On Wed, Jun 21, 2017 at 02:21:14PM -0700, Tahsin Erdogan wrote:
> We don't need acls on xattr inodes because they are not directly
> accessible from user mode.
>
> Besides lockdep complains about recursive locking of xattr_sem as seen
> below.
>
> =============================================
> [ INFO: possible recursive locking detected ]
> 4.11.0-rc8+ #402 Not tainted
> ---------------------------------------------
> python/1894 is trying to acquire lock:
> (&ei->xattr_sem){++++..}, at: [<ffffffff804878a6>] ext4_xattr_get+0x66/0x270
>
> but task is already holding lock:
> (&ei->xattr_sem){++++..}, at: [<ffffffff80489500>] ext4_xattr_set_handle+0xa0/0x5d0
>
> other info that might help us debug this:
> Possible unsafe locking scenario:
>
> CPU0
> ----
> lock(&ei->xattr_sem);
> lock(&ei->xattr_sem);
>
> *** DEADLOCK ***
>
> May be due to missing lock nesting notation
>
> 3 locks held by python/1894:
> #0: (sb_writers#10){.+.+.+}, at: [<ffffffff803d829f>] mnt_want_write+0x1f/0x50
> #1: (&sb->s_type->i_mutex_key#15){+.+...}, at: [<ffffffff803dda27>] vfs_setxattr+0x57/0xb0
> #2: (&ei->xattr_sem){++++..}, at: [<ffffffff80489500>] ext4_xattr_set_handle+0xa0/0x5d0
>
> stack backtrace:
> CPU: 0 PID: 1894 Comm: python Not tainted 4.11.0-rc8+ #402
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
> Call Trace:
> dump_stack+0x67/0x99
> __lock_acquire+0x5f3/0x1830
> lock_acquire+0xb5/0x1d0
> down_read+0x2f/0x60
> ext4_xattr_get+0x66/0x270
> ext4_get_acl+0x43/0x1e0
> get_acl+0x72/0xf0
> posix_acl_create+0x5e/0x170
> ext4_init_acl+0x21/0xc0
> __ext4_new_inode+0xffd/0x16b0
> ext4_xattr_set_entry+0x5ea/0xb70
> ext4_xattr_block_set+0x1b5/0x970
> ext4_xattr_set_handle+0x351/0x5d0
> ext4_xattr_set+0x124/0x180
> ext4_xattr_user_set+0x34/0x40
> __vfs_setxattr+0x66/0x80
> __vfs_setxattr_noperm+0x69/0x1c0
> vfs_setxattr+0xa2/0xb0
> setxattr+0x129/0x160
> path_setxattr+0x87/0xb0
> SyS_setxattr+0xf/0x20
> entry_SYSCALL_64_fastpath+0x18/0xad
>
> Signed-off-by: Tahsin Erdogan <tahsin@xxxxxxxxxx>
Thanks, added to the ext4 patch queue.
- Ted
