Re: [PATCH 4.4 48/76] libceph: force GFP_NOIO for socket allocations

[Michal Hocko]

On Tue 28-03-17 14:30:45, Greg KH wrote:
> 4.4-stable review patch.  If anyone has any objections, please let me know.

I haven't seen the original patch but the changelog makes me worried.
How exactly this is a problem? Where do we lockup? Does rbd/libceph take
any xfs locks?

> ------------------
> 
> From: Ilya Dryomov <idryomov@xxxxxxxxx>
> 
> commit 633ee407b9d15a75ac9740ba9d3338815e1fcb95 upstream.
> 
> sock_alloc_inode() allocates socket+inode and socket_wq with
> GFP_KERNEL, which is not allowed on the writeback path:
> 
>     Workqueue: ceph-msgr con_work [libceph]
>     ffff8810871cb018 0000000000000046 0000000000000000 ffff881085d40000
>     0000000000012b00 ffff881025cad428 ffff8810871cbfd8 0000000000012b00
>     ffff880102fc1000 ffff881085d40000 ffff8810871cb038 ffff8810871cb148
>     Call Trace:
>     [<ffffffff816dd629>] schedule+0x29/0x70
>     [<ffffffff816e066d>] schedule_timeout+0x1bd/0x200
>     [<ffffffff81093ffc>] ? ttwu_do_wakeup+0x2c/0x120
>     [<ffffffff81094266>] ? ttwu_do_activate.constprop.135+0x66/0x70
>     [<ffffffff816deb5f>] wait_for_completion+0xbf/0x180
>     [<ffffffff81097cd0>] ? try_to_wake_up+0x390/0x390
>     [<ffffffff81086335>] flush_work+0x165/0x250
>     [<ffffffff81082940>] ? worker_detach_from_pool+0xd0/0xd0
>     [<ffffffffa03b65b1>] xlog_cil_force_lsn+0x81/0x200 [xfs]
>     [<ffffffff816d6b42>] ? __slab_free+0xee/0x234
>     [<ffffffffa03b4b1d>] _xfs_log_force_lsn+0x4d/0x2c0 [xfs]
>     [<ffffffff811adc1e>] ? lookup_page_cgroup_used+0xe/0x30
>     [<ffffffffa039a723>] ? xfs_reclaim_inode+0xa3/0x330 [xfs]
>     [<ffffffffa03b4dcf>] xfs_log_force_lsn+0x3f/0xf0 [xfs]
>     [<ffffffffa039a723>] ? xfs_reclaim_inode+0xa3/0x330 [xfs]
>     [<ffffffffa03a62c6>] xfs_iunpin_wait+0xc6/0x1a0 [xfs]
>     [<ffffffff810aa250>] ? wake_atomic_t_function+0x40/0x40
>     [<ffffffffa039a723>] xfs_reclaim_inode+0xa3/0x330 [xfs]
>     [<ffffffffa039ac07>] xfs_reclaim_inodes_ag+0x257/0x3d0 [xfs]
>     [<ffffffffa039bb13>] xfs_reclaim_inodes_nr+0x33/0x40 [xfs]
>     [<ffffffffa03ab745>] xfs_fs_free_cached_objects+0x15/0x20 [xfs]
>     [<ffffffff811c0c18>] super_cache_scan+0x178/0x180
>     [<ffffffff8115912e>] shrink_slab_node+0x14e/0x340
>     [<ffffffff811afc3b>] ? mem_cgroup_iter+0x16b/0x450
>     [<ffffffff8115af70>] shrink_slab+0x100/0x140
>     [<ffffffff8115e425>] do_try_to_free_pages+0x335/0x490
>     [<ffffffff8115e7f9>] try_to_free_pages+0xb9/0x1f0
>     [<ffffffff816d56e4>] ? __alloc_pages_direct_compact+0x69/0x1be
>     [<ffffffff81150cba>] __alloc_pages_nodemask+0x69a/0xb40
>     [<ffffffff8119743e>] alloc_pages_current+0x9e/0x110
>     [<ffffffff811a0ac5>] new_slab+0x2c5/0x390
>     [<ffffffff816d71c4>] __slab_alloc+0x33b/0x459
>     [<ffffffff815b906d>] ? sock_alloc_inode+0x2d/0xd0
>     [<ffffffff8164bda1>] ? inet_sendmsg+0x71/0xc0
>     [<ffffffff815b906d>] ? sock_alloc_inode+0x2d/0xd0
>     [<ffffffff811a21f2>] kmem_cache_alloc+0x1a2/0x1b0
>     [<ffffffff815b906d>] sock_alloc_inode+0x2d/0xd0
>     [<ffffffff811d8566>] alloc_inode+0x26/0xa0
>     [<ffffffff811da04a>] new_inode_pseudo+0x1a/0x70
>     [<ffffffff815b933e>] sock_alloc+0x1e/0x80
>     [<ffffffff815ba855>] __sock_create+0x95/0x220
>     [<ffffffff815baa04>] sock_create_kern+0x24/0x30
>     [<ffffffffa04794d9>] con_work+0xef9/0x2050 [libceph]
>     [<ffffffffa04aa9ec>] ? rbd_img_request_submit+0x4c/0x60 [rbd]
>     [<ffffffff81084c19>] process_one_work+0x159/0x4f0
>     [<ffffffff8108561b>] worker_thread+0x11b/0x530
>     [<ffffffff81085500>] ? create_worker+0x1d0/0x1d0
>     [<ffffffff8108b6f9>] kthread+0xc9/0xe0
>     [<ffffffff8108b630>] ? flush_kthread_worker+0x90/0x90
>     [<ffffffff816e1b98>] ret_from_fork+0x58/0x90
>     [<ffffffff8108b630>] ? flush_kthread_worker+0x90/0x90
> 
> Use memalloc_noio_{save,restore}() to temporarily force GFP_NOIO here.
> 
> Link: http://tracker.ceph.com/issues/19309
> Reported-by: Sergey Jerusalimov <wintchester@xxxxxxxxx>
> Signed-off-by: Ilya Dryomov <idryomov@xxxxxxxxx>
> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> 
> ---
>  net/ceph/messenger.c |    6 ++++++
>  1 file changed, 6 insertions(+)
> 
> --- a/net/ceph/messenger.c
> +++ b/net/ceph/messenger.c
> @@ -7,6 +7,7 @@
>  #include <linux/kthread.h>
>  #include <linux/net.h>
>  #include <linux/nsproxy.h>
> +#include <linux/sched.h>
>  #include <linux/slab.h>
>  #include <linux/socket.h>
>  #include <linux/string.h>
> @@ -478,11 +479,16 @@ static int ceph_tcp_connect(struct ceph_
>  {
>  	struct sockaddr_storage *paddr = &con->peer_addr.in_addr;
>  	struct socket *sock;
> +	unsigned int noio_flag;
>  	int ret;
>  
>  	BUG_ON(con->sock);
> +
> +	/* sock_create_kern() allocates with GFP_KERNEL */
> +	noio_flag = memalloc_noio_save();
>  	ret = sock_create_kern(read_pnet(&con->msgr->net), paddr->ss_family,
>  			       SOCK_STREAM, IPPROTO_TCP, &sock);
> +	memalloc_noio_restore(noio_flag);
>  	if (ret)
>  		return ret;
>  	sock->sk->sk_allocation = GFP_NOFS;
> 

-- 
Michal Hocko
SUSE Labs