There is not much point in skipping zones during allocation based on the
dirty usage which they'll never contribute to. And we'd like to avoid
page reclaim waits when writing to ramfs/sysfs etc.
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Greg Thelen <gthelen@google.com>
Cc: Ying Han <yinghan@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-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>
Taking i_mutex in hugetlbfs_read() can result in deadlock with mmap as
explained below
Thread A:
read() on hugetlbfs
hugetlbfs_read() called
i_mutex grabbed
hugetlbfs_read_actor() called
__copy_to_user() called
page fault is triggered
Thread B, sharing address space with A:
mmap() the same file
->mmap_sem is grabbed on task_B->mm->mmap_sem
hugetlbfs_file_mmap() is called
attempt to grab ->i_mutex and block waiting for A to give it up
Thread A:
pagefault handled blocked on attempt to grab task_A->mm->mmap_sem,
which happens to be the same thing as task_B->mm->mmap_sem. Block waiting
for B to give it up.
AFAIU the i_mutex locking was added to hugetlbfs_read() as per
http://lkml.indiana.edu/hypermail/linux/kernel/0707.2/3066.html to take
care of the race between truncate and read. This patch fixes this by
looking at page->mapping under lock_page() (find_lock_page()) to ensure
that the inode didn't get truncated in the range during a parallel read.
Ideally we can extend the patch to make sure we don't increase i_size in
mmap. But that will break userspace, because applications will now have
to use truncate(2) to increase i_size in hugetlbfs.
Based on the original patch from Hillf Danton.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Cc: <stable@kernel.org> [everything after 2007 :)]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
While testing AMS (Active Memory Sharing) / CMO (Cooperative Memory
Overcommit) on powerpc, we tripped the following:
kernel BUG at mm/bootmem.c:483!
cpu 0x0: Vector: 700 (Program Check) at [c000000000c03940]
pc: c000000000a62bd8: .alloc_bootmem_core+0x90/0x39c
lr: c000000000a64bcc: .sparse_early_usemaps_alloc_node+0x84/0x29c
sp: c000000000c03bc0
msr: 8000000000021032
current = 0xc000000000b0cce0
paca = 0xc000000001d80000
pid = 0, comm = swapper
kernel BUG at mm/bootmem.c:483!
enter ? for help
[c000000000c03c80] c000000000a64bcc
.sparse_early_usemaps_alloc_node+0x84/0x29c
[c000000000c03d50] c000000000a64f10 .sparse_init+0x12c/0x28c
[c000000000c03e20] c000000000a474f4 .setup_arch+0x20c/0x294
[c000000000c03ee0] c000000000a4079c .start_kernel+0xb4/0x460
[c000000000c03f90] c000000000009670 .start_here_common+0x1c/0x2c
This is
BUG_ON(limit && goal + size > limit);
and after some debugging, it seems that
goal = 0x7ffff000000
limit = 0x80000000000
and sparse_early_usemaps_alloc_node ->
sparse_early_usemaps_alloc_pgdat_section calls
return alloc_bootmem_section(usemap_size() * count, section_nr);
This is on a system with 8TB available via the AMS pool, and as a quirk
of AMS in firmware, all of that memory shows up in node 0. So, we end
up with an allocation that will fail the goal/limit constraints.
In theory, we could "fall-back" to alloc_bootmem_node() in
sparse_early_usemaps_alloc_node(), but since we actually have HOTREMOVE
defined, we'll BUG_ON() instead. A simple solution appears to be to
unconditionally remove the limit condition in alloc_bootmem_section,
meaning allocations are allowed to cross section boundaries (necessary
for systems of this size).
Johannes Weiner pointed out that if alloc_bootmem_section() no longer
guarantees section-locality, we need check_usemap_section_nr() to print
possible cross-dependencies between node descriptors and the usemaps
allocated through it. That makes the two loops in
sparse_early_usemaps_alloc_node() identical, so re-factor the code a
bit.
