Commit Graph

240995 Commits

Author SHA1 Message Date
Namhyung Kim 1d16871d8c mm: batch-free pcp list if possible
free_pcppages_bulk() frees pages from pcp lists in a round-robin fashion
by keeping batch_free counter.  But it doesn't need to spin if there is
only one non-empty list.  This can be checked by batch_free ==
MIGRATE_PCPTYPES.

[akpm@linux-foundation.org: fix comment]
Signed-off-by: Namhyung Kim <namhyung@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Minchan Kim e64a782fec mm: change __remove_from_page_cache()
Now we renamed remove_from_page_cache with delete_from_page_cache.  As
consistency of __remove_from_swap_cache and remove_from_swap_cache, we
change internal page cache handling function name, too.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Minchan Kim 702cfbf93a mm: goodbye remove_from_page_cache()
Now delete_from_page_cache() replaces remove_from_page_cache().  So we
remove remove_from_page_cache so fs or something out of mainline will
notice it when compile time and can fix it.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Minchan Kim 5adc7b518b mm: truncate: change remove_from_page_cache
This patch series changes remove_from_page_cache()'s page ref counting
rule.  Page cache ref count is decreased in delete_from_page_cache().  So
we don't need to decrease the page reference in callers.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Nick Piggin <npiggin@kernel.dk>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Minchan Kim 4c73b1bc6b mm: shmem: change remove_from_page_cache
This patch series changes remove_from_page_cache()'s page ref counting
rule.  Page cache ref count is decreased in delete_from_page_cache().  So
we don't need to decrease the page reference in callers.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Minchan Kim bd65cb86c9 mm: hugetlbfs: change remove_from_page_cache
This patch series changes remove_from_page_cache()'s page ref counting
rule.  Page cache ref count is decreased in delete_from_page_cache().  So
we don't need to decrease the page reference in callers.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: William Irwin <wli@holomorphy.com>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Minchan Kim 97cecb5a25 mm: introduce delete_from_page_cache()
Presently we increase the page refcount in add_to_page_cache() but don't
decrease it in remove_from_page_cache().  Such asymmetry adds confusion,
requiring that callers notice it and a comment explaining why they release
a page reference.  It's not a good API.

A long time ago, Hugh tried it (http://lkml.org/lkml/2004/10/24/140) but
gave up because reiser4's drop_page() had to unlock the page between
removing it from page cache and doing the page_cache_release().  But now
the situation is changed.  I think at least things in current mainline
don't have any obstacles.  The problem is for out-of-mainline filesystems
- if they have done such things as reiser4, this patch could be a problem
but they will discover this at compile time since we remove
remove_from_page_cache().

This patch:

This function works as just wrapper remove_from_page_cache().  The
difference is that it decreases page references in itself.  So caller have
to make sure it has a page reference before calling.

This patch is ready for removing remove_from_page_cache().

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Christoph Hellwig <hch@infradead.org>
Acked-by: Hugh Dickins <hughd@google.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Edward Shishkin <edward.shishkin@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Miklos Szeredi ef6a3c6311 mm: add replace_page_cache_page() function
This function basically does:

     remove_from_page_cache(old);
     page_cache_release(old);
     add_to_page_cache_locked(new);

Except it does this atomically, so there's no possibility for the "add" to
fail because of a race.

If memory cgroups are enabled, then the memory cgroup charge is also moved
from the old page to the new.

This function is currently used by fuse to move pages into the page cache
on read, instead of copying the page contents.

[minchan.kim@gmail.com: add freepage() hook to replace_page_cache_page()]
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Acked-by: Rik van Riel <riel@redhat.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Gleb Natapov 318b275fbc mm: allow GUP to fail instead of waiting on a page
GUP user may want to try to acquire a reference to a page if it is already
in memory, but not if IO, to bring it in, is needed.  For example KVM may
tell vcpu to schedule another guest process if current one is trying to
access swapped out page.  Meanwhile, the page will be swapped in and the
guest process, that depends on it, will be able to run again.

