Date: Tue, 21 Apr 2009 19:45:03 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-fs@freebsd.org, freebsd-geom@freebsd.org Subject: Re: glabel for ufs: size check is overzealous? Message-ID: <49EDF80F.3070105@icyb.net.ua> In-Reply-To: <gskrld$vo0$1@ger.gmane.org> References: <49EDCA21.70908@icyb.net.ua> <gskrld$vo0$1@ger.gmane.org>
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on 21/04/2009 19:18 Ivan Voras said the following: > Andriy Gapon wrote: >> glabel insists that for UFS2 the following must hold true: >> pp->mediasize / fs->fs_fsize == fs->fs_size >> >> But in reality it doesn't have to be this way, there can be valid reasons to make >> filesystem smaller than available raw media size. >> >> I understand that this is a good sanity check, but maybe there are other ways to >> extra-check that we see a proper superblock, without imposing the limitation in >> question. > > Shouldn't fsck complain of this inconsistency? I don't see why it should and - no, it actually does not. fsck checks only filesystem's internal consistency, it doesn't check media size, etc. > If it doesn't and the [UF]FS code doesn't, I don't see why glabel should > continue to check it. Struct fs has a tonne of int32 fields, some of > which are only used for information whose length is a couple of bits - > if checking magic isn't enough (and it probably is), there are other > fields that can be validated. Maybe this is a check against disk space being re-used for some other fs and super-block staying sufficiently intact. But, OTOH, fs_fsize and fs_size could still match the raw media in this case too. If some extra sanity checks are needed in addition to magic then fs_bmask/fs_fmask/fs_bshift/fs_fshift and/or any other derived fields could be used. -- Andriy Gapon
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