nilfs2: fix possible circular locking for get information ioctls
This is one of two patches which are to correct possible circular
locking between mm->mmap_sem and nilfs->ns_segctor_sem.
The problem was detected by lockdep check as follows:
=======================================================
[ INFO: possible circular locking dependency detected ]
2.6.30-rc3-nilfs-00002-g3552613 #6
-------------------------------------------------------
mmap/5418 is trying to acquire lock:
(&nilfs->ns_segctor_sem){++++.+}, at: [<d0d0e852>] 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
[<c023c730>] copy_to_user+0x2c/0xfc
[<d0d11b4f>] nilfs_ioctl_wrap_copy+0x103/0x160 [nilfs2]
[<d0d11fa9>] nilfs_ioctl+0x30a/0x3b0 [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
[<d0d0e852>] 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
other info that might help us debug this:
1 lock held by mmap/5418:
#0: (&mm->mmap_sem){++++++}, at: [<c043700a>] do_page_fault+0x1d8/0x30a
stack backtrace:
Pid: 5418, comm: mmap Not tainted 2.6.30-rc3-nilfs-00002-g3552613 #6
Call Trace:
[<c0432145>] ? printk+0xf/0x12
[<c0145c48>] print_circular_bug_tail+0xaa/0xb5
[<c0146e0b>] __lock_acquire+0xdcc/0x13b0
[<d0d10149>] ? nilfs_sufile_get_stat+0x1e/0x105 [nilfs2]
[<c013b59a>] ? up_read+0x16/0x2c
[<d0d10225>] ? nilfs_sufile_get_stat+0xfa/0x105 [nilfs2]
[<c01474a9>] lock_acquire+0xba/0xdd
[<d0d0e852>] ? nilfs_transaction_begin+0xb6/0x10c [nilfs2]
[<c0433f1d>] down_read+0x2a/0x3e
[<d0d0e852>] ? nilfs_transaction_begin+0xb6/0x10c [nilfs2]
[<d0d0e852>] nilfs_transaction_begin+0xb6/0x10c [nilfs2]
[<d0cfe0e5>] nilfs_page_mkwrite+0xe7/0x154 [nilfs2]
[<c0183b0b>] __do_fault+0x165/0x376
[<c01855cd>] handle_mm_fault+0x287/0x5d1
[<c043700a>] ? do_page_fault+0x1d8/0x30a
[<c013b54f>] ? down_read_trylock+0x39/0x43
[<c043712d>] do_page_fault+0x2fb/0x30a
[<c0436e32>] ? do_page_fault+0x0/0x30a
[<c0435462>] error_code+0x72/0x78
[<c0436e32>] ? do_page_fault+0x0/0x30a
This makes the lock granularity of nilfs->ns_segctor_sem finer than
that of the mmap semaphore for ioctl commands except
nilfs_clean_segments().
The successive patch ("nilfs2: fix lock order reversal in
nilfs_clean_segments ioctl") is required to fully resolve the problem.
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index be387c6..e3c693d 100644
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -147,29 +147,12 @@
nilfs_ioctl_do_get_cpinfo(struct the_nilfs *nilfs, __u64 *posp, int flags,
void *buf, size_t size, size_t nmembs)
{
- return nilfs_cpfile_get_cpinfo(nilfs->ns_cpfile, posp, flags, buf,
- nmembs);
-}
-
-static int nilfs_ioctl_get_cpinfo(struct inode *inode, struct file *filp,
- unsigned int cmd, void __user *argp)
-{
- struct the_nilfs *nilfs = NILFS_SB(inode->i_sb)->s_nilfs;
- struct nilfs_argv argv;
int ret;
- if (copy_from_user(&argv, argp, sizeof(argv)))
- return -EFAULT;
-
down_read(&nilfs->ns_segctor_sem);
- ret = nilfs_ioctl_wrap_copy(nilfs, &argv, _IOC_DIR(cmd),
- nilfs_ioctl_do_get_cpinfo);
+ ret = nilfs_cpfile_get_cpinfo(nilfs->ns_cpfile, posp, flags, buf,
+ nmembs);
up_read(&nilfs->ns_segctor_sem);
- if (ret < 0)
- return ret;
-
- if (copy_to_user(argp, &argv, sizeof(argv)))
- ret = -EFAULT;
return ret;
}
@@ -195,28 +178,11 @@
nilfs_ioctl_do_get_suinfo(struct the_nilfs *nilfs, __u64 *posp, int flags,
void *buf, size_t size, size_t nmembs)
{
- return nilfs_sufile_get_suinfo(nilfs->ns_sufile, *posp, buf, nmembs);
-}
-
-static int nilfs_ioctl_get_suinfo(struct inode *inode, struct file *filp,
- unsigned int cmd, void __user *argp)
-{
- struct the_nilfs *nilfs = NILFS_SB(inode->i_sb)->s_nilfs;