This patch adds FAULT_FLAG_RETRY_NOWAIT (suggested by Linus) and
FOLL_NOWAIT follow_page flags.  FAULT_FLAG_RETRY_NOWAIT, when used in
conjunction with VM_FAULT_ALLOW_RETRY, indicates to handle_mm_fault that
it shouldn't drop mmap_sem and wait on a page, but return VM_FAULT_RETRY
instead.

[akpm@linux-foundation.org: improve FOLL_NOWAIT comment]
Signed-off-by: Gleb Natapov <gleb@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Hugh Dickins <hughd@google.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: Michel Lespinasse <walken@google.com>
Cc: Avi Kivity <avi@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:02 -07:00
Prarit Bhargava 5fda1bd5b8 mm: notifier_from_errno() cleanup
While looking at some other notifier callbacks I noticed this code could
use a simple cleanup.

notifier_from_errno() no longer needs the if (ret)/else conditional.  That
same conditional is now done in notifier_from_errno().

Signed-off-by: Prarit Bhargava <prarit@redhat.com>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Pekka Enberg <penberg@cs.helsinki.fi>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:01 -07:00
David Rientjes cbf978bfb1 oom: suppress nodes that are not allowed from meminfo on page alloc failure
Displaying extremely verbose meminfo for all nodes on the system is
overkill for page allocation failures when the context restricts that
allocation to only a subset of nodes.  We don't particularly care about
the state of all nodes when some are not allowed in the current context,
they can have an abundance of memory but we can't allocate from that part
of memory.

This patch suppresses disallowed nodes from the meminfo dump on a page
allocation failure if the context requires it.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:01 -07:00
David Rientjes 29423e77c0 oom: suppress show_mem() for many nodes in irq context on page alloc failure
When a page allocation failure occurs, show_mem() is called to dump the
state of the VM so users may understand what happened to get into that
condition.

This output, however, can be extremely verbose.  In irq context, it may
result in significant delays that incur NMI watchdog timeouts when the
machine is large (we use CONFIG_NODES_SHIFT > 8 here to define a "large"
machine since the length of the show_mem() output is proportional to the
number of possible nodes).

This patch suppresses the show_mem() call in irq context when the kernel
has CONFIG_NODES_SHIFT > 8.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:01 -07:00
David Rientjes ddd588b5dd oom: suppress nodes that are not allowed from meminfo on oom kill
The oom killer is extremely verbose for machines with a large number of
cpus and/or nodes.  This verbosity can often be harmful if it causes other
important messages to be scrolled from the kernel log and incurs a
signicant time delay, specifically for kernels with CONFIG_NODES_SHIFT >
8.

This patch causes only memory information to be displayed for nodes that
are allowed by current's cpuset when dumping the VM state.  Information
for all other nodes is irrelevant to the oom condition; we don't care if
there's an abundance of memory elsewhere if we can't access it.

This only affects the behavior of dumping memory information when an oom
is triggered.  Other dumps, such as for sysrq+m, still display the
unfiltered form when using the existing show_mem() interface.

Additionally, the per-cpu pageset statistics are extremely verbose in oom
killer output, so it is now suppressed.  This removes

	nodes_weight(current->mems_allowed) * (1 + nr_cpus)

lines from the oom killer output.

Callers may use __show_mem(SHOW_MEM_FILTER_NODES) to filter disallowed
nodes.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:01 -07:00
Eric Dumazet 94dcf29a11 kthread: use kthread_create_on_node()
ksoftirqd, kworker, migration, and pktgend kthreads can be created with
kthread_create_on_node(), to get proper NUMA affinities for their stack and
task_struct.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:01 -07:00
Eric Dumazet 207205a2ba kthread: NUMA aware kthread_create_on_node()
All kthreads being created from a single helper task, they all use memory
from a single node for their kernel stack and task struct.

This patch suite creates kthread_create_on_node(), adding a 'cpu' parameter
to parameters already used by kthread_create().

This parameter serves in allocating memory for the new kthread on its
memory node if possible.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:01 -07:00
Eric Dumazet b6a84016bd mm: NUMA aware alloc_thread_info_node()
Add a node parameter to alloc_thread_info(), and change its name to
alloc_thread_info_node()

This change is needed to allow NUMA aware kthread_create_on_cpu()

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:01 -07:00
Eric Dumazet 504f52b543 mm: NUMA aware alloc_task_struct_node()
All kthreads being created from a single helper task, they all use memory
from a single node for their kernel stack and task struct.

