[Drbd-dev] [patch] __bio_clone() behaviour

[Philipp Reisner]

Am Mittwoch, 26. Januar 2005 17:46 schrieb Lars Marowsky-Bree:
> With the __bio_clone() bugfix by Jens Axboe (in the recent 2.6.10-ac
> kernels or SLES9 SP1) which causes __bio_clone() to copy the bi_io_vec,
> it would always try to copy the _maximum_ size, as defined by
> bio_src->bi_max_vecs:
>
> inline void __bio_clone(struct bio *bio, struct bio *bio_src)
> {
>         request_queue_t *q = bdev_get_queue(bio_src->bi_bdev);
>         memcpy(bio->bi_io_vec, bio_src->bi_io_vec, bio_src->bi_max_vecs *
> sizeof(struct bio_vec)); ...
>
> drbd however only has space for a single iovec (because it's all
> statically allocated right now), and so the memcpy would silently
> overwrite memory.
>
> The attached patch 'fixes' this up.
>
> Note that it is a bit ugly but safe, as drbd already asserts that
> bi_vcnt == 1 anyway.
>
> FWIW, drbd seems to be the only user of __bio_clone() I could find,
> there's no in-tree users, everything goes through bio_clone() otherwise,
> which would have dynamically allocated the properly sized structures.
>

This really gives me the feeling that I should not have done the 
0.7.9 release. --- The only one to blame is myself, who thought it 
would be a nice idea to have the same release as SUSE.
Bullshit -> The next release will only happen when I am convinced
that the new release is necessary, and that it will not be a 
disaster.


BTW, regarind this patch: We now modify someone else's BIO. 
     Is this a good idea ?

-Philipp
-- 
: Dipl-Ing Philipp Reisner                      Tel +43-1-8178292-50 :
: LINBIT Information Technologies GmbH          Fax +43-1-8178292-82 :
: Schönbrunnerstr 244, 1120 Vienna, Austria    http://www.linbit.com :