problem in restoring mountpoint in Solaris

Hi,
I am restoring the existing mount point on Solaris and getting below mentioned error

mount: /dev/dsk/c0t2d0s6 is already mounted or /billing is busy

I uses truss command to see the output and snapshot is below. Please help me to restore the mount point,

# truss -fa mount -F /dev/dsk/c0t2d0s6 /billing
15020: execve("/sbin/mount", 0xFFBFFD4C, 0xFFBFFD60) argc = 4
15020: argv: mount -F /dev/dsk/c0t2d0s6 /billing
15020: resolvepath("/lib/ld.so.1", "/lib/ld.so.1", 1023) = 12
15020: resolvepath("/sbin/mount", "/sbin/mount", 1023) = 11
15020: stat("/sbin/mount", 0xFFBFFB28) = 0
15020: open("/var/ld/ld.config", O_RDONLY) Err#2 ENOENT
15020: stat("/lib/libcmd.so.1", 0xFFBFF648) = 0
15020: resolvepath("/lib/libcmd.so.1", "/lib/libcmd.so.1", 1023) = 16
15020: open("/lib/libcmd.so.1", O_RDONLY) = 3
15020: mmap(0x00010000, 8192, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_ALIGN, 3, 0) = 0xFF3A0000
15020: mmap(0x00010000, 90112, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE|MAP_ANON|MAP_ALIGN, -1, 0) = 0xFF380000
15020: mmap(0xFF380000, 9948, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_TEXT, 3, 0) = 0xFF380000
15020: mmap(0xFF394000, 1027, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_INITDATA, 3, 16384) = 0xFF394000
15020: munmap(0xFF384000, 65536) = 0
15020: memcntl(0xFF380000, 3336, MC_ADVISE, MADV_WILLNEED, 0, 0) = 0
15020: close(3) = 0
15020: stat("/lib/libc.so.1", 0xFFBFF648) = 0
15020: resolvepath("/lib/libc.so.1", "/lib/libc.so.1", 1023) = 14
15020: open("/lib/libc.so.1", O_RDONLY) = 3
15020: mmap(0xFF3A0000, 8192, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED, 3, 0) = 0xFF3A0000
15020: mmap(0x00010000, 991232, PROT_NONE, MAP_PRIVATE|MAP_NORESERVE|MAP_ANON|MAP_ALIGN, -1, 0) = 0xFF280000
15020: mmap(0xFF280000, 882285, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_TEXT, 3, 0) = 0xFF280000
15020: mmap(0xFF368000, 29469, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_INITDATA, 3, 884736) = 0xFF368000
15020: mmap(0xFF370000, 2592, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_FIXED|MAP_ANON, -1, 0) = 0xFF370000
15020: munmap(0xFF358000, 65536) = 0
15020: memcntl(0xFF280000, 139784, MC_ADVISE, MADV_WILLNEED, 0, 0) = 0
15020: close(3) = 0
15020: munmap(0xFF3A0000, 8192) = 0
15020: mmap(0x00010000, 24576, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANON|MAP_ALIGN, -1, 0) = 0xFF3A0000
15020: getcontext(0xFFBFF820)
15020: getrlimit(RLIMIT_STACK, 0xFFBFF800) = 0
15020: getpid() = 15020 [15019]
15020: setustack(0xFF3A2088)
15020: brk(0x00027248) = 0
15020: brk(0x00029248) = 0
15020: stat("/platform/FJSV,GPUZC-M/lib/libc_psr.so.1", 0xFFBFF420) = 0
15020: resolvepath("/platform/FJSV,GPUZC-M/lib/libc_psr.so.1", "/platform/FJSV,GPUZC-M/lib/libc_psr.so.1", 1023) = 40
15020: open("/platform/FJSV,GPUZC-M/lib/libc_psr.so.1", O_RDONLY) = 3
15020: mmap(0x00010000, 8192, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_ALIGN, 3, 0) = 0xFF270000
15020: mmap(0x00000000, 8192, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE|MAP_ANON, -1, 0) = 0xFF260000
15020: close(3) = 0
15020: open("/etc/vfstab", O_RDONLY) = 3
15020: llseek(3, 0, SEEK_CUR) = 0
15020: fstat64(3, 0xFFBFF8C0) = 0
15020: brk(0x00029248) = 0
15020: brk(0x0002B248) = 0
15020: fstat64(3, 0xFFBFF768) = 0
15020: ioctl(3, TCGETA, 0xFFBFF84C) Err#25 ENOTTY
15020: read(3, " # d e v i c e\t\t d e v".., 8192) = 821
15020: read(3, 0x00028064, 8192) = 0
15020: llseek(3, 0, SEEK_SET) = 0
15020: read(3, " # d e v i c e\t\t d e v".., 8192) = 821
15020: read(3, 0x00028064, 8192) = 0
15020: llseek(3, 0, SEEK_CUR) = 821
15020: llseek(3, 0, SEEK_SET) = 0
15020: llseek(3, 0, SEEK_CUR) = 0
15020: read(3, " # d e v i c e\t\t d e v".., 8192) = 821
15020: read(3, 0x00028064, 8192) = 0
15020: llseek(3, 0, SEEK_SET) = 0
15020: stat64("/billing", 0xFFBFFAE0) = 0
15020: read(3, " # d e v i c e\t\t d e v".., 8192) = 821
15020: read(3, 0x00028064, 8192) = 0
15020: llseek(3, 0, SEEK_CUR) = 821
15020: close(3) = 0
15020: fstat64(2, 0xFFBFEBA0) = 0
mount15020: write(2, " m o u n t", 5) = 5
: FSType 15020: write(2, " : F S T y p e ", 9) = 9
/dev/dsk/c0t2d0s615020: write(2, " / d e v / d s k / c 0 t".., 17) = 17
exceeds 15020: write(2, " e x c e e d s ", 9) = 9
815020: write(2, " 8", 1) = 1
characters
15020: write(2, " c h a r a c t e r s\n", 12) = 12
15020: _exit(1)
#

sounds like it might already be mounted. please paste the output of the mount command with no arguments.

you can use fuser -cu /billing and see if there any user/ process running ?

other option is umount -f /billing and mount the file system.

fuser -ck /billing
Force unmount the filesystem then try restoring
umount -f /billing