[1/7] lockdep: teach lockdep about memalloc_noio_save

Commit Message

Michal Hocko March 6, 2017, 1:14 p.m. UTC

From: Nikolay Borisov <[e-mail]>

Commit 21caf2fc1931 ("mm: teach mm by current context info to not do I/O
during memory allocation") added the memalloc_noio_(save|restore) functions
to enable people to modify the MM behavior by disabling I/O during memory
allocation. This was further extended in Fixes: 934f3072c17c ("mm: clear
__GFP_FS when PF_MEMALLOC_NOIO is set"). memalloc_noio_* functions prevent
allocation paths recursing back into the filesystem without explicitly
changing the flags for every allocation site. However, lockdep hasn't been
keeping up with the changes and it entirely misses handling the memalloc_noio
adjustments. Instead, it is left to the callers of __lockdep_trace_alloc to
call the function after they have shaven the respective GFP flags which
can lead to false positives:

[  644.173373] =================================
[  644.174012] [ INFO: inconsistent lock state ]
[  644.174012] 4.10.0-nbor #134 Not tainted
[  644.174012] ---------------------------------
[  644.174012] inconsistent {IN-RECLAIM_FS-W} -> {RECLAIM_FS-ON-W} usage.
[  644.174012] fsstress/3365 [HC0[0]:SC0[0]:HE1:SE1] takes:
[  644.174012]  (&xfs_nondir_ilock_class){++++?.}, at: [<ffffffff8136f231>] xfs_ilock+0x141/0x230
[  644.174012] {IN-RECLAIM_FS-W} state was registered at:
[  644.174012]   __lock_acquire+0x62a/0x17c0
[  644.174012]   lock_acquire+0xc5/0x220
[  644.174012]   down_write_nested+0x4f/0x90
[  644.174012]   xfs_ilock+0x141/0x230
[  644.174012]   xfs_reclaim_inode+0x12a/0x320
[  644.174012]   xfs_reclaim_inodes_ag+0x2c8/0x4e0
[  644.174012]   xfs_reclaim_inodes_nr+0x33/0x40
[  644.174012]   xfs_fs_free_cached_objects+0x19/0x20
[  644.174012]   super_cache_scan+0x191/0x1a0
[  644.174012]   shrink_slab+0x26f/0x5f0
[  644.174012]   shrink_node+0xf9/0x2f0
[  644.174012]   kswapd+0x356/0x920
[  644.174012]   kthread+0x10c/0x140
[  644.174012]   ret_from_fork+0x31/0x40
[  644.174012] irq event stamp: 173777
[  644.174012] hardirqs last  enabled at (173777): [<ffffffff8105b440>] __local_bh_enable_ip+0x70/0xc0
[  644.174012] hardirqs last disabled at (173775): [<ffffffff8105b407>] __local_bh_enable_ip+0x37/0xc0
[  644.174012] softirqs last  enabled at (173776): [<ffffffff81357e2a>] _xfs_buf_find+0x67a/0xb70
[  644.174012] softirqs last disabled at (173774): [<ffffffff81357d8b>] _xfs_buf_find+0x5db/0xb70
[  644.174012]
[  644.174012] other info that might help us debug this:
[  644.174012]  Possible unsafe locking scenario:
[  644.174012]
[  644.174012]        CPU0
[  644.174012]        ----
[  644.174012]   lock(&xfs_nondir_ilock_class);
[  644.174012]   <Interrupt>
[  644.174012]     lock(&xfs_nondir_ilock_class);
[  644.174012]
[  644.174012]  *** DEADLOCK ***
[  644.174012]
[  644.174012] 4 locks held by fsstress/3365:
[  644.174012]  #0:  (sb_writers#10){++++++}, at: [<ffffffff81208d04>] mnt_want_write+0x24/0x50
[  644.174012]  #1:  (&sb->s_type->i_mutex_key#12){++++++}, at: [<ffffffff8120ea2f>] vfs_setxattr+0x6f/0xb0
[  644.174012]  #2:  (sb_internal#2){++++++}, at: [<ffffffff8138185c>] xfs_trans_alloc+0xfc/0x140
[  644.174012]  #3:  (&xfs_nondir_ilock_class){++++?.}, at: [<ffffffff8136f231>] xfs_ilock+0x141/0x230
[  644.174012]
[  644.174012] stack backtrace:
[  644.174012] CPU: 0 PID: 3365 Comm: fsstress Not tainted 4.10.0-nbor #134
[  644.174012] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Ubuntu-1.8.2-1ubuntu1 04/01/2014
[  644.174012] Call Trace:
[  644.174012]  dump_stack+0x85/0xc9
[  644.174012]  print_usage_bug.part.37+0x284/0x293
[  644.174012]  ? print_shortest_lock_dependencies+0x1b0/0x1b0
[  644.174012]  mark_lock+0x27e/0x660
[  644.174012]  mark_held_locks+0x66/0x90
[  644.174012]  lockdep_trace_alloc+0x6f/0xd0
[  644.174012]  kmem_cache_alloc_node_trace+0x3a/0x2c0
[  644.174012]  ? vm_map_ram+0x2a1/0x510
[  644.174012]  vm_map_ram+0x2a1/0x510
[  644.174012]  ? vm_map_ram+0x46/0x510
[  644.174012]  _xfs_buf_map_pages+0x77/0x140
[  644.174012]  xfs_buf_get_map+0x185/0x2a0
[  644.174012]  xfs_attr_rmtval_set+0x233/0x430
[  644.174012]  xfs_attr_leaf_addname+0x2d2/0x500
[  644.174012]  xfs_attr_set+0x214/0x420
[  644.174012]  xfs_xattr_set+0x59/0xb0
[  644.174012]  __vfs_setxattr+0x76/0xa0
[  644.174012]  __vfs_setxattr_noperm+0x5e/0xf0
[  644.174012]  vfs_setxattr+0xae/0xb0
[  644.174012]  ? __might_fault+0x43/0xa0
[  644.174012]  setxattr+0x15e/0x1a0
[  644.174012]  ? __lock_is_held+0x53/0x90
[  644.174012]  ? rcu_read_lock_sched_held+0x93/0xa0
[  644.174012]  ? rcu_sync_lockdep_assert+0x2f/0x60
[  644.174012]  ? __sb_start_write+0x130/0x1d0
[  644.174012]  ? mnt_want_write+0x24/0x50
[  644.174012]  path_setxattr+0x8f/0xc0
[  644.174012]  SyS_lsetxattr+0x11/0x20
[  644.174012]  entry_SYSCALL_64_fastpath+0x23/0xc6

