LVM snapshots are a problem for the btrfs devices management. BTRFS assumes that each device have an unique 'device UUID'. A LVM snapshot breaks this assumption.
This causes a lot of problems if some btrfs device are snapshotted: - the set of devices for a btrfs multi-volume filesystem may be mixed (i.e. some NON snapshotted device with some snapshotted devices) - /proc/mount may returns a wrong device. In the mailing list some posts reported these incidents. This patch allows btrfs to skip LVM snapshot during the device scan phase. But if you need to consider a LVM snapshot you can set the environment variable BTRFS_SKIP_LVM_SNAPSHOT to "no". In this case the old behavior is applied. To check if a device is a LVM snapshot, it is checked the 'udev' device property 'DM_UDEV_LOW_PRIORITY_FLAG' . If it is set to 1, the device has to be skipped. As consequence, btrfs now depends also by the libudev. The last patch is a check to ensure that the devices list doesn't contain two devices with the same dev.uuid. This check is performed *ONLY* when btrfs collects the information about all devices ( i.e. btrfs device scan <device> is not this case). This patch addresses the following cases: - scanning performed by udev rules - "btrfs device scan" performed in the initramdisk - btrfs device scan <device> - other programs which call btrfs_scan_lblkid() BR G.Baroncelli -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