This patch suite creates kthread_create_on_cpu(), adding a 'cpu' parameter
to parameters already used by kthread_create().

This parameter serves in allocating memory for the new kthread on its
memory node if available.

Users of this new function are : ksoftirqd, kworker, migration, pktgend...

This patch:

Add a node parameter to alloc_task_struct(), and change its name to
alloc_task_struct_node()

This change is needed to allow NUMA aware kthread_create_on_cpu()

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Rusty Russell <rusty@rustcorp.com.au>
Cc: Tejun Heo <tj@kernel.org>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: David Howells <dhowells@redhat.com>
Cc: <linux-arch@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:01 -07:00
Minchan Kim 9d502c1c8d mm/compaction: check migrate_pages's return value instead of list_empty()
Many migrate_page's caller check return value instead of list_empy by
cf608ac19c ("mm: compaction: fix COMPACTPAGEFAILED counting").  This patch
makes compaction's migrate_pages consistent with others.  This patch
should not change old behavior.

Signed-off-by: Minchan Kim <minchan.kim@gmail.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Andrea Arcangeli d527caf22e mm: compaction: prevent kswapd compacting memory to reduce CPU usage
This patch reverts 5a03b051 ("thp: use compaction in kswapd for GFP_ATOMIC
order > 0") due to reports stating that kswapd CPU usage was higher and
IRQs were being disabled more frequently.  This was reported at
http://www.spinics.net/linux/fedora/alsa-user/msg09885.html.

Without this patch applied, CPU usage by kswapd hovers around the 20% mark
according to the tester (Arthur Marsh:
http://www.spinics.net/linux/fedora/alsa-user/msg09899.html).  With this
patch applied, it's around 2%.

The problem is not related to THP which specifies __GFP_NO_KSWAPD but is
triggered by high-order allocations hitting the low watermark for their
order and waking kswapd on kernels with CONFIG_COMPACTION set.  The most
common trigger for this is network cards configured for jumbo frames but
it's also possible it'll be triggered by fork-heavy workloads (order-1)
and some wireless cards which depend on order-1 allocations.

The symptoms for the user will be high CPU usage by kswapd in low-memory
situations which could be confused with another writeback problem.  While
a patch like 5a03b051 may be reintroduced in the future, this patch plays
it safe for now and reverts it.

[mel@csn.ul.ie: Beefed up the changelog]
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Mel Gorman <mel@csn.ul.ie>
Reported-by: Arthur Marsh <arthur.marsh@internode.on.net>
Tested-by: Arthur Marsh <arthur.marsh@internode.on.net>
Cc: <stable@kernel.org>		[2.6.38.1]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Nick Piggin 89699605fe mm: vmap area cache
Provide a free area cache for the vmalloc virtual address allocator, based
on the algorithm used by the user virtual memory allocator.

This reduces the number of rbtree operations and linear traversals over
the vmap extents in order to find a free area, by starting off at the last
point that a free area was found.

The free area cache is reset if areas are freed behind it, or if we are
searching for a smaller area or alignment than last time.  So allocation
patterns are not changed (verified by corner-case and random test cases in
userspace testing).

This solves a regression caused by lazy vunmap TLB purging introduced in
db64fe02 (mm: rewrite vmap layer).  That patch will leave extents in the
vmap allocator after they are vunmapped, and until a significant number
accumulate that can be flushed in a single batch.  So in a workload that
vmalloc/vfree frequently, a chain of extents will build up from
VMALLOC_START address, which have to be iterated over each time (giving an
O(n) type of behaviour).

After this patch, the search will start from where it left off, giving
closer to an amortized O(1).

This is verified to solve regressions reported Steven in GFS2, and Avi in
KVM.

Hugh's update:

: I tried out the recent mmotm, and on one machine was fortunate to hit
: the BUG_ON(first->va_start < addr) which seems to have been stalling
: your vmap area cache patch ever since May.

