Hi, on my system I have some read-only device mapper targets. They are old LVM instances which I made read-only using (lvchange -p r LV) in order to preserve their contents. One of them contains a partitioned hard disk image. # dmsetup info /dev/dm-29 > Name: HDD-OLD--rost--image > State: ACTIVE (READ-ONLY) > Read Ahead: 12288 > Tables present: LIVE > Open count: 1 > Event number: 0 > Major, minor: 253, 29 > Number of targets: 1 > UUID: LVM-PGTIP3IjFCE4UHM9fFGxuVhKR4FmCXO0gwvX8HW6JBs2dfxj6lYyKOmDLyxsDf0B In order to mount a few partitions of it, I used kpartx to map the partitions. # kpartx -a /dev/dm-29 This works fine, except the READ-ONLY does not seem to stick. # dmsetup ls --tree > [...] > HDD-OLD--rost--imagep1 (253:30) > └─HDD-OLD--rost--image (253:29) > [...] # dmsetup info /dev/mapper/HDD-OLD--rost--imagep1 > Name: HDD-OLD--rost--imagep1 > State: ACTIVE > Read Ahead: 256 > Tables present: LIVE > Open count: 0 > Event number: 0 > Major, minor: 253, 30 > Number of targets: 1 > UUID: part1-LVM-PGTIP3IjFCE4UHM9fFGxuVhKR4FmCXO0gwvX8HW6JBs2dfxj6lYyKOmDLyxsDf0B And it's completely writable. I tried to use losetup --partscan as an alternative to kpartx, which kind of works, except the kernel believes the loop device to be writable and gives a lot of I/O error messages and the filesystem behaves oddly. > [ 3136.455451] Buffer I/O error on device loop0p1, logical block 1568 > [ 3136.455454] lost page write due to I/O error on loop0p1 > [ 3136.455466] loop: Write error at byte offset 36003840, length 4096. > [ 3136.455469] Buffer I/O error on device loop0p1, logical block 8534 > [ 3136.455472] lost page write due to I/O error on loop0p1 > [ 3136.455478] loop: Write error at byte offset 5094449152, length 4096. > [...] This doesn't happen for other read-only devices (such as /dev/cdrom). I can work around it using losetup --read-only, just wondering if this is expected behaviour at all or not? I never used read-only dm/LV before, but my expectation was that the read-only property in one place would also affect all devices that derive from it... I'm using kernel 3.11.4 if it makes any difference. Regards Andreas Klauer -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
