Am 03.04.2014 03:38, schrieb Dave Reisner: > On Wed, Apr 02, 2014 at 10:41:30AM -0400, Dave Reisner wrote: >> As of linux 3.14, the initramfs device will have both major and >> minor 0, causing our paranoia check to fail. Make this version agnostic >> by checking the filesystem type, rather than a device number. >> >> Signed-off-by: Dave Reisner <dreisner@xxxxxxxxxxxxx> >> --- >> This is essentially what busybox's switch_root does. I don't think there's much >> value in checking the devno at all, as it seems to be a needless restriction. >> Let's just allow deleting anything that looks like non-persistent storage. > > A bisect of the kernel reveals that 9e30cc9595303 is the responsible > change. It seems the kernel maintains its own mounts which are never > exposed to userspace (which also would explain the FSID gaps in > /proc/self/mountinfo). An instance of sysfs used to be one of these > kernel only mounts but, for some time now, has not needed to be. The > mentioned commit removes this kern_mount() call for sysfs, making the > initramfs the first entry in the mount table -- FSID 0 instead of 1. > > I guess FSIDs are about as reliable as the numbering on block devices, > and this comparison in switch_root was never really the right > approach... Thanks for getting to the bottom of this Dave. I guess going the way of busybox (checking for RAMFS or TMPFS) is the right thing to do, as your patch suggests.
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