On Sun, Sep 18, 2016 at 11:31:17PM +0100, Al Viro wrote: > At the moment there are 11 callers (10 in mainline; one more added in > conversion of vmsplice_to_pipe() to new pipe locking, but it's irrelevant > anyway - it gets fed an iovec-backed iov_iter). I'm looking through those > right now, hopefully will come up with something sane... FWIW, I wonder how many of those users are ready to cope with compound pages in the first place; they end up passed to * skb_fill_page_desc(). Probably OK (as in all of them, modulo calculating the number of pages and ranges for them). * shoved into scatterlist, which gets passed to virtqueue_add_sgs(). Need to check virtio to see what happens there. * shoved into nfs ->wb_page and fed into nfs_pageio_add_request() and machinery behind it. These, BTW, are reachable by pipe_buffer-derived ones at the moment (splice to O_DIRECT nfs file). The code looks like it's playing fast and loose with ->wb_page - in some cases it's an NFS pagecache one, in some - anything from userland, and there are places like inode = page_file_mapping(req->wb_page)->host; which will do nasty things if they are ever reached by the second kind. nfs_pgio_rpcsetup() looks like it won't be happy with compound pages, but again, I'm not familiar enough with that code to tell if it's reachable from nfs_pageio_add_request(). * shoved into scatterlist, which gets fed into crypto/*.c machinery. No way for a pipe_buffer stuff to get there, fortunately, because I would be very surprised if it works correctly with compound pages and large ranges in those. * shoved into lustre ->ldp_pages; almost certainly not ready for compound pages. * fed to ceph_osd_data_pages_init(); again, practically certain not to be ready. * put into dio_submit ->pages[], eventually fed to bio_add_page(); that might be fixable, but it would take some massage in fs/direct-io.c * fuse - probably OK, but that's only on a fairly cursory look. It certainly won't be easy to verify in details ;-/ -- 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