[akpm@linux-foundation.org: code simplification]
Signed-off-by: Nishanth Aravamudan <nacc@us.ibm.com>
Cc: Dave Hansen <haveblue@us.ibm.com>
Cc: Anton Blanchard <anton@au1.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Ben Herrenschmidt <benh@kernel.crashing.org>
Cc: Robert Jennings <rcj@linux.vnet.ibm.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: <stable@vger.kernel.org> [3.3.1]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This cpu hotplug hook was accidentally removed in commit 00a62ce91e
("mm: fix Committed_AS underflow on large NR_CPUS environment")
The visible effect of this accident: some pages are borrowed in per-cpu
page-vectors. Truncate can deal with it, but these pages cannot be
reused while this cpu is offline. So this is like a temporary memory
leak.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Eric B Munson <ebmunson@us.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Christoph Lameter <cl@linux-foundation.org>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Migration functions perform the rcu_read_unlock too early. As a result
the task pointed to may change from under us. This can result in an oops,
as reported by Dave Hansen in https://lkml.org/lkml/2012/2/23/302.
The following patch extend the period of the rcu_read_lock until after the
permissions checks are done. We also take a refcount so that the task
reference is stable when calling security check functions and performing
cpuset node validation (which takes a mutex).
The refcount is dropped before actual page migration occurs so there is no
change to the refcounts held during page migration.
Also move the determination of the mm of the task struct to immediately
before the do_migrate*() calls so that it is clear that we switch from
handling the task during permission checks to the mm for the actual
migration. Since the determination is only done once and we then no
longer use the task_struct we can be sure that we operate on a specific
address space that will not change from under us.
[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Christoph Lameter <cl@linux.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Reported-by: Dave Hansen <dave@linux.vnet.ibm.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Andrea Arcangeli pointed out to me that a check in __memory_failure()
which was intended to prevent THP tail pages from being checked for the
absence of the PG_lru flag (something that is always the case), was also
preventing THP head pages from being checked.
A THP head page could actually benefit from the call to shake_page() by
ending up being put back to a LRU, provided it had been waiting in a
pagevec array.
Andrea suggested that the "!PageTransCompound(p)" in the if-statement
should be replaced by a "!PageTransTail(p)", thus allowing THP head pages
to be checked and possibly shaken.
Signed-off-by: Dean Nelson <dnelson@redhat.com>
Cc: Jin Dongming <jin.dongming@np.css.fujitsu.com>
Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Hidetoshi Seto <seto.hidetoshi@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Adds to generic xattr support introduced in Linux 3.0 by implementing
initxattrs callback. This enables consulting of security attributes from
LSM and EVM when inode is created.
[hughd@google.com: moved under CONFIG_TMPFS_XATTR, with memcpy in shmem_xattr_alloc]
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@intel.com>
Reviewed-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The oom killer chooses not to kill a thread if:
- an eligible thread has already been oom killed and has yet to exit,
and
- an eligible thread is exiting but has yet to free all its memory and
is not the thread attempting to currently allocate memory.
SysRq+F manually invokes the global oom killer to kill a memory-hogging
task. This is normally done as a last resort to free memory when no
progress is being made or to test the oom killer itself.
For both uses, we always want to kill a thread and never defer. This
patch causes SysRq+F to always kill an eligible thread and can be used to
force a kill even if another oom killed thread has failed to exit.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When unmapping a given VM range, we could bail out if a reference page is
supplied and is unmapped, which is a minor optimization.
Signed-off-by: Hillf Danton <dhillf@gmail.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The behavior of THP can either be toggled through sysfs in runtime or
using a kernel cmdline parameter 'transparent_hugepage='. Document the
latter in kernel-parameters.txt
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Cc: Andrea Arcangeli <aarcange@redhat.com>
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>
When shrinking inactive lru list, isolated pages are queued on locally
private list, so the lock-hold time could be reduced if pages are counted
without lock protection.
To achieve that, firstly updating reclaim stat is delayed until the
putback stage, after reacquiring the lru lock.
Secondly, operations related to vm and zone stats are now proteced with
preemption disabled as they are per-cpu operations.
Signed-off-by: Hillf Danton <dhillf@gmail.com>
Acked-by: Hugh Dickins <hughd@google.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This declaration is not used anymore, remove it.
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Reduce code duplication by calling anon_vma_chain_link() from
anon_vma_prepare().
Also move anon_vmal_chain_link() to a more suitable location in the file.
Signed-off-by: Kautuk Consul <consul.kautuk@gmail.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Hugh Dickins <hughd@google.com>
Reviewed-by: KAMEZWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Acked-by: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When gathering surplus pages, the number of needed pages is recomputed
after reacquiring hugetlb lock to catch changes in resv_huge_pages and
free_huge_pages. Plus it is recomputed with the number of newly allocated
pages involved.