: I can get you addresses etc, I did dump a few out; but once I stared
: at them, it was easier just to look at the code: and I cannot see how
: you would be so sure that first->va_start < addr, once you've done
: that addr = ALIGN(max(...), align) above, if align is over 0x1000
: (align was 0x8000 or 0x4000 in the cases I hit: ioremaps like Steve).

: I originally got around it by just changing the
: 		if (first->va_start < addr) {
: to
: 		while (first->va_start < addr) {
: without thinking about it any further; but that seemed unsatisfactory,
: why would we want to loop here when we've got another very similar
: loop just below it?

: I am never going to admit how long I've spent trying to grasp your
: "while (n)" rbtree loop just above this, the one with the peculiar
: 		if (!first && tmp->va_start < addr + size)
: in.  That's unfamiliar to me, I'm guessing it's designed to save a
: subsequent rb_next() in a few circumstances (at risk of then setting
: a wrong cached_hole_size?); but they did appear few to me, and I didn't
: feel I could sign off something with that in when I don't grasp it,
: and it seems responsible for extra code and mistaken BUG_ON below it.

: I've reverted to the familiar rbtree loop that find_vma() does (but
: with va_end >= addr as you had, to respect the additional guard page):
: and then (given that cached_hole_size starts out 0) I don't see the
: need for any complications below it.  If you do want to keep that loop
: as you had it, please add a comment to explain what it's trying to do,
: and where addr is relative to first when you emerge from it.

: Aren't your tests "size <= cached_hole_size" and
: "addr + size > first->va_start" forgetting the guard page we want
: before the next area?  I've changed those.

: I have not changed your many "addr + size - 1 < addr" overflow tests,
: but have since come to wonder, shouldn't they be "addr + size < addr"
: tests - won't the vend checks go wrong if addr + size is 0?

: I have added a few comments - Wolfgang Wander's 2.6.13 description of
: 1363c3cd86 Avoiding mmap fragmentation
: helped me a lot, perhaps a pointer to that would be good too.  And I found
: it easier to understand when I renamed cached_start slightly and moved the
: overflow label down.

: This patch would go after your mm-vmap-area-cache.patch in mmotm.
: Trivially, nobody is going to get that BUG_ON with this patch, and it
: appears to work fine on my machines; but I have not given it anything like
: the testing you did on your original, and may have broken all the
: performance you were aiming for.  Please take a look and test it out
: integrate with yours if you're satisfied - thanks.

[akpm@linux-foundation.org: add locking comment]
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: Minchan Kim <minchan.kim@gmail.com>
Reported-and-tested-by: Steven Whitehouse <swhiteho@redhat.com>
Reported-and-tested-by: Avi Kivity <avi@redhat.com>
Tested-by: "Barry J. Marson" <bmarson@redhat.com>
Cc: Prarit Bhargava <prarit@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Robert Morell ef0a5e80f5 pwm_backlight: add check_fb() hook
In systems with multiple framebuffer devices, one of the devices might be
blanked while another is unblanked.  In order for the backlight blanking
logic to know whether to turn off the backlight for a particular
framebuffer's blanking notification, it needs to be able to check if a
given framebuffer device corresponds to the backlight.

This plumbs the check_fb hook from core backlight through the
pwm_backlight helper to allow platform code to plug in a check_fb hook.

Signed-off-by: Robert Morell <rmorell@nvidia.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Arun Murthy <arun.murthy@stericsson.com>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Axel Lin 0508e04e05 drivers/video/backlight/jornada720_*.c: make needlessly global symbols static
The following symbols are needlessly defined global: jornada_bl_init,
jornada_bl_exit, jornada_lcd_init, jornada_lcd_exit.

Make them static.

Signed-off-by: Axel Lin <axel.lin@gmail.com>
Acked-by: Kristoffer Ericson <kristoffer.ericson@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Randy Dunlap b372412e15 backlight: apple_bl depends on ACPI
apple_bl uses ACPI interfaces (data & code), so it should depend on ACPI.

  drivers/video/backlight/apple_bl.c:142: warning: 'struct acpi_device' declared inside parameter list
  drivers/video/backlight/apple_bl.c:142: warning: its scope is only this definition or declaration, which is probably not what you want
  drivers/video/backlight/apple_bl.c:201: warning: 'struct acpi_device' declared inside parameter list
  drivers/video/backlight/apple_bl.c:215: error: variable 'apple_bl_driver' has initializer but incomplete type
  drivers/video/backlight/apple_bl.c:216: error: unknown field 'name' specified in initializer
  ...

