| Message ID | 1406191369-6746-9-git-send-email-ilya.dryomov@inktank.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 07/24/2014 03:42 AM, Ilya Dryomov wrote: > If we are mapping a snapshot, we must read in the parent_overlap value > of that snapshot instead of that of the base image. Not doing so may > in particular result in us returning zeros instead of user data: > > # cat overlap-snap.sh > #!/bin/bash > rbd create --size 10 --image-format 2 foo > FOO_DEV=$(rbd map foo) > dd if=/dev/urandom of=/dev/rbd0 bs=1M &>/dev/null > echo "Base image" > dd if=$FOO_DEV bs=1 count=16 skip=$(((4 << 20) - 8)) 2>/dev/null | xxd > rbd snap create foo@snap > rbd snap protect foo@snap > rbd clone foo@snap bar > rbd snap create bar@snap > BAR_DEV=$(rbd map bar@snap) > echo "Snapshot" > dd if=$BAR_DEV bs=1 count=16 skip=$(((4 << 20) - 8)) 2>/dev/null | xxd > rbd resize --allow-shrink --size 4 bar > echo "Snapshot after base image resize" > dd if=$BAR_DEV bs=1 count=16 skip=$(((4 << 20) - 8)) 2>/dev/null | xxd > > # ./overlap-snap.sh > Base image > 0000000: e781 e33b d34b 2225 6034 2845 a2e3 36ed ...;.K"%`4(E..6. > Snapshot > 0000000: e781 e33b d34b 2225 6034 2845 a2e3 36ed ...;.K"%`4(E..6. > Resizing image: 100% complete...done. > Snapshot after base image resize > 0000000: e781 e33b d34b 2225 0000 0000 0000 0000 ...;.K"%........ > > Even though bar@snap was taken with the old bar parent_overlap (8M), > reads from bar@snap beyond the new bar parent_overlap (4M) return > zeroes. Fix it. > > Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com> > --- > drivers/block/rbd.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c > index c4606987e9d1..cbc89fa9a677 100644 > --- a/drivers/block/rbd.c > +++ b/drivers/block/rbd.c > @@ -4020,7 +4020,7 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev) > goto out_err; > } > > - snapid = cpu_to_le64(CEPH_NOSNAP); > + snapid = cpu_to_le64(rbd_dev->spec->snap_id); Well that's just an outright bug. It's been there since the original commit that added parent support: 86b00e0 rbd: get parent spec for version 2 images Parent images *must* be snapshots, so this was never right. I bet that was hard to figure out... Looks good. Reviewed-by: Alex Elder <elder@linaro.org> > ret = rbd_obj_method_sync(rbd_dev, rbd_dev->header_name, > "rbd", "get_parent", > &snapid, sizeof (snapid), > -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/block/rbd.c b/drivers/block/rbd.c index c4606987e9d1..cbc89fa9a677 100644 --- a/drivers/block/rbd.c +++ b/drivers/block/rbd.c @@ -4020,7 +4020,7 @@ static int rbd_dev_v2_parent_info(struct rbd_device *rbd_dev) goto out_err; } - snapid = cpu_to_le64(CEPH_NOSNAP); + snapid = cpu_to_le64(rbd_dev->spec->snap_id); ret = rbd_obj_method_sync(rbd_dev, rbd_dev->header_name, "rbd", "get_parent", &snapid, sizeof (snapid),
If we are mapping a snapshot, we must read in the parent_overlap value of that snapshot instead of that of the base image. Not doing so may in particular result in us returning zeros instead of user data: # cat overlap-snap.sh #!/bin/bash rbd create --size 10 --image-format 2 foo FOO_DEV=$(rbd map foo) dd if=/dev/urandom of=/dev/rbd0 bs=1M &>/dev/null echo "Base image" dd if=$FOO_DEV bs=1 count=16 skip=$(((4 << 20) - 8)) 2>/dev/null | xxd rbd snap create foo@snap rbd snap protect foo@snap rbd clone foo@snap bar rbd snap create bar@snap BAR_DEV=$(rbd map bar@snap) echo "Snapshot" dd if=$BAR_DEV bs=1 count=16 skip=$(((4 << 20) - 8)) 2>/dev/null | xxd rbd resize --allow-shrink --size 4 bar echo "Snapshot after base image resize" dd if=$BAR_DEV bs=1 count=16 skip=$(((4 << 20) - 8)) 2>/dev/null | xxd # ./overlap-snap.sh Base image 0000000: e781 e33b d34b 2225 6034 2845 a2e3 36ed ...;.K"%`4(E..6. Snapshot 0000000: e781 e33b d34b 2225 6034 2845 a2e3 36ed ...;.K"%`4(E..6. Resizing image: 100% complete...done. Snapshot after base image resize 0000000: e781 e33b d34b 2225 0000 0000 0000 0000 ...;.K"%........ Even though bar@snap was taken with the old bar parent_overlap (8M), reads from bar@snap beyond the new bar parent_overlap (4M) return zeroes. Fix it. Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com> --- drivers/block/rbd.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)