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.
Thanks,
NeilBrown
---
NeilBrown (18):
Structural cleanup for filesystem-based swap
MM: create new mm/swap.h header file.
MM: use ->swap_rw for reads from SWP_FS_OPS swap-space
MM: perform async writes to SWP_FS_OPS swap-space
MM: reclaim mustn't enter FS for SWP_FS_OPS swap-space
MM: submit multipage reads for SWP_FS_OPS swap-space
MM: submit multipage write for SWP_FS_OPS swap-space
MM: Add AS_CAN_DIO mapping flag
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.
drivers/block/loop.c | 4 +-
fs/fcntl.c | 5 +-
fs/inode.c | 3 +
fs/nfs/direct.c | 56 ++++++----
fs/nfs/file.c | 25 +++--
fs/nfs/inode.c | 1 +
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 | 2 +-
fs/overlayfs/file.c | 10 +-
include/linux/fs.h | 2 +-
include/linux/nfs_fs.h | 11 +-
include/linux/nfs_xdr.h | 2 +
include/linux/pagemap.h | 3 +-
include/linux/sunrpc/auth.h | 1 +
include/linux/sunrpc/sched.h | 1 -
include/linux/swap.h | 121 --------------------
include/linux/writeback.h | 7 ++
include/trace/events/sunrpc.h | 1 -
mm/madvise.c | 9 +-
mm/memory.c | 3 +-
mm/mincore.c | 1 +
mm/page_alloc.c | 1 +
mm/page_io.c | 189 ++++++++++++++++++++++++++------
mm/shmem.c | 1 +
mm/swap.h | 140 +++++++++++++++++++++++
mm/swap_state.c | 32 ++++--
mm/swapfile.c | 6 +
mm/util.c | 1 +
mm/vmscan.c | 31 +++++-
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/xprt.c | 19 ++--
net/sunrpc/xprtrdma/transport.c | 10 +-
net/sunrpc/xprtsock.c | 8 ++
41 files changed, 558 insertions(+), 274 deletions(-)
create mode 100644 mm/swap.h
--
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