Thus freeing pages can be deferred a bit to see if the final page request
is satisfied, though pages could be allocated less than needed.
Signed-off-by: Hillf Danton <dhillf@gmail.com>
Reviewed-by: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Stuart Foster reported on bugzilla that copying large amounts of data
from NTFS caused an OOM kill on 32-bit X86 with 16G of memory. Andrew
Morton correctly identified that the problem was NTFS was using 512
blocks meaning each page had 8 buffer_heads in low memory pinning it.
In the past, direct reclaim used to scan highmem even if the allocating
process did not specify __GFP_HIGHMEM but not any more. kswapd no longer
will reclaim from zones that are above the high watermark. The intention
in both cases was to minimise unnecessary reclaim. The downside is on
machines with large amounts of highmem that lowmem can be fully consumed
by buffer_heads with nothing trying to free them.
The following patch is based on a suggestion by Andrew Morton to extend
the buffer_heads_over_limit case to force kswapd and direct reclaim to
scan the highmem zone regardless of the allocation request or watermarks.
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=42578
[hughd@google.com: move buffer_heads_over_limit check up]
[akpm@linux-foundation.org: buffer_heads_over_limit is unlikely]
Reported-by: Stuart Foster <smf.linux@ntlworld.com>
Tested-by: Stuart Foster <smf.linux@ntlworld.com>
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Since commit 2a11c8ea20 ("kconfig: Introduce IS_ENABLED(),
IS_BUILTIN() and IS_MODULE()") there is a generic grep-friendly method
for checking config options in C expressions.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently a local variable of pagemap entry in pagemap_pte_range() is
named pfn and typed with u64, but it's not correct (pfn should be unsigned
long.)
This patch introduces special type for pagemap entries and replaces code
with it.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
page-types, which is a common user of pagemap, gets aware of thp with this
patch. This helps system admins and kernel hackers know about how thp
works. Here is a sample output of page-types over a thp:
$ page-types -p <pid> --raw --list
voffset offset len flags
...
7f9d40200 3f8400 1 ___U_lA____Ma_bH______t____________
7f9d40201 3f8401 1ff ________________T_____t____________
flags page-count MB symbolic-flags long-symbolic-flags
0x0000000000410000 511 1 ________________T_____t____________ compound_tail,thp
0x000000000040d868 1 0 ___U_lA____Ma_bH______t____________ uptodate,lru,active,mmap,anonymous,swapbacked,compound_head,thp
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Acked-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This flag shows that a given page is a subpage of a transparent hugepage.
It helps us debug and test the kernel by showing physical address of thp.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Wu Fengguang <fengguang.wu@intel.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently when we check if we can handle thp as it is or we need to split
it into regular sized pages, we hold page table lock prior to check
whether a given pmd is mapping thp or not. Because of this, when it's not
"huge pmd" we suffer from unnecessary lock/unlock overhead. To remove it,
this patch introduces a optimized check function and replace several
similar logics with it.
[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Thp split is not necessary if we explicitly check whether pmds are mapping
thps or not. This patch introduces this check and adds code to generate
pagemap entries for pmds mapping thps, which results in less performance
impact of pagemap on thp.
Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Wu Fengguang <fengguang.wu@intel.com>
Cc: Andrea Arcangeli <aarcange@redhat.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>
If the required size is bigger than cached_hole_size it is better to
search from free_area_cache - it is easier to get a free region,
specifically for the 64 bit process whose address space is large enough
Do it just as hugetlb_get_unmapped_area_topdown() in arch/x86/mm/hugetlbpage.c
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In the current code, cached_hole_size is set to the maximum value if the
unmapped vma is less that free_area_cache so the next search will search
from the base address.
Actually, we can keep cached_hole_size so that if the next required size
is more than cached_hole_size, it can search from free_area_cache.
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Search again only if some holes may be skipped in the first pass.
[akpm@linux-foundation.org: clean up crazy compound definition]
Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
"order" is -1 when compacting via /proc/sys/vm/compact_memory. Making
it unsigned causes a bug in __compact_pgdat() when we test:
if (cc->order < 0 || !compaction_deferred(zone, cc->order))
compact_zone(zone, cc);
[akpm@linux-foundation.org: make __compact_pgdat()'s comparison match other code sites]
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Cc: Minchan Kim <minchan@kernel.org>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
I get this lockdep warning from swapping load on linux-next, due to
"vmscan: kswapd carefully call compaction".
