The end of line character doesn't exist on end of help in all case, check it
first.
Signed-off-by: NEgry Gabor <gaboregry@t-online.hu>
Cc: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The gettext doesn't handle the {CONFIG}:00000 markers as sources.  I added a
simple comment prefix for them.
Signed-off-by: NEgry Gabor <gaboregry@t-online.hu>
Cc: Arnaldo Carvalho de Melo <acme@conectiva.com.br>
Cc: Roman Zippel <zippel@linux-m68k.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add page_state info to the per-node meminfo file in sysfs.  This is mostly
just for informational purposes.

The lack of this information was brought up recently during a discussion
regarding pagecache clearing, and I put this patch together to test out one
of the suggestions.

It seems like interesting info to have, so I'm submitting the patch.
Signed-off-by: NMartin Hicks <mort@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a "smaps" entry to /proc/pid: show howmuch memory is resident in each
mapping.

People that want to perform a memory consumption analysing can use it
mainly if someone needs to figure out which libraries can be reduced for
embedded systems.  So the new features are the physical size of shared and
clean [or dirty]; private and clean [or dirty].

Take a look the example below:

# cat /proc/4576/smaps

08048000-080dc000 r-xp /bin/bash
Size:               592 KB
Rss:                500 KB
Shared_Clean:       500 KB
Shared_Dirty:         0 KB
Private_Clean:        0 KB
Private_Dirty:        0 KB
080dc000-080e2000 rw-p /bin/bash
Size:                24 KB
Rss:                 24 KB
Shared_Clean:         0 KB
Shared_Dirty:         0 KB
Private_Clean:        0 KB
Private_Dirty:       24 KB
080e2000-08116000 rw-p
Size:               208 KB
Rss:                208 KB
Shared_Clean:         0 KB
Shared_Dirty:         0 KB
Private_Clean:        0 KB
Private_Dirty:      208 KB
b7e2b000-b7e34000 r-xp /lib/tls/libnss_files-2.3.2.so
Size:                36 KB
Rss:                 12 KB
Shared_Clean:        12 KB
Shared_Dirty:         0 KB
Private_Clean:        0 KB
Private_Dirty:        0 KB
...

(Includes a cleanup from "Richard Purdie" <rpurdie@rpsys.net>)

From: Torsten Foertsch <torsten.foertsch@gmx.net>

show_smap calls first show_map and then prints its additional information to
the seq_file.  show_map checks if all it has to print fits into the buffer and
if yes marks the current vma as written.  While that is correct for show_map
it is not for show_smap.  Here the vma should be marked as written only after
the additional information is also written.

The attached patch cures the problem.  It moves the functionality of the
show_map function to a new function show_map_internal that is called with an
additional struct mem_size_stats* argument.  Then show_map calls
show_map_internal with NULL as struct mem_size_stats* whereas show_smap calls
it with a real pointer.  Now the final

	if (m->count < m->size)  /* vma is copied successfully */
		m->version = (vma != get_gate_vma(task))? vma->vm_start: 0;

is done only if the whole entry fits into the buffer.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Proposed by and based on a patch from Eric Dumazet <dada1@cosmosbay.com>:
This patch removes unnecessary critical section in ksize() function, as
cli/sti are rather expensive on modern CPUS.

It additionally adds a docbook entry for ksize() and further simplifies the
code.
Signed-Off-By: NManfred Spraul <manfred@colorfullife.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Mostobjects returned by __cache_alloc() will be written by the caller,
(but not all callers want to write all the object, but just at the
begining) prefetchw() tells the modern CPU to think about the future
writes, ie start some memory transactions in advance.
Signed-off-by: NEric Dumazet <dada1@cosmosbay.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Any architecture that has hardware updated A/D bits that require
synchronization against other processors during PTE operations can benefit
from doing non-atomic PTE updates during address space destruction.
Originally done on i386, now ported to x86_64.

Doing a read/write pair instead of an xchg() operation saves the implicit
lock, which turns out to be a big win on 32-bit (esp w PAE).
Signed-off-by: NZachary Amsden <zach@vmware.com>
Cc: Andi Kleen <ak@muc.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a new accessor for PTEs, which passes the full hint from the mmu_gather
struct; this allows architectures with hardware pagetables to optimize away
atomic PTE operations when destroying an address space.  Removing the
locked operation should allow better pipelining of memory access in this
loop.  I measured an average savings of 30-35 cycles per zap_pte_range on
the first 500 destructions on Pentium-M, but I believe the optimization
would win more on older processors which still assert the bus lock on xchg
for an exclusive cacheline.

