[052/103] reiserfs: fix unwanted reiserfs lock recursion

[Greg KH <gregkh@suse.de>]

2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Frederic Weisbecker <fweisbec@gmail.com>

commit 9d8117e72bf453dd9d85e0cd322ce4a0f8bccbc0 upstream.

Prevent from recursively locking the reiserfs lock in reiserfs_unpack()
because we may call journal_begin() that requires the lock to be taken
only once, otherwise it won't be able to release the lock while taking
other mutexes, ending up in inverted dependencies between the journal
mutex and the reiserfs lock for example.

This fixes:

  =======================================================
  [ INFO: possible circular locking dependency detected ]
  2.6.35.4.4a #3
  -------------------------------------------------------
  lilo/1620 is trying to acquire lock:
   (&journal->j_mutex){+.+...}, at: [<d0325bff>] do_journal_begin_r+0x7f/0x340 [reiserfs]

  but task is already holding lock:
   (&REISERFS_SB(s)->lock){+.+.+.}, at: [<d032a278>] reiserfs_write_lock+0x28/0x40 [reiserfs]

  which lock already depends on the new lock.

  the existing dependency chain (in reverse order) is:

  -> #1 (&REISERFS_SB(s)->lock){+.+.+.}:
         [<c10562b7>] lock_acquire+0x67/0x80
         [<c12facad>] __mutex_lock_common+0x4d/0x410
         [<c12fb0c8>] mutex_lock_nested+0x18/0x20
         [<d032a278>] reiserfs_write_lock+0x28/0x40 [reiserfs]
         [<d0325c06>] do_journal_begin_r+0x86/0x340 [reiserfs]
         [<d0325f77>] journal_begin+0x77/0x140 [reiserfs]
         [<d0315be4>] reiserfs_remount+0x224/0x530 [reiserfs]
         [<c10b6a20>] do_remount_sb+0x60/0x110
         [<c10cee25>] do_mount+0x625/0x790
         [<c10cf014>] sys_mount+0x84/0xb0
         [<c12fca3d>] syscall_call+0x7/0xb

  -> #0 (&journal->j_mutex){+.+...}:
         [<c10560f6>] __lock_acquire+0x1026/0x1180
         [<c10562b7>] lock_acquire+0x67/0x80
         [<c12facad>] __mutex_lock_common+0x4d/0x410
         [<c12fb0c8>] mutex_lock_nested+0x18/0x20
         [<d0325bff>] do_journal_begin_r+0x7f/0x340 [reiserfs]
         [<d0325f77>] journal_begin+0x77/0x140 [reiserfs]
         [<d0326271>] reiserfs_persistent_transaction+0x41/0x90 [reiserfs]
         [<d030d06c>] reiserfs_get_block+0x22c/0x1530 [reiserfs]
         [<c10db9db>] __block_prepare_write+0x1bb/0x3a0
         [<c10dbbe6>] block_prepare_write+0x26/0x40
         [<d030b738>] reiserfs_prepare_write+0x88/0x170 [reiserfs]
         [<d03294d6>] reiserfs_unpack+0xe6/0x120 [reiserfs]
         [<d0329782>] reiserfs_ioctl+0x272/0x320 [reiserfs]
         [<c10c3188>] vfs_ioctl+0x28/0xa0
         [<c10c3bbd>] do_vfs_ioctl+0x32d/0x5c0
         [<c10c3eb3>] sys_ioctl+0x63/0x70
         [<c12fca3d>] syscall_call+0x7/0xb

  other info that might help us debug this:

  2 locks held by lilo/1620:
   #0:  (&sb->s_type->i_mutex_key#8){+.+.+.}, at: [<d032945a>] reiserfs_unpack+0x6a/0x120 [reiserfs]
   #1:  (&REISERFS_SB(s)->lock){+.+.+.}, at: [<d032a278>] reiserfs_write_lock+0x28/0x40 [reiserfs]

  stack backtrace:
  Pid: 1620, comm: lilo Not tainted 2.6.35.4.4a #3
  Call Trace:
   [<c10560f6>] __lock_acquire+0x1026/0x1180
   [<c10562b7>] lock_acquire+0x67/0x80
   [<c12facad>] __mutex_lock_common+0x4d/0x410
   [<c12fb0c8>] mutex_lock_nested+0x18/0x20
   [<d0325bff>] do_journal_begin_r+0x7f/0x340 [reiserfs]
   [<d0325f77>] journal_begin+0x77/0x140 [reiserfs]
   [<d0326271>] reiserfs_persistent_transaction+0x41/0x90 [reiserfs]
   [<d030d06c>] reiserfs_get_block+0x22c/0x1530 [reiserfs]
   [<c10db9db>] __block_prepare_write+0x1bb/0x3a0
   [<c10dbbe6>] block_prepare_write+0x26/0x40
   [<d030b738>] reiserfs_prepare_write+0x88/0x170 [reiserfs]
   [<d03294d6>] reiserfs_unpack+0xe6/0x120 [reiserfs]
   [<d0329782>] reiserfs_ioctl+0x272/0x320 [reiserfs]
   [<c10c3188>] vfs_ioctl+0x28/0xa0
   [<c10c3bbd>] do_vfs_ioctl+0x32d/0x5c0
   [<c10c3eb3>] sys_ioctl+0x63/0x70
   [<c12fca3d>] syscall_call+0x7/0xb

Reported-by: Jarek Poplawski <jarkao2@gmail.com>
Tested-by: Jarek Poplawski <jarkao2@gmail.com>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

---
 fs/reiserfs/ioctl.c |    5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

--- a/fs/reiserfs/ioctl.c
+++ b/fs/reiserfs/ioctl.c
@@ -170,6 +170,7 @@ int reiserfs_prepare_write(struct file *
 int reiserfs_unpack(struct inode *inode, struct file *filp)
 {
 	int retval = 0;
+	int depth;
 	int index;
 	struct page *page;
 	struct address_space *mapping;
@@ -189,7 +190,7 @@ int reiserfs_unpack(struct inode *inode,
 	 ** us
 	 */
 	reiserfs_mutex_lock_safe(&inode->i_mutex, inode->i_sb);
-	reiserfs_write_lock(inode->i_sb);
+	depth = reiserfs_write_lock_once(inode->i_sb);
 
 	write_from = inode->i_size & (blocksize - 1);
 	/* if we are on a block boundary, we are already unpacked.  */
@@ -224,6 +225,6 @@ int reiserfs_unpack(struct inode *inode,
 
       out:
 	mutex_unlock(&inode->i_mutex);
-	reiserfs_write_unlock(inode->i_sb);
+	reiserfs_write_unlock_once(inode->i_sb, depth);
 	return retval;
 }