Dne Út 18. září 2012 04:16:27 Jan Kara napsal(a): > On Mon 17-09-12 12:15:46, Hugh Dickins wrote: > > On Mon, 17 Sep 2012, Jan Kara wrote: > > > I tripped over a crash in reiserfs which happened due to > > > PageSwapCache > > > > > > page being passed to reiserfs_set_page_dirty(). Now it's not that hard > > > to make reiserfs_set_page_dirty() check that case but I really wonder: > > > Does it make sense to call mapping->a_ops->set_page_dirty() for a > > > PageSwapCache page? The page is going to be written via direct IO so > > > from the POV of the filesystem there's no need for any dirtiness > > > tracking. Also there are several ->set_page_dirty() implementations > > > which will spectacularly crash because they do things like > > > page->mapping->host, or call > > > __set_page_dirty_buffers() which expects buffer heads in page->private. > > > Or what is the reason for calling filesystem's set_page_dirty() > > > function? > > > > This is a question for Mel, really: it used not to call the filesystem. > > > > But my reading of the 3.6 code says that it still will not call the > > filesystem, unless the filesystem (only nfs) provides a swap_activate > > method, which should be the only case in which SWP_FILE gets set. > > And I rather think Mel does want to use the filesystem set_page_dirty > > in that case. Am I misreading? > > > > Did you see this on a vanilla kernel? Or is it possible that you have > > a private patch merged in, with something else sharing the SWP_FILE bit > > (defined in include/linux/swap.h) by mistake? > > Argh, sorry. It is indeed a SLES specific bug. I missed that SWP_FILE bit > gets set only when swap_activate() is provided (SLES code works a bit > differently in this area but I wasn't really looking into that since I was > focused elsewhere). > > So just one minor nit for Mel. SWP_FILE looks like a bit confusing name for > a flag that gets set only for some swap files ;) At least I didn't pay > attention to it because I thought it's set for all of them. Maybe call it > SWP_FILE_CALL_AOPS or something like that? Same here. In fact, I believed that other filesystems only work by accident (because they don't have to access the mapping). I'm not even sure about the semantics of the swap_activate operation. Is this documented somewhere? Petr Tesarik SUSE Linux -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href