Staging: zram: Remove useless offset calculation in handle_uncompressed_page()

The offset of uncompressed page is always zero: handle_uncompressed_page()
doesn't have to care about it.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Staging: zram: Refactor zram_read/write() functions

This patch refactor the code of zram_read/write() functions. It does
not removes a lot of duplicate code alone, but is mostly a helper for
the third patch of this series (Staging: zram: allow partial page
operations).

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Staging: zram: allow partial page operations

Commit 7b19b8d45b216ff3186f066b31937bdbde066f08 (zram: Prevent overflow
in logical block size) introduced ZRAM_LOGICAL_BLOCK_SIZE constant to
prevent overflow of logical block size on 64k page kernel.
However, the current implementation of zram only allow operation on block
of the same size as a page. That makes theorically legit 4k requests fail
on 64k page kernel.

This patch makes zram allow operation on partial pages. Basically, it
means we still do operations on full pages internally, but only copy the
relevent segments from/to the user memory.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Staging: zram: Replace mutex lock by a R/W semaphore

Currently, nothing protects zram table from concurrent access.
For instance, ZRAM_UNCOMPRESSED bit can be cleared by zram_free_page()
called from a concurrent write between the time ZRAM_UNCOMPRESSED has
been set and the time it is tested to unmap KM_USER0 in
zram_bvec_write(). This ultimately leads to kernel panic.

Also, a read request can occurs when the page has been freed by a
running write request and before it has been updated, leading to
zero filled block being incorrectly read and "Read before write"
error message.

This patch replace the current mutex by a rw_semaphore. It extends
the protection to zram table (currently, only compression buffers are
protected) and read requests (currently, only write requests are
protected).

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Staging: zram: Fix kunmapping order

This patch fixes the unmapping order of KM_USER0/1 in
handle_uncompressed_page() and zram_read() so that kmap()/kunmap() calls
are correctly nested.

Reported-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Reviewed-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
staging: zram: make global var "devices" use unique name

The global variable "devices" is too general to be global.
This patch switches the name to be "zram_devices".

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
staging: zram: make global var "num_devices" use unique name

The global variable "num_devices" is too general to be
global. This patch switches the name to be "zram_num_devices".

Signed-off-by: Noah Watkins <noahwatkins@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
staging: zram: fix zram locking

Currently init_lock only prevents concurrent execution of zram_init_device()
and zram_reset_device() but not zram_make_request() nor sysfs store functions.

This patch changes init_lock into a rw_semaphore. A write lock is taken by
init, reset and store functions, a read lock is taken by zram_make_request().
Also, avoids to release the lock before calling __zram_reset_device() for
cleaning after a failed init, thus preventing any concurrent task to see an
inconsistent state of zram.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
staging: zram: prevent accessing an unallocated table when init fails early

When the allocation of zram->table fails, we set zram->disksize to zero
to prevent accessing the unallocated table entries during cleanup.
However, we currently don't take this precaution when the initialization
fails earlier.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
zram: Fix sparse warnings

Fixes sparse warning:
zram_drv.c:666:6: warning: symbol 'zram_slot_free_notify' was not
declared. Should it be static?

Also, max_zpage_size is now size_t just to be consistent with data-type
of other variables maintaining sizes of various kinds.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Staging: zram: Add a missing GFP_KERNEL specifier in zram_init_device()

The allocation of zram->compress_buffer is misssing a GFP_* specifier.
This is equivalent to GFP_NOWAIT but it is more likely a omission.
Since the allocation just above it uses GFP_KERNEL, there is no reason
to use GFP_NOWAIT here. Therefore, add GFP_KERNEL.

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
staging: zram: Rename module parameter

zram accepts number of devices to be created
as a module parameter. This was renamed from
num_devices to zram_num_devices (without updating
the documentation!) since num_devices was declared
as a non-static global variable, polluting the global
namespace. Now, we declare it as a static variable
and revert back the name change.

The documentation (zram.txt) already mentions
num_devices as the module parameter name.

Signed-off-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zram: handle mem suffixes in disk size zram_sysfs parameter

Use memparse() to allow mem suffixes in disksize sysfs number.
Examples:
    echo 256K > /sys/block/zram0/disksize
    echo 512M > /sys/block/zram0/disksize
    echo 1G > /sys/block/zram0/disksize

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>

Conflicts:
	drivers/staging/zram/zram_sysfs.c
staging: zram: simplify num_devices paramater

Simplify dealing with num_devices when initializing zram.
Also cleanup some of the output messages.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zram: show correct disksize

The ->disksize variable stores values in units of bytes,
print the correct size in Kb

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
zram: Fix deadlock bug in partial read/write

Now zram allocates new page with GFP_KERNEL in zram I/O path
if IO is partial. Unfortunately, It may cause deadlock with
reclaim path like below.

write_page from fs
fs_lock
allocation(GFP_KERNEL)
reclaim
pageout
				write_page from fs
				fs_lock <-- deadlock

This patch fixes it by using GFP_NOIO.  In read path, we
reorganize code flow so that kmap_atomic is called after the
GFP_NOIO allocation.

Cc: stable@vger.kernel.org
Acked-by: Jerome Marchand <jmarchand@redhat.com>
Acked-by: Nitin Gupta <ngupta@vflare.org>
[ penberg@kernel.org: don't use GFP_ATOMIC ]
Signed-off-by: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[steven@steven676.net: make apply to pre-zsmalloc 3.0 version]
zram: force disksize setting before using zram

Now zram document syas "set disksize is optional"
but partly it's wrong. When you try to use zram firstly after
booting, you must set disksize, otherwise zram can't work because
zram gendisk's size is 0. But once you do it, you can use zram freely
after reset because reset doesn't reset to zero paradoxically.
So in this time, disksize setting is optional.:(
It's inconsitent for user behavior and not straightforward.

This patch forces always setting disksize firstly before using zram.
Yes. It changes current behavior so someone could complain when
he upgrades zram. Apparently it could be a problem if zram is mainline
but it still lives in staging so behavior could be changed for right
way to go. Let them excuse.

Acked-by: Jerome Marchand <jmarchand@redhat.com>
Acked-by: Nitin Gupta <ngupta@vflare.org>
Acked-by: Dan Magenheimer <dan.magenheimer@oracle.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
zram: give up lazy initialization of zram metadata

1) User of zram normally do mkfs.xxx or mkswap before using
   the zram block device(ex, normally, do it at booting time)
   It ends up allocating such metadata of zram before real usage so
   benefit of lazy initialzation would be mitigated.

2) Some user want to use zram when memory pressure is high.(ie, load zram
   dynamically, NOT booting time). It does make sense because people don't
   want to waste memory until memory pressure is high(ie, where zram is really
   helpful time). In this case, lazy initialzation could be failed easily
   because we will use GFP_NOIO instead of GFP_KERNEL for avoiding deadlock.
   So the benefit of lazy initialzation would be mitigated, too.

3) Metadata overhead is not critical and Nitin has a plan to diet it.
   4K : 12 byte(64bit machine) -> 64G : 192M so 0.3% isn't big overhead
   If insane user use such big zram device up to 20, it could consume 6% of ram
   but efficieny of zram will cover the waste.

So this patch gives up lazy initialization and instead we initialize metadata
at disksize setting time.

Acked-by: Jerome Marchand <jmarchand@redhat.com>
Acked-by: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
zram: fix warning of print format

kbuild bot whinges due to print format mistmatch caused by
zram: force disksize setting before using zram.

This patch fixes it.

Reported-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
staging: zram: __zram_reset_device() can be static

Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Cc: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>