17 Oct, 2007
3 commits
-
zone->lock is quite an "inner" lock and mostly constrained to page alloc as
well, so like slab locks, it probably isn't something that is critically
important to document here. However unlike slab locks, zone lock could be
used more widely in future, and page_alloc.c might possibly have more
business to do tricky things with pagecache than does slab. So... I don't
think it hurts to document it.Signed-off-by: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Slab constructors currently have a flags parameter that is never used. And
the order of the arguments is opposite to other slab functions. The object
pointer is placed before the kmem_cache pointer.Convert
ctor(void *object, struct kmem_cache *s, unsigned long flags)
to
ctor(struct kmem_cache *s, void *object)
throughout the kernel
[akpm@linux-foundation.org: coupla fixes]
Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Current ia64 kernel flushes icache by lazy_mmu_prot_update() *after*
set_pte(). This is too late. This patch removes lazy_mmu_prot_update and
add modfied set_pte() for flushing if necessary.This patch flush icache of a page when
new pte has exec bit.
&& new pte has present bit
&& new pte is user's page.
&& (old *ptep is not present
|| new pte's pfn is not same to old *ptep's ptn)
&& new pte's page has no Pg_arch_1 bit.
Pg_arch_1 is set when a page is cache consistent.I think this condition checks are much easier to understand than considering
"Where sync_icache_dcache() should be inserted ?".pte_user() for ia64 was removed by http://lkml.org/lkml/2007/6/12/67 as
clean-up. So, I added it again.Signed-off-by: KAMEZAWA Hiroyuki
Cc: "Luck, Tony"
Cc: Christoph Lameter
Cc: Hugh Dickins
Cc: Nick Piggin
Acked-by: David S. Miller
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
20 Jul, 2007
2 commits
-
Slab destructors were no longer supported after Christoph's
c59def9f222d44bb7e2f0a559f2906191a0862d7 change. They've been
BUGs for both slab and slub, and slob never supported them
either.This rips out support for the dtor pointer from kmem_cache_create()
completely and fixes up every single callsite in the kernel (there were
about 224, not including the slab allocator definitions themselves,
or the documentation references).Signed-off-by: Paul Mundt
-
Nonlinear mappings are (AFAIKS) simply a virtual memory concept that encodes
the virtual address -> file offset differently from linear mappings.->populate is a layering violation because the filesystem/pagecache code
should need to know anything about the virtual memory mapping. The hitch here
is that the ->nopage handler didn't pass down enough information (ie. pgoff).
But it is more logical to pass pgoff rather than have the ->nopage function
calculate it itself anyway (because that's a similar layering violation).Having the populate handler install the pte itself is likewise a nasty thing
to be doing.This patch introduces a new fault handler that replaces ->nopage and
->populate and (later) ->nopfn. Most of the old mechanism is still in place
so there is a lot of duplication and nice cleanups that can be removed if
everyone switches over.The rationale for doing this in the first place is that nonlinear mappings are
subject to the pagefault vs invalidate/truncate race too, and it seemed stupid
to duplicate the synchronisation logic rather than just consolidate the two.After this patch, MAP_NONBLOCK no longer sets up ptes for pages present in
pagecache. Seems like a fringe functionality anyway.NOPAGE_REFAULT is removed. This should be implemented with ->fault, and no
users have hit mainline yet.[akpm@linux-foundation.org: cleanup]
[randy.dunlap@oracle.com: doc. fixes for readahead]
[akpm@linux-foundation.org: build fix]
Signed-off-by: Nick Piggin
Signed-off-by: Randy Dunlap
Cc: Mark Fasheh
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
29 Jun, 2007
1 commit
-
validate_anon_vma gave a useful check on the integrity of the anon_vma list
when Andrea was developing obj rmap; but it was not enabled in SLES9
itself, nor in mainline, until Nick changed commented-out RMAP_DEBUG to
configurable CONFIG_DEBUG_VM in 2.6.17. Now Petr Vandrovec reports that
its BUG_ON(mapcount > 100000) can easily crash a CONFIG_DEBUG_VM=y system.That limit was just an arbitrary number to protect against an infinite
loop. We could raise it to something enormous (depending on sizeof struct
vma and size of memory?); but I rather think validate_anon_vma has outlived
its usefulness, and is better just removed - which gives a magnificent
performance boost to anything like Petr's test program ;)Of course, a very long anon_vma list is bad news for preemption latency,
and I believe there has been one recent report of such: let's not forget
that, but validate_anon_vma only makes it worse not better.Signed-off-by: Hugh Dickins
Cc: Petr Vandrovec
Acked-by: Nick Piggin
Cc: Andrea Arcangeli
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
17 May, 2007
2 commits
-
Re-introduce rmap verification patches that Hugh removed when he removed
PG_map_lock. PG_map_lock actually isn't needed to synchronise access to
anonymous pages, because PG_locked and PTL together already do.These checks were important in discovering and fixing a rare rmap corruption
in SLES9.Signed-off-by: Nick Piggin
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
SLAB_CTOR_CONSTRUCTOR is always specified. No point in checking it.