=================================
[ INFO: inconsistent lock state ]
3.3.0-rc2-next-20120201 #5 Not tainted
---------------------------------
inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
kswapd0/28 [HC0[0]:SC0[0]:HE1:SE1] takes:
(pcpu_alloc_mutex){+.+.?.}, at: [<ffffffff810d6684>] pcpu_alloc+0x67/0x325
{RECLAIM_FS-ON-W} state was registered at:
[<ffffffff81099b75>] mark_held_locks+0xd7/0x103
[<ffffffff8109a13c>] lockdep_trace_alloc+0x85/0x9e
[<ffffffff810f6bdc>] __kmalloc+0x6c/0x14b
[<ffffffff810d57fd>] pcpu_mem_zalloc+0x59/0x62
[<ffffffff810d5d16>] pcpu_extend_area_map+0x26/0xb1
[<ffffffff810d679f>] pcpu_alloc+0x182/0x325
[<ffffffff810d694d>] __alloc_percpu+0xb/0xd
[<ffffffff8142ebfd>] snmp_mib_init+0x1e/0x2e
[<ffffffff8185cd8d>] ipv4_mib_init_net+0x7a/0x184
[<ffffffff813dc963>] ops_init.clone.0+0x6b/0x73
[<ffffffff813dc9cc>] register_pernet_operations+0x61/0xa0
[<ffffffff813dca8e>] register_pernet_subsys+0x29/0x42
[<ffffffff8185d044>] inet_init+0x1ad/0x252
[<ffffffff810002e3>] do_one_initcall+0x7a/0x12f
[<ffffffff81832bc5>] kernel_init+0x9d/0x11e
[<ffffffff814e51e4>] kernel_thread_helper+0x4/0x10
irq event stamp: 656613
hardirqs last enabled at (656613): [<ffffffff814e0ddc>] __mutex_unlock_slowpath+0x104/0x128
hardirqs last disabled at (656612): [<ffffffff814e0d34>] __mutex_unlock_slowpath+0x5c/0x128
softirqs last enabled at (655568): [<ffffffff8105b4a5>] __do_softirq+0x120/0x136
softirqs last disabled at (654757): [<ffffffff814e52dc>] call_softirq+0x1c/0x30
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(pcpu_alloc_mutex);
<Interrupt>
lock(pcpu_alloc_mutex);
*** DEADLOCK ***
no locks held by kswapd0/28.
stack backtrace:
Pid: 28, comm: kswapd0 Not tainted 3.3.0-rc2-next-20120201 #5
Call Trace:
[<ffffffff810981f4>] print_usage_bug+0x1bf/0x1d0
[<ffffffff81096c3e>] ? print_irq_inversion_bug+0x1d9/0x1d9
[<ffffffff810982c0>] mark_lock_irq+0xbb/0x22e
[<ffffffff810c5399>] ? free_hot_cold_page+0x13d/0x14f
[<ffffffff81098684>] mark_lock+0x251/0x331
[<ffffffff81098893>] mark_irqflags+0x12f/0x141
[<ffffffff81098e32>] __lock_acquire+0x58d/0x753
[<ffffffff810d6684>] ? pcpu_alloc+0x67/0x325
[<ffffffff81099433>] lock_acquire+0x54/0x6a
[<ffffffff810d6684>] ? pcpu_alloc+0x67/0x325
[<ffffffff8107a5b8>] ? add_preempt_count+0xa9/0xae
[<ffffffff814e0a21>] mutex_lock_nested+0x5e/0x315
[<ffffffff810d6684>] ? pcpu_alloc+0x67/0x325
[<ffffffff81098f81>] ? __lock_acquire+0x6dc/0x753
[<ffffffff810c9fb0>] ? __pagevec_release+0x2c/0x2c
[<ffffffff810d6684>] pcpu_alloc+0x67/0x325
[<ffffffff810c9fb0>] ? __pagevec_release+0x2c/0x2c
[<ffffffff810d694d>] __alloc_percpu+0xb/0xd
[<ffffffff8106c35e>] schedule_on_each_cpu+0x23/0x110
[<ffffffff810c9fcb>] lru_add_drain_all+0x10/0x12
[<ffffffff810f126f>] __compact_pgdat+0x20/0x182
[<ffffffff810f15c2>] compact_pgdat+0x27/0x29
[<ffffffff810c306b>] ? zone_watermark_ok+0x1a/0x1c
[<ffffffff810cdf6f>] balance_pgdat+0x732/0x751
[<ffffffff810ce0ed>] kswapd+0x15f/0x178
[<ffffffff810cdf8e>] ? balance_pgdat+0x751/0x751
[<ffffffff8106fd11>] kthread+0x84/0x8c
[<ffffffff814e51e4>] kernel_thread_helper+0x4/0x10
[<ffffffff810787ed>] ? finish_task_switch+0x85/0xea
[<ffffffff814e3861>] ? retint_restore_args+0xe/0xe
[<ffffffff8106fc8d>] ? __init_kthread_worker+0x56/0x56
[<ffffffff814e51e0>] ? gs_change+0xb/0xb
The RECLAIM_FS notations indicate that it's doing the GFP_FS checking that
Nick hacked into lockdep a while back: I think we're intended to read that
"<Interrupt>" in the DEADLOCK scenario as "<Direct reclaim>".
