nilfs2: fix lock order reversal in chcp operation
Will fix the following lock order reversal lockdep detected:
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.32-rc6 #7
-------------------------------------------------------
chcp/30157 is trying to acquire lock:
(&nilfs->ns_mount_mutex){+.+.+.}, at: [<fed7cfcc>] nilfs_cpfile_change_cpmode+0x46/0x752 [nilfs2]
but task is already holding lock:
(&nilfs->ns_segctor_sem){++++.+}, at: [<fed7ca32>] nilfs_transaction_begin+0xba/0x110 [nilfs2]
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (&nilfs->ns_segctor_sem){++++.+}:
[<c105799c>] __lock_acquire+0x109c/0x139d
[<c1057d26>] lock_acquire+0x89/0xa0
[<c14151e2>] down_read+0x31/0x45
[<fed6d77b>] nilfs_attach_checkpoint+0x8f/0x16b [nilfs2]
[<fed6e393>] nilfs_get_sb+0x3e7/0x653 [nilfs2]
[<c10c0ccb>] vfs_kern_mount+0x8b/0x124
[<c10c0db2>] do_kern_mount+0x37/0xc3
[<c10d7517>] do_mount+0x64d/0x69d
[<c10d75cd>] sys_mount+0x66/0x95
[<c1002a14>] sysenter_do_call+0x12/0x32
-> #1 (&type->s_umount_key#31/1){+.+.+.}:
[<c105799c>] __lock_acquire+0x109c/0x139d
[<c1057d26>] lock_acquire+0x89/0xa0
[<c104c0f3>] down_write_nested+0x34/0x52
[<c10c08fe>] sget+0x22e/0x389
[<fed6e133>] nilfs_get_sb+0x187/0x653 [nilfs2]
[<c10c0ccb>] vfs_kern_mount+0x8b/0x124
[<c10c0db2>] do_kern_mount+0x37/0xc3
[<c10d7517>] do_mount+0x64d/0x69d
[<c10d75cd>] sys_mount+0x66/0x95
[<c1002a14>] sysenter_do_call+0x12/0x32
-> #0 (&nilfs->ns_mount_mutex){+.+.+.}:
[<c1057727>] __lock_acquire+0xe27/0x139d
[<c1057d26>] lock_acquire+0x89/0xa0
[<c1414d63>] mutex_lock_nested+0x41/0x23e
[<fed7cfcc>] nilfs_cpfile_change_cpmode+0x46/0x752 [nilfs2]
[<fed801b2>] nilfs_ioctl+0x11a/0x7da [nilfs2]
[<c10cca12>] vfs_ioctl+0x27/0x6e
[<c10ccf93>] do_vfs_ioctl+0x491/0x4db
[<c10cd022>] sys_ioctl+0x45/0x5f
[<c1002a14>] sysenter_do_call+0x12/0x32
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
2 files changed