2016/06/16