Hi all, I played around lockdep recently and found 2 lockdep warnings. These 2 patches fix them. Regards, Tao
Tao Ma
2010-Sep-07 05:30 UTC
[Ocfs2-devel] [PATCH 1/2] ocfs2/lockdep: Move ip_xattr_sem out of ocfs2_xattr_get_nolock.
As the name shows, we shouldn't have any lock in ocfs2_xattr_get_nolock. so lift ip_xattr_sem to the caller. This should be safe for us since the only 2 callers are: 1. ocfs2_xattr_get which will lock the resources. 2. ocfs2_mknod which don't need this locking. And this also resolves the following lockdep warning. ======================================================[ INFO: possible circular locking dependency detected ] 2.6.35+ #5 ------------------------------------------------------- reflink/30027 is trying to acquire lock: (&oi->ip_alloc_sem){+.+.+.}, at: [<ffffffffa0673b67>] ocfs2_reflink_ioctl+0x69a/0x1226 [ocfs2] but task is already holding lock: (&oi->ip_xattr_sem){++++..}, at: [<ffffffffa0673b58>] ocfs2_reflink_ioctl+0x68b/0x1226 [ocfs2] which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #3 (&oi->ip_xattr_sem){++++..}: [<ffffffff82064d6d>] __lock_acquire+0x79a/0x7f1 [<ffffffff82065a81>] lock_acquire+0xc6/0xed [<ffffffff82339650>] down_read+0x34/0x47 [<ffffffffa0691cb8>] ocfs2_xattr_get_nolock+0xa0/0x4e6 [ocfs2] [<ffffffffa069d64f>] ocfs2_get_acl_nolock+0x5c/0x132 [ocfs2] [<ffffffffa069d9c7>] ocfs2_init_acl+0x60/0x243 [ocfs2] [<ffffffffa066499d>] ocfs2_mknod+0xae8/0xfea [ocfs2] [<ffffffffa0665041>] ocfs2_create+0x9d/0x105 [ocfs2] [<ffffffff820e1c83>] vfs_create+0x9b/0xf4 [<ffffffff820e20bb>] do_last+0x2fd/0x5be [<ffffffff820e31c0>] do_filp_open+0x1fb/0x572 [<ffffffff820d6cf6>] do_sys_open+0x5a/0xe7 [<ffffffff820d6dac>] sys_open+0x1b/0x1d [<ffffffff8200296b>] system_call_fastpath+0x16/0x1b -> #2 (jbd2_handle){+.+...}: [<ffffffff82064d6d>] __lock_acquire+0x79a/0x7f1 [<ffffffff82065a81>] lock_acquire+0xc6/0xed [<ffffffffa0604ff8>] start_this_handle+0x4a3/0x4bc [jbd2] [<ffffffffa06051d6>] jbd2__journal_start+0xba/0xee [jbd2] [<ffffffffa0605218>] jbd2_journal_start+0xe/0x10 [jbd2] [<ffffffffa065ca34>] ocfs2_start_trans+0xb7/0x19b [ocfs2] [<ffffffffa06645f3>] ocfs2_mknod+0x73e/0xfea [ocfs2] [<ffffffffa0665041>] ocfs2_create+0x9d/0x105 [ocfs2] [<ffffffff820e1c83>] vfs_create+0x9b/0xf4 [<ffffffff820e20bb>] do_last+0x2fd/0x5be [<ffffffff820e31c0>] do_filp_open+0x1fb/0x572 [<ffffffff820d6cf6>] do_sys_open+0x5a/0xe7 [<ffffffff820d6dac>] sys_open+0x1b/0x1d [<ffffffff8200296b>] system_call_fastpath+0x16/0x1b -> #1 (&journal->j_trans_barrier){.+.+..}: [<ffffffff82064d6d>] __lock_acquire+0x79a/0x7f1 [<ffffffff82064fa9>] lock_release_non_nested+0x1e5/0x24b [<ffffffff82065999>] lock_release+0x158/0x17a [<ffffffff823389f6>] __mutex_unlock_slowpath+0xbf/0x11b [<ffffffff82338a5b>] mutex_unlock+0x9/0xb [<ffffffffa0679673>] ocfs2_free_ac_resource+0x31/0x67 [ocfs2] [<ffffffffa067c6bc>] ocfs2_free_alloc_context+0x11/0x1d [ocfs2] [<ffffffffa0633de0>] ocfs2_write_begin_nolock+0x141e/0x159b [ocfs2] [<ffffffffa0635523>] ocfs2_write_begin+0x11e/0x1e7 [ocfs2] [<ffffffff820a1297>] generic_file_buffered_write+0x10c/0x210 [<ffffffffa0653624>] ocfs2_file_aio_write+0x4cc/0x6d3 [ocfs2] [<ffffffff820d822d>] do_sync_write+0xc2/0x106 [<ffffffff820d897b>] vfs_write+0xae/0x131 [<ffffffff820d8e55>] sys_write+0x47/0x6f [<ffffffff8200296b>] system_call_fastpath+0x16/0x1b -> #0 (&oi->ip_alloc_sem){+.