I'm hazy, I have not reached any conclusion as to whether it's right to
complain or not; but I believe it's uneasy about kswapd now doing the
mutex_lock(&pcpu_alloc_mutex) which lru_add_drain_all() entails. Nor have
I reached any conclusion as to whether it's important for kswapd to do
that draining or not.
But so as not to get blocked on this, with lockdep disabled from giving
further reports, here's a patch which removes the lru_add_drain_all() from
kswapd's callpath (and calls it only once from compact_nodes(), instead of
once per node).
Signed-off-by: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Currently a failed order-9 (transparent hugepage) compaction can lead to
memory compaction being temporarily disabled for a memory zone. Even if
we only need compaction for an order 2 allocation, eg. for jumbo frames
networking.
The fix is relatively straightforward: keep track of the highest order at
which compaction is succeeding, and only defer compaction for orders at
which compaction is failing.
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With CONFIG_COMPACTION enabled, kswapd does not try to free contiguous
free pages, even when it is woken for a higher order request.
This could be bad for eg. jumbo frame network allocations, which are done
from interrupt context and cannot compact memory themselves. Higher than
before allocation failure rates in the network receive path have been
observed in kernels with compaction enabled.
Teach kswapd to defragment the memory zones in a node, but only if
required and compaction is not deferred in a zone.
[akpm@linux-foundation.org: reduce scope of zones_need_compaction]
Signed-off-by: Rik van Riel <riel@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
When built with CONFIG_COMPACTION, kswapd should not try to free
contiguous pages, because it is not trying hard enough to have a real
chance at being successful, but still disrupts the LRU enough to break
other things.
Do not do higher order page isolation unless we really are in lumpy
reclaim mode.
Stop reclaiming pages once we have enough free pages that compaction can
deal with things, and we hit the normal order 0 watermarks used by kswapd.
Also remove a line of code that increments balanced right before exiting
the function.
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Mel Gorman <mel@csn.ul.ie>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Hillf Danton <dhillf@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Ever since abandoning the virtual scan of processes, for scalability
reasons, swap space has been a little more fragmented than before. This
can lead to the situation where a large memory user is killed, swap space
ends up full of "holes" and swapin readahead is totally ineffective.
On my home system, after killing a leaky firefox it took over an hour to
page just under 2GB of memory back in, slowing the virtual machines down
to a crawl.
This patch makes swapin readahead simply skip over holes, instead of
stopping at them. This allows the system to swap things back in at rates
of several MB/second, instead of a few hundred kB/second.
The checks done in valid_swaphandles are already done in
read_swap_cache_async as well, allowing us to remove a fair amount of
code.
[akpm@linux-foundation.org: fix it for page_cluster >= 32]
Signed-off-by: Rik van Riel <riel@redhat.com>
Cc: Minchan Kim <minchan.kim@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Mel Gorman <mgorman@suse.de>
Cc: Adrian Drzewiecki <z@drze.net>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The value of nr_reclaimed is the number of pages reclaimed in the current
round of the loop, whereas nr_to_reclaim should be compared with the
number of pages reclaimed in all rounds.
In each round of the loop, reclaimed pages are cut off from the reclaim
goal, and the loop stops once the goal achieved.
