f2fs: introduce sb_status sysfs node

f2fs: introduce sb_status sysfs node

Introduce /sys/fs/f2fs/<devname>/stat/sb_status to show superblock
status in real time as a hexadecimal value.

value           sb status macro                 description

0x1             SBI_IS_DIRTY,                   /* dirty flag for checkpoint */
0x2             SBI_IS_CLOSE,                   /* specify unmounting */
0x4             SBI_NEED_FSCK,                  /* need fsck.f2fs to fix */
0x8             SBI_POR_DOING,                  /* recovery is doing or not */
0x10            SBI_NEED_SB_WRITE,              /* need to recover superblock */
0x20            SBI_NEED_CP,                    /* need to checkpoint */
0x40            SBI_IS_SHUTDOWN,                /* shutdown by ioctl */
0x80            SBI_IS_RECOVERED,               /* recovered orphan/data */
0x100           SBI_CP_DISABLED,                /* CP was disabled last mount */
0x200           SBI_CP_DISABLED_QUICK,          /* CP was disabled quickly */
0x400           SBI_QUOTA_NEED_FLUSH,           /* need to flush quota info in CP */
0x800           SBI_QUOTA_SKIP_FLUSH,           /* skip flushing quota in current CP */
0x1000          SBI_QUOTA_NEED_REPAIR,          /* quota file may be corrupted */
0x2000          SBI_IS_RESIZEFS,                /* resizefs is in process */

Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>