In message <Pine.LNX.4.64.0710222101420.23513@xxxxxxxxxxxxxxxxxxxxxx>, Hugh Dickins writes: > On Mon, 15 Oct 2007, Pekka Enberg wrote: > > > > I wonder whether _not setting_ BDI_CAP_NO_WRITEBACK implies that > > ->writepage() will never return AOP_WRITEPAGE_ACTIVATE for > > !wbc->for_reclaim case which would explain why we haven't hit this bug > > before. Hugh, Andrew? > > Only ramdisk and shmem have been returning AOP_WRITEPAGE_ACTIVATE. > Both of those set BDI_CAP_NO_WRITEBACK. ramdisk never returned it > if !wbc->for_reclaim. I contend that shmem shouldn't either: it's > a special code to get the LRU rotation right, not useful elsewhere. > Though Documentation/filesystems/vfs.txt does imply wider use. Yes, based on vfs.txt I figured unionfs should return AOP_WRITEPAGE_ACTIVATE. But, now that unionfs has ->writepages which won't even call the lower writepage if BDI_CAP_NO_WRITEBACK is on, then perhaps I no longer need unionfs_writepage to bother checking for AOP_WRITEPAGE_ACTIVATE, or even return it up? But, a future file system _could_ return AOP_WRITEPAGE_ACTIVATE w/o setting BDI_CAP_NO_WRITEBACK, right? In that case, unionfs will still need to handle AOP_WRITEPAGE_ACTIVATE in ->writepage, right? > I think this is where people use the phrase "go figure" ;) > > Hugh 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
