linux/net/sctp
Mel Gorman c76562b670 netvm: prevent a stream-specific deadlock
This patch series is based on top of "Swap-over-NBD without deadlocking
v15" as it depends on the same reservation of PF_MEMALLOC reserves logic.

When a user or administrator requires swap for their application, they
create a swap partition and file, format it with mkswap and activate it
with swapon.  In diskless systems this is not an option so if swap if
required then swapping over the network is considered.  The two likely
scenarios are when blade servers are used as part of a cluster where the
form factor or maintenance costs do not allow the use of disks and thin
clients.

The Linux Terminal Server Project recommends the use of the Network Block
Device (NBD) for swap but this is not always an option.  There is no
guarantee that the network attached storage (NAS) device is running Linux
or supports NBD.  However, it is likely that it supports NFS so there are
users that want support for swapping over NFS despite any performance
concern.  Some distributions currently carry patches that support swapping
over NFS but it would be preferable to support it in the mainline kernel.

Patch 1 avoids a stream-specific deadlock that potentially affects TCP.

Patch 2 is a small modification to SELinux to avoid using PFMEMALLOC
	reserves.

Patch 3 adds three helpers for filesystems to handle swap cache pages.
	For example, page_file_mapping() returns page->mapping for
	file-backed pages and the address_space of the underlying
	swap file for swap cache pages.

Patch 4 adds two address_space_operations to allow a filesystem
	to pin all metadata relevant to a swapfile in memory. Upon
	successful activation, the swapfile is marked SWP_FILE and
	the address space operation ->direct_IO is used for writing
	and ->readpage for reading in swap pages.

Patch 5 notes that patch 3 is bolting
	filesystem-specific-swapfile-support onto the side and that
	the default handlers have different information to what
	is available to the filesystem. This patch refactors the
	code so that there are generic handlers for each of the new
	address_space operations.

Patch 6 adds an API to allow a vector of kernel addresses to be
	translated to struct pages and pinned for IO.

Patch 7 adds support for using highmem pages for swap by kmapping
	the pages before calling the direct_IO handler.

Patch 8 updates NFS to use the helpers from patch 3 where necessary.

Patch 9 avoids setting PF_private on PG_swapcache pages within NFS.

Patch 10 implements the new swapfile-related address_space operations
	for NFS and teaches the direct IO handler how to manage
	kernel addresses.

Patch 11 prevents page allocator recursions in NFS by using GFP_NOIO
	where appropriate.

Patch 12 fixes a NULL pointer dereference that occurs when using
	swap-over-NFS.

With the patches applied, it is possible to mount a swapfile that is on an
NFS filesystem.  Swap performance is not great with a swap stress test
taking roughly twice as long to complete than if the swap device was
backed by NBD.

This patch: netvm: prevent a stream-specific deadlock

It could happen that all !SOCK_MEMALLOC sockets have buffered so much data
that we're over the global rmem limit.  This will prevent SOCK_MEMALLOC
buffers from receiving data, which will prevent userspace from running,
which is needed to reduce the buffered data.

Fix this by exempting the SOCK_MEMALLOC sockets from the rmem limit.  Once
this change it applied, it is important that sockets that set
SOCK_MEMALLOC do not clear the flag until the socket is being torn down.
If this happens, a warning is generated and the tokens reclaimed to avoid
accounting errors until the bug is fixed.

[davem@davemloft.net: Warning about clearing SOCK_MEMALLOC]
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Christoph Hellwig <hch@infradead.org>
Cc: Mike Christie <michaelc@cs.wisc.edu>
Cc: Eric B Munson <emunson@mgebm.net>
Cc: Sebastian Andrzej Siewior <sebastian@breakpoint.cc>
Cc: Mel Gorman <mgorman@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-07-31 18:42:47 -07:00
..
Kconfig sctp: implement sctp association probing module 2010-04-30 22:41:09 -04:00
Makefile sctp: implement sctp association probing module 2010-04-30 22:41:09 -04:00
associola.c sctp: Implement quick failover draft from tsvwg 2012-07-22 12:13:46 -07:00
auth.c sctp: better integer overflow check in sctp_auth_create_key() 2011-11-29 15:51:03 -05:00
bind_addr.c net: Remove casts of void * 2011-06-16 23:19:27 -04:00
chunk.c net/sctp: Use pr_fmt and pr_<level> 2010-08-26 14:11:48 -07:00
command.c [SCTP]: Remove sctp_add_cmd_sf wrapper bloat 2008-03-27 17:54:29 -07:00
debug.c sctp: remove completely unsed EMPTY state 2011-04-20 01:51:03 -07:00
endpointola.c treewide: Fix typos in various parts of the kernel, and fix some comments. 2011-12-02 14:57:31 +01:00
input.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2012-07-19 11:17:30 -07:00
inqueue.c net/sctp: Use pr_fmt and pr_<level> 2010-08-26 14:11:48 -07:00
ipv6.c ipv6: Add redirect support to all protocol icmp error handlers. 2012-07-12 00:25:15 -07:00
objcnt.c net/sctp: Use pr_fmt and pr_<level> 2010-08-26 14:11:48 -07:00
output.c sctp: Adjust PMTU updates to accomodate route invalidation. 2012-07-16 03:57:14 -07:00
outqueue.c sctp: Implement quick failover draft from tsvwg 2012-07-22 12:13:46 -07:00
primitive.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
probe.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next-2.6 2010-10-23 11:47:02 -07:00
proc.c net: Add export.h for EXPORT_SYMBOL/THIS_MODULE to non-modules 2011-10-31 19:30:30 -04:00
protocol.c ipv4: Prepare for change of rt->rt_iif encoding. 2012-07-23 16:36:26 -07:00
sm_make_chunk.c sctp: fix sparse warning for sctp_init_cause_fixed 2012-07-16 23:23:52 -07:00
sm_sideeffect.c sctp: Implement quick failover draft from tsvwg 2012-07-22 12:13:46 -07:00
sm_statefuns.c net: Convert net_ratelimit uses to net_<level>_ratelimited 2012-05-15 13:45:03 -04:00
sm_statetable.c sctp: Enforce retransmission limit during shutdown 2011-07-07 14:08:44 -07:00
socket.c sctp: Implement quick failover draft from tsvwg 2012-07-22 12:13:46 -07:00
ssnmap.c include cleanup: Update gfp.h and slab.h includes to prepare for breaking implicit slab.h inclusion from percpu.h 2010-03-30 22:02:32 +09:00
sysctl.c sctp: Implement quick failover draft from tsvwg 2012-07-22 12:13:46 -07:00
transport.c Merge branch 'kill_rtcache' 2012-07-22 17:04:15 -07:00
tsnmap.c sctp: be more restrictive in transport selection on bundled sacks 2012-06-30 22:44:35 -07:00
ulpevent.c netvm: prevent a stream-specific deadlock 2012-07-31 18:42:47 -07:00
ulpqueue.c sctp: be more restrictive in transport selection on bundled sacks 2012-06-30 22:44:35 -07:00