Hi, On Sun, May 05, 2019 at 07:50:09AM +0000, Maksim Fomin wrote: > Good day. > > Since 5.0 btrfs supports swap files. Does it support hibernation into a swap file? > > With kernel version 5.0.10 (archlinux) and btrfs-progs 4.20.2 (unlikely to be relevant, but still) when I try to hibernate with systemctl or by directly manipulating '/sys/power/resume' and '/sys/power/resume_offset', the kernel logs: > > PM: Cannot find swap device, try swapon -a > PM: Cannot get swap writer > > After digging into this issue I suspect that currently btrfs does not support hibernation into swap file (or does it?). Furthermore, I suspect that kernel mechanism of accessing swap file via 'resume_offset' is unreliable in btrfs case because it is more likely (comparing to other fs) to move files across filesystem which invalidates swap file offset, so the whole idea is dubious. So, > > 1) does btrfs supports hibernation into swap file? > 2) is there mechanism to lock swap file? for the reference https://bugzilla.kernel.org/show_bug.cgi?id=202803 and https://github.com/systemd/systemd/issues/11939
