tentatively merged the first 13 of this series into cifs-2.6.git for-next (pending additional testing and any more review comments) On Thu, Feb 16, 2023 at 3:47 PM David Howells <dhowells@xxxxxxxxxx> wrote: > > Hi Steve, > > Here's an updated version of my patchset to make the cifs/smb3 driver pass > iov_iters down to the lowest layers where they can be passed directly to > the network transport rather than passing lists of pages around. > > The series deals with the following issues: > > (-) By pinning pages, it fixes the race between concurrent DIO read and > fork, whereby the pages containing the DIO read buffer may end up > belonging to the child process and not the parent - with the result > that the parent might not see the retrieved data. > > (-) cifs shouldn't take refs on pages extracted from non-user-backed > iterators (eg. KVEC). With these changes, cifs will apply the > appropriate cleanup. Note that there is the possibility the network > transport might, but that's beyond the scope of this patchset. > > (-) Making it easier to transition to using folios in cifs rather than > pages by dealing with them through BVEC and XARRAY iterators. > > The first five patches add two facilities to the VM/VFS core, excerpts from > my iov-extract branch[1] that are required in order to do the cifs > iteratorisation: > > (*) Future replacements for file-splicing in the form of functions > filemap_splice_read() and direct_splice_read(). These allow file > splicing to be done without the use of an ITER_PIPE iterator, without > the need to take refs on the pages extracted from KVEC/BVEC/XARRAY > iterators. This is necessary to use iov_iter_extract_pages(). > > [!] Note that whilst these are added in core code, they are only used > by cifs at this point. > > (*) Add iov_iter_extract_pages(), a replacement for iov_iter_get_pages*() > that uses FOLL_PIN on user pages (IOVEC, UBUF) and doesn't pin kernel > pages (BVEC, KVEC, XARRAY). This allows cifs to do the page pinning > correctly. > > [!] Note that whilst this is added in core code, it is only used by > cifs at this point - though a corresponding change is made to the > flags argument of iov_iter_get_pages*() so that it doesn't take FOLL_* > flags, but rather takes iov_iter_extraction_t flags that are > translated internally to FOLL_* flags. > > Then there's a couple of patches to make cifs use the new splice functions. > > The series continues with a couple of patches that add stuff to netfslib > that I want to use there as well as in cifs: > > (*) Add a netfslib function to extract and pin pages from an ITER_IOBUF or > ITER_UBUF iterator into an ITER_BVEC iterator. > > (*) Add a netfslib function to extract pages from an iterator that's of > type ITER_UBUF/IOVEC/BVEC/KVEC/XARRAY and add them to a scatterlist. > The cleanup will need to be done as for iov_iter_extract_pages(). > > BVEC, KVEC and XARRAY iterators can be rendered into elements that > span multiple pages. > > Added to that are some cifs helpers that work with iterators: > > (*) Add a function to walk through an ITER_BVEC/KVEC/XARRAY iterator and > add elements to an RDMA SGE list. Only the DMA addresses are stored, > and an element may span multiple pages (say if an xarray contains a > multipage folio). > > (*) Add a function to walk through an ITER_BVEC/KVEC/XARRAY iterator and > pass the contents into a shash function. > > (*) Add functions to walk through an ITER_XARRAY iterator and perform > various sorts of cleanup on the folios held therein, to be used on I/O > completion. > > (*) Add a function to read from the transport TCP socket directly into an > iterator. > > Finally come the patches that actually do the work of iteratorising cifs: > > (*) The main patch. Replace page lists with iterators. It extracts the > pages from ITER_UBUF and ITER_IOVEC iterators to an ITER_BVEC > iterator, pinning or getting refs on them, before passing them down as > the I/O may be done from a worker thread. > > The iterator is extracted into a scatterlist in order to talk to the > crypto interface or to do RDMA. > > (*) In the cifs RDMA code, extract the iterator into an RDMA SGE[] list, > removing the scatterlist intermediate - at least for smbd_send(). > There appear to be other ways for cifs to talk to the RDMA layer that > don't go through that that I haven't managed to work out. > > (*) Remove a chunk of now-unused code. > > (*) Allow DIO to/from KVEC-type iterators. > > I've pushed the patches here also: > > https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=iov-cifs > > David > > Link: https://lore.kernel.org/r/20230214171330.2722188-1-dhowells@xxxxxxxxxx/ [1] > Link: https://lore.kernel.org/r/166697254399.61150.1256557652599252121.stgit@xxxxxxxxxxxxxxxxxxxxxx/ > Link: https://lore.kernel.org/r/20230131182855.4027499-1-dhowells@xxxxxxxxxx/ # v1 > > David Howells (17): > mm: Pass info, not iter, into filemap_get_pages() > splice: Add a func to do a splice from a buffered file without > ITER_PIPE > splice: Add a func to do a splice from an O_DIRECT file without > ITER_PIPE > iov_iter: Define flags to qualify page extraction. > iov_iter: Add a function to extract a page list from an iterator > splice: Export filemap/direct_splice_read() > cifs: Implement splice_read to pass down ITER_BVEC not ITER_PIPE > netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator > netfs: Add a function to extract an iterator into a scatterlist > cifs: Add a function to build an RDMA SGE list from an iterator > cifs: Add a function to Hash the contents of an iterator > cifs: Add some helper functions > cifs: Add a function to read into an iter from a socket > cifs: Change the I/O paths to use an iterator rather than a page list > cifs: Build the RDMA SGE list directly from an iterator > cifs: Remove unused code > cifs: DIO to/from KVEC-type iterators should now work > > block/bio.c | 6 +- > block/blk-map.c | 8 +- > fs/cifs/Kconfig | 1 + > fs/cifs/cifsencrypt.c | 172 +++- > fs/cifs/cifsfs.c | 12 +- > fs/cifs/cifsfs.h | 6 + > fs/cifs/cifsglob.h | 66 +- > fs/cifs/cifsproto.h | 11 +- > fs/cifs/cifssmb.c | 15 +- > fs/cifs/connect.c | 14 + > fs/cifs/file.c | 1772 ++++++++++++++++--------------------- > fs/cifs/fscache.c | 22 +- > fs/cifs/fscache.h | 10 +- > fs/cifs/misc.c | 128 +-- > fs/cifs/smb2ops.c | 362 ++++---- > fs/cifs/smb2pdu.c | 53 +- > fs/cifs/smbdirect.c | 535 ++++++----- > fs/cifs/smbdirect.h | 7 +- > fs/cifs/transport.c | 54 +- > fs/netfs/Makefile | 1 + > fs/netfs/iterator.c | 371 ++++++++ > fs/splice.c | 93 ++ > include/linux/fs.h | 6 + > include/linux/netfs.h | 8 + > include/linux/pipe_fs_i.h | 20 + > include/linux/uio.h | 35 +- > lib/iov_iter.c | 284 +++++- > mm/filemap.c | 156 +++- > mm/internal.h | 6 + > mm/vmalloc.c | 1 + > 30 files changed, 2515 insertions(+), 1720 deletions(-) > create mode 100644 fs/netfs/iterator.c > -- Thanks, Steve
