On Mon, Aug 11 2025, Darrick J. Wong wrote: > On Fri, Aug 01, 2025 at 11:15:26AM +0100, Luis Henriques wrote: >> On Thu, Jul 31 2025, Darrick J. Wong wrote: >> >> > On Thu, Jul 31, 2025 at 09:04:58AM -0400, Theodore Ts'o wrote: >> >> On Tue, Jul 29, 2025 at 04:38:54PM -0700, Darrick J. Wong wrote: >> >> > >> >> > Just speaking for fuse2fs here -- that would be kinda nifty if libfuse >> >> > could restart itself. It's unclear if doing so will actually enable us >> >> > to clear the condition that caused the failure in the first place, but I >> >> > suppose fuse2fs /does/ have e2fsck -fy at hand. So maybe restarts >> >> > aren't totally crazy. >> >> >> >> I'm trying to understand what the failure scenario is here. Is this >> >> if the userspace fuse server (i.e., fuse2fs) has crashed? If so, what >> >> is supposed to happen with respect to open files, metadata and data >> >> modifications which were in transit, etc.? Sure, fuse2fs could run >> >> e2fsck -fy, but if there are dirty inode on the system, that's going >> >> potentally to be out of sync, right? >> >> >> >> What are the recovery semantics that we hope to be able to provide? >> > >> > <echoing what we said on the ext4 call this morning> >> > >> > With iomap, most of the dirty state is in the kernel, so I think the new >> > fuse2fs instance would poke the kernel with FUSE_NOTIFY_RESTARTED, which >> > would initiate GETATTR requests on all the cached inodes to validate >> > that they still exist; and then resend all the unacknowledged requests >> > that were pending at the time. It might be the case that you have to >> > that in the reverse order; I only know enough about the design of fuse >> > to suspect that to be true. >> > >> > Anyhow once those are complete, I think we can resume operations with >> > the surviving inodes. The ones that fail the GETATTR revalidation are >> > fuse_make_bad'd, which effectively revokes them. >> >> Ah! Interesting, I have been playing a bit with sending LOOKUP requests, >> but probably GETATTR is a better option. >> >> So, are you currently working on any of this? Are you implementing this >> new NOTIFY_RESTARTED request? I guess it's time for me to have a closer >> look at fuse2fs too. > > Nope, right now I'm concentrating on making sure the fuse/iomap IO path > works reliably; and converting fuse2fs to be a lowlevel fuse server. Great, thanks for clarifying. > Eliminating all the path walking stuff that the highlevel fuse library > does reduces the fstests runtime from 7.9 to 3.5h, and turning on iomap > cuts that to 2.2h. Wow! those are quite impressive numbers. Looking forward to look into those fuse2fs improvements! Cheers, -- Luís
