From 0719d3434747889b314a1e8add776418c4148bcf Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Wed, 30 Dec 2009 00:39:22 +0100 Subject: [PATCH] reiserfs: Fix reiserfs lock <-> i_xattr_sem dependency inversion i_xattr_sem depends on the reiserfs lock. But after we grab i_xattr_sem, we may relax/relock the reiserfs lock while waiting on a freezed filesystem, creating a dependency inversion between the two locks. In order to avoid the i_xattr_sem -> reiserfs lock dependency, let's create a reiserfs_down_read_safe() that acts like reiserfs_mutex_lock_safe(): relax the reiserfs lock while grabbing another lock to avoid undesired dependencies induced by the heivyweight reiserfs lock. This fixes the following warning: [ 990.005931] ======================================================= [ 990.012373] [ INFO: possible circular locking dependency detected ] [ 990.013233] 2.6.33-rc1 #1 [ 990.013233] ------------------------------------------------------- [ 990.013233] dbench/1891 is trying to acquire lock: [ 990.013233] (&REISERFS_SB(s)->lock){+.+.+.}, at: [] reiserfs_write_lock+0x35/0x50 [ 990.013233] [ 990.013233] but task is already holding lock: [ 990.013233] (&REISERFS_I(inode)->i_xattr_sem){+.+.+.}, at: [] reiserfs_xattr_set_handle+0x8a/0x470 [ 990.013233] [ 990.013233] which lock already depends on the new lock. [ 990.013233] [ 990.013233] [ 990.013233] the existing dependency chain (in reverse order) is: [ 990.013233] [ 990.013233] -> #1 (&REISERFS_I(inode)->i_xattr_sem){+.+.+.}: [ 990.013233] [] __lock_acquire+0xf9c/0x1560 [ 990.013233] [] lock_acquire+0x8f/0xb0 [ 990.013233] [] down_write+0x44/0x80 [ 990.013233] [] reiserfs_xattr_set_handle+0x8a/0x470 [ 990.013233] [] reiserfs_xattr_set+0xb0/0x150 [ 990.013233] [] user_set+0x8a/0x90 [ 990.013233] [] reiserfs_setxattr+0xaa/0xb0 [ 990.013233] [] __vfs_setxattr_noperm+0x36/0xa0 [ 990.013233] [] vfs_setxattr+0xbc/0xc0 [ 990.013233] [] setxattr+0xc0/0x150 [ 990.013233] [] sys_fsetxattr+0x8d/0xa0 [ 990.013233] [] system_call_fastpath+0x16/0x1b [ 990.013233] [ 990.013233] -> #0 (&REISERFS_SB(s)->lock){+.+.+.}: [ 990.013233] [] __lock_acquire+0x12d0/0x1560 [ 990.013233] [] lock_acquire+0x8f/0xb0 [ 990.013233] [] __mutex_lock_common+0x47/0x3b0 [ 990.013233] [] mutex_lock_nested+0x3e/0x50 [ 990.013233] [] reiserfs_write_lock+0x35/0x50 [ 990.013233] [] reiserfs_prepare_write+0x45/0x180 [ 990.013233] [] reiserfs_xattr_set_handle+0x2a6/0x470 [ 990.013233] [] reiserfs_xattr_set+0xb0/0x150 [ 990.013233] [] user_set+0x8a/0x90 [ 990.013233] [] reiserfs_setxattr+0xaa/0xb0 [ 990.013233] [] __vfs_setxattr_noperm+0x36/0xa0 [ 990.013233] [] vfs_setxattr+0xbc/0xc0 [ 990.013233] [] setxattr+0xc0/0x150 [ 990.013233] [] sys_fsetxattr+0x8d/0xa0 [ 990.013233] [] system_call_fastpath+0x16/0x1b [ 990.013233] [ 990.013233] other info that might help us debug this: [ 990.013233] [ 990.013233] 2 locks held by dbench/1891: [ 990.013233] #0: (&sb->s_type->i_mutex_key#12){+.+.+.}, at: [] vfs_setxattr+0x78/0xc0 [ 990.013233] #1: (&REISERFS_I(inode)->i_xattr_sem){+.