Hi,
在 2025/08/21 17:02, Christoph Hellwig 写道:
On Thu, Aug 21, 2025 at 04:56:33PM +0800, Yu Kuai wrote:
Can you give some examples as how to chain the right way?
fs/xfs/xfs_bio_io.c: xfs_rw_bdev
Just take a look, this is
old bio->new bio
while bio split is:
new_bio->old bio
So xfs_rw_bdev won't flag old bio as BIO_CHAIN, while old bio will still
be resubmitted to current->bio_list, hence this patch won't break this
case, right?
I'll take look at all the bio_chain() callers other than split case to
make sure.
fs/xfs/xfs_buf.c: xfs_buf_submit_bio
This is a little different, new bio -> old bio, while new bio is
resubmitted, the new bio still don't have flag BIO_CHAIN, so this is not
affected by this patch.
fs/xfs/xfs_log.c: xlog_write_iclog
This is the same as above.
BTW, for all
the io split case, should this order be fixed? I feel we should, this
disorder can happen on any stack case, where top max_sector is greater
than stacked disk.
Yes, I've been trying get Bart to fix this for a while instead of
putting in a workaround very similar to the one proposed here,
but so far nothing happened.
Do you mean this thread?
Fix bio splitting by the crypto fallback code
I'll take look at all the callers of bio_chain(), in theory, we'll have
different use cases like:
1) chain old -> new, or chain new -> old
2) put old or new to current->bio_list, currently always in the tail,
we might want a new case to the head;
Perhaps it'll make sense to add high level helpers to do the chain
and resubmit and convert all callers to use new helpers, want do you
think?
Thanks,
Kuai
.