Signed-off-by: Hillf Danton <dhillf@gmail.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Rik van Riel <riel@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
With tons of reclaim_mode (defined as one field of struct scan_control)
already in the file, it is clearer to rename the local reclaim_mode when
setting up the isolation mode.
Signed-off-by: Hillf Danton <dhillf@gmail.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Warn about non-zero rss counters at final mmdrop.
This check will prevent reoccurences of bugs such as that fixed in "mm:
fix rss count leakage during migration".
I didn't hide this check under CONFIG_VM_DEBUG because it rather small and
rss counters cover whole page-table management, so this is a good
invariant.
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Cc: Hugh Dickins <hughd@google.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
printk_ratelimit() uses the global ratelimit state for all printks. The
oom killer should not be subjected to this state just because another
subsystem or driver may be flooding the kernel log.
This patch introduces printk ratelimiting specifically for the oom killer.
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
If a thread is chosen for oom kill and is already PF_EXITING, then the oom
killer simply sets TIF_MEMDIE and returns. This allows the thread to have
access to memory reserves so that it may quickly exit. This logic is
preceeded with a comment saying there's no need to alarm the sysadmin.
This patch adds truth to that statement.
There's no need to emit any warning about the oom condition if the thread
is already exiting since it will not be killed. In this condition, just
silently return the oom killer since its only giving access to memory
reserves and is otherwise a no-op.
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
oom_kill_task() has a single caller, so fold it into its parent function,
oom_kill_process(). Slightly reduces the number of lines in the oom
killer.
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
oom_kill_task() returns non-zero iff the chosen process does not have any
threads with an attached ->mm.
In such a case, it's better to just return to the page allocator and retry
the allocation because memory could have been freed in the interim and the
oom condition may no longer exist. It's unnecessary to loop in the oom
killer and find another thread to kill.
This allows both oom_kill_task() and oom_kill_process() to be converted to
void functions. If the oom condition persists, the oom killer will be
recalled.
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Acked-by: Michal Hocko <mhocko@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Use the new helper function introduced in commit 5e6292c0f2 ("signal:
add block_sigmask() for adding sigmask to current->blocked") which
centralises the code for updating current->blocked after successfully
delivering a signal and reduces the amount of duplicate code across
architectures. In the past some architectures got this code wrong, so
using this helper function should stop that from happening again.
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
As described in commit e6fa16ab9c ("signal: sigprocmask() should do
retarget_shared_pending()") the modification of current->blocked is
incorrect as we need to check whether the signal we're about to block is
pending in the shared queue.
Also, use the new helper function introduced in commit 5e6292c0f2
("signal: add block_sigmask() for adding sigmask to current->blocked")
which centralises the code for updating current->blocked after
successfully delivering a signal and reduces the amount of duplicate code
across architectures. In the past some architectures got this code wrong,
so using this helper function should stop that from happening again.
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
setup_frame() needs to return an indication of whether it succeeded or
failed in setting up the signal stack frame. If setup_frame() fails then
we must not modify current->blocked.
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
get_signal_to_deliver() already resets the signal handler if SA_ONESHOT
is set in ka->sa.sa_flags, there's no need to do it again in
handle_signal().
Furthermore, because we were modifying ka->sa.sa_handler (which is a
copy of sighand->action[]) instead of sighand->action[] the original
code actually had no effect on signal delivery.
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Instead of open coding the sequence from force_sigsegv() just call it.
This also fixes a bug because we were modifying ka->sa.sa_handler (which
is a copy of sighand->action[]), whereas the intention of the code was to
modify sighand->action[] directly.
As the original code was working with a copy it had no effect on signal
delivery.
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
The following program illustrates the problem:
char buf[8192];
int fd = open("/proc/self/maps", O_RDONLY);
n = pread(fd, buf, sizeof(buf), 0);
printf("%d\n", n);
/* lseek(fd, 0, SEEK_CUR); */ /* Uncomment to work around */
n = pread(fd, buf, sizeof(buf), 0);
printf("%d\n", n);
The second printf() prints zero, but uncommenting the lseek() corrects its
behaviour.
To fix, make seq_read() mirror seq_lseek() when processing changes in
*ppos. Restore m->version first, then if required traverse and update
read_pos on success.
