Re: VFS deadlock ?

From: Al Viro
Date: Thu Mar 21 2013 - 15:29:43 EST


On Thu, Mar 21, 2013 at 03:06:53PM -0400, Dave Jones wrote:

> Showing all locks held in the system:
> 4 locks on stack by trinity-child2/7669:
> #0: blocked: (sb_writers#4){.+.+.+}, instance: ffff8801292d17d8, at: [<ffffffff811df134>] mnt_want_write+0x24/0x50
> #1: held: (&type->s_vfs_rename_key){+.+.+.}, instance: ffff8801292d1928, at: [<ffffffff811c6f5e>] lock_rename+0x3e/0x120
> #2: held: (&type->i_mutex_dir_key#2/1){+.+.+.}, instance: ffff880110b3a858, at: [<ffffffff811c701e>] lock_rename+0xfe/0x120
> #3: blocked: (&type->i_mutex_dir_key#2/2){+.+.+.}, instance: ffff880110b3a858, at: [<ffffffff811c7034>] lock_rename+0x114/0x120

#0 oddity aside, that looks very much like directory aliased by two different
dentries. Try to add
BUG_ON(p1->d_inode == p2->d_inode);
just before
mutex_lock(&p1->d_inode->i_sb->s_vfs_rename_mutex);
and see if it triggers.
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