Update: I made some new measurements, and this saves exactly 26 cycles over
ptep_get_and_clear on Pentium M.  On P4, with a PAE kernel, this saves 180
cycles per ptep_get_and_clear, for a whopping 92160 cycles savings for a
full address space destruction.

pte_clear_full is not yet used, but is provided for future optimizations
(in particular, when running inside of a hypervisor that queues page table
updates, the full hint allows us to avoid queueing unnecessary page table
update for an address space in the process of being destroyed.

This is not a huge win, but it does help a bit, and sets the stage for
further hypervisor optimization of the mm layer on all architectures.
Signed-off-by: NZachary Amsden <zach@vmware.com>
Cc: Christoph Lameter <christoph@lameter.com>
Cc: <linux-mm@kvack.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This is used only in slab.c and each architecture gets to define whcih
underlying type is to be used.

Seems a bit silly - move it to slab.c and use the same type for all
architectures: unsigned int.
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I don't think we need to call hugetlb_clean_stale_pgtable() anymore
in 2.6.13 because of the rework with free_pgtables().  It now collect
all the pte page at the time of munmap.  It used to only collect page
table pages when entire one pgd can be freed and left with staled pte
pages.  Not anymore with 2.6.13.  This function will never be called
and We should turn it into a BUG_ON.

I also spotted two problems here, not Adam's fault :-)
(1) in huge_pte_alloc(), it looks like a bug to me that pud is not
    checked before calling pmd_alloc()
(2) in hugetlb_clean_stale_pgtable(), it also missed a call to
    pmd_free_tlb.  I think a tlb flush is required to flush the mapping
    for the page table itself when we clear out the pmd pointing to a
    pte page.  However, since hugetlb_clean_stale_pgtable() is never
    called, so it won't trigger the bug.
Signed-off-by: NKen Chen <kenneth.w.chen@intel.com>
Cc: Adam Litke <agl@us.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

For demand faulting, we cannot assume that the page tables will be
populated.  Do what the rest of the architectures do and test p?d_present()
while walking down the page table.
Signed-off-by: NAdam Litke <agl@us.ibm.com>
Cc: <linux-mm@kvack.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Initial Post (Wed, 17 Aug 2005)

This patch moves the
	if (! pte_none(*pte))
		hugetlb_clean_stale_pgtable(pte);
logic into huge_pte_alloc() so all of its callers can be immune to the bug
described by Kenneth Chen at http://lkml.org/lkml/2004/6/16/246

> It turns out there is a bug in hugetlb_prefault(): with 3 level page table,
> huge_pte_alloc() might return a pmd that points to a PTE page. It happens
> if the virtual address for hugetlb mmap is recycled from previously used
> normal page mmap. free_pgtables() might not scrub the pmd entry on
> munmap and hugetlb_prefault skips on any pmd presence regardless what type
> it is.

Unless I am missing something, it seems more correct to place the check inside
huge_pte_alloc() to prevent a the same bug wherever a huge pte is allocated.
It also allows checking for this condition when lazily faulting huge pages
later in the series.
Signed-off-by: NAdam Litke <agl@us.ibm.com>
Cc: <linux-mm@kvack.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch adds a macro pte_huge(pte) for i386/x86_64 which is needed by a
patch later in the series.  Instead of repeating (_PAGE_PRESENT |
_PAGE_PSE), I've added __LARGE_PTE to i386 to match x86_64.
Signed-off-by: NAdam Litke <agl@us.ibm.com>
Cc: <linux-mm@kvack.org>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Version 6 of the ARM architecture introduces the concept of 16MB pages
(supersections) and 36-bit (40-bit actually, but nobody uses this) physical
addresses.  36-bit addressed memory and I/O and ARMv6 can only be mapped
using supersections and the requirement on these is that both virtual and
physical addresses be 16MB aligned.  In trying to add support for ioremap()
of 36-bit I/O, we run into the issue that get_vm_area() allows for a
maximum of 512K alignment via the IOREMAP_MAX_ORDER constant.  To work
around this, we can:

- Allocate a larger VM area than needed (size + (1ul << IOREMAP_MAX_ORDER))
  and then align the pointer ourselves, but this ends up with 512K of
  wasted VM per ioremap().

