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Re: [Qemu-devel] [PATCH 0/4] block: Drop BDS.filename

From: Kevin Wolf
Subject: Re: [Qemu-devel] [PATCH 0/4] block: Drop BDS.filename
Date: Tue, 3 Feb 2015 10:32:05 +0100
User-agent: Mutt/1.5.21 (2010-09-15)

Am 24.09.2014 um 21:48 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.

Surprisingly (or not), this one needs rebasing.

I tried it and it doesn't look too hard, but it's a little bit more than
what I'm comfortable with doing while applying a series.


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