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Acked-by: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Matthew Garrett 39b3dee76f mbp_nvidia_bl: rename to apple_bl
It works on hardware other than Macbook Pros, and it works on GPUs other
than Nvidia.  It should even work on iMacs, so change the name to match
reality more precisely and include an alias so existing users don't get
confused.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Cc: Mourad De Clerck <mourad@aquazul.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Matthew Garrett 99fd28e194 mbp_nvidia_bl: check that the backlight control functions
The SMI-based backlight control functionality may fail to work if the
system is running under EFI rather than BIOS.  Check that the hardware
responds as expected, and exit if it doesn't.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Cc: Mourad De Clerck <mourad@aquazul.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Matthew Garrett 23a9847f0d mbp_nvidia_bl: remove DMI dependency
This driver only has to deal with two different classes of hardware, but
right now it needs new DMI entries for every new machine. It turns out
that there's an ACPI device that uniquely identifies Apples with backlights,
so this patch reworks the driver into an ACPI one, identifies the hardware
by checking the PCI vendor of the root bridge and strips out all the DMI
code. It also changes the config text to clarify that it works on devices
other than Macbook Pros and GPUs other than nvidia.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Cc: Mourad De Clerck <mourad@aquazul.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Matthew Garrett 9661e92c10 acpi: tie ACPI backlight devices to PCI devices if possible
Dual-GPU machines may provide more than one ACPI backlight interface.  Tie
the backlight device to the GPU in order to allow userspace to identify
the correct interface.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Airlie <airlied@linux.ie>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Sedat Dilek <sedat.dilek@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:44:00 -07:00
Matthew Garrett 7eae3efa13 nouveau: change the backlight parent device to the connector, not the PCI dev
We may eventually end up with per-connector backlights, especially with
ddcci devices.  Make sure that the parent node for the backlight device is
the connector rather than the PCI device.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Airlie <airlied@linux.ie>
Cc: Alex Deucher <alexdeucher@gmail.com>
Acked-by: Ben Skeggs <bskeggs@redhat.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Sedat Dilek <sedat.dilek@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:59 -07:00
Michel Dänzer 63ec0119d3 radeon: expose backlight class device for legacy LVDS encoder
Allows e.g. power management daemons to control the backlight level. Inspired
by the corresponding code in radeonfb.

[mjg@redhat.com: updated to add backlight type and make the connector the parent device]
Signed-off-by: Michel Dänzer <michel@daenzer.net>
Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Airlie <airlied@linux.ie>
Acked-by: Alex Deucher <alexdeucher@gmail.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Tested-by: Sedat Dilek <sedat.dilek@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:59 -07:00
Matthew Garrett bb7ca747f8 backlight: add backlight type
There may be multiple ways of controlling the backlight on a given
machine.  Allow drivers to expose the type of interface they are
providing, making it possible for userspace to make appropriate policy
decisions.

Signed-off-by: Matthew Garrett <mjg@redhat.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: David Airlie <airlied@linux.ie>
Cc: Alex Deucher <alexdeucher@gmail.com>
Cc: Ben Skeggs <bskeggs@redhat.com>
Cc: Zhang Rui <rui.zhang@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:59 -07:00
Vasiliy Kulikov ccd7510fd8 drivers/leds/leds-lp5523.c: world-writable engine* sysfs files
Don't allow everybody to change LED settings.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:59 -07:00
Vasiliy Kulikov 67d1da79b2 drivers/leds/leds-lp5521.c: world-writable sysfs engine* files
Don't allow everybody to change LED settings.

Signed-off-by: Vasiliy Kulikov <segoon@openwall.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:59 -07:00
Donghwa Lee 1baf0eb397 drivers/vidfeo/backlight: ld9040 amoled driver support
Add a ld9040 amoled panel driver.

