On Tue, Aug 22, 2023 at 2:03 PM Miklos Szeredi <miklos@xxxxxxxxxx> wrote: > > On Tue, 22 Aug 2023 at 12:18, Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > > On Mon, Aug 21, 2023 at 6:27 PM Amir Goldstein <amir73il@xxxxxxxxx> wrote: > > > > Getting back to this. > > > Did you mean something like that? (only compile tested) > > > > > > https://github.com/amir73il/linux/commits/backing_fs > > > > > > If yes, then I wonder: > > > 1. Is the difference between FUSE_IOCB_MASK and OVL_IOCB_MASK > > > (i.e. the APPEND flag) intentional? > > Setting IOCB_APPEND on the backing file doesn't make a difference as > long as the backing file is not modified during the write. > > In overlayfs the case of the backing file being modified is not > defined, so I guess that's the reason to omit it. However I don't see > a problem with setting it on the backing file either, the file > size/position is synchronized after the write, so nothing bad should > happen if the backing file was modified. > That raises the question if FUSE passthrough behavior is defined when backing file is being modified. Should it be any different than ovl? I don't really care if we set IOCB_APPEND or not, just if we need a different mask for ovl and FUSE. > > > 2. What would be the right way to do ovl_copyattr() on io completion? > > > Pass another completion handler to read/write helpers? > > > This seems a bit ugly. Do you have a nicer idea? > > > > > Ugh, I missed that little detail. I don't have a better idea than to > use a callback function. > Ok. added the cleanup callback. I think it's not that bad? https://github.com/amir73il/linux/commits/backing_fs > > > > Hmm. Looking closer, ovl_copyattr() in ovl_aio_cleanup_handler() > > seems a bit racy as it is not done under inode_lock(). > > Decided to fix that by taking ovl inode spinlock inside ovl_copyattr() and did the same for ovl_file_accessed() for read ops. I've found and fixed two other issues with aio completion on this branch, one of them is a fix for a possible realfile refcount leak, so will probably need to backport this one. Thanks, Amir.