- Provide a new __get_vm_area_aligned() API and make __get_vm_area() sit
  on top of this. I did this and it works but I don't like the idea
  adding another VM API just for this one case.

- My preferred solution which is to allow the architecture to override
  the IOREMAP_MAX_ORDER constant with it's own version.
Signed-off-by: NDeepak Saxena <dsaxena@plexity.net>
Cc: Russell King <rmk@arm.linux.org.uk>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

_PAGE_FILE does not indicate whether a file is in page / swap cache, it is
set just for non-linear PTE's.  Correct the comment for i386, x86_64, UML.
Also clearify _PAGE_NONE.
Signed-off-by: NPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

If !vma->vm-ops we already BUG above, so retesting it is useless.  The
compiler cannot optimize this because BUG is a macro and is not thus marked
noreturn; that should possibly be fixed.
Signed-off-by: NPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Either shmem_getpage returns a failure, or it found a page, or it was told
it couldn't do any I/O.  So it's useless to check nonblock in the else
branch.  We could add a BUG() there but I preferred to comment the
offending function.

This was taken out from one Ingo Molnar's old patch I'm resurrecting.
Signed-off-by: NPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Fix a small spelling mistake.  subtile->subtle
Signed-off-by: NMartin Hicks <mort@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

smp_entry_t -> swap_entry_t
Signed-off-by: NPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Better late than never, I've at last reviewed the madvise vma merging
going into 2.6.13.  Remove a pointless check and fix two little bugs -
a simple test (with /proc/<pid>/maps hacked to show ReadHints) showed
both mismerges in practice: though being madvise, neither was disastrous.

1. Correct placement of the success label in madvise_behavior: as in
   mprotect_fixup and mlock_fixup, it is necessary to update vm_flags
   when vma_merge succeeds (to handle the exceptional Case 8 noted in
   the comments above vma_merge itself).

2. Correct initial value of prev when starting part way into a vma: as
   in sys_mprotect and do_mlock, it needs to be set to vma in this case
   (vma_merge handles only that minimum of cases shown in its comments).

3. If find_vma_prev sets prev, then the vma it returns is prev->vm_next,
   so it's pointless to make that same assignment again in sys_madvise.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Christoph Lameter and Marcelo Tosatti asked to get rid of the
atomic_inc_and_test() to cleanup the atomic ops in the zone reclaim code.
Signed-off-by: NMartin Hicks <mort@sgi.com>
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Add a capability check to sys_set_zone_reclaim().  This syscall is not
something that should be available to a user.
Signed-off-by: NMartin Hicks <mort@sgi.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This bitop does not need to be atomic because it is performed when there will
be no references to the page (ie.  the page is being freed).
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

filemap_xip's nopage routine maps the ZERO_PAGE into readonly mappings, if it
has no data page to map there: then if the hole in the file is later filled,
__xip_unmap uses an rmap technique to replace the ZERO_PAGEs mapped for that
offset by the newly allocated file page, so that established mappings will see
the newly written data.

However, on MIPS (alone) there's not one but as many as eight ZERO_PAGEs,
chosen for coloring by user virtual address; and if mremap has meanwhile been
used to move a mapping containing a ZERO_PAGE, it will generally not match the
ZERO_PAGE(address) __xip_unmap is looking for.

To maintain XIP's established mappings correctly on MIPS, we need Nick's fix
to mremap's move_one_page (originally presented as an optimization), to
replace the ZERO_PAGE appropriate to the old address by the ZERO_PAGE
appropriate to the new address.

(But when I first saw this, I was thinking the ZERO_PAGEs themselves would get
corrupted, very bad.  Now I think it's the other way round, that the
established mappings will fail to see the newly written data: incorrect, but
not corrupting everything else.  Whether filemap_xip's technique is generally
safe, I'd hesitate to say in a hurry: it's interesting, but we've never tried
to do that in tmpfs.)
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Thanks to Bill Irwin for pointing this out.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Microoptimise page_add_anon_rmap.  Although these expressions are used only in
the taken branch of the if() statement, the compiler can't reorder them inside
because atomic_inc_and_test is a barrier.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Just be clear that VM_RESERVED pages here are a bug, and the test is not there
because they are expected.
Signed-off-by: NNick Piggin <npiggin@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This patch was recently discussed on linux-mm:
http://marc.theaimsgroup.com/?t=112085728500002&r=1&w=2

