---- 在 星期三, 2021-12-01 21:46:10 Jan Kara <jack@xxxxxxx> 撰写 ---- > On Wed 01-12-21 09:19:17, Amir Goldstein wrote: > > On Wed, Dec 1, 2021 at 8:31 AM Chengguang Xu <cgxu519@xxxxxxxxxxxx> wrote: > > > So the final solution to handle all the concerns looks like accurately > > > mark overlay inode diry on modification and re-mark dirty only for > > > mmaped file in ->write_inode(). > > > > > > Hi Miklos, Jan > > > > > > Will you agree with new proposal above? > > > > > > > Maybe you can still pull off a simpler version by remarking dirty only > > writably mmapped upper AND inode_is_open_for_write(upper)? > > Well, if inode is writeably mapped, it must be also open for write, doesn't > it? That's right. > The VMA of the mapping will hold file open. It's a bit tricky but currently ovl_mmap() will replace file to realfile in upper layer and release overlayfs file. So overlayfs file itself will not have any relationship with the VMA anymore after mmap(). Thanks, Chengguang > So remarking overlay inode > dirty during writeback while inode_is_open_for_write(upper) looks like > reasonably easy and presumably there won't be that many inodes open for > writing for this to become big overhead? > > > If I am not mistaken, if you always mark overlay inode dirty on ovl_flush() > > of FMODE_WRITE file, there is nothing that can make upper inode dirty > > after last close (if upper is not mmaped), so one more inode sync should > > be enough. No? > > But we still need to catch other dirtying events like timestamp updates, > truncate(2) etc. to mark overlay inode dirty. Not sure how reliably that > can be done... > > Honza > -- > Jan Kara <jack@xxxxxxxx> > SUSE Labs, CR >