- struct nilfs_argv argv;
int ret;
- if (copy_from_user(&argv, argp, sizeof(argv)))
- return -EFAULT;
-
down_read(&nilfs->ns_segctor_sem);
- ret = nilfs_ioctl_wrap_copy(nilfs, &argv, _IOC_DIR(cmd),
- nilfs_ioctl_do_get_suinfo);
+ ret = nilfs_sufile_get_suinfo(nilfs->ns_sufile, *posp, buf, nmembs);
up_read(&nilfs->ns_segctor_sem);
- if (ret < 0)
- return ret;
-
- if (copy_to_user(argp, &argv, sizeof(argv)))
- ret = -EFAULT;
return ret;
}
@@ -242,28 +208,11 @@
nilfs_ioctl_do_get_vinfo(struct the_nilfs *nilfs, __u64 *posp, int flags,
void *buf, size_t size, size_t nmembs)
{
- return nilfs_dat_get_vinfo(nilfs_dat_inode(nilfs), buf, nmembs);
-}
-
-static int nilfs_ioctl_get_vinfo(struct inode *inode, struct file *filp,
- unsigned int cmd, void __user *argp)
-{
- struct the_nilfs *nilfs = NILFS_SB(inode->i_sb)->s_nilfs;
- struct nilfs_argv argv;
int ret;
- if (copy_from_user(&argv, argp, sizeof(argv)))
- return -EFAULT;
-
down_read(&nilfs->ns_segctor_sem);
- ret = nilfs_ioctl_wrap_copy(nilfs, &argv, _IOC_DIR(cmd),
- nilfs_ioctl_do_get_vinfo);
+ ret = nilfs_dat_get_vinfo(nilfs_dat_inode(nilfs), buf, nmembs);
up_read(&nilfs->ns_segctor_sem);
- if (ret < 0)
- return ret;
-
- if (copy_to_user(argp, &argv, sizeof(argv)))
- ret = -EFAULT;
return ret;
}
@@ -276,17 +225,21 @@
struct nilfs_bdesc *bdescs = buf;
int ret, i;
+ down_read(&nilfs->ns_segctor_sem);
for (i = 0; i < nmembs; i++) {
ret = nilfs_bmap_lookup_at_level(bmap,
bdescs[i].bd_offset,
bdescs[i].bd_level + 1,
&bdescs[i].bd_blocknr);
if (ret < 0) {
- if (ret != -ENOENT)
+ if (ret != -ENOENT) {
+ up_read(&nilfs->ns_segctor_sem);
return ret;
+ }
bdescs[i].bd_blocknr = 0;
}
}
+ up_read(&nilfs->ns_segctor_sem);
return nmembs;
}
@@ -300,10 +253,8 @@
if (copy_from_user(&argv, argp, sizeof(argv)))
return -EFAULT;
- down_read(&nilfs->ns_segctor_sem);
ret = nilfs_ioctl_wrap_copy(nilfs, &argv, _IOC_DIR(cmd),
nilfs_ioctl_do_get_bdescs);
- up_read(&nilfs->ns_segctor_sem);
if (ret < 0)
return ret;
@@ -623,6 +574,29 @@
return 0;
}
+static int nilfs_ioctl_get_info(struct inode *inode, struct file *filp,
+ unsigned int cmd, void __user *argp,
+ ssize_t (*dofunc)(struct the_nilfs *,
+ __u64 *, int,
+ void *, size_t, size_t))
+
+{
+ struct the_nilfs *nilfs = NILFS_SB(inode->i_sb)->s_nilfs;
+ struct nilfs_argv argv;
+ int ret;
+
+ if (copy_from_user(&argv, argp, sizeof(argv)))
+ return -EFAULT;
+
+ ret = nilfs_ioctl_wrap_copy(nilfs, &argv, _IOC_DIR(cmd), dofunc);
+ if (ret < 0)
+ return ret;
+
+ if (copy_to_user(argp, &argv, sizeof(argv)))
+ ret = -EFAULT;
+ return ret;
+}
+
long nilfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct inode *inode = filp->f_dentry->d_inode;
@@ -634,16 +608,18 @@
case NILFS_IOCTL_DELETE_CHECKPOINT:
return nilfs_ioctl_delete_checkpoint(inode, filp, cmd, argp);
case NILFS_IOCTL_GET_CPINFO:
- return nilfs_ioctl_get_cpinfo(inode, filp, cmd, argp);
+ return nilfs_ioctl_get_info(inode, filp, cmd, argp,
+ nilfs_ioctl_do_get_cpinfo);
case NILFS_IOCTL_GET_CPSTAT:
return nilfs_ioctl_get_cpstat(inode, filp, cmd, argp);
case NILFS_IOCTL_GET_SUINFO:
- return nilfs_ioctl_get_suinfo(inode, filp, cmd, argp);
+ return nilfs_ioctl_get_info(inode, filp, cmd, argp,
+ nilfs_ioctl_do_get_suinfo);
case NILFS_IOCTL_GET_SUSTAT:
return nilfs_ioctl_get_sustat(inode, filp, cmd, argp);
case NILFS_IOCTL_GET_VINFO:
- /* XXX: rename to ??? */
- return nilfs_ioctl_get_vinfo(inode, filp, cmd, argp);
+ return nilfs_ioctl_get_info(inode, filp, cmd, argp,
+ nilfs_ioctl_do_get_vinfo);
case NILFS_IOCTL_GET_BDESCS:
return nilfs_ioctl_get_bdescs(inode, filp, cmd, argp);
case NILFS_IOCTL_CLEAN_SEGMENTS: