linux.git/arch/powerpc, branch v2.6.26-rc7

Reinstate ZERO_PAGE optimization in 'get_user_pages()' and fix XIP

2008-06-20T18:18:25+00:00

KAMEZAWA Hiroyuki and Oleg Nesterov point out that since the commit
557ed1fa2620dc119adb86b34c614e152a629a80 ("remove ZERO_PAGE") removed
the ZERO_PAGE from the VM mappings, any users of get_user_pages() will
generally now populate the VM with real empty pages needlessly.

We used to get the ZERO_PAGE when we did the "handle_mm_fault()", but
since fault handling no longer uses ZERO_PAGE for new anonymous pages,
we now need to handle that special case in follow_page() instead.

In particular, the removal of ZERO_PAGE effectively removed the core
file writing optimization where we would skip writing pages that had not
been populated at all, and increased memory pressure a lot by allocating
all those useless newly zeroed pages.

This reinstates the optimization by making the unmapped PTE case the
same as for a non-existent page table, which already did this correctly.

While at it, this also fixes the XIP case for follow_page(), where the
caller could not differentiate between the case of a page that simply
could not be used (because it had no "struct page" associated with it)
and a page that just wasn't mapped.

We do that by simply returning an error pointer for pages that could not
be turned into a "struct page *".  The error is arbitrarily picked to be
EFAULT, since that was what get_user_pages() already used for the
equivalent IO-mapped page case.

[ Also removed an impossible test for pte_offset_map_lock() failing:
  that's not how that function works ]

Acked-by: Oleg Nesterov 
Acked-by: Nick Piggin 
Cc: KAMEZAWA Hiroyuki 
Cc: Hugh Dickins 
Cc: Andrew Morton 
Cc: Ingo Molnar 
Cc: Roland McGrath 
Signed-off-by: Linus Torvalds

[POWERPC] Clear sub-page HPTE present bits when demoting page size

2008-06-18T11:40:43+00:00

When we demote a slice from 64k to 4k, and we are about to insert an
HPTE for a 4k subpage and we notice that there is an existing 64k
HPTE, we first invalidate that HPTE before inserting the new 4k
subpage HPTE.  Since the bits that encode which hash bucket the old
HPTE was in overlap with the bits that encode which of the 16 subpages
have HPTEs, we need to clear out the subpage HPTE-present bits before
starting to insert HPTEs for the 4k subpages.  If we don't do that, we
can erroneously think that a subpage already has an HPTE when it
doesn't.

That in itself wouldn't be such a problem except that when we go to
update the HPTE that we think is present on machines with a
hypervisor, the hypervisor can tell us that the HPTE we think is there
is actually there even though it isn't, which can lead to a process
getting stuck in a loop, continually faulting.  The reason for the
confusion is that the AVPN (abbreviated virtual page number) we are
looking for in the HPTE for a 4k subpage can actually match the AVPN
in a stale HPTE for another 64k page.  For example, the HPTE for
the 4k subpage at 0x84000f000 will be in the same hash bucket and have
the same AVPN as the HPTE for the 64k page at 0x8400f0000.

This fixes the code to clear out the subpage HPTE-present bits.

Signed-off-by: Paul Mackerras

[POWERPC] 4xx: Clear new TLB cache attribute bits in Data Storage vector

2008-06-18T11:40:43+00:00

A recent commit added support for the new 440x6 and 464 cores that have the
added WL1, IL1I, IL1D, IL2I, and ILD2 bits for the caching attributes in the
TLBs.  The new bits were cleared in the finish_tlb_load function, however a
similar bit of code was missed in the DataStorage interrupt vector.

Signed-off-by: Josh Boyer 
Signed-off-by: Paul Mackerras

[POWERPC] Turn on ATA_SFF so we get SATA_SVW back in defconfigs

2008-06-16T11:14:12+00:00

This enables CONFIG_ATA_SFF in the defconfigs that are intended to
work on a G5 powermac, i.e. g5_defconfig and ppc64_defconfig.  Since
the support for the SATA cell in the K2 chipset is provided by the
sata_svw.c driver, and that depends on CONFIG_ATA_SFF, we need to turn
that and CONFIG_SATA_SVW back on so we can get to the hard disk on G5s.