Signed-off-by: Donghwa Lee <dh09.lee@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Inki Dae <inki.dae@samsung.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:59 -07:00
Uwe Kleine-König 9517f925f2 leds: make *struct gpio_led_platform_data.leds const
And fix a typo.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:59 -07:00
Shreshtha Kumar Sahu b1e6b7068f leds: add driver for LM3530 ALS
Simple backlight driver for National Semiconductor LM3530.  Presently only
manual mode is supported, PWM and ALS support to be added.

Signed-off-by: Shreshtha Kumar Sahu <shreshthakumar.sahu@stericsson.com>
Cc: Linus Walleij <linus.walleij@stericsson.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:59 -07:00
Mark Brown 551ea73838 leds: convert bd2802 driver to dev_pm_ops
There is a move to deprecate bus-specific PM operations and move to using
dev_pm_ops instead in order to reduce the amount of boilerplate code in
buses and facilitiate updates to the PM core.  Do this move for the bs2802
driver.

[akpm@linux-foundation.org: fix warnings]
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: Kim Kyuwon <q1.kim@samsung.com>
Cc: Kim Kyuwon <chammoru@gmail.com>
Cc: Richard Purdie <rpurdie@rpsys.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:58 -07:00
Phil Carmody 8d2587970b cgroups: if you list_empty() a head then don't list_del() it
list_del() leaves poison in the prev and next pointers.  The next
list_empty() will compare those poisons, and say the list isn't empty.
Any list operations that assume the node is on a list because of such a
check will be fooled into dereferencing poison.  One needs to INIT the
node after the del, and fortunately there's already a wrapper for that -
list_del_init().

Some of the dels are followed by deallocations, so can be ignored, and one
can be merged with an add to make a move.  Apart from that, I erred on the
side of caution in making nodes list_empty()-queriable.

Signed-off-by: Phil Carmody <ext-phil.2.carmody@nokia.com>
Reviewed-by: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Acked-by: Kirill A. Shutemov <kirill@shutemov.name>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:58 -07:00
David Rientjes edd45544c6 oom: avoid deferring oom killer if exiting task is being traced
The oom killer naturally defers killing anything if it finds an eligible
task that is already exiting and has yet to detach its ->mm.  This avoids
unnecessarily killing tasks when one is already in the exit path and may
free enough memory that the oom killer is no longer needed.  This is
detected by PF_EXITING since threads that have already detached its ->mm
are no longer considered at all.

The problem with always deferring when a thread is PF_EXITING, however, is
that it may never actually exit when being traced, specifically if another
task is tracing it with PTRACE_O_TRACEEXIT.  The oom killer does not want
to defer in this case since there is no guarantee that thread will ever
exit without intervention.

This patch will now only defer the oom killer when a thread is PF_EXITING
and no ptracer has stopped its progress in the exit path.  It also ensures
that a child is sacrificed for the chosen parent only if it has a
different ->mm as the comment implies: this ensures that the thread group
leader is always targeted appropriately.

Signed-off-by: David Rientjes <rientjes@google.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: <stable@kernel.org>		[2.6.38.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:58 -07:00
Andrey Vagin 30e2b41f20 oom: skip zombies when iterating tasklist
We shouldn't defer oom killing if a thread has already detached its ->mm
and still has TIF_MEMDIE set.  Memory needs to be freed, so find kill
other threads that pin the same ->mm or find another task to kill.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: <stable@kernel.org>		[2.6.38.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:58 -07:00
David Rientjes 3a5dda7a17 oom: prevent unnecessary oom kills or kernel panics
This patch prevents unnecessary oom kills or kernel panics by reverting
two commits:

	495789a5 (oom: make oom_score to per-process value)
	cef1d352 (oom: multi threaded process coredump don't make deadlock)

First, 495789a5 (oom: make oom_score to per-process value) ignores the
fact that all threads in a thread group do not necessarily exit at the
same time.

It is imperative that select_bad_process() detect threads that are in the
exit path, specifically those with PF_EXITING set, to prevent needlessly
killing additional tasks.  If a process is oom killed and the thread group
leader exits, select_bad_process() cannot detect the other threads that
are PF_EXITING by iterating over only processes.  Thus, it currently
chooses another task unnecessarily for oom kill or panics the machine when
nothing else is eligible.

