Andreas Dilger wrote:
I _think_ Alex is asking "what happens if during a transaction undergoing
checkpoint of blocks to filesystem (not the last one in the journal) is
interrupted by a crash and upon restart the partially-checkpointed
transaction is found to have a checksum error?"
yup, thanks for clarification.
what do we do if transaction in the journal is found with wrong
checksum? leave partial transaction in-place?
The sanity of the transaction is checked in PASS_SCAN. And if checksum
is found to be incorrect for nth transaction then last transaction which
is written to disk is (n - 1).
The recovery.c code (AFAIK) does not do replay for any transaction that
does not have a valid checksum, or transactions beyond that. If the
bad transaction had already started chekpoint (i.e. isn't the last
committed transaction) then the journal _should_ return an error up to
the filesystem, so it can call ext4_error() at startup. For e2fsck
(which normally does journal replay & recovery) it can do a full
filesystem check at this point.
hmm. it actually can be last transaction (following no activity?)
thanks, Alex
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