linux-kernel - Re: UDF: alternate anchor block detection

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Message-ID: <20111004145156.GA4183@joi.lan>
Date:	Tue, 4 Oct 2011 16:51:56 +0200
From:	Marcin Slusarz <marcin.slusarz@...il.com>
To:	Amit Sahrawat <amit.sahrawat83@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: UDF: alternate anchor block detection

On Mon, Oct 03, 2011 at 05:16:15PM +0530, Amit Sahrawat wrote:
> While mounting UDF media, when the primary AVDP is not found at block
> 256, UDF code tries to read-in the alternate AVDP.
> In the function udf_find_anchor, udf_scan_anchors is called 3 times,
> where each call to udf_scan_anchors read 12 blocks.
> In case there is no alternate AVDP stored, a total of 36 blocks are
> read before mount fails - causing time delay for Mount Failure.
> 
> 1) After first call to udf_scan_anchors and before the second call
> there is varconv conversion, for the older drivers, which skips 7
> blocks after every 32 blocks. What are these older drivers? Do we
> still require this code?

I'm not sure what "drivers" are you talking about, but "UDF_SET_FLAG(sb,
UDF_FLAG_VARCONV)" does not convert anything - it just sets superblock
flag.

> 2) After varconv conversion, why is there a third call to
> udf_scan_anchors? In the 1st call and 3rd call to udf_scan_anchors,
> exactly same blocks are read, so this 3rd call seems to be redundant.

Because UDF_FLAG_VARCONV changes behavior of udf_scan_anchors.

Marcin
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