staging: zram: correct obsolete comment on max_zpage_size

Zram doesn't use xv_malloc any more so it doesn't have
limitation about zobj_header.

Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zram: Fix handling of incompressible pages

Change 130f315a (staging: zram: remove special handle of uncompressed page)
introduced a bug in the handling of incompressible pages which resulted in
memory allocation failure for such pages.

When a page expands on compression, say from 4K to 4K+30, we were trying to
do zsmalloc(pool, 4K+30). However, the maximum size which zsmalloc can
allocate is PAGE_SIZE (for obvious reasons), so such allocation requests
always return failure (0).

For a page that has compressed size larger than the original size (this may
happen with already compressed or random data), there is no point storing
the compressed version as that would take more space and would also require
time for decompression when needed again. So, the fix is to store any page,
whose compressed size exceeds a threshold (max_zpage_size), as-it-is i.e.
without compression.  Memory required for storing this uncompressed page can
then be requested from zsmalloc which supports PAGE_SIZE sized allocations.

Lastly, the fix checks that we do not attempt to "decompress" the page which
we stored in the uncompressed form -- we just memcpy() out such pages.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Reported-by: viechweg@gmail.com
Reported-by: paerley@gmail.com
Reported-by: wu.tommy@gmail.com
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zram: factor-out zram_decompress_page() function

zram_bvec_read() shared decompress functionality with zram_read_before_write() function.
Factor-out and make commonly used zram_decompress_page() function, which also simplified
error handling in zram_bvec_read().

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Reviewed-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: Add angle bracket before and after the URL

Add missing angle bracket before and after the URL.

Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zram: fix invalid memory references during disk write

Fixes a bug introduced by commit c8f2f0db1 ("zram: Fix handling
of incompressible pages") which caused invalid memory references
during disk write. Invalid references could occur in two cases:
 - Incoming data expands on compression: In this case, reference was
made to kunmap()'ed bio page.
 - Partial (non PAGE_SIZE) write with incompressible data: In this
case, reference was made to a kfree()'ed buffer.

Fixes bug 50081:
https://bugzilla.kernel.org/show_bug.cgi?id=50081

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Cc: stable <stable@vger.kernel.org>
Reported-by: Mihail Kasadjikov <hamer.mk@gmail.com>
Reported-by: Tomas M <tomas@slax.org>
Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zsmalloc: prevent mappping in interrupt context

Because we use per-cpu mapping areas shared among the
pools/users, we can't allow mapping in interrupt context
because it can corrupt another users mappings.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zsmalloc: add page table mapping method

This patchset provides page mapping via the page table.
On some archs, most notably ARM, this method has been
demonstrated to be faster than copying.

The logic controlling the method selection (copy vs page table)
is controlled by the definition of USE_PGTABLE_MAPPING which
is/can be defined for any arch that performs better with page
table mapping.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Paul Reioux <reioux@gmail.com>

Conflicts:
	drivers/staging/zsmalloc/zsmalloc-main.c
zsmalloc: collapse internal .h into .c

The patch collapses in the internal zsmalloc_int.h into
the zsmalloc-main.c file.

This is done in preparation for the promotion to mm/ where
separate internal headers are discouraged.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Acked-by: Nitin Gupta <ngupta@vflare.org>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zsmalloc: comment zs_create_pool function

Just as with zs_malloc() and zs_map_object(), it is worth
formally commenting the zs_create_pool() function.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zsmalloc: make CLASS_DELTA relative to PAGE_SIZE

Right now ZS_SIZE_CLASS_DELTA is hardcoded to be 16.  This
creates 254 classes for systems with 4k pages. However, on
PPC64 with 64k pages, it creates 4095 classes which is far
too many.

This patch makes ZS_SIZE_CLASS_DELTA relative to PAGE_SIZE
so that regardless of the page size, there will be the same
number of classes.

Acked-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zsmalloc: Fix TLB coherency and build problem

Recently, Matt Sealey reported he fail to build zsmalloc caused by
using of local_flush_tlb_kernel_range which are architecture dependent
function so !CONFIG_SMP in ARM couldn't implement it so it ends up
build error following as.

  MODPOST 216 modules
  LZMA    arch/arm/boot/compressed/piggy.lzma
  AS      arch/arm/boot/compressed/lib1funcs.o
ERROR: "v7wbi_flush_kern_tlb_range"
[drivers/staging/zsmalloc/zsmalloc.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2
make: *** Waiting for unfinished jobs....

The reason we used that function is copy method by [1]
was really slow in ARM but at that time.

More severe problem is ARM can prefetch speculatively on other CPUs
so under us, other TLBs can have an entry only if we do flush local
CPU. Russell King pointed that. Thanks!
We don't have many choices except using flush_tlb_kernel_range.

My experiment in ARMv7 processor 4 core didn't make any difference with
zsmapbench[2] between local_flush_tlb_kernel_range and flush_tlb_kernel_range
but still page-table based is much better than copy-based.

* bigger is better.

1. local_flush_tlb_kernel_range: 3918795 mappings
2. flush_tlb_kernel_range : 3989538 mappings
3. copy-based: 635158 mappings

This patch replace local_flush_tlb_kernel_range with
flush_tlb_kernel_range which are avaialbe in all architectures
because we already have used it in vmalloc allocator which are
generic one so build problem should go away and performane loss
shoud be void.

[1] f553646, zsmalloc: add page table mapping method
[2] https://github.com/spartacus06/zsmapbench

Cc: stable@vger.kernel.org
Cc: Dan Magenheimer <dan.magenheimer@oracle.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Konrad Rzeszutek Wilk <konrad@darnok.org>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Reported-by: Matt Sealey <matt@genesi-usa.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zsmalloc: remove unused pool name

zs_create_pool() currently takes a name argument which is
never used in any useful way.

This patch removes it.

Signed-off-by: Seth Jennings <sjenning@linux.vnet.ibm.com>
Acked-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zsmalloc: Fix link error on ARM

Testing the arm chromebook config against the upstream
kernel produces a linker error for the zsmalloc module from
staging. The symbol flush_tlb_kernel_range is not available
there. Fix this by removing the reimplementation of
unmap_kernel_range in the zsmalloc module and using the
function directly. The unmap_kernel_range function is not
usable by modules, so also disallow building the driver as a
module for now.

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging/zsmalloc: don't use pgtable-mapping from modules

Building zsmalloc as a module does not work on ARM because it uses
an interface that is not exported:

ERROR: "flush_tlb_kernel_range" [drivers/staging/zsmalloc/zsmalloc.ko] undefined!

Since this is only used as a performance optimization and only on ARM,
we can avoid the problem simply by not using that optimization when
building zsmalloc it is a loadable module.

flush_tlb_kernel_range is often an inline function, but out of the
architectures that use an extern function, only powerpc exports
it.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Seth Jennings <sjenning@linux.vnet.ibm.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
zcache-main.c: fix compilation error due to API update

Signed-off-by: Paul Reioux <reioux@gmail.com>
mm: frontswap: remove casting from function calls through ops structure

Removes unneeded casts.

Reviewed-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>