By iterating over threads instead, it is possible to detect threads that
are exiting and nominate them for oom kill so they get access to memory
reserves.

Second, cef1d352 (oom: multi threaded process coredump don't make
deadlock) erroneously avoids making the oom killer a no-op when an
eligible thread other than current isfound to be exiting.  We want to
detect this situation so that we may allow that exiting thread time to
exit and free its memory; if it is able to exit on its own, that should
free memory so current is no loner oom.  If it is not able to exit on its
own, the oom killer will nominate it for oom kill which, in this case,
only means it will get access to memory reserves.

Without this change, it is easy for the oom killer to unnecessarily target
tasks when all threads of a victim don't exit before the thread group
leader or, in the worst case, panic the machine.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Andrey Vagin <avagin@openvz.org>
Cc: <stable@kernel.org>		[2.6.38.x]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:58 -07:00
Mel Gorman 52c50567d8 mm: swap: unlock swapfile inode mutex before closing file on bad swapfiles
If an administrator tries to swapon a file backed by NFS, the inode mutex is
taken (as it is for any swapfile) but later identified to be a bad swapfile
due to the lack of bmap and tries to cleanup. During cleanup, an attempt is
made to close the file but with inode->i_mutex still held. Closing an NFS
file syncs it which tries to acquire the inode mutex leading to deadlock. If
lockdep is enabled the following appears on the console;

    =============================================
    [ INFO: possible recursive locking detected ]
    2.6.38-rc8-autobuild #1
    ---------------------------------------------
    swapon/2192 is trying to acquire lock:
     (&sb->s_type->i_mutex_key#13){+.+.+.}, at: vfs_fsync_range+0x47/0x7c

    but task is already holding lock:
     (&sb->s_type->i_mutex_key#13){+.+.+.}, at: sys_swapon+0x28d/0xae7

    other info that might help us debug this:
    1 lock held by swapon/2192:
     #0:  (&sb->s_type->i_mutex_key#13){+.+.+.}, at: sys_swapon+0x28d/0xae7

    stack backtrace:
    Pid: 2192, comm: swapon Not tainted 2.6.38-rc8-autobuild #1
    Call Trace:
        __lock_acquire+0x2eb/0x1623
        find_get_pages_tag+0x14a/0x174
        pagevec_lookup_tag+0x25/0x2e
        vfs_fsync_range+0x47/0x7c
        lock_acquire+0xd3/0x100
        vfs_fsync_range+0x47/0x7c
        nfs_flush_one+0x0/0xdf [nfs]
        mutex_lock_nested+0x40/0x2b1
        vfs_fsync_range+0x47/0x7c
        vfs_fsync_range+0x47/0x7c
        vfs_fsync+0x1c/0x1e
        nfs_file_flush+0x64/0x69 [nfs]
        filp_close+0x43/0x72
        sys_swapon+0xa39/0xae7
        sysret_check+0x2e/0x69
        system_call_fastpath+0x16/0x1b

This patch releases the mutex if its held before calling filep_close()
so swapon fails as expected without deadlock when the swapfile is backed
by NFS.  If accepted for 2.6.39, it should also be considered a -stable
candidate for 2.6.38 and 2.6.37.

Signed-off-by: Mel Gorman <mgorman@suse.de>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: <stable@kernel.org>		[2.6.37+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:58 -07:00
Andrew Morton c7a1fcd8e6 include/asm-generic/unistd.h: fix syncfs syscall number
syncfs() is duplicating name_to_handle_at() due to a merging mistake.

