On Fri, May 06, 2016 at 10:45:12PM +0200, Paolo Valente wrote: > When a bio is split, the newly created bio must be associated with the > same blkcg as the original bio (if BLK_CGROUP is enabled). If this > operation is not performed, then the new bio is not associated with > any group, and the group of the current task is returned when the > group of the bio is requested. > > Depending on the frequency of splits, this may cause a large > percentage of the bios belonging to a given group to be treated as if > belonging to other groups (in most cases as if belonging to the root > group). The expected group isolation may thereby be then broken. > > This commit adds the missing association in bio_split. > > Signed-off-by: Paolo Valente <[email protected]>
Acked-by: Tejun Heo <[email protected]> > --- > block/bio.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/block/bio.c b/block/bio.c > index 807d25e..c4a3834 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -1811,6 +1811,11 @@ struct bio *bio_split(struct bio *bio, int sectors, > > bio_advance(bio, split->bi_iter.bi_size); > > +#ifdef CONFIG_BLK_CGROUP > + if (bio->bi_css) > + bio_associate_blkcg(split, bio->bi_css); > +#endif And yeah, we need to encapsulate this better to avoid scattering CONFIG_BLK_CGROUP but that's for another patch. Thanks. -- tejun
