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? Thanks Hugh for having a look. Honza -- Jan Kara <jack@xxxxxxx> SUSE Labs, CR -- 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>