[dm-devel] Another metadata corruption issue in dm-cache

[Steinar H. Gunderson]

On Sun, Feb 16, 2014 at 05:51:13PM +0100, Steinar H. Gunderson wrote:
>   [233728.674456] device-mapper: space map common: unable to decrement a reference count below 0

Actually a similar issue to this seems to have manifested itself in 3.13 even
after I nuked all the metadata; the dmsetup status line now reads:

cache: 0 35161337856 cache 1728/131072 2772587 12086450 2085299 1111070 0 260440 265439 4294967295 1 writeback 2 migration_threshold 2048 4 random_threshold 8 sequential_threshold 512

Occasionally, the 4294967295 dips up to 0 or 1, and then goes straight back
down again. So there seems to be an off-by-one somewhere in the counting of
blocks.

/* Steinar */
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