ondemand: set default sampling rate to 50k for battery savings
update defconfig
mm:writeback: Disables writeback function while screen is on ..
and bring it back when screen is off.
binfmt_elf.c: use get_random_int() to fix entropy depleting.
mm.h: bump VM_MAX_READAHEAD to 512kb
block,elevator: use new hashtable implementation
Switch elevator to use the new hashtable implementation. This reduces the
amount of generic unrelated code in the elevator.

This also removes the dymanic allocation of the hash table. The size of the table is
constant so there's no point in paying the price of an extra dereference when accessing
it.

This patch depends on d9b482c ("hashtable: introduce a small and naive
hashtable") which was merged in v3.6.

Signed-off-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
slub: fix a possible memory leak
ext4: prevent kernel panic in case of uninitialized jinode
In some cases the kernel crash occurs during system suspend/resume:

[ 4095.041351] Unable to handle kernel NULL pointer dereference at virtual address 00000000
[ 4095.050689] pgd = c0004000
[ 4095.053985] [00000000] *pgd=00000000
[ 4095.058807] Internal error: Oops: 5 [#1] PREEMPT SMP
[ 4095.064483] Modules linked in: wl12xx mac80211 pvrsrvkm_sgx540_120 cfg80211 compat [last unloaded: wl12xx_sdio]
[ 4095.064575] CPU: 1    Tainted: G    B        (3.0.31-01807-gfac16a0 #1)
[ 4095.064605] PC is at jbd2_journal_file_inode+0x38/0x118
[ 4095.064666] LR is at mpage_da_map_and_submit+0x48c/0x618
[ 4095.064697] pc : [<c01da5a8>]    lr : [<c01aeac0>]    psr: 60000013
[ 4095.064697] sp : c6e07c80  ip : c6e07ca0  fp : c6e07c9c
[ 4095.064727] r10: 00000001  r9 : c6e06000  r8 : 00000179
[ 4095.064758] r7 : c6e07ca0  r6 : c73b8400  r5 : 00000000  r4 : c59a7d80
[ 4095.064758] r3 : 00000038  r2 : 00000800  r1 : 00000000  r0 : c7754fc0
[ 4095.064788] Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment kernel
[ 4095.064819] Control: 10c5387d  Table: 86cc804a  DAC: 00000015
[ 4095.064849]
[ 4095.064849] PC: 0xc01da528:
[ 4095.064880] a528  0a000003 e3a05000 e1a00005 e24bd020 e89da9f0 e5951010 e3e06000 e14b22dc
.....
[ 4095.070373] 7fe0: c00a48ac 00000013 00000000 c6e07ff8 c00a48ac c00c0a94 84752f09 60772177
[ 4095.070404] Backtrace:
[ 4095.070465] [<c01da570>] (jbd2_journal_file_inode+0x0/0x118) from [<c01aeac0>] (mpage_da_map_and_submit+0x48c/0x618)
[ 4095.070495]  r7:c6e07ca0 r6:c6e07d00 r5:c6e07d90 r4:c7754fc0
[ 4095.070556] [<c01ae634>] (mpage_da_map_and_submit+0x0/0x618) from [<c01af40c>] (ext4_da_writepages+0x2a4/0x5c8)
[ 4095.070617] [<c01af168>] (ext4_da_writepages+0x0/0x5c8) from [<c0112af4>] (do_writepages+0x34/0x40)
[ 4095.070678] [<c0112ac0>] (do_writepages+0x0/0x40) from [<c01645a4>] (writeback_single_inode+0xd4/0x288)
[ 4095.070709] [<c01644d0>] (writeback_single_inode+0x0/0x288) from [<c0164ed4>] (writeback_sb_inodes+0xb4/0x184)
[ 4095.070770] [<c0164e20>] (writeback_sb_inodes+0x0/0x184) from [<c01655a0>] (writeback_inodes_wb+0xc4/0x13c)
[ 4095.070831] [<c01654dc>] (writeback_inodes_wb+0x0/0x13c) from [<c01658f0>] (wb_writeback+0x2d8/0x464)
[ 4095.070861] [<c0165618>] (wb_writeback+0x0/0x464) from [<c0165cb8>] (wb_do_writeback+0x23c/0x2c4)
[ 4095.070922] [<c0165a7c>] (wb_do_writeback+0x0/0x2c4) from [<c0165df4>] (bdi_writeback_thread+0xb4/0x2dc)
[ 4095.070953] [<c0165d40>] (bdi_writeback_thread+0x0/0x2dc) from [<c00c0b18>] (kthread+0x90/0x98)
[ 4095.071014] [<c00c0a88>] (kthread+0x0/0x98) from [<c00a48ac>] (do_exit+0x0/0x72c)
[ 4095.071044]  r7:00000013 r6:c00a48ac r5:c00c0a88 r4:c78c7ec4
[ 4095.071105] Code: e89da8f0 e5963000 e3130002 1afffffa (e5913000)
[ 4095.071166] ---[ end trace 7fe9f9b727e5cf78 ]---
[ 4095.071197] Kernel panic - not syncing: Fatal exception

The probably reason of such behaviour is an inode opened in READ mode
has been marked as 'dirty' somehow and written back by ext4_da_writepages.
Cause jinode == NULL it could lead to the kernel panic.

The patch prevents kernel panic and helps to investigate the problem
providing an inode number.

Change-Id: I1d77a011b580db682b8e2d122ef3d5e44e0ce5c7
Signed-off-by: Volodymyr Mieshkov <volodymyr.mieshkov@ti.com>
random: prevent add_input from doing anything
hashtable: introduce a small and naive hashtable
This hashtable implementation is using hlist buckets to provide a simple
hashtable to prevent it from getting reimplemented all over the kernel.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
[ Merging this now, so that subsystems can start applying Sasha's
  patches that use this   - Linus ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>