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Subject[PATCH] jfs: possible deadlocks - continue
For some reasons my post about "possible deadlocks"
didn't appear in jfs-discussion@lists.sourceforge.net.

>====================================
>[ BUG: possible deadlock detected! ]
>------------------------------------
>mount/5587 is trying to acquire lock:
> (&jfs_ip->commit_mutex){--..}, at: [<c02f7096>] mutex_lock+0x12/0x15
>
>but task is already holding lock:
> (&jfs_ip->commit_mutex){--..}, at: [<c02f7096>] mutex_lock+0x12/0x15
>
>which could potentially lead to deadlocks!
>
>other info that might help us debug this:
>2 locks held by mount/5587:
> #0: (&inode->i_mutex){--..}, at: [<c02f7096>] mutex_lock+0x12/0x15
> #1: (&jfs_ip->commit_mutex){--..}, at: [<c02f7096>] mutex_lock+0x12/0x15
>
>stack backtrace:
> [<c0103095>] show_trace+0x16/0x19
> [<c0103562>] dump_stack+0x1a/0x1f
> [<c012ddd7>] __lockdep_acquire+0x6c6/0x907
> [<c012e063>] lockdep_acquire+0x4b/0x63
> [<c02f6f0c>] __mutex_lock_slowpath+0xa4/0x21c
> [<c02f7096>] mutex_lock+0x12/0x15
> [<c01b99be>] jfs_create+0x90/0x2b8
> [<c0161016>] vfs_create+0x91/0xda
> [<c0163939>] open_namei+0x15a/0x5b0
> [<c015326c>] do_filp_open+0x22/0x39
> [<c01541a8>] do_sys_open+0x40/0xbc
> [<c015424d>] sys_open+0x13/0x15
> [<c02f875d>] sysenter_past_esp+0x56/0x8d

I should add that this happened during boot, when root jfs
file system become from ro->rw

I look at code, and see that
1)locks wasn't release in the opposite order in which
they were taken
2)in jfs_rename we lock new_ip, and in "error path" we didn't unlock it
3)I see strange expression: "! !"

May be this worth to fix?

Signed-off-by: Evgeniy Dushistov <dushistov@mail.ru>

---
Index: linux-2.6.16/fs/jfs/namei.c
===================================================================
--- linux-2.6.16.orig/fs/jfs/namei.c
+++ linux-2.6.16/fs/jfs/namei.c
@@ -165,8 +165,8 @@ static int jfs_create(struct inode *dip,

out3:
txEnd(tid);
- mutex_unlock(&JFS_IP(dip)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(dip)->commit_mutex);
if (rc) {
free_ea_wmap(ip);
ip->i_nlink = 0;
@@ -300,8 +300,8 @@ static int jfs_mkdir(struct inode *dip,

out3:
txEnd(tid);
- mutex_unlock(&JFS_IP(dip)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(dip)->commit_mutex);
if (rc) {
free_ea_wmap(ip);
ip->i_nlink = 0;
@@ -384,8 +384,8 @@ static int jfs_rmdir(struct inode *dip,
if (rc == -EIO)
txAbort(tid, 1);
txEnd(tid);
- mutex_unlock(&JFS_IP(dip)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(dip)->commit_mutex);

goto out2;
}
@@ -422,8 +422,8 @@ static int jfs_rmdir(struct inode *dip,

txEnd(tid);

- mutex_unlock(&JFS_IP(dip)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(dip)->commit_mutex);

/*
* Truncating the directory index table is not guaranteed. It
@@ -503,8 +503,8 @@ static int jfs_unlink(struct inode *dip,
if (rc == -EIO)
txAbort(tid, 1); /* Marks FS Dirty */
txEnd(tid);
- mutex_unlock(&JFS_IP(dip)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(dip)->commit_mutex);
IWRITE_UNLOCK(ip);
goto out1;
}
@@ -527,8 +527,8 @@ static int jfs_unlink(struct inode *dip,
if ((new_size = commitZeroLink(tid, ip)) < 0) {
txAbort(tid, 1); /* Marks FS Dirty */
txEnd(tid);
- mutex_unlock(&JFS_IP(dip)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(dip)->commit_mutex);
IWRITE_UNLOCK(ip);
rc = new_size;
goto out1;
@@ -556,9 +556,8 @@ static int jfs_unlink(struct inode *dip,

txEnd(tid);

- mutex_unlock(&JFS_IP(dip)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
-
+ mutex_unlock(&JFS_IP(dip)->commit_mutex);

while (new_size && (rc == 0)) {
tid = txBegin(dip->i_sb, 0);
@@ -847,8 +846,8 @@ static int jfs_link(struct dentry *old_d
out:
txEnd(tid);

- mutex_unlock(&JFS_IP(dir)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(dir)->commit_mutex);

jfs_info("jfs_link: rc:%d", rc);
return rc;
@@ -1037,8 +1036,8 @@ static int jfs_symlink(struct inode *dip

out3:
txEnd(tid);
- mutex_unlock(&JFS_IP(dip)->commit_mutex);
mutex_unlock(&JFS_IP(ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(dip)->commit_mutex);
if (rc) {
free_ea_wmap(ip);
ip->i_nlink = 0;
@@ -1160,10 +1159,11 @@ static int jfs_rename(struct inode *old_
if (S_ISDIR(new_ip->i_mode)) {
new_ip->i_nlink--;
if (new_ip->i_nlink) {
- mutex_unlock(&JFS_IP(new_dir)->commit_mutex);
- mutex_unlock(&JFS_IP(old_ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(new_ip)->commit_mutex);
if (old_dir != new_dir)
mutex_unlock(&JFS_IP(old_dir)->commit_mutex);
+ mutex_unlock(&JFS_IP(old_ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(new_dir)->commit_mutex);
if (!S_ISDIR(old_ip->i_mode) && new_ip)
IWRITE_UNLOCK(new_ip);
jfs_error(new_ip->i_sb,
@@ -1281,13 +1281,12 @@ static int jfs_rename(struct inode *old_

out4:
txEnd(tid);
-
- mutex_unlock(&JFS_IP(new_dir)->commit_mutex);
- mutex_unlock(&JFS_IP(old_ip)->commit_mutex);
- if (old_dir != new_dir)
- mutex_unlock(&JFS_IP(old_dir)->commit_mutex);
if (new_ip)
mutex_unlock(&JFS_IP(new_ip)->commit_mutex);
+ if (old_dir != new_dir)
+ mutex_unlock(&JFS_IP(old_dir)->commit_mutex);
+ mutex_unlock(&JFS_IP(old_ip)->commit_mutex);
+ mutex_unlock(&JFS_IP(new_dir)->commit_mutex);

while (new_size && (rc == 0)) {
tid = txBegin(new_ip->i_sb, 0);
Index: linux-2.6.16/fs/jfs/jfs_txnmgr.c
===================================================================
--- linux-2.6.16.orig/fs/jfs/jfs_txnmgr.c
+++ linux-2.6.16/fs/jfs/jfs_txnmgr.c
@@ -2944,7 +2944,7 @@ int jfs_sync(void *arg)
* Inode is being freed
*/
list_del_init(&jfs_ip->anon_inode_list);
- } else if (! !mutex_trylock(&jfs_ip->commit_mutex)) {
+ } else if (mutex_trylock(&jfs_ip->commit_mutex)) {
/*
* inode will be removed from anonymous list
* when it is committed
--
/Evgeniy

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