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From: | John Snow |
Subject: | Re: [Qemu-devel] [PATCH RFC v2 8/8] migration: add migration/dirty-bitmap.c |
Date: | Fri, 13 Feb 2015 12:32:48 -0500 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.4.0 |
On 02/13/2015 04:06 AM, Vladimir Sementsov-Ogievskiy wrote:
+ + blk_mig_reset_dirty_cursor(); + dirty_phase(f, false); + + QSIMPLEQ_FOREACH(dbms, &dirty_bitmap_mig_state.dbms_list, entry) { + uint8_t flags = DIRTY_BITMAP_MIG_FLAG_DEVICE_NAME | + DIRTY_BITMAP_MIG_FLAG_BITMAP_NAME | + DIRTY_BITMAP_MIG_FLAG_ENABLED; + + qemu_put_byte(f, flags); + qemu_put_name(f, bdrv_get_device_name(dbms->bs)); + qemu_put_name(f, bdrv_dirty_bitmap_name(dbms->bitmap)); + qemu_put_byte(f, bdrv_dirty_bitmap_enabled(dbms->bitmap)); + } + + qemu_put_byte(f, DIRTY_BITMAP_MIG_FLAG_EOS); + + DPRINTF("Dirty bitmaps migration completed\n"); + + dirty_bitmap_mig_cleanup(); + return 0; +} +I suppose we don't need a flag that distinctly SAYS this is the end section, since we can tell by omission of DIRTY_BITMAP_MIG_FLAG_NORMAL_CHUNK or ZERO_CHUNK.Hmm. I think it simplifies the logic (to use EOS after each section). And the same approach is in migration/block.c.. It's a question about which format is better: "Each section for dirty_bitmap_load ends with EOS" or "Each section for dirty_bitmap_load ends with EOS except the last one. The last one may be recognized by absent NORMAL_CHUNK and ZERO_CHUNK"Oh, sorry, no, it's important EOS. There are several blocks with no *_CHUNK! Several bitmaps. And loop in dirty_bitmap_load will read them iteratively, and it will finish when find EOS.
Sorry, I worded that poorly. I was wondering why you didn't have an explicit "end of bitmap" flag, and I realized that you are doing this check essentially by the absence of the NORMAL_CHUNK/ZERO_CHUNK flags.
This is really just a comment on my part; I was expecting a more distinct "It is now safe to rebuild the bitmap" flag and was just commenting on why we didn't necessarily need one.
I think in another comment I point out that an "end of bitmap" flag might make the loading function simpler, and I still think that might be nice.
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