Addresses https://bugzilla.kernel.org/show_bug.cgi?id=11856
Signed-off-by: Earl Chew <echew@ixiacom.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
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>
Fix a code indentation in the function intel_idle_cpu_init that looks
confusing.o
Suggested-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Reviewed-by: Srivatsa S. Bhat <srivatsa.bhat@linux.vnet.ibm.com>
Signed-off-by: Marcos Paulo de Souza <marcos.mage@gmail.com>
Cc: "Brown, Len" <len.brown@intel.com>
Cc: Len Brown <lenb@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
i386 allnoconfig:
fs/namei.c: In function 'has_zero':
fs/namei.c:1617: warning: integer constant is too large for 'unsigned long' type
fs/namei.c:1617: warning: integer constant is too large for 'unsigned long' type
fs/namei.c: In function 'hash_name':
fs/namei.c:1635: warning: integer constant is too large for 'unsigned long' type
There must be a tidier way of doing this.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
In some cases it may happen that pmd_none_or_clear_bad() is called with
the mmap_sem hold in read mode. In those cases the huge page faults can
allocate hugepmds under pmd_none_or_clear_bad() and that can trigger a
false positive from pmd_bad() that will not like to see a pmd
materializing as trans huge.
It's not khugepaged causing the problem, khugepaged holds the mmap_sem
in write mode (and all those sites must hold the mmap_sem in read mode
to prevent pagetables to go away from under them, during code review it
seems vm86 mode on 32bit kernels requires that too unless it's
restricted to 1 thread per process or UP builds). The race is only with
the huge pagefaults that can convert a pmd_none() into a
pmd_trans_huge().
Effectively all these pmd_none_or_clear_bad() sites running with
mmap_sem in read mode are somewhat speculative with the page faults, and
the result is always undefined when they run simultaneously. This is
probably why it wasn't common to run into this. For example if the
madvise(MADV_DONTNEED) runs zap_page_range() shortly before the page
fault, the hugepage will not be zapped, if the page fault runs first it
will be zapped.
Altering pmd_bad() not to error out if it finds hugepmds won't be enough
to fix this, because zap_pmd_range would then proceed to call
zap_pte_range (which would be incorrect if the pmd become a
pmd_trans_huge()).
The simplest way to fix this is to read the pmd in the local stack
(regardless of what we read, no need of actual CPU barriers, only
compiler barrier needed), and be sure it is not changing under the code
that computes its value. Even if the real pmd is changing under the
value we hold on the stack, we don't care. If we actually end up in
zap_pte_range it means the pmd was not none already and it was not huge,
and it can't become huge from under us (khugepaged locking explained
above).
All we need is to enforce that there is no way anymore that in a code
path like below, pmd_trans_huge can be false, but pmd_none_or_clear_bad
can run into a hugepmd. The overhead of a barrier() is just a compiler
tweak and should not be measurable (I only added it for THP builds). I
don't exclude different compiler versions may have prevented the race
too by caching the value of *pmd on the stack (that hasn't been
verified, but it wouldn't be impossible considering
pmd_none_or_clear_bad, pmd_bad, pmd_trans_huge, pmd_none are all inlines
and there's no external function called in between pmd_trans_huge and
pmd_none_or_clear_bad).
if (pmd_trans_huge(*pmd)) {
if (next-addr != HPAGE_PMD_SIZE) {
VM_BUG_ON(!rwsem_is_locked(&tlb->mm->mmap_sem));
split_huge_page_pmd(vma->vm_mm, pmd);
} else if (zap_huge_pmd(tlb, vma, pmd, addr))
continue;
/* fall through */
}
if (pmd_none_or_clear_bad(pmd))
Because this race condition could be exercised without special
privileges this was reported in CVE-2012-1179.
The race was identified and fully explained by Ulrich who debugged it.
I'm quoting his accurate explanation below, for reference.
====== start quote =======
mapcount 0 page_mapcount 1
kernel BUG at mm/huge_memory.c:1384!
At some point prior to the panic, a "bad pmd ..." message similar to the
following is logged on the console:
mm/memory.c:145: bad pmd ffff8800376e1f98(80000000314000e7).
The "bad pmd ..." message is logged by pmd_clear_bad() before it clears
the page's PMD table entry.
143 void pmd_clear_bad(pmd_t *pmd)
144 {
-> 145 pmd_ERROR(*pmd);
146 pmd_clear(pmd);
147 }
After the PMD table entry has been cleared, there is an inconsistency
between the actual number of PMD table entries that are mapping the page
and the page's map count (_mapcount field in struct page). When the page
is subsequently reclaimed, __split_huge_page() detects this inconsistency.
