Date: Mon, 5 Jan 2009 16:13:52 -0600 From: "Rick C. Petty" <rick-freebsd2008@kiwi-computer.com> To: freebsd-stable@FreeBSD.ORG, david@catwhisker.org Subject: Re: newfs(8) parameters from "dumpfs -m" have bad -s value? Message-ID: <20090105221352.GB35524@keira.kiwi-computer.com> In-Reply-To: <200901051923.n05JNrwt038325@lurza.secnetix.de> References: <20090102153455.GR4100@albert.catwhisker.org> <200901051923.n05JNrwt038325@lurza.secnetix.de>
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On Mon, Jan 05, 2009 at 08:23:53PM +0100, Oliver Fromme wrote:
>
> This seems to be a bug in dumpfs(8). It simply prints
> the value of the fs_size field of the superblock, which
> is wrong.
>
> The -s option of newfs(8) expects the available size in
> sectors (i.e. 512 bytes), but the fs_size field contains
> the size of the file system in 2KB units. This seems to
> be the fragment size, but I'm not sure if this is just
This *is* the fragment size. UFS/FFS uses the plain term "block" to mean
the fragment size. All blocks are indexed with this number, unlike "block
size" which is almost always 8 fragments ("blocks"). Confusing.
> So, dumpfs(8) needs to be fixed to perform the proper
> calculations when printing the value for the -s option.
> Unfortunately I'm not sufficiently much of a UFS guru
> to offer a fix. My best guess would be to multiply the
> fs_size value by the fragment size (measured in 512 byte
> units), i.e. multiply by 4 in the most common case.
> But I'm afraid the real solution is not that simple.
The sector size and filesystem size parameters in newfs are remnants.
Everything is converted to number of media sectors (sector size as
specified by the device). So one could assume for dumpfs to always use
512, since it's rarely different, and multiply fs_size by fs_fsize and
divide by 512, and then output "-S 512".
Better yet would be to add a parameter ("-z" perhaps) to newfs(8) to accept
number of bytes instead of multiples of sectorsize.
I would be willing to write up patches for dumpfs and newfs to both add the
raw byte size and the 512-byte sector size handling to correct said
mistake, unless someone else would rather.
-- Rick C. Petty
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