In message <Pine.LNX.4.64.0710142049000.13119@xxxxxxxxxxxxxxxxxxxxx>, Pekka J Enberg writes: > Hi Erez, > > On Sun, 14 Oct 2007, Erez Zadok wrote: > > In unionfs_writepage() I tried to emulate as best possible what the lower > > f/s will have returned to the VFS. Since tmpfs's ->writepage can return > > AOP_WRITEPAGE_ACTIVATE and re-mark its page as dirty, I did the same in > > unionfs: mark again my page as dirty, and return AOP_WRITEPAGE_ACTIVATE. > > > > Should I be doing something different when unionfs stacks on top of tmpfs? > > (BTW, this is probably also relevant to ecryptfs.) > > Look at mm/filemap.c:__filemap_fdatawrite_range(). You shouldn't be > calling unionfs_writepage() _at all_ if the lower mapping has > BDI_CAP_NO_WRITEBACK capability set. Perhaps something like the totally > untested patch below? > > Pekka [...] Pekka, with a small change to your patch (to handle time-based cache coherency), your patch worked well and passed all my tests. Thanks. So now I wonder if we still need the patch to prevent AOP_WRITEPAGE_ACTIVATE from being returned to userland. I guess we still need it, b/c even with your patch, generic_writepages() can return AOP_WRITEPAGE_ACTIVATE back to the VFS and we need to ensure that doesn't "leak" outside the kernel. Erez. - To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
