On Wed, Nov 18, 2020 at 09:24:04AM +0200, Amir Goldstein wrote: > On Tue, Nov 17, 2020 at 8:29 PM Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > > > On Tue, Nov 17, 2020 at 08:03:16PM +0200, Amir Goldstein wrote: > > > > > C. "shutdown" the filesystem if writeback errors happened and return > > > > > EIO from any read, like some blockdev filesystems will do in face > > > > > of metadata write errors > > > > > > > > > > I happen to have a branch ready for that ;-) > > > > > https://github.com/amir73il/linux/commits/ovl-shutdown > > > > > > > > > > > > This branch seems to implement shutdown ioctl. So it will still need > > > > glue code to detect writeback failure in upper/ and trigger shutdown > > > > internally? > > > > > > > > > > Yes. > > > ovl_get_acess() can check both the administrative ofs->goingdown > > > command and the upper writeback error condition for volatile ovl > > > or something like that. > > > > This approach will not help mmaped() pages though, if I do. > > > > - Store to addr > > - msync > > - Load from addr > > > > There is a chance that I can still read back old data. > > > > msync does not go through overlay. It goes directly to upper fs, > so it will sync pages and return error on volatile overlay as well. Ok. Its because vma->vm_file points to realfile. So even for volatile containers we only avoid fsync/syncfs and not msync. msync will directly call into upper/. > > Maybe there will still be weird corner cases, but the shutdown approach > should cover most or all of the interesting cases. Agreed. Vivek
