From c1ea985c710f41e97f1c72c29bbf367375370f0b Mon Sep 17 00:00:00 2001 From: Ryusuke Konishi Date: Thu, 12 Nov 2009 00:13:32 +0900 Subject: [PATCH] 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: [] nilfs_cpfile_change_cpmode+0x46/0x752 [nilfs2] but task is already holding lock: (&nilfs->ns_segctor_sem){++++.+}, at: [] 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){++++.+}: [] __lock_acquire+0x109c/0x139d [] lock_acquire+0x89/0xa0 [] down_read+0x31/0x45 [] nilfs_attach_checkpoint+0x8f/0x16b [nilfs2] [] nilfs_get_sb+0x3e7/0x653 [nilfs2] [] vfs_kern_mount+0x8b/0x124 [] do_kern_mount+0x37/0xc3 [] do_mount+0x64d/0x69d [] sys_mount+0x66/0x95 [] sysenter_do_call+0x12/0x32 -> #1 (&type->s_umount_key#31/1){+.+.+.}: [] __lock_acquire+0x109c/0x139d [] lock_acquire+0x89/0xa0 [] down_write_nested+0x34/0x52 [] sget+0x22e/0x389 [] nilfs_get_sb+0x187/0x653 [nilfs2] [] vfs_kern_mount+0x8b/0x124 [] do_kern_mount+0x37/0xc3 [] do_mount+0x64d/0x69d [] sys_mount+0x66/0x95 [] sysenter_do_call+0x12/0x32 -> #0 (&nilfs->ns_mount_mutex){+.+.+.}: [] __lock_acquire+0xe27/0x139d [] lock_acquire+0x89/0xa0 [] mutex_lock_nested+0x41/0x23e [] nilfs_cpfile_change_cpmode+0x46/0x752 [nilfs2] [] nilfs_ioctl+0x11a/0x7da [nilfs2] [] vfs_ioctl+0x27/0x6e [] do_vfs_ioctl+0x491/0x4db [] sys_ioctl+0x45/0x5f [] sysenter_do_call+0x12/0x32 Signed-off-by: Ryusuke Konishi --- fs/nilfs2/cpfile.c | 2 -- fs/nilfs2/ioctl.c | 6 +++++- 2 files changed, 5 insertions(+), 3 deletions(-) diff --git a/fs/nilfs2/cpfile.c b/fs/nilfs2/cpfile.c index 1c6cfb59128..3f5d5d06f53 100644 --- a/fs/nilfs2/cpfile.c +++ b/fs/nilfs2/cpfile.c @@ -871,7 +871,6 @@ int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode) * exclusive with a new mount job. Though it doesn't cover * umount, it's enough for the purpose. */ - mutex_lock(&nilfs->ns_mount_mutex); if (nilfs_checkpoint_is_mounted(nilfs, cno, 1)) { /* Current implementation does not have to protect plain read-only mounts since they are exclusive @@ -880,7 +879,6 @@ int nilfs_cpfile_change_cpmode(struct inode *cpfile, __u64 cno, int mode) ret = -EBUSY; } else ret = nilfs_cpfile_clear_snapshot(cpfile, cno); - mutex_unlock(&nilfs->ns_mount_mutex); return ret; case NILFS_SNAPSHOT: return nilfs_cpfile_set_snapshot(cpfile, cno); diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c index d24057d58f1..f6af76042d8 100644 --- a/fs/nilfs2/ioctl.c +++ b/fs/nilfs2/ioctl.c @@ -99,7 +99,8 @@ static int nilfs_ioctl_wrap_copy(struct the_nilfs *nilfs, static int nilfs_ioctl_change_cpmode(struct inode *inode, struct file *filp, unsigned int cmd, void __user *argp) { - struct inode *cpfile = NILFS_SB(inode->i_sb)->s_nilfs->ns_cpfile; + struct the_nilfs *nilfs = NILFS_SB(inode->i_sb)->s_nilfs; + struct inode *cpfile = nilfs->ns_cpfile; struct nilfs_transaction_info ti; struct nilfs_cpmode cpmode; int ret; @@ -109,14 +110,17 @@ static int nilfs_ioctl_change_cpmode(struct inode *inode, struct file *filp, if (copy_from_user(&cpmode, argp, sizeof(cpmode))) return -EFAULT; + mutex_lock(&nilfs->ns_mount_mutex); nilfs_transaction_begin(inode->i_sb, &ti, 0); ret = nilfs_cpfile_change_cpmode( cpfile, cpmode.cm_cno, cpmode.cm_mode); if (unlikely(ret < 0)) { nilfs_transaction_abort(inode->i_sb); + mutex_unlock(&nilfs->ns_mount_mutex); return ret; } nilfs_transaction_commit(inode->i_sb); /* never fails */ + mutex_unlock(&nilfs->ns_mount_mutex); return ret; }