I inherited a large code base from Ray for page migration.  There was a
small patch in there that I find to be very useful since it allows the
display of the locality of the pages in use by a process.  I reworked that
patch and came up with a /proc/<pid>/numa_maps that gives more information
about the vma's of a process.  numa_maps is indexes by the start address
found in /proc/<pid>/maps.  F.e.  with this patch you can see the page use
of the "getty" process:

margin:/proc/12008 # cat maps
00000000-00004000 r--p 00000000 00:00 0
2000000000000000-200000000002c000 r-xp 00000000 08:04 516                /lib/ld-2.3.3.so
2000000000038000-2000000000040000 rw-p 00028000 08:04 516                /lib/ld-2.3.3.so
2000000000040000-2000000000044000 rw-p 2000000000040000 00:00 0
2000000000058000-2000000000260000 r-xp 00000000 08:04 54707842           /lib/tls/libc.so.6.1
2000000000260000-2000000000268000 ---p 00208000 08:04 54707842           /lib/tls/libc.so.6.1
2000000000268000-2000000000274000 rw-p 00200000 08:04 54707842           /lib/tls/libc.so.6.1
2000000000274000-2000000000280000 rw-p 2000000000274000 00:00 0
2000000000280000-20000000002b4000 r--p 00000000 08:04 9126923            /usr/lib/locale/en_US.utf8/LC_CTYPE
2000000000300000-2000000000308000 r--s 00000000 08:04 60071467           /usr/lib/gconv/gconv-modules.cache
2000000000318000-2000000000328000 rw-p 2000000000318000 00:00 0
4000000000000000-4000000000008000 r-xp 00000000 08:04 29576399           /sbin/mingetty
6000000000004000-6000000000008000 rw-p 00004000 08:04 29576399           /sbin/mingetty
6000000000008000-600000000002c000 rw-p 6000000000008000 00:00 0          [heap]
60000fff7fffc000-60000fff80000000 rw-p 60000fff7fffc000 00:00 0
60000ffffff44000-60000ffffff98000 rw-p 60000ffffff44000 00:00 0          [stack]
a000000000000000-a000000000020000 ---p 00000000 00:00 0                  [vdso]

cat numa_maps
2000000000000000 default MaxRef=43 Pages=11 Mapped=11 N0=4 N1=3 N2=2 N3=2
2000000000038000 default MaxRef=1 Pages=2 Mapped=2 Anon=2 N0=2
2000000000040000 default MaxRef=1 Pages=1 Mapped=1 Anon=1 N0=1
2000000000058000 default MaxRef=43 Pages=61 Mapped=61 N0=14 N1=15 N2=16 N3=16
2000000000268000 default MaxRef=1 Pages=2 Mapped=2 Anon=2 N0=2
2000000000274000 default MaxRef=1 Pages=3 Mapped=3 Anon=3 N0=3
2000000000280000 default MaxRef=8 Pages=3 Mapped=3 N0=3
2000000000300000 default MaxRef=8 Pages=2 Mapped=2 N0=2
2000000000318000 default MaxRef=1 Pages=1 Mapped=1 Anon=1 N2=1
4000000000000000 default MaxRef=6 Pages=2 Mapped=2 N1=2
6000000000004000 default MaxRef=1 Pages=1 Mapped=1 Anon=1 N0=1
6000000000008000 default MaxRef=1 Pages=1 Mapped=1 Anon=1 N0=1
60000fff7fffc000 default MaxRef=1 Pages=1 Mapped=1 Anon=1 N0=1
60000ffffff44000 default MaxRef=1 Pages=1 Mapped=1 Anon=1 N0=1

getty uses ld.so.  The first vma is the code segment which is used by 43
other processes and the pages are evenly distributed over the 4 nodes.

The second vma is the process specific data portion for ld.so.  This is
only one page.

The display format is:

<startaddress>	 Links to information in /proc/<pid>/map
<memory policy>  This can be "default" "interleave={}", "prefer=<node>" or "bind={<zones>}"
MaxRef=		<maximum reference to a page in this vma>
Pages=		<Nr of pages in use>
Mapped=		<Nr of pages with mapcount >
Anon=		<nr of anonymous pages>
Nx=		<Nr of pages on Node x>