+.+.}: [<ffffffff82063f92>] validate_chain+0x727/0xd68 [<ffffffff82064d6d>] __lock_acquire+0x79a/0x7f1 [<ffffffff82065a81>] lock_acquire+0xc6/0xed [<ffffffff82339694>] down_write+0x31/0x52 [<ffffffffa0673b67>] ocfs2_reflink_ioctl+0x69a/0x1226 [ocfs2] [<ffffffffa06599f6>] ocfs2_ioctl+0x61a/0x656 [ocfs2] [<ffffffff820e53ac>] vfs_ioctl+0x2a/0x9d [<ffffffff820e5903>] do_vfs_ioctl+0x45d/0x4ae [<ffffffff820e59ab>] sys_ioctl+0x57/0x7a [<ffffffff8200296b>] system_call_fastpath+0x16/0x1b Signed-off-by: Tao Ma <tao.ma at oracle.com> --- fs/ocfs2/xattr.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c index d03469f..06fa5e7 100644 --- a/fs/ocfs2/xattr.c +++ b/fs/ocfs2/xattr.c @@ -1286,13 +1286,11 @@ int ocfs2_xattr_get_nolock(struct inode *inode, xis.inode_bh = xbs.inode_bh = di_bh; di = (struct ocfs2_dinode *)di_bh->b_data; - down_read(&oi->ip_xattr_sem); ret = ocfs2_xattr_ibody_get(inode, name_index, name, buffer, buffer_size, &xis); if (ret == -ENODATA && di->i_xattr_loc) ret = ocfs2_xattr_block_get(inode, name_index, name, buffer, buffer_size, &xbs); - up_read(&oi->ip_xattr_sem); return ret; } @@ -1316,8 +1314,10 @@ static int ocfs2_xattr_get(struct inode *inode, mlog_errno(ret); return ret; } + down_read(&OCFS2_I(inode)->ip_xattr_sem); ret = ocfs2_xattr_get_nolock(inode, di_bh, name_index, name, buffer, buffer_size); + up_read(&OCFS2_I(inode)->ip_xattr_sem); ocfs2_inode_unlock(inode, 0); -- 1.7.1.GIT
Tao Ma
2010-Sep-07 05:30 UTC
[Ocfs2-devel] [PATCH 2/2] ocfs2: Fix lockdep warning in reflink.
This patch change mutex_lock to a new subclass and add a new inode lock subclass for the target inode which caused this lockdep warning. ============================================[ INFO: possible recursive locking detected ] 2.6.35+ #5 --------------------------------------------- reflink/11086 is trying to acquire lock: (Meta){+++++.}, at: [<ffffffffa06f9d65>] ocfs2_reflink_ioctl+0x898/0x1229 [ocfs2] but task is already holding lock: (Meta){+++++.}, at: [<ffffffffa06f9aa0>] ocfs2_reflink_ioctl+0x5d3/0x1229 [ocfs2] other info that might help us debug this: 6 locks held by reflink/11086: #0: (&sb->s_type->i_mutex_key#15/1){+.+.+.}, at: [<ffffffff820e09ec>] lookup_create+0x26/0x97 #1: (&sb->s_type->i_mutex_key#15){+.+.+.}, at: [<ffffffffa06f99a0>] ocfs2_reflink_ioctl+0x4d3/0x1229 [ocfs2] #2: (Meta){+++++.}, at: [<ffffffffa06f9aa0>] ocfs2_reflink_ioctl+0x5d3/0x1229 [ocfs2] #3: (&oi->ip_xattr_sem){+.+.+.}, at: [<ffffffffa06f9b58>] ocfs2_reflink_ioctl+0x68b/0x1229 [ocfs2] #4: (&oi->ip_alloc_sem){+.+.+.}, at: [<ffffffffa06f9b67>] ocfs2_reflink_ioctl+0x69a/0x1229 [ocfs2] #5: (&sb->s_type->i_mutex_key#15/2){+.+...}, at: [<ffffffffa06f9d4f>] ocfs2_reflink_ioctl+0x882/0x1229 [ocfs2] stack backtrace: Pid: 11086, comm: reflink Not tainted 2.6.35+ #5 Call Trace: [<ffffffff82063dd9>] validate_chain+0x56e/0xd68 [<ffffffff82062275>] ? mark_held_locks+0x49/0x69 [<ffffffff82064d6d>] __lock_acquire+0x79a/0x7f1 [<ffffffff82065a81>] lock_acquire+0xc6/0xed [<ffffffffa06f9d65>] ? ocfs2_reflink_ioctl+0x898/0x1229 [ocfs2] [<ffffffffa06c9ade>] __ocfs2_cluster_lock+0x975/0xa0d [ocfs2] [<ffffffffa06f9d65>] ? ocfs2_reflink_ioctl+0x898/0x1229 [ocfs2] [<ffffffffa06e107b>] ? ocfs2_wait_for_recovery+0x15/0x8a [ocfs2] [<ffffffffa06cb6ea>] ocfs2_inode_lock_full_nested+0x1ac/0xdc5 [ocfs2] [<ffffffffa06f9d65>] ? ocfs2_reflink_ioctl+0x898/0x1229 [ocfs2] [<ffffffff820623a0>] ? trace_hardirqs_on_caller+0x10b/0x12f [<ffffffff82060193>] ? debug_mutex_free_waiter+0x4f/0x53 [<ffffffffa06f9d65>] ocfs2_reflink_ioctl+0x898/0x1229 [ocfs2] [<ffffffffa06ce24a>] ? ocfs2_file_lock_res_init+0x66/0x78 [ocfs2] [<ffffffff820bb2d2>] ? might_fault+0x40/0x8d [<ffffffffa06df9f6>] ocfs2_ioctl+0x61a/0x656 [ocfs2] [<ffffffff820ee5d3>] ? mntput_no_expire+0x1d/0xb0 [<ffffffff820e07b3>] ? path_put+0x2c/0x31 [<ffffffff820e53ac>] vfs_ioctl+0x2a/0x9d [<ffffffff820e5903>] do_vfs_ioctl+0x45d/0x4ae [<ffffffff8233a7f6>] ? _raw_spin_unlock+0x26/0x2a [<ffffffff8200299c>] ? sysret_check+0x27/0x62 [<ffffffff820e59ab>] sys_ioctl+0x57/0x7a [<ffffffff8200296b>] system_call_fastpath+0x16/0x1b Signed-off-by: Tao Ma <tao.ma at oracle.com> --- fs/ocfs2/dlmglue.h | 1 + fs/ocfs2/refcounttree.c | 5 +++-- 2 files changed, 4 insertions(+), 2 deletions(-) diff --git a/fs/ocfs2/dlmglue.h b/fs/ocfs2/dlmglue.h index d1ce48e..1d596d8 100644 --- a/fs/ocfs2/dlmglue.h +++ b/fs/ocfs2/dlmglue.h @@ -84,6 +84,7 @@ enum { OI_LS_PARENT, OI_LS_RENAME1, OI_LS_RENAME2, + OI_LS_REFLINK_TARGET, }; int ocfs2_dlm_init(struct ocfs2_super *osb); diff --git a/fs/ocfs2/refcounttree.c b/fs/ocfs2/refcounttree.c index 73a11cc..588cacd 100644 --- a/fs/ocfs2/refcounttree.c +++ b/fs/ocfs2/refcounttree.c @@ -4200,8 +4200,9 @@ static int __ocfs2_reflink(struct dentry *old_dentry, goto out; } - mutex_lock(&new_inode->i_mutex); - ret = ocfs2_inode_lock(new_inode, &new_bh, 1); + mutex_lock_nested(&new_inode->i_mutex, I_MUTEX_CHILD); + ret = ocfs2_inode_lock_nested(new_inode, &new_bh, 1, + OI_LS_REFLINK_TARGET); if (ret) { mlog_errno(ret); goto out_unlock; -- 1.7.1.GIT
Joel Becker
2010-Sep-10 16:21 UTC
[Ocfs2-devel] [PATCH 2/2] ocfs2: Fix lockdep warning in reflink.
On Tue, Sep 07, 2010 at 01:30:06PM +0800, Tao Ma wrote:> This patch change mutex_lock to a new subclass and > add a new inode lock subclass for the target inode > which caused this lockdep warning.This patch is now in the fixes branch of ocfs2.git. Joel -- "There is no sincerer love than the love of food." - George Bernard Shaw Joel Becker Consulting Software Developer Oracle E-mail: joel.becker at oracle.com Phone: (650) 506-8127