Re: Boot failure with ext2 and initrds
From: Andrew Morton
Date: Thu Nov 16 2006 - 02:23:05 EST
On Wed, 15 Nov 2006 22:55:43 -0800
Mingming Cao <cmm@xxxxxxxxxx> wrote:
> Hmm, maxblocks, in bitmap_search_next_usable_block(), is the end block
> number of the range to search, not the lengh of the range. maxblocks
> get passed to ext2_find_next_zero_bit(), where it expecting to take the
> _size_ of the range to search instead...
> Something like this: (this is not a patch)
> @@ -524,7 +524,7 @@ bitmap_search_next_usable_block(ext2_grp
> ext2_grpblk_t next;
> - next = ext2_find_next_zero_bit(bh->b_data, maxblocks, start);
> + next = ext2_find_next_zero_bit(bh->b_data, maxblocks-start + 1, start);
> if (next >= maxblocks)
> return -1;
> return next;
yes, the `size' arg to find_next_zero_bit() represents the number of bits
to scan at `offset'.
So I think your change is correctish. But we don't want the "+ 1", do we?
If we're right then this bug could cause the code to scan off the end of the
bitmap. But it won't explain Hugh's bug, because of the if (next >= maxblocks).
btw, how come try_to_extend_reservation() uses spin_trylock?
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