Signed-off-by: Paul Mackerras

[POWERPC] Remove ppc32's export of console_drivers

2008-06-16T05:00:56+00:00

There are no in-tree uses of the export any more and in linux-next there
is a change that exports it globally which causes warnings:

WARNING: vmlinux: 'console_drivers' exported twice. Previous export was in vmlinux

and in one case (mpc85xx_defconfig) a build error:

kernel/built-in.o: In function `__crc_console_drivers':
(*ABS*+0x1eb0e6f5): multiple definition of `__crc_console_drivers'

So remove the export now.  Also, there is no longer any need to include
linux/console.h.

Signed-off-by: Stephen Rothwell 
Signed-off-by: Paul Mackerras

[POWERPC] Fix -Os kernel builds with newer gcc versions

2008-06-16T05:00:54+00:00

GCC 4.4.x looks to be adding support for generating out-of-line register
saves/restores based on:

http://gcc.gnu.org/ml/gcc-patches/2008-04/msg01678.html

This breaks the kernel if we enable CONFIG_CC_OPTIMIZE_FOR_SIZE.  To fix
this we add the use the save/restore code from gcc and simplified it down
for our needs (integer only).

Additionally, we have to link this code into each module.  The other
solution was to add EXPORT_SYMBOL() which meant going through the
trampoline which seemed nonsensical for these out-of-line routines.

Finally, we add some checks to prom_init_check.sh to ignore the
out-of-line save/restore functions.

Signed-off-by: Kumar Gala 
Signed-off-by: Paul Mackerras

[POWERPC] Fix bootwrapper builds with newer gcc versions

2008-06-16T05:00:52+00:00

GCC 4.4.x looks to be adding support for generating out-of-line register
saves/restores based on:

http://gcc.gnu.org/ml/gcc-patches/2008-04/msg01678.html

This breaks the bootwrapper as we'd need to link with libgcc to get the
implementation of the register save/restores.

To workaround this issue, we just stole the save/restore code from gcc
and simplified it down for our needs (integer only).

Signed-off-by: Kumar Gala 
Signed-off-by: Paul Mackerras

[POWERPC] Fix warning in pseries/eeh_driver.c

2008-06-16T05:00:44+00:00

Fix this:

/usr/src/devel/arch/powerpc/platforms/pseries/eeh_driver.c: In function 'print_device_node_tree':
/usr/src/devel/arch/powerpc/platforms/pseries/eeh_driver.c:55: warning: ISO C90 forbids mixed declarations and code

also make that function look like it's part of Linux.

Signed-off-by: Andrew Morton 
Acked-by: Benjamin Herrenschmidt 
Signed-off-by: Paul Mackerras

[POWERPC] Add missing of_node_put in pseries/nvram.c

2008-06-16T05:00:32+00:00

of_node_put is needed before discarding a value received from
of_find_node_by_type, eg in error handling code.

The semantic patch that makes the change is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// 
@@
struct device_node *n;
struct device_node *n1;
struct device_node *n2;
statement S;
identifier f1,f2;
expression E1,E2;
constant C;
@@

n = of_find_node_by_type(...)
...
if (!n) S
... when != of_node_put(n)
    when != n1 = f1(n,...)
    when != E1 = n
    when any
    when strict
(
+ of_node_put(n);
  return -C;
|
  of_node_put(n);
|
  n2 = f2(n,...)
|
  E2 = n
|
  return ...;
)
// 

Signed-off-by: Julia Lawall 
Acked-by: Stephen Rothwell 
Signed-off-by: Paul Mackerras

[POWERPC] Fix return value check logic in debugfs virq_mapping setup

2008-06-16T05:00:25+00:00

debugfs_create_file() returns a non-NULL (non-zero) value in case of
success, not a NULL value.

This fixes this non-critical boot-time debugging error message:

[    1.316386] calling  irq_debugfs_init+0x0/0x50
[    1.316399] initcall irq_debugfs_init+0x0/0x50 returned -12 after 0 msecs
[    1.316411] initcall irq_debugfs_init+0x0/0x50 returned with error code -12

Signed-off-by: Emil Medve 
Acked-by: Michael Ellerman 
Signed-off-by: Paul Mackerras