Signed-off-by: Christoph Lameter
Cc: David Howells
Cc: Jens Axboe
Cc: Steven French
Cc: Michael Halcrow
Cc: OGAWA Hirofumi
Cc: Miklos Szeredi
Cc: Steven Whitehouse
Cc: Roman Zippel
Cc: David Woodhouse
Cc: Dave Kleikamp
Cc: Trond Myklebust
Cc: "J. Bruce Fields"
Cc: Anton Altaparmakov
Cc: Mark Fasheh
Cc: Paul Mackerras
Cc: Christoph Hellwig
Cc: Jan Kara
Cc: David Chinner
Cc: "David S. Miller"
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
09 May, 2007
1 commit
-
This implements deferred IO support in fbdev. Deferred IO is a way to delay
and repurpose IO. This implementation is done using mm's page_mkwrite and
page_mkclean hooks in order to detect, delay and then rewrite IO. This
functionality is used by hecubafb.[adaplas]
This is useful for graphics hardware with no directly addressable/mappable
framebuffer. Implementing this will allow the "framebuffer" to be accesible
from user space via mmap().Signed-off-by: Jaya Kumar
Signed-off-by: Antonino Daplas
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
08 May, 2007
1 commit
-
I have never seen a use of SLAB_DEBUG_INITIAL. It is only supported by
SLAB.I think its purpose was to have a callback after an object has been freed
to verify that the state is the constructor state again? The callback is
performed before each freeing of an object.I would think that it is much easier to check the object state manually
before the free. That also places the check near the code object
manipulation of the object.Also the SLAB_DEBUG_INITIAL callback is only performed if the kernel was
compiled with SLAB debugging on. If there would be code in a constructor
handling SLAB_DEBUG_INITIAL then it would have to be conditional on
SLAB_DEBUG otherwise it would just be dead code. But there is no such code
in the kernel. I think SLUB_DEBUG_INITIAL is too problematic to make real
use of, difficult to understand and there are easier ways to accomplish the
same effect (i.e. add debug code before kfree).There is a related flag SLAB_CTOR_VERIFY that is frequently checked to be
clear in fs inode caches. Remove the pointless checks (they would even be
pointless without removeal of SLAB_DEBUG_INITIAL) from the fs constructors.This is the last slab flag that SLUB did not support. Remove the check for
unimplemented flags from SLUB.Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
27 Apr, 2007
1 commit
-
The page_test_and_clear_dirty primitive really consists of two
operations, page_test_dirty and the page_clear_dirty. The combination
of the two is not an atomic operation, so it makes more sense to have
two separate operations instead of one.
In addition to the improved readability of the s390 version of
SetPageUptodate, it now avoids the page_test_dirty operation which is
an insert-storage-key-extended (iske) instruction which is an expensive
operation.Signed-off-by: Martin Schwidefsky
04 Apr, 2007
1 commit
-
The git commit c2fda5fed81eea077363b285b66eafce20dfd45a which
added the page_test_and_clear_dirty call to page_mkclean and the
git commit 7658cc289288b8ae7dd2c2224549a048431222b3 which fixes
the "nasty and subtle race in shared mmap'ed page writeback"
problem in clear_page_dirty_for_io cause data corruption on s390.The effect of the two changes is that for every call to
clear_page_dirty_for_io a page_test_and_clear_dirty is done. If
the per page dirty bit is set set_page_dirty is called. Strangly
clear_page_dirty_for_io is called for not-uptodate pages, e.g.
over this call-chain:[] clear_page_dirty_for_io+0x12a/0x130
[] generic_writepages+0x258/0x3e0
[] do_writepages+0x76/0x7c
[] __writeback_single_inode+0xba/0x3e4
[] sync_sb_inodes+0x23e/0x398
[] writeback_inodes+0x12e/0x140
[] wb_kupdate+0xd2/0x178
[] pdflush+0x162/0x23cThe bad news now is that page_test_and_clear_dirty might claim
that a not-uptodate page is dirty since SetPageUptodate which
resets the per page dirty bit has not yet been called. The page
writeback that follows clobbers the data on disk.The simplest solution to this problem is to move the call to
page_test_and_clear_dirty under the "if (page_mapped(page))".
