* Jeff Layton: > On Mon, 2022-09-12 at 14:13 +0200, Florian Weimer wrote: >> * Jeff Layton: >> >> > To do this we'd need 2 64-bit fields in the on-disk and in-memory >> > superblocks for ext4, xfs and btrfs. On the first mount after a crash, >> > the filesystem would need to bump s_version_max by the significant >> > increment (2^40 bits or whatever). On a "clean" mount, it wouldn't need >> > to do that. >> > >> > Would there be a way to ensure that the new s_version_max value has made >> > it to disk? Bumping it by a large value and hoping for the best might be >> > ok for most cases, but there are always outliers, so it might be >> > worthwhile to make an i_version increment wait on that if necessary. >> >> How common are unclean shutdowns in practice? Do ex64/XFS/btrfs keep >> counters in the superblocks for journal replays that can be read easily? >> >> Several useful i_version applications could be negatively impacted by >> frequent i_version invalidation. >> > > One would hope "not very often", but Oopses _are_ something that happens > occasionally, even in very stable environments, and it would be best if > what we're building can cope with them. I was wondering if such unclean shutdown events are associated with SSD “unsafe shutdowns”, as identified by the SMART counter. I think those aren't necessarily restricted to oopses or various forms of powerless (maybe depending on file system/devicemapper configuration)? I admit it's possible that the file system is shut down cleanly before the kernel requests the power-off state from the firmware, but the underlying SSD is not. Thanks, Florian