1381 if (mapcount != page_mapcount(page))
1382 printk(KERN_ERR "mapcount %d page_mapcount %d\n",
1383 mapcount, page_mapcount(page));
-> 1384 BUG_ON(mapcount != page_mapcount(page));
The root cause of the problem is a race of two threads in a multithreaded
process. Thread B incurs a page fault on a virtual address that has never
been accessed (PMD entry is zero) while Thread A is executing an madvise()
system call on a virtual address within the same 2 MB (huge page) range.
virtual address space
.---------------------.
| |
| |
.-|---------------------|
| | |
| | |<-- B(fault)
| | |
2 MB | |/////////////////////|-.
huge < |/////////////////////| > A(range)
page | |/////////////////////|-'
| | |
| | |
'-|---------------------|
| |
| |
'---------------------'
- Thread A is executing an madvise(..., MADV_DONTNEED) system call
on the virtual address range "A(range)" shown in the picture.
sys_madvise
// Acquire the semaphore in shared mode.
down_read(¤t->mm->mmap_sem)
...
madvise_vma
switch (behavior)
case MADV_DONTNEED:
madvise_dontneed
zap_page_range
unmap_vmas
unmap_page_range
zap_pud_range
zap_pmd_range
//
// Assume that this huge page has never been accessed.
// I.e. content of the PMD entry is zero (not mapped).
//
if (pmd_trans_huge(*pmd)) {
// We don't get here due to the above assumption.
}
//
// Assume that Thread B incurred a page fault and
.---------> // sneaks in here as shown below.
| //
| if (pmd_none_or_clear_bad(pmd))
| {
| if (unlikely(pmd_bad(*pmd)))
| pmd_clear_bad
| {
| pmd_ERROR
| // Log "bad pmd ..." message here.
| pmd_clear
| // Clear the page's PMD entry.
| // Thread B incremented the map count
| // in page_add_new_anon_rmap(), but
| // now the page is no longer mapped
| // by a PMD entry (-> inconsistency).
| }
| }
|
v
- Thread B is handling a page fault on virtual address "B(fault)" shown
in the picture.
...
do_page_fault
__do_page_fault
// Acquire the semaphore in shared mode.
down_read_trylock(&mm->mmap_sem)
...
handle_mm_fault
if (pmd_none(*pmd) && transparent_hugepage_enabled(vma))
// We get here due to the above assumption (PMD entry is zero).
do_huge_pmd_anonymous_page
alloc_hugepage_vma
// Allocate a new transparent huge page here.
...
__do_huge_pmd_anonymous_page
...
spin_lock(&mm->page_table_lock)
...
page_add_new_anon_rmap
// Here we increment the page's map count (starts at -1).
atomic_set(&page->_mapcount, 0)
set_pmd_at
// Here we set the page's PMD entry which will be cleared
// when Thread A calls pmd_clear_bad().
...
spin_unlock(&mm->page_table_lock)
The mmap_sem does not prevent the race because both threads are acquiring
it in shared mode (down_read). Thread B holds the page_table_lock while
the page's map count and PMD table entry are updated. However, Thread A
does not synchronize on that lock.
====== end quote =======
[akpm@linux-foundation.org: checkpatch fixes]
Reported-by: Ulrich Obergfell <uobergfe@redhat.com>
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Hugh Dickins <hughd@google.com>
Cc: Dave Jones <davej@redhat.com>
Acked-by: Larry Woodman <lwoodman@redhat.com>
Acked-by: Rik van Riel <riel@redhat.com>
Cc: <stable@vger.kernel.org> [2.6.38+]
Cc: Mark Salter <msalter@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This set includes one trivial fix, and one simple recovery
speed up. Directory recovery can use the standard hash table
to find resources rather than always searching the linear
recovery list.
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Merge tag 'dlm-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/teigland/linux-dlm
Pull dlm updates for 3.4 from David Teigland:
"This set includes one trivial fix, and one simple recovery speed up.
Directory recovery can use the standard hash table to find resources
rather than always searching the linear recovery list."
* tag 'dlm-3.4' of git://git.kernel.org/pub/scm/linux/kernel/git/teigland/linux-dlm:
dlm: last element of dlm_local_addr[] never used
dlm: fix slow rsb search in dir recovery