If a file backed page is mapped it is uptodate.Signed-off-by: Martin Schwidefsky
02 Mar, 2007
1 commit
-
page_lock_anon_vma() uses spin_lock() to block RCU. This doesn't work with
PREEMPT_RCU, we have to do rcu_read_lock() explicitely. Otherwise, it is
theoretically possible that slab returns anon_vma's memory to the system
before we do spin_unlock(&anon_vma->lock).[ Hugh points out that this only matters for PREEMPT_RCU, which isn't merged
yet, and may never be. Regardless, this patch is conceptually the
right thing to do, even if it doesn't matter at this point. - Linus ]Signed-off-by: Oleg Nesterov
Cc: Paul McKenney
Cc: Nick Piggin
Cc: Christoph Lameter
Acked-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
31 Dec, 2006
1 commit
-
(akpm: macros are wonderful)
Signed-off-by: Al Viro
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
23 Dec, 2006
2 commits
-
- add flush_cache_page() for all those virtual indexed cache
architectures.- handle s390.
Signed-off-by: Peter Zijlstra
Signed-off-by: Linus Torvalds -
Add more debugging in the rmap code in an attempt to locate to source of
the occasional "mapcount went negative" assertions.Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
21 Oct, 2006
1 commit
-
Clarify lockorder comments now that sys_msync dropps mmap_sem before
calling do_fsync.Signed-off-by: Nick Piggin
Signed-off-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
12 Oct, 2006
1 commit
-
We have a persistent dribble of reports of this BUG triggering. Its extended
diagnostics were recently made conditional on CONFIG_DEBUG_VM, which was a bad
idea - we want to know about it.Signed-off-by: Dave Jones
Cc: Nick Piggin
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
26 Sep, 2006
1 commit
-
Tracking of dirty pages in shared writeable mmap()s.
The idea is simple: write protect clean shared writeable pages, catch the
write-fault, make writeable and set dirty. On page write-back clean all the
PTE dirty bits and write protect them once again.The implementation is a tad harder, mainly because the default
backing_dev_info capabilities were too loosely maintained. Hence it is not
enough to test the backing_dev_info for cap_account_dirty.The current heuristic is as follows, a VMA is eligible when:
- its shared writeable
(vm_flags & (VM_WRITE|VM_SHARED)) == (VM_WRITE|VM_SHARED)
- it is not a 'special' mapping
(vm_flags & (VM_PFNMAP|VM_INSERTPAGE)) == 0
- the backing_dev_info is cap_account_dirty
mapping_cap_account_dirty(vma->vm_file->f_mapping)
- f_op->mmap() didn't change the default page protectionPage from remap_pfn_range() are explicitly excluded because their COW
semantics are already horrid enough (see vm_normal_page() in do_wp_page()) and
because they don't have a backing store anyway.mprotect() is taught about the new behaviour as well. However it overrides
the last condition.Cleaning the pages on write-back is done with page_mkclean() a new rmap call.
