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author | Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> | 2009-05-10 13:41:43 (GMT) |
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committer | Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> | 2009-05-11 05:54:41 (GMT) |
commit | 4f6b828837b4e3836f2c9ac2f0eab9773b6c1327 (patch) | |
tree | 9baa69b0ef44a0c604be831300fd5215c0355be0 /fs/nilfs2/segment.c | |
parent | 47eb6b9c8fa963c9f49967ad1d9d7ec947d15b68 (diff) | |
download | linux-fsl-qoriq-4f6b828837b4e3836f2c9ac2f0eab9773b6c1327.tar.xz |
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/segment.c')
-rw-r--r-- | fs/nilfs2/segment.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/fs/nilfs2/segment.c b/fs/nilfs2/segment.c index fb70ec3..22c7f65 100644 --- a/fs/nilfs2/segment.c +++ b/fs/nilfs2/segment.c @@ -2589,7 +2589,8 @@ nilfs_remove_written_gcinodes(struct the_nilfs *nilfs, struct list_head *head) } } -int nilfs_clean_segments(struct super_block *sb, void __user *argp) +int nilfs_clean_segments(struct super_block *sb, struct nilfs_argv *argv, + void **kbufs) { struct nilfs_sb_info *sbi = NILFS_SB(sb); struct nilfs_sc_info *sci = NILFS_SC(sbi); @@ -2606,7 +2607,7 @@ int nilfs_clean_segments(struct super_block *sb, void __user *argp) err = nilfs_init_gcdat_inode(nilfs); if (unlikely(err)) goto out_unlock; - err = nilfs_ioctl_prepare_clean_segments(nilfs, argp); + err = nilfs_ioctl_prepare_clean_segments(nilfs, argv, kbufs); if (unlikely(err)) goto out_unlock; |