+.+.}, at: [] reiserfs_xattr_set_handle+0x8a/0x470 [ 990.013233] [ 990.013233] stack backtrace: [ 990.013233] Pid: 1891, comm: dbench Not tainted 2.6.33-rc1 #1 [ 990.013233] Call Trace: [ 990.013233] [] print_circular_bug+0xe9/0xf0 [ 990.013233] [] __lock_acquire+0x12d0/0x1560 [ 990.013233] [] ? reiserfs_xattr_set_handle+0x8a/0x470 [ 990.013233] [] lock_acquire+0x8f/0xb0 [ 990.013233] [] ? reiserfs_write_lock+0x35/0x50 [ 990.013233] [] ? reiserfs_xattr_set_handle+0x8a/0x470 [ 990.013233] [] __mutex_lock_common+0x47/0x3b0 [ 990.013233] [] ? reiserfs_write_lock+0x35/0x50 [ 990.013233] [] ? reiserfs_write_lock+0x35/0x50 [ 990.013233] [] ? mark_held_locks+0x72/0xa0 [ 990.013233] [] ? __mutex_unlock_slowpath+0xbd/0x140 [ 990.013233] [] ? trace_hardirqs_on_caller+0x14d/0x1a0 [ 990.013233] [] mutex_lock_nested+0x3e/0x50 [ 990.013233] [] reiserfs_write_lock+0x35/0x50 [ 990.013233] [] reiserfs_prepare_write+0x45/0x180 [ 990.013233] [] reiserfs_xattr_set_handle+0x2a6/0x470 [ 990.013233] [] reiserfs_xattr_set+0xb0/0x150 [ 990.013233] [] ? __mutex_lock_common+0x284/0x3b0 [ 990.013233] [] user_set+0x8a/0x90 [ 990.013233] [] reiserfs_setxattr+0xaa/0xb0 [ 990.013233] [] __vfs_setxattr_noperm+0x36/0xa0 [ 990.013233] [] vfs_setxattr+0xbc/0xc0 [ 990.013233] [] setxattr+0xc0/0x150 [ 990.013233] [] ? sched_clock_cpu+0xb8/0x100 [ 990.013233] [] ? trace_hardirqs_off+0xd/0x10 [ 990.013233] [] ? cpu_clock+0x43/0x50 [ 990.013233] [] ? fget+0xb0/0x110 [ 990.013233] [] ? fget+0x0/0x110 [ 990.013233] [] ? sysret_check+0x27/0x62 [ 990.013233] [] sys_fsetxattr+0x8d/0xa0 [ 990.013233] [] system_call_fastpath+0x16/0x1b Reported-and-tested-by: Christian Kujau Signed-off-by: Frederic Weisbecker Cc: Alexander Beregalov Cc: Chris Mason Cc: Ingo Molnar --- fs/reiserfs/xattr.c | 2 +- include/linux/reiserfs_fs.h | 8 ++++++++ 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/fs/reiserfs/xattr.c b/fs/reiserfs/xattr.c index 8891cd88a3f4..a0e2e7acdc75 100644 --- a/fs/reiserfs/xattr.c +++ b/fs/reiserfs/xattr.c @@ -484,7 +484,7 @@ reiserfs_xattr_set_handle(struct reiserfs_transaction_handle *th, if (IS_ERR(dentry)) return PTR_ERR(dentry); - down_write(&REISERFS_I(inode)->i_xattr_sem); + reiserfs_down_read_safe(&REISERFS_I(inode)->i_xattr_sem, inode->i_sb); xahash = xattr_hash(buffer, buffer_size); while (buffer_pos < buffer_size || buffer_pos == 0) { diff --git a/include/linux/reiserfs_fs.h b/include/linux/reiserfs_fs.h index 4351b49e2b1e..35d3f459b0ac 100644 --- a/include/linux/reiserfs_fs.h +++ b/include/linux/reiserfs_fs.h @@ -106,6 +106,14 @@ reiserfs_mutex_lock_nested_safe(struct mutex *m, unsigned int subclass, reiserfs_write_lock(s); } +static inline void +reiserfs_down_read_safe(struct rw_semaphore *sem, struct super_block *s) +{ + reiserfs_write_unlock(s); + down_read(sem); + reiserfs_write_lock(s); +} + /* * When we schedule, we usually want to also release the write lock, * according to the previous bkl based locking scheme of reiserfs. -- 2.30.2