This version of the series addresses the review comments received, particularly from Christof. Thanks to all for review and testing. The patch adding mm/swap.h got a minor conflict when I rebaesd on 5.17-rc1, suggestion that it could easily get more conflicts in the future. It might be good if it could land before 5.17 comes out, to avoid (some of) those conflicts. I think (Though haven't checked) that all the NFS patch patches except NFS: rename nfs_direct_IO and use as ->swap_rw NFS: swap IO handling is slightly different for O_DIRECT IO can land independently of the MM patches, and can be moved to the end of the series. Maybe they could be held until after 5.18-rc1 if we agree to proceed with these in the next merge window. Intro from previous series is below. Thanks, NeilBrown swap-over-NFS currently has a variety of problems. swap writes call generic_write_checks(), which always fails on a swap file, so it completely fails. Even without this, various deadlocks are possible - largely due to improvements in NFS memory allocation (using NOFS instead of ATOMIC) which weren't tested against swap-out. NFS is the only filesystem that has supported fs-based swap IO, and it hasn't worked for several releases, so now is a convenient time to clean up the swap-via-filesystem interfaces - we cannot break anything ! So the first few patches here clean up and improve various parts of the swap-via-filesystem code. ->activate_swap() is given a cleaner interface, a new ->swap_rw is introduced instead of burdening ->direct_IO, etc. Current swap-to-filesystem code only ever submits single-page reads and writes. These patches change that to allow multi-page IO when adjacent requests are submitted. Writes are also changed to be async rather than sync. This substantially speeds up write throughput for swap-over-NFS. Some of the NFS patches can land independently of the MM patches. A few require the MM patches to land first. --- NeilBrown (23): MM: create new mm/swap.h header file. MM: extend block-plugging to cover all swap reads with read-ahead MM: drop swap_set_page_dirty MM: move responsibility for setting SWP_FS_OPS to ->swap_activate MM: reclaim mustn't enter FS for SWP_FS_OPS swap-space MM: introduce ->swap_rw and use it for reads from SWP_FS_OPS swap-space MM: perform async writes to SWP_FS_OPS swap-space using ->swap_rw DOC: update documentation for swap_activate and swap_rw MM: submit multipage reads for SWP_FS_OPS swap-space MM: submit multipage write for SWP_FS_OPS swap-space VFS: Add FMODE_CAN_ODIRECT file flag NFS: remove IS_SWAPFILE hack NFS: rename nfs_direct_IO and use as ->swap_rw NFS: swap IO handling is slightly different for O_DIRECT IO SUNRPC/call_alloc: async tasks mustn't block waiting for memory SUNRPC/auth: async tasks mustn't block waiting for memory SUNRPC/xprt: async tasks mustn't block waiting for memory SUNRPC: remove scheduling boost for "SWAPPER" tasks. NFS: discard NFS_RPC_SWAPFLAGS and RPC_TASK_ROOTCREDS SUNRPC: improve 'swap' handling: scheduling and PF_MEMALLOC NFSv4: keep state manager thread active if swap is enabled NFS: swap-out must always use STABLE writes. SUNRPC: lock against ->sock changing during sysfs read Documentation/filesystems/locking.rst | 18 ++- Documentation/filesystems/vfs.rst | 17 ++- drivers/block/loop.c | 4 +- fs/cifs/file.c | 7 +- fs/fcntl.c | 9 +- fs/nfs/direct.c | 56 ++++--- fs/nfs/file.c | 39 +++-- fs/nfs/nfs4_fs.h | 1 + fs/nfs/nfs4proc.c | 20 +++ fs/nfs/nfs4state.c | 39 ++++- fs/nfs/read.c | 4 - fs/nfs/write.c | 2 + fs/open.c | 9 +- fs/overlayfs/file.c | 13 +- include/linux/fs.h | 4 + include/linux/nfs_fs.h | 11 +- include/linux/nfs_xdr.h | 2 + include/linux/sunrpc/auth.h | 1 + include/linux/sunrpc/sched.h | 1 - include/linux/swap.h | 7 +- include/linux/writeback.h | 7 + include/trace/events/sunrpc.h | 1 - mm/madvise.c | 8 +- mm/memory.c | 2 +- mm/page_io.c | 210 ++++++++++++++++++++------ mm/swap.h | 26 +++- mm/swap_state.c | 33 ++-- mm/swapfile.c | 13 +- mm/vmscan.c | 38 +++-- net/sunrpc/auth.c | 8 +- net/sunrpc/auth_gss/auth_gss.c | 6 +- net/sunrpc/auth_unix.c | 10 +- net/sunrpc/clnt.c | 7 +- net/sunrpc/sched.c | 29 ++-- net/sunrpc/sysfs.c | 5 +- net/sunrpc/xprt.c | 19 +-- net/sunrpc/xprtrdma/transport.c | 10 +- net/sunrpc/xprtsock.c | 15 +- 38 files changed, 505 insertions(+), 206 deletions(-) -- Signature