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由 Ilya Dryomov 提交于
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=$(rbd map foo) dd if=/dev/urandom of=$FOO_DEV 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 is 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: NIlya Dryomov <ilya.dryomov@inktank.com> Reviewed-by: NAlex Elder <elder@linaro.org>
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