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Re: [Qemu-block] [PATCH v3 0/5] block: Drop BDS.filename


From: Kevin Wolf
Subject: Re: [Qemu-block] [PATCH v3 0/5] block: Drop BDS.filename
Date: Thu, 13 Aug 2015 17:30:34 +0200
User-agent: Mutt/1.5.21 (2010-09-15)

Am 12.08.2015 um 17:48 hat Max Reitz geschrieben:
> The BDS filename field is generally only used when opening disk images
> or emitting error or warning messages, the only exception to this rule
> is the map command of qemu-img. However, using exact_filename there
> instead should not be a problem. Therefore, we can drop the filename
> field from the BlockDriverState and use a function instead which builds
> the filename from scratch when called.
> 
> This is slower than reading a static char array but the problem of that
> static array is that it may become obsolete due to changes in any
> BlockDriverState or in the BDS graph. Using a function which rebuilds
> the filename every time it is called resolves this problem.
> 
> The disadvantage of worse performance is negligible, on the other hand.
> After patch 2 of this series, which replaces some queries of
> BDS.filename by reads from somewhere else (mostly BDS.exact_filename),
> the filename field is only used when a disk image is opened or some
> message should be emitted, both of which cases do not suffer from the
> performance hit.

Apart from patch 2:

Reviewed-by: Kevin Wolf <address@hidden>



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