linux/fs/jbd/commit.c

914 lines
27 KiB

ext3 can fail badly when device stops accepting BIO_RW_BARRIER requests Some devices - notably dm and md - can change their behaviour in response to BIO_RW_BARRIER requests. They might start out accepting such requests but on reconfiguration, they find out that they cannot any more. ext3 (and other filesystems) deal with this by always testing if BIO_RW_BARRIER requests fail with EOPNOTSUPP, and retrying the write requests without the barrier (probably after waiting for any pending writes to complete). However there is a bug in the handling for this for ext3. When ext3 (jbd actually) decides to submit a BIO_RW_BARRIER request, it sets the buffer_ordered flag on the buffer head. If the request completes successfully, the flag STAYS SET. Other code might then write the same buffer_head after the device has been reconfigured to not accept barriers. This write will then fail, but the "other code" is not ready to handle EOPNOTSUPP errors and the error will be treated as fatal. This can be seen without having to reconfigure a device at exactly the wrong time by putting: if (buffer_ordered(bh)) printk("OH DEAR, and ordered buffer\n"); in the while loop in "commit phase 5" of journal_commit_transaction. If it ever prints the "OH DEAR ..." message (as it does sometimes for me), then that request could (in different circumstances) have failed with EOPNOTSUPP, but that isn't tested for. My proposed fix is to clear the buffer_ordered flag after it has been used, as in the following patch. Signed-off-by: Neil Brown <neilb@suse.de> Cc: <linux-ext4@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-08 04:22:13 -08:00
[PATCH] jbd: fix BUG in journal_commit_transaction() Fix possible assertion failure in journal_commit_transaction() on jh->b_next_transaction == NULL (when we are processing BJ_Forget list and buffer is not jbddirty). !jbddirty buffers can be placed on BJ_Forget list for example by journal_forget() or by __dispose_buffer() - generally such buffer means that it has been freed by this transaction. Freed buffers should not be reallocated until the transaction has committed (that's why we have the assertion there) but they *can* be reallocated when the transaction has already been committed to disk and we are just processing the BJ_Forget list (as soon as we remove b_committed_data from the bitmap bh, ext3 will be able to reallocate buffers freed by the committing transaction). So we have to also count with the case that the buffer has been reallocated and b_next_transaction has been already set. And one more subtle point: it can happen that we manage to reallocate the buffer and also mark it jbddirty. Then we also add the freed buffer to the checkpoint list of the committing trasaction. But that should do no harm. Non-jbddirty buffers should be filed to BJ_Reserved and not BJ_Metadata list. It can actually happen that we refile such buffers during the commit phase when we reallocate in the running transaction blocks deleted in committing transaction (and that can happen if the committing transaction already wrote all the data and is just cleaning up BJ_Forget list). Signed-off-by: Jan Kara <jack@suse.cz> Acked-by: "Stephen C. Tweedie" <sct@redhat.com> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-23 02:05:25 -07:00