Cc: Sage Weil <sage@newdream.net>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 17:43:58 -07:00
Linus Torvalds 01ba825146 Merge branch 'slab/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6
* 'slab/urgent' of git://git.kernel.org/pub/scm/linux/kernel/git/penberg/slab-2.6:
  slub: Add statistics for this_cmpxchg_double failures
  slub: Add missing irq restore for the OOM path
2011-03-22 16:26:57 -07:00
Linus Torvalds ab70a1d7c7 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ericvh/v9fs:
  [net/9p]: Introduce basic flow-control for VirtIO transport.
  9p: use the updated offset given by generic_write_checks
  [net/9p] Don't re-pin pages on retrying virtqueue_add_buf().
  [net/9p] Set the condition just before waking up.
  [net/9p] unconditional wake_up to proc waiting for space on VirtIO ring
  fs/9p: Add v9fs_dentry2v9ses
  fs/9p: Attach writeback_fid on first open with WR flag
  fs/9p: Open writeback fid in O_SYNC mode
  fs/9p: Use truncate_setsize instead of vmtruncate
  net/9p: Fix compile warning
  net/9p: Convert the in the 9p rpc call path to GFP_NOFS
  fs/9p: Fix race in initializing writeback fid
2011-03-22 16:26:10 -07:00
Linus Torvalds 0adfc56ce8 Merge git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client
* git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client:
  rbd: use watch/notify for changes in rbd header
  libceph: add lingering request and watch/notify event framework
  rbd: update email address in Documentation
  ceph: rename dentry_release -> d_release, fix comment
  ceph: add request to the tail of unsafe write list
  ceph: remove request from unsafe list if it is canceled/timed out
  ceph: move readahead default to fs/ceph from libceph
  ceph: add ino32 mount option
  ceph: update common header files
  ceph: remove debugfs debug cruft
  libceph: fix osd request queuing on osdmap updates
  ceph: preserve I_COMPLETE across rename
  libceph: Fix base64-decoding when input ends in newline.
2011-03-22 16:25:25 -07:00
Linus Torvalds f23eb2b2b2 tty: stop using "delayed_work" in the tty layer
Using delayed-work for tty flip buffers ends up causing us to wait for
the next tick to complete some actions.  That's usually not all that
noticeable, but for certain latency-critical workloads it ends up being
totally unacceptable.

As an extreme case of this, passing a token back-and-forth over a pty
will take two ticks per iteration, so even just a thousand iterations
will take 8 seconds assuming a common 250Hz configuration.

Avoiding the whole delayed work issue brings that ping-pong test-case
down to 0.009s on my machine.

In more practical terms, this latency has been a performance problem for
things like dive computer simulators (simulating the serial interface
using the ptys) and for other environments (Alan mentions a CP/M emulator).

Reported-by: Jef Driesen <jefdriesen@telenet.be>
Acked-by: Greg KH <gregkh@suse.de>
Acked-by: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-03-22 16:17:32 -07:00
Venkateswararao Jujjuri (JV) 68da9ba4ee [net/9p]: Introduce basic flow-control for VirtIO transport.
Recent zerocopy work in the 9P VirtIO transport maps and pins
user buffers into kernel memory for the server to work on them.
Since the user process can initiate this kind of pinning with a simple
read/write call, thousands of IO threads initiated by the user process can
hog the system resources and could result into denial of service.

This patch introduces flow control to avoid that extreme scenario.

The ceiling limit to avoid denial of service attacks is set to relatively
high (nr_free_pagecache_pages()/4) so that it won't interfere with
regular usage, but can step in extreme cases to limit the total system
hang. Since we don't have a global structure to accommodate this variable,
I choose the virtio_chan as the home for this.

Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Reviewed-by: Badari Pulavarty <pbadari@us.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
2011-03-22 16:32:50 -05:00
M. Mohan Kumar aaf0ef1d2b 9p: use the updated offset given by generic_write_checks
Without this fix, even if a file is opened in O_APPEND mode, data will be
written at current file position instead of end of file.

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
2011-03-22 16:32:49 -05:00
Venkateswararao Jujjuri (JV) 316ad5501c [net/9p] Don't re-pin pages on retrying virtqueue_add_buf().
Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
2011-03-22 16:32:48 -05:00
Venkateswararao Jujjuri (JV) a01a984035 [net/9p] Set the condition just before waking up.
Given that the sprious wake-ups are common, we need to move the
condition setting right next to the wake_up().  After setting the condition
to req->status = REQ_STATUS_RCVD, sprious wakeups may cause the
virtqueue back on the free list for someone else to use.
This may result in kernel panic while relasing the pinned pages
in p9_release_req_pages().

Also rearranged the while loop in req_done() for better redability.

Signed-off-by: Venkateswararao Jujjuri <jvrao@linux.vnet.ibm.com>
Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
2011-03-22 16:32:47 -05:00