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Re: [Qemu-devel] [PATCH] qcow2: adjust qcow2_co_flush_to_os -> qcow2_co_
From: |
Kevin Wolf |
Subject: |
Re: [Qemu-devel] [PATCH] qcow2: adjust qcow2_co_flush_to_os -> qcow2_co_flush_to_disk |
Date: |
Mon, 14 May 2012 16:04:17 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:11.0) Gecko/20120329 Thunderbird/11.0.1 |
Am 14.05.2012 15:51, schrieb address@hidden:
> From: Zhi Yong Wu <address@hidden>
>
> qcow2_co_flush_to_os() actually flush all cached data to the disk. To keep
> its name consistent with its actual function, adjust its name accordingly.
>
> Signed-off-by: Zhi Yong Wu <address@hidden>
This patch is plain wrong.
You're aware that you're not changing a name, but functionality here?
Have a look at block_int.h for the semantics of each function:
/*
* Flushes all data that was already written to the OS all the way
down to
* the disk (for example raw-posix calls fsync()).
*/
int coroutine_fn (*bdrv_co_flush_to_disk)(BlockDriverState *bs);
/*
* Flushes all internal caches to the OS. The data may still sit in a
* writeback cache of the host OS, but it will survive a crash of
the qemu
* process.
*/
int coroutine_fn (*bdrv_co_flush_to_os)(BlockDriverState *bs);
Apart from that, it's not even intentional that qcow2 does a
bdrv_flush() even if it didn't write out any cache entries. If we
optimise the cache code a bit, this might disappear in the future.
Kevin