| Message ID | 1402489929-16466-1-git-send-email-lczerner@redhat.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Mike Snitzer |
| Headers | show |
On Wed, Jun 11 2014 at 8:32am -0400, Lukas Czerner <lczerner@redhat.com> wrote: > Currently if the underlying device is discard capable and the > discard_passdown is enabled, the discard_granularity will be inherited > from that device. > > This will pose a problem in the case that the device discard_granularity > is smaller than thin volume chunk size, because in that case discard > requests will not be chunk size aligned so it will be ignored by > dm-thin. > > Fix this by setting thin volume discard granularity to the bigger of the > two max(device discard_granularity, thin volume chunk size). Strictly > speaking it is not necessary to get the bigger of the two, because > the thin volume chunk size will always be >= device discard_granularity. > However I believe that the reason for this is only because dm-thin can > not handle discard requests bigger than chunk size which is hopefully > going to change soon. This way it is future proof. > > RHBZ: 1106856 > > Reported-by: Zdenek Kabelac <zkabelac@fedoraproject.org> > Signed-off-by: Lukas Czerner <lczerner@redhat.com> Hi Lukas, I missed this submission on dm-devel until now. But I had already picked this patch up earlier from the BZ, see the patch I staged in linux-next here: https://git.kernel.org/cgit/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=for-next&id=09869de57ed2728ae3c619803932a86cb0e2c4f8 -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
ack On Wed, Jun 11, 2014 at 02:32:09PM +0200, Lukas Czerner wrote: > Currently if the underlying device is discard capable and the > discard_passdown is enabled, the discard_granularity will be inherited > from that device. > > This will pose a problem in the case that the device discard_granularity > is smaller than thin volume chunk size, because in that case discard > requests will not be chunk size aligned so it will be ignored by > dm-thin. > > Fix this by setting thin volume discard granularity to the bigger of the > two max(device discard_granularity, thin volume chunk size). Strictly > speaking it is not necessary to get the bigger of the two, because > the thin volume chunk size will always be >= device discard_granularity. > However I believe that the reason for this is only because dm-thin can > not handle discard requests bigger than chunk size which is hopefully > going to change soon. This way it is future proof. > > RHBZ: 1106856 > > Reported-by: Zdenek Kabelac <zkabelac@fedoraproject.org> > Signed-off-by: Lukas Czerner <lczerner@redhat.com> > --- > drivers/md/dm-thin.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c > index 242ac2e..fdd7089 100644 > --- a/drivers/md/dm-thin.c > +++ b/drivers/md/dm-thin.c > @@ -3068,7 +3068,9 @@ static void set_discard_limits(struct pool_c *pt, struct queue_limits *limits) > */ > if (pt->adjusted_pf.discard_passdown) { > data_limits = &bdev_get_queue(pt->data_dev->bdev)->limits; > - limits->discard_granularity = data_limits->discard_granularity; > + limits->discard_granularity = > + max(data_limits->discard_granularity, > + pool->sectors_per_block << SECTOR_SHIFT); > } else > limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT; > } > -- > 1.8.3.1 > > -- > dm-devel mailing list > dm-devel@redhat.com > https://www.redhat.com/mailman/listinfo/dm-devel -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
diff --git a/drivers/md/dm-thin.c b/drivers/md/dm-thin.c index 242ac2e..fdd7089 100644 --- a/drivers/md/dm-thin.c +++ b/drivers/md/dm-thin.c @@ -3068,7 +3068,9 @@ static void set_discard_limits(struct pool_c *pt, struct queue_limits *limits) */ if (pt->adjusted_pf.discard_passdown) { data_limits = &bdev_get_queue(pt->data_dev->bdev)->limits; - limits->discard_granularity = data_limits->discard_granularity; + limits->discard_granularity = + max(data_limits->discard_granularity, + pool->sectors_per_block << SECTOR_SHIFT); } else limits->discard_granularity = pool->sectors_per_block << SECTOR_SHIFT; }
Currently if the underlying device is discard capable and the discard_passdown is enabled, the discard_granularity will be inherited from that device. This will pose a problem in the case that the device discard_granularity is smaller than thin volume chunk size, because in that case discard requests will not be chunk size aligned so it will be ignored by dm-thin. Fix this by setting thin volume discard granularity to the bigger of the two max(device discard_granularity, thin volume chunk size). Strictly speaking it is not necessary to get the bigger of the two, because the thin volume chunk size will always be >= device discard_granularity. However I believe that the reason for this is only because dm-thin can not handle discard requests bigger than chunk size which is hopefully going to change soon. This way it is future proof. RHBZ: 1106856 Reported-by: Zdenek Kabelac <zkabelac@fedoraproject.org> Signed-off-by: Lukas Czerner <lczerner@redhat.com> --- drivers/md/dm-thin.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)