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Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver |
Date: |
Tue, 21 May 2013 17:11:57 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130514 Thunderbird/17.0.6 |
Il 21/05/2013 15:34, Stefan Hajnoczi ha scritto:
> /**
> * hbitmap_iter_init:
> [...]
> * position of the iterator is also okay. However, concurrent resetting of
> * bits can lead to unexpected behavior if the iterator has not yet reached
> * those bits.
> */
> void hbitmap_iter_init(HBitmapIter *hbi, const HBitmap *hb, uint64_t first);
>
> This worries me. We would initialize the bitmap to all 1s. Backing up
> a cluster resets the bit. But the documentation says it is not safe to
> reset bits while iterating?
Hmm, right. But do we need the bitmap at all? We can just use
bdrv_is_allocated like bdrv_co_do_readv does.
The code has a comment:
> + /* immediately set bitmap (avoid coroutine race) */
> + hbitmap_set(job->bitmap, start, 1);
but wouldn't this be avoided anyway, because of the mutual exclusion
between overlapping requests?
Paolo
- Re: [Qemu-devel] [PATCH v3 5/8] blockdev: rename BlkTransactionStates to singular, (continued)
- [Qemu-devel] [PATCH v3 3/8] block: add drive-backup QMP command, Stefan Hajnoczi, 2013/05/15
- [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Stefan Hajnoczi, 2013/05/15
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Wenchao Xia, 2013/05/15
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Paolo Bonzini, 2013/05/20
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Stefan Hajnoczi, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Dietmar Maurer, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Paolo Bonzini, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Dietmar Maurer, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Paolo Bonzini, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Dietmar Maurer, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Dietmar Maurer, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Paolo Bonzini, 2013/05/21
- Re: [Qemu-devel] [PATCH v3 2/8] block: add basic backup support to block driver, Stefan Hajnoczi, 2013/05/22
[Qemu-devel] [PATCH v3 7/8] blockdev: add Abort transaction, Stefan Hajnoczi, 2013/05/15