Re: scary ext2 filesystem question

Theodore Y. Ts'o (tytso@mit.edu)
Sat, 2 Jan 1999 00:39:54 -0500

Well, the confusing part is that fsck reports some size/count changes
(I don't remember the exact error message right now), something like
inode number x, was y, should be z, corrected. Now, if I write down
that inode numbers, and find corresponding files after fsck finishes,
they are in many cases corrupted (maybe in all cases?). I was always
wondering, what would happen if fsck DID NOT repair the files. After
all, it knows that older value.

What likely happened is that part of the metadata (an indirect block,
containing a block reference) got written out to disk, while another
part of the metadata (the inode, containing the size of the file)
didn't make it out to disk. In this case, e2fsck errs on the side of
not losing data, which means that instead of throwing away the newly
allocated block, it will expand the size field in the inode.

Now, what that UPS can't do is prevent me from "improving" kernel
sources and making mistakes along a way. If you by any chance get hold
of a model with such functionality, please inform me fast where should
I go and buy it. :)

Well, you could simply not make mistakes. <grin>

- Ted

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