Re: allocating files with indirect blocks (was: choosing the file system block size)

To: tech-kern%NetBSD.org@localhost
Subject: Re: allocating files with indirect blocks (was: choosing the file system block size)
From: Mouse <mouse%Rodents-Montreal.ORG@localhost>
Date: Mon, 14 May 2012 10:50:41 -0400 (EDT)

>> For files large enough to need indirect blocks, (a) the size is
>> rounded up to the block size, not the frag size
> Why is that so?

I don't know why the FFS designers made that choice.  I've always
assumed it was for some kind of efficiency reason, but that is
speculation on my part.

If you mean, where in the code this is done, look at
sys/ufs/ffs/ffs_balloc.c; search for NDADDR.  I see two relevant tests
per FFS version (two in ffs_balloc_ufs1 and two in ffs_balloc_ufs2, or
only two total when I look at pre-FFSv2 code).

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References:
- choosing the file system block size
  - From: Edgar Fuß
- Re: choosing the file system block size
  - From: Mouse
- allocating files with indirect blocks (was: choosing the file system block size)
  - From: Edgar Fuß

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