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authorRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2009-05-10 09:41:43 -0400
committerRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>2009-05-11 01:54:41 -0400
commit4f6b828837b4e3836f2c9ac2f0eab9773b6c1327 (patch)
tree9baa69b0ef44a0c604be831300fd5215c0355be0 /fs/nilfs2/nilfs.h
parent47eb6b9c8fa963c9f49967ad1d9d7ec947d15b68 (diff)
nilfs2: fix lock order reversal in nilfs_clean_segments ioctl
This is a companion patch to ("nilfs2: fix possible circular locking for get information ioctls"). This corrects lock order reversal between mm->mmap_sem and nilfs->ns_segctor_sem in nilfs_clean_segments() which was detected by lockdep check: ======================================================= [ INFO: possible circular locking dependency detected ] 2.6.30-rc3-nilfs-00003-g360bdc1 #7 ------------------------------------------------------- mmap/5294 is trying to acquire lock: (&nilfs->ns_segctor_sem){++++.+}, at: [<d0d0e846>] nilfs_transaction_begin+0xb6/0x10c [nilfs2] but task is already holding lock: (&mm->mmap_sem){++++++}, at: [<c043700a>] do_page_fault+0x1d8/0x30a which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #1 (&mm->mmap_sem){++++++}: [<c01470a5>] __lock_acquire+0x1066/0x13b0 [<c01474a9>] lock_acquire+0xba/0xdd [<c01836bc>] might_fault+0x68/0x88 [<c023c61d>] copy_from_user+0x2a/0x111 [<d0d120d0>] nilfs_ioctl_prepare_clean_segments+0x1d/0xf1 [nilfs2] [<d0d0e2aa>] nilfs_clean_segments+0x6d/0x1b9 [nilfs2] [<d0d11f68>] nilfs_ioctl+0x2ad/0x318 [nilfs2] [<c01a3be7>] vfs_ioctl+0x22/0x69 [<c01a408e>] do_vfs_ioctl+0x460/0x499 [<c01a4107>] sys_ioctl+0x40/0x5a [<c01031a4>] sysenter_do_call+0x12/0x38 [<ffffffff>] 0xffffffff -> #0 (&nilfs->ns_segctor_sem){++++.+}: [<c0146e0b>] __lock_acquire+0xdcc/0x13b0 [<c01474a9>] lock_acquire+0xba/0xdd [<c0433f1d>] down_read+0x2a/0x3e [<d0d0e846>] nilfs_transaction_begin+0xb6/0x10c [nilfs2] [<d0cfe0e5>] nilfs_page_mkwrite+0xe7/0x154 [nilfs2] [<c0183b0b>] __do_fault+0x165/0x376 [<c01855cd>] handle_mm_fault+0x287/0x5d1 [<c043712d>] do_page_fault+0x2fb/0x30a [<c0435462>] error_code+0x72/0x78 [<ffffffff>] 0xffffffff where nilfs_clean_segments() holds: nilfs->ns_segctor_sem -> copy_from_user() --> page fault -> mm->mmap_sem And, page fault path may hold: page fault -> mm->mmap_sem --> nilfs_page_mkwrite() -> nilfs->ns_segctor_sem Even though nilfs_clean_segments() does not perform write access on given user pages, it may cause deadlock because nilfs->ns_segctor_sem is shared per device and mm->mmap_sem can be shared with other tasks. To avoid this problem, this patch moves all calls of copy_from_user() outside the nilfs->ns_segctor_sem lock in the ioctl. Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Diffstat (limited to 'fs/nilfs2/nilfs.h')
-rw-r--r--fs/nilfs2/nilfs.h3
1 files changed, 2 insertions, 1 deletions
diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index 3d0c18a16db1..da6fc0bba2e5 100644
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -236,7 +236,8 @@ extern int nilfs_sync_file(struct file *, struct dentry *, int);
236 236
237/* ioctl.c */ 237/* ioctl.c */
238long nilfs_ioctl(struct file *, unsigned int, unsigned long); 238long nilfs_ioctl(struct file *, unsigned int, unsigned long);
239int nilfs_ioctl_prepare_clean_segments(struct the_nilfs *, void __user *); 239int nilfs_ioctl_prepare_clean_segments(struct the_nilfs *, struct nilfs_argv *,
240 void **);
240 241
241/* inode.c */ 242/* inode.c */
242extern struct inode *nilfs_new_inode(struct inode *, int); 243extern struct inode *nilfs_new_inode(struct inode *, int);