It can be called on any page, but is currently only implemented for mapped
pages, if the page is found the be of a VMA that accounts dirty pages it will
also wrprotect the PTE.Finally, in fs/buffers.c:try_to_free_buffers(); remove clear_page_dirty() from
under ->private_lock. This seems to be safe, since ->private_lock is used to
serialize access to the buffers, not the page itself. This is needed because
clear_page_dirty() will call into page_mkclean() and would thereby violate
locking order.[dhowells@redhat.com: Provide a page_mkclean() implementation for NOMMU]
Signed-off-by: Peter Zijlstra
Cc: Hugh Dickins
Signed-off-by: David Howells
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
01 Jul, 2006
2 commits
-
The current NR_FILE_MAPPED is used by zone reclaim and the dirty load
calculation as the number of mapped pagecache pages. However, that is not
true. NR_FILE_MAPPED includes the mapped anonymous pages. This patch
separates those and therefore allows an accurate tracking of the anonymous
pages per zone.It then becomes possible to determine the number of unmapped pages per zone
and we can avoid scanning for unmapped pages if there are none.Also it may now be possible to determine the mapped/unmapped ratio in
get_dirty_limit. Isnt the number of anonymous pages irrelevant in that
calculation?Note that this will change the meaning of the number of mapped pages reported
in /proc/vmstat /proc/meminfo and in the per node statistics. This may affect
user space tools that monitor these counters! NR_FILE_MAPPED works like
NR_FILE_DIRTY. It is only valid for pagecache pages.Signed-off-by: Christoph Lameter
Cc: Trond Myklebust
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
nr_mapped is important because it allows a determination of how many pages of
a zone are not mapped, which would allow a more efficient means of determining
when we need to reclaim memory in a zone.We take the nr_mapped field out of the page state structure and define a new
per zone counter named NR_FILE_MAPPED (the anonymous pages will be split off
from NR_MAPPED in the next patch).We replace the use of nr_mapped in various kernel locations. This avoids the
looping over all processors in try_to_free_pages(), writeback, reclaim (swap +
zone reclaim).[akpm@osdl.org: bugfix]
Signed-off-by: Christoph Lameter
Cc: Trond Myklebust
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
26 Jun, 2006
1 commit
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Hugh clarified the role of VM_LOCKED. So we can now implement page
migration for mlocked pages.Allow the migration of mlocked pages. This means that try_to_unmap must
unmap mlocked pages in the migration case.Signed-off-by: Christoph Lameter
Acked-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
23 Jun, 2006
5 commits
-
This implements the use of migration entries to preserve ptes of file backed
pages during migration. Processes can therefore be migrated back and forth
without loosing their connection to pagecache pages.Note that we implement the migration entries only for linear mappings.
Nonlinear mappings still require the unmapping of the ptes for migration.And another writepage() ugliness shows up. writepage() can drop the page
lock. Therefore we have to remove migration ptes before calling writepages()
in order to avoid having migration entries point to unlocked pages.Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
If we install a migration entry then the rss not really decreases since the
page is just moved somewhere else. We can save ourselves the work of
decrementing and later incrementing which will just eventually cause cacheline
bouncing.Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Rip the page migration logic out.
Remove all code that has to do with swapping during page migration.
This also guts the ability to migrate pages to swap. No one used that so lets
let it go for good.Page migration should be a bit broken after this patch.
Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Implement read/write migration ptes
We take the upper two swapfiles for the two types of migration ptes and define
a series of macros in swapops.h.The VM is modified to handle the migration entries. migration entries can
only be encountered when the page they are pointing to is locked. This limits
the number of places one has to fix. We also check in copy_pte_range and in
mprotect_pte_range() for migration ptes.We check for migration ptes in do_swap_cache and call a function that will
then wait on the page lock. This allows us to effectively stop all accesses
to apge.Migration entries are created by try_to_unmap if called for migration and
removed by local functions in migrate.cFrom: Hugh Dickins
Several times while testing swapless page migration (I've no NUMA, just
hacking it up to migrate recklessly while running load), I've hit the
BUG_ON(!PageLocked(p)) in migration_entry_to_page.This comes from an orphaned migration entry, unrelated to the current
correctly locked migration, but hit by remove_anon_migration_ptes as it
checks an address in each vma of the anon_vma list.Such an orphan may be left behind if an earlier migration raced with fork:
copy_one_pte can duplicate a migration entry from parent to child, after
remove_anon_migration_ptes has checked the child vma, but before it has
removed it from the parent vma. (If the process were later to fault on this
orphaned entry, it would hit the same BUG from migration_entry_wait.)This could be fixed by locking anon_vma in copy_one_pte, but we'd rather
not. There's no such problem with file pages, because vma_prio_tree_add
adds child vma after parent vma, and the page table locking at each end is
enough to serialize. Follow that example with anon_vma: add new vmas to the
tail instead of the head.(There's no corresponding problem when inserting migration entries,
because a missed pte will leave the page count and mapcount high, which is
allowed for. And there's no corresponding problem when migrating via swap,
because a leftover swap entry will be correctly faulted. But the swapless
method has no refcounting of its entries.)From: Ingo Molnar
pte_unmap_unlock() takes the pte pointer as an argument.
From: Hugh Dickins
Several times while testing swapless page migration, gcc has tried to exec
a pointer instead of a string: smells like COW mappings are not being
properly write-protected on fork.The protection in copy_one_pte looks very convincing, until at last you
realize that the second arg to make_migration_entry is a boolean "write",
and SWP_MIGRATION_READ is 30.Anyway, it's better done like in change_pte_range, using
is_write_migration_entry and make_migration_entry_read.From: Hugh Dickins
Remove unnecessary obfuscation from sys_swapon's range check on swap type,
which blew up causing memory corruption once swapless migration made
MAX_SWAPFILES no longer 2 ^ MAX_SWAPFILES_SHIFT.Signed-off-by: Hugh Dickins
Acked-by: Martin Schwidefsky
Signed-off-by: Hugh Dickins
Signed-off-by: Christoph Lameter
Signed-off-by: Ingo Molnar
From: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
migrate is a better name since it is only used by page migration.
Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
22 Mar, 2006
2 commits
-
Put a few more checks under CONFIG_DEBUG_VM
Signed-off-by: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We have struct kmem_cache now so use it instead of the old typedef.
Signed-off-by: Pekka Enberg
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
10 Mar, 2006
1 commit
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Remove two early-development BUG_ONs from page_add_file_rmap.
The pfn_valid test (originally useful for checking that nobody passed an
artificial struct page) comes too late, since we already have the struct
page.The PageAnon test (useful when anon was first distinguished from file rmap)
prevents ->nopage implementations from reusing ->mapping, which would
otherwise be available.Signed-off-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
01 Mar, 2006
1 commit
-
remove_from_swap() currently attempts to use page_lock_anon_vma to obtain
an anon_vma lock. That is not working since the page may have been
remapped via swap ptes in order to move the page.However, do_migrate_pages() obtain the mmap_sem lock and therefore there is
a guarantee that the anonymous vma will not vanish from under us. There is
therefore no need to use page_lock_anon_vma.Signed-off-by: Christoph Lameter
Acked-by: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
02 Feb, 2006
3 commits
-
Migrate a page with buffers without requiring writeback
This introduces a new address space operation migratepage() that may be used
by a filesystem to implement its own version of page migration.A version is provided that migrates buffers attached to pages. Some
filesystems (ext2, ext3, xfs) are modified to utilize this feature.The swapper address space operation are modified so that a regular
migrate_page() will occur for anonymous pages without writeback (migrate_pages
forces every anonymous page to have a swap entry).Signed-off-by: Mike Kravetz
Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add remove_from_swap
remove_from_swap() allows the restoration of the pte entries that existed
before page migration occurred for anonymous pages by walking the reverse
maps. This reduces swap use and establishes regular pte's without the need
for page faults.Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Add direct migration support with fall back to swap.
Direct migration support on top of the swap based page migration facility.
This allows the direct migration of anonymous pages and the migration of file
backed pages by dropping the associated buffers (requires writeout).Fall back to swap out if necessary.
The patch is based on lots of patches from the hotplug project but the code
was restructured, documented and simplified as much as possible.Note that an additional patch that defines the migrate_page() method for
filesystems is necessary in order to avoid writeback for anonymous and file
backed pages.Signed-off-by: KAMEZAWA Hiroyuki
Signed-off-by: Mike Kravetz
Signed-off-by: Christoph Lameter
Signed-off-by: Alexey Dobriyan
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
19 Jan, 2006
1 commit
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Migration code currently does not take a reference to target page
properly, so between unlocking the pte and trying to take a new
reference to the page with isolate_lru_page, anything could happen to
it.Fix this by holding the pte lock until we get a chance to elevate the
refcount.Other small cleanups while we're here.
Signed-off-by: Nick Piggin
Signed-off-by: Christoph Lameter
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
10 Jan, 2006
1 commit
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This patch converts the inode semaphore to a mutex. I have tested it on
XFS and compiled as much as one can consider on an ia64. Anyway your
luck with it might be different.Modified-by: Ingo Molnar
(finished the conversion)
Signed-off-by: Jes Sorensen
Signed-off-by: Ingo Molnar
09 Jan, 2006
1 commit
-
We seem to be hitting this assertion failure too often for it to be
hardware bugs.Cc: Hugh Dickins
Cc: Nick Piggin
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
07 Jan, 2006
2 commits
-
Optimise page_state manipulations by introducing interrupt unsafe accessors
to page_state fields. Callers must provide their own locking (either
disable interrupts or not update from interrupt context).Switch over the hot callsites that can easily be moved under interrupts off
sections.Signed-off-by: Nick Piggin
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
Optimise rmap functions by minimising atomic operations when we know there
will be no concurrent modifications.Signed-off-by: Nick Piggin
Cc: Hugh Dickins
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
30 Nov, 2005
1 commit
-
I image this showed up because of "unused var..." when the changes
occured, because flush_cache_page() is a noop in most places. This
showed up for me on parisc however, where flush_cache_page() is a real
function.Signed-off-by: Linus Torvalds
