Date: Tue, 12 Feb 2008 11:47:34 +0000 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: Andriy Gapon <avg@icyb.net.ua> Cc: freebsd-fs@FreeBSD.org, freebsd-hackers@FreeBSD.org, Pav Lucistnik <pav@FreeBSD.org>, Bruce Evans <bde@zeta.org.au> Subject: Re: fs/udf: vm pages "overlap" while reading large dir Message-ID: <4299.1202816854@critter.freebsd.dk> In-Reply-To: Your message of "Tue, 12 Feb 2008 13:24:34 %2B0200." <47B181F2.2070808@icyb.net.ua>
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In message <47B181F2.2070808@icyb.net.ua>, Andriy Gapon writes:
>2.3. this code passes to bread blkno that is calculated as 4*sector,
>where sector is a number of a physical 2048-byte sector. [**]
>[**] - I think that this is a requirement of buffcache system, because
>internally it performs many calculations that seem to assume that block
>size is always 512.
Yes, the buf-cache works in 512 bytes units throughout.
>3.1. for a fresh buf getlbk would assign the following:
>bsize = bo->bo_bsize;
>offset = blkno * bsize;
That's clearly wrong.
We need to assert that the blkno is aligned to the start of a sector
and use the 512 byte units, so I guess it would be:
offset = dbtob(blkno);
KASSERT(!(offset & (bsize - 1)), ("suitable diagnostic"));
--
Poul-Henning Kamp | UNIX since Zilog Zeus 3.20
phk@FreeBSD.ORG | TCP/IP since RFC 956
FreeBSD committer | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.
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