On Sun, Jan 23, 2011 at 11:02:16PM +0100, Goffredo Baroncelli wrote: > On 01/23/2011 07:18 PM, Hugo Mills wrote: > > Hi, Felix, > > > > On Sat, Jan 22, 2011 at 04:56:12PM +0100, Felix Blanke wrote: > >> It was a simple: > >> > >> mkfs.btrfs -L backup -d single /dev/loop2 > >> > >> But it also happens without the options, like: > >> > >> mkfs.btrfs /dev/loop2 > >> > >> > >> /dev/loop2 is a loop device, which is aes encrypted. The output of "losetup /dev/loop2": > >> > >> /dev/loop2: [0010]:5324 > >> (/dev/disk/by-id/ata-WDC_WD6400AAKS-22A7B2_WD-WCASY7780706-part3) encryption=AES128 > >> > >> > >> Thanks you for looking into this! > >> While writing this I read your second mail. The strace output is attached. > > > > OK, I've traced through the functions being called, and I really > > can't see where it could be truncating the name, unless your system > > has a stupidly small value of PATH_MAX. > > It seems that when mkfs.btrfs checks if the passed block device is > already mounted, uses the ioctl LOOP_GET_STATUS [1]. This ioctl has as > argument the struct loop_info. > > This ioctl, should return the info about the back-end of the loop > device. The file name is returned via the "lo_name" field, which is an > array of 64 char...[2] Good catch, Goffredo. I completely missed that. Interestingly, on my system, lo_name is indeed defined as 64 chars, but I don't see Felix's problem. When I do losetup on the /dev/disk/by-id/... link, my version of losetup seems to be following the link: # losetup /dev/loop1 /dev/disk/by-id/dm-uuid-LVM-XRQLHQNa0xEeIZL4ofuBGIcfkr1Dhry8YHhkjaw4bvZA4meDFQfEMy5elIsVNeWl # losetup -a /dev/loop1: [0005]:1423915 (/dev/mapper/ruthven-btemp) I'm running Debian, and the mount package version 2.17.2-5 (losetup is part of mount, it seems). > Felix, what is the output of the following command ? > > /sbin/losetup -a > > If my analysis is correct, this command should return the filename > trunked at the 64th character too. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- Sometimes, when I'm alone, I Google myself. ---
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