The content of the proc-file is self-evident.  If this would be tied into
the sparsemem system then the contents of this file would not be too
useful.
Signed-off-by: NChristoph Lameter <clameter@sgi.com>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Remove the three get_mm_counter(mm, rss) tests from rmap.c: there was a
time when testing rss was important to avoid a particular race between
dup_mmap and the anonmm rmap; but now it's just a rather silly pseudo-
optimization, made even more obscure by the get_mm_counter macro.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Three of the four BUG_ONs in delete_from_swap_cache are immediately
repeated in __delete_from_swap_cache: delete those and add the one.  But
perhaps mm/ is altogether overprovisioned with historic BUGs?
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Aha, swsusp dips into swap_info[], better update it to swap_lock.  It's
bitflipping flags with 0xFF, so get_swap_page will allocate from only the one
chosen device: let's change that to flip SWP_WRITEOK.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The idea of a swap_device_lock per device, and a swap_list_lock over them all,
is appealing; but in practice almost every holder of swap_device_lock must
already hold swap_list_lock, which defeats the purpose of the split.

The only exceptions have been swap_duplicate, valid_swaphandles and an
untrodden path in try_to_unuse (plus a few places added in this series).
valid_swaphandles doesn't show up high in profiles, but swap_duplicate does
demand attention.  However, with the hold time in get_swap_pages so much
reduced, I've not yet found a load and set of swap device priorities to show
even swap_duplicate benefitting from the split.  Certainly the split is mere
overhead in the common case of a single swap device.

So, replace swap_list_lock and swap_device_lock by spinlock_t swap_lock
(generally we seem to prefer an _ in the name, and not hide in a macro).

If someone can show a regression in swap_duplicate, then probably we should
add a hashlock for the swap_map entries alone (shorts being anatomic), so as
to help the case of the single swap device too.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The get_swap_page/scan_swap_map latency can be so bad that even those without
preemption configured deserve relief: periodically cond_resched.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

get_swap_page has often shown up on latency traces, doing lengthy scans while
holding two spinlocks.  swap_list_lock is already dropped, now scan_swap_map
drop swap_device_lock before scanning the swap_map.

While scanning for an empty cluster, don't worry that racing tasks may
allocate what was free and free what was allocated; but when allocating an
entry, check it's still free after retaking the lock.  Avoid dropping the lock
in the expected common path.  No barriers beyond the locks, just let the
cookie crumble; highest_bit limit is volatile, but benign.

Guard against swapoff: must check SWP_WRITEOK before allocating, must raise
SWP_SCANNING reference count while in scan_swap_map, swapoff wait for that to
fall - just use schedule_timeout, we don't want to burden scan_swap_map
itself, and it's very unlikely that anyone can really still be in
scan_swap_map once swapoff gets this far.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Rewrite scan_swap_map to allocate in just the same way as before (taking the
next free entry SWAPFILE_CLUSTER-1 times, then restarting at the lowest wholly
empty cluster, falling back to lowest entry if none), but with a view towards
dropping the lock in the next patch.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Rewrite get_swap_page to allocate in just the same sequence as before, but
without holding swap_list_lock across its scan_swap_map.  Decrement
nr_swap_pages and update swap_list.next in advance, while still holding
swap_list_lock.  Skip full devices by testing highest_bit.  Swapoff hold
swap_device_lock as well as swap_list_lock to clear SWP_WRITEOK.  Reduces lock
contention when there are parallel swap devices of the same priority.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

This makes negligible difference in practice: but swap_list.next should not be
updated to a higher prio in the general helper swap_info_get, but rather in
swap_entry_free; and then only in the case when entry is actually freed.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The swap header's unsigned int last_page determines the range of swap pages,
but swap_info has been using int or unsigned long in some cases: use unsigned
int throughout (except, in several places a local unsigned long is useful to
avoid overflows when adding).
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NJens Axboe <axboe@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

The "Adding %dk swap" message shows the number of swap extents, as a guide to
how fragmented the swapfile may be.  But a useful further guide is what total
extent they span across (sometimes scarily large).

And there's no need to keep nr_extents in swap_info: it's unused after the
initial message, so save a little space by keeping it on stack.
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

There are several comments that swap's extent_list.prev points to the lowest
extent: that's not so, it's extent_list.next which points to it, as you'd
expect.  And a couple of loops in add_swap_extent which go all the way through
the list, when they should just add to the other end.

Fix those up, and let map_swap_page search the list forwards: profiles shows
it to be twice as quick that way - because prefetch works better on how the
structs are typically kmalloc'ed?  or because usually more is written to than
read from swap, and swap is allocated ascendingly?
Signed-off-by: NHugh Dickins <hugh@veritas.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>