Let's fix this by making lockdep explicitly do the shaving of respective
GFP flags.

Fixes: 934f3072c17c ("mm: clear __GFP_FS when PF_MEMALLOC_NOIO is set")
Acked-by: Michal Hocko <[e-mail]>
Acked-by: Peter Zijlstra (Intel) <[e-mail]>
Signed-off-by: Nikolay Borisov <[e-mail]>
Signed-off-by: Michal Hocko <[e-mail]>
---
 kernel/locking/lockdep.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

Patch

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 12e38c213b70..25c33dcd86d7 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -30,6 +30,7 @@ 
 #include <linux/sched.h>
 #include <linux/sched/clock.h>
 #include <linux/sched/task.h>
+#include <linux/sched/mm.h>
 #include <linux/delay.h>
 #include <linux/module.h>
 #include <linux/proc_fs.h>
@@ -2863,6 +2864,8 @@  static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
 	if (unlikely(!debug_locks))
 		return;
 
+	gfp_mask = memalloc_noio_flags(gfp_mask);
+
 	/* no reclaim without waiting on it */
 	if (!(gfp_mask & __GFP_DIRECT_RECLAIM))
 		return;
@@ -3854,7 +3857,7 @@  EXPORT_SYMBOL_GPL(lock_unpin_lock);
 
 void lockdep_set_current_reclaim_state(gfp_t gfp_mask)
 {
-	current->lockdep_reclaim_gfp = gfp_mask;
+	current->lockdep_reclaim_gfp = memalloc_noio_flags(gfp_mask);
 }
 
 void lockdep_clear_current_reclaim_state(void)