sysfs: Fix memory leak in sysfs_sd_setsecdata().

This patch fixies follwing two memory leak patterns that reported by kmemleak.
sysfs_sd_setsecdata() is called during sys_lsetxattr() operation.
It checks sd->s_iattr is NULL or not. Then if it is NULL, it calls
sysfs_init_inode_attrs() to allocate memory.
That code is this.

iattrs = sd->s_iattr;
if (!iattrs)
                iattrs = sysfs_init_inode_attrs(sd);

The iattrs recieves sysfs_init_inode_attrs()'s result,  but sd->s_iattr
doesn't know the address. so it needs to set correct address to
sd->s_iattr to free memory in other function.

unreferenced object 0xffff880250b73e60 (size 32):
  comm "systemd", pid 1, jiffies 4294683888 (age 94.553s)
  hex dump (first 32 bytes):
    73 79 73 74 65 6d 5f 75 3a 6f 62 6a 65 63 74 5f  system_u:object_
    72 3a 73 79 73 66 73 5f 74 3a 73 30 00 00 00 00  r:sysfs_t:s0....
  backtrace:
    [<ffffffff814cb1d0>] kmemleak_alloc+0x73/0x98
    [<ffffffff811270ab>] __kmalloc+0x100/0x12c
    [<ffffffff8120775a>] context_struct_to_string+0x106/0x210
    [<ffffffff81207cc1>] security_sid_to_context_core+0x10b/0x129
    [<ffffffff812090ef>] security_sid_to_context+0x10/0x12
    [<ffffffff811fb0da>] selinux_inode_getsecurity+0x7d/0xa8
    [<ffffffff811fb127>] selinux_inode_getsecctx+0x22/0x2e
    [<ffffffff811f4d62>] security_inode_getsecctx+0x16/0x18
    [<ffffffff81191dad>] sysfs_setxattr+0x96/0x117
    [<ffffffff811542f0>] __vfs_setxattr_noperm+0x73/0xd9
    [<ffffffff811543d9>] vfs_setxattr+0x83/0xa1
    [<ffffffff811544c6>] setxattr+0xcf/0x101
    [<ffffffff81154745>] sys_lsetxattr+0x6a/0x8f
    [<ffffffff814efda9>] system_call_fastpath+0x16/0x1b
    [<ffffffffffffffff>] 0xffffffffffffffff
unreferenced object 0xffff88024163c5a0 (size 96):
  comm "systemd", pid 1, jiffies 4294683888 (age 94.553s)
  hex dump (first 32 bytes):
    00 00 00 00 ed 41 00 00 00 00 00 00 00 00 00 00  .....A..........
    00 00 00 00 00 00 00 00 0c 64 42 4f 00 00 00 00  .........dBO....
  backtrace:
    [<ffffffff814cb1d0>] kmemleak_alloc+0x73/0x98
    [<ffffffff81127402>] kmem_cache_alloc_trace+0xc4/0xee
    [<ffffffff81191cbe>] sysfs_init_inode_attrs+0x2a/0x83
    [<ffffffff81191dd6>] sysfs_setxattr+0xbf/0x117
    [<ffffffff811542f0>] __vfs_setxattr_noperm+0x73/0xd9
    [<ffffffff811543d9>] vfs_setxattr+0x83/0xa1
    [<ffffffff811544c6>] setxattr+0xcf/0x101
    [<ffffffff81154745>] sys_lsetxattr+0x6a/0x8f
    [<ffffffff814efda9>] system_call_fastpath+0x16/0x1b
    [<ffffffffffffffff>] 0xffffffffffffffff
`

Signed-off-by: Masami Ichikawa <masami256@gmail.com>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
makefile: enable cache

Conflicts:
	Makefile
defconfig: enable ksm
Revert "[PATCH 4/4] block, bfq: add Early Queue Merge (EQM) to BFQ-v6r2 for 3.1.0"

This reverts commit 5462f000d40eb613a8e544d09b461fc7d763de41.
Revert "[PATCH 3/4] block: introduce the BFQ-v6r2 I/O sched for 3.1"

This reverts commit 019a0107b0508b06ae5f30c2c6e410b1ef411e2d.
Revert "[PATCH 2/4] block: cgroups, kconfig, build bits for BFQ-v6r2-3.1"

This reverts commit ed50439f4724f002066e22e59dff1feaa08008aa.

Conflicts:
	block/bfq-iosched.c
Revert "[PATCH 2/4] block: cgroups, kconfig, build bits for BFQ-v6r2-3.1"

This reverts commit 57e9eeb1d03b904755b86f6c240539a6a99839c7.
Revert "[PATCH 1/4] block: prepare I/O context code for BFQ-v6r2 for 3.1"

This reverts commit 6bb77599c2f022a0a610261f93e9596e3bd9ae3d.
BFQ v7r2