Staging: Fixes string split across lines in zram

Fixes the following checkpatch warning in zram_drv.c:
WARNING: quoted string split across lines

Signed-off-by: Marlies Ruck <marlies.ruck@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: avoid invalid memory access in zram_exit()

Memory for zram->disk object may have already been freed after returning
from destroy_device(zram), then it's unsafe for zram_reset_device(zram)
to access zram->disk again.

We can't solve this bug by flipping the order of destroy_device(zram)
and zram_reset_device(zram), that will cause deadlock issues to the
zram sysfs handler.

So fix it by holding an extra reference to zram->disk before calling
destroy_device(zram).

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: use zram->lock to protect zram_free_page() in swap free notify path

zram_slot_free_notify() is free-running without any protection from
concurrent operations. So there are race conditions between
zram_bvec_read()/zram_bvec_write() and zram_slot_free_notify(),
and possible consequences include:
1) Trigger BUG_ON(!handle) on zram_bvec_write() side.
2) Access to freed pages on zram_bvec_read() side.
3) Break some fields (bad_compress, good_compress, pages_stored)
   in zram->stats if the swap layer makes concurrently call to
   zram_slot_free_notify().

So enhance zram_slot_free_notify() to acquire writer lock on zram->lock
before calling zram_free_page().

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: destroy all devices on error recovery path in zram_init()

On error recovery path of zram_init(), it leaks the zram device object
causing the failure. So change create_device() to free allocated
resources on error path.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Acked-by: Jerome Marchand <jmarchan@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: avoid double free in function zram_bvec_write()

When doing a patial write and the whole page is filled with zero,
zram_bvec_write() will free uncmem twice.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: avoid access beyond the zram device

Function valid_io_request() should verify the entire request are within
the zram device address range. Otherwise it may cause invalid memory
access when accessing/modifying zram->meta->table[index] because the
'index' is out of range. Then it may access non-exist memory, randomly
modify memory belong to other subsystems, which is hard to track down.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: kill unused zram_get_num_devices()

Now there's no caller of zram_get_num_devices(), so kill it.
And change zram_devices to static because it's only used in zram_drv.c.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: optimize memory operations with clear_page()/copy_page()

Some architectures provides architecture-specific, optimized version of
clear_page()/copy_page(), which may have better performance than
memset()/memcpy(). So use clear_page()/copy_page() to optimize zram
performance if possible.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: protect sysfs handler from invalid memory access

Use zram->init_lock to protect access to zram->meta, otherwise it
may cause invalid memory access if zram->meta has been freed by
zram_reset_device().

This issue may be triggered by:
Thread 1:
while true; do cat mem_used_total; done
Thread 2:
while true; do echo 8M > disksize; echo 1 > reset; done

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: simplify and optimize dev_to_zram()

Simplify and optimize dev_to_zram() without walking the zram_devices
array.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: use atomic64_xxx() to replace zram_stat64_xxx()

Use atomic64_xxx() to replace open-coded zram_stat64_xxx().
Some architectures have native support of atomic64 operations,
so we can get rid of the spin_lock() in zram_stat64_xxx().
On the other hand, for platforms use generic version of atomic64
implement, it may cause an extra save/restore of the interrupt
flag.  So it's a tradeoff.

Signed-off-by: Jiang Liu <jiang.liu@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: remove zram_sysfs file (v2)

Move zram sysfs code to zram drv and remove zram_sysfs.c
file. This gives ability to make static a number of previously
exported zram functions, used from zram sysfs, e.g. internal zram
zram_meta_alloc/free(). We also can drop zram_drv wrapper
functions, used from zram sysfs:
e.g. zram_reset_device()/__zram_reset_device() pair.

v2: as suggested by Greg K-H, move MODULE description to the
bottom of the file.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: allow request end to coincide with disksize

Pass valid_io_request() checks if request end coincides with disksize
(end equals bound), only fail if we attempt to read beyond the bound.

mkfs.ext2 produces numerous errors:
[ 2164.632747] quiet_error: 1 callbacks suppressed
[ 2164.633260] Buffer I/O error on device zram0, logical block 153599
[ 2164.633265] lost page write due to I/O error on zram0

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: zram: protect zram_reset_device() call

Commit 9b3bb7abcdf2df0f1b2657e6cbc9d06bc2b3b36f (remove
zram_sysfs file (v2)) accidentally made zram_reset_device()
racy. Protect zram_reset_device() call with zram->lock.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Jerome Marchand <jmarchand@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
staging: zram: Add auto loading of module if user opens /dev/zram.

Greg spotted that said driver is not subscribing to the automagic
mechanism of auto-loading if a user tries to open /dev/zram.

This fixes it.

CC: Minchan Kim <minchan@kernel.org>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: prevent data loss in error cases of function zram_bvec_write()

In function zram_bvec_write(), previous data at the index is
already freed by function zram_free_page().
When failed to compress or zs_malloc, there is no way to restore old data.
Therefore, free previous data when it's about to update.

Also, no need to check whether table is not empty outside of
function zram_free_page(), because the function properly checks inside.

Signed-off-by: Sunghan Suh <sunghan.suh@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
Staging: zram: zram_drv.c: Fixed Error of trailing whitespace

Fixed by removing trailing whitespace

Signed-off-by: Kumar Gaurav <kumargauravgupta3@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: fix invalid memory access

[1] tried to fix invalid memory access on zram->disk but it didn't
fix properly because get_disk failed during module exit path.

Actually, we don't need to reset zram->disk's capacity to zero
in module exit path so that this patch introduces new argument
"reset_capacity" on zram_reset_divice and it only reset it when
reset_store is called.

[1] 6030ea9b,  zram: avoid invalid memory access in zram_exit()

Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jiang Liu <jiang.liu@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: don't grab mutex in zram_slot_free_noity

[1] introduced down_write in zram_slot_free_notify to prevent race
between zram_slot_free_notify and zram_bvec_[read|write]. The race
could happen if somebody who has right permission to open swap device
is reading swap device while it is used by swap in parallel.

However, zram_slot_free_notify is called with holding spin_lock of
swap layer so we shouldn't avoid holing mutex. Otherwise, lockdep
warns it.

This patch adds new list to handle free slot and workqueue
so zram_slot_free_notify just registers slot index to be freed and
registers the request to workqueue. If workqueue is expired,
it holds mutex_lock so there is no problem any more.

If any I/O is issued, zram handles pending slot-free request
caused by zram_slot_free_notify right before handling issued
request because workqueue wouldn't be expired yet so zram I/O
request handling function can miss it.

Lastly, when zram is reset, flush_work could handle all of pending
free request so we shouldn't have memory leak.

NOTE: If zram_slot_free_notify's kmalloc with GFP_ATOMIC would be
failed, the slot will be freed when next write I/O write the slot.

[1] [57ab0485, zram: use zram->lock to protect zram_free_page()
    in swap free notify path]

* from v2
  * refactoring

* from v1
  * totally redesign

Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jiang Liu <jiang.liu@huawei.com>
Cc: stable@vger.kernel.org
Signed-off-by: Minchan Kim <minchan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
zram: Disable allocation failure logging

Disable the logging of errors when allocations fail
for zram pages. This avoid excessive logging when system is
very low on memory.

Signed-off-by: Olav Haugan <ohaugan@codeaurora.org>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>