@@ -1853,12 +1853,20 @@ xfs_inodegc_worker(
struct xfs_inodegc, work);
struct llist_node *node = llist_del_all(&gc->list);
struct xfs_inode *ip, *n;
+ unsigned int nofs_flag;
WRITE_ONCE(gc->items, 0);
if (!node)
return;
+ /*
+ * We can allocate memory here while doing writeback on behalf of
+ * memory reclaim. To avoid memory allocation deadlocks set the
+ * task-wide nofs context for the following operations.
+ */
+ nofs_flag = memalloc_nofs_save();
+
ip = llist_entry(node, struct xfs_inode, i_gclist);
trace_xfs_inodegc_worker(ip->i_mount, READ_ONCE(gc->shrinker_hits));
@@ -1867,6 +1875,8 @@ xfs_inodegc_worker(
xfs_iflags_set(ip, XFS_INACTIVATING);
xfs_inodegc_inactivate(ip);
}
+
+ memalloc_nofs_restore(nofs_flag);
}
/*
We are doing a test about deleting a large number of files when memory is low. A deadlock problem was found. [ 1240.279183] -> #1 (fs_reclaim){+.+.}-{0:0}: [ 1240.280450] lock_acquire+0x197/0x460 [ 1240.281548] fs_reclaim_acquire.part.0+0x20/0x30 [ 1240.282625] kmem_cache_alloc+0x2b/0x940 [ 1240.283816] xfs_trans_alloc+0x8a/0x8b0 [ 1240.284757] xfs_inactive_ifree+0xe4/0x4e0 [ 1240.285935] xfs_inactive+0x4e9/0x8a0 [ 1240.286836] xfs_inodegc_worker+0x160/0x5e0 [ 1240.287969] process_one_work+0xa19/0x16b0 [ 1240.289030] worker_thread+0x9e/0x1050 [ 1240.290131] kthread+0x34f/0x460 [ 1240.290999] ret_from_fork+0x22/0x30 [ 1240.291905] [ 1240.291905] -> #0 ((work_completion)(&gc->work)){+.+.}-{0:0}: [ 1240.293569] check_prev_add+0x160/0x2490 [ 1240.294473] __lock_acquire+0x2c4d/0x5160 [ 1240.295544] lock_acquire+0x197/0x460 [ 1240.296403] __flush_work+0x6bc/0xa20 [ 1240.297522] xfs_inode_mark_reclaimable+0x6f0/0xdc0 [ 1240.298649] destroy_inode+0xc6/0x1b0 [ 1240.299677] dispose_list+0xe1/0x1d0 [ 1240.300567] prune_icache_sb+0xec/0x150 [ 1240.301794] super_cache_scan+0x2c9/0x480 [ 1240.302776] do_shrink_slab+0x3f0/0xaa0 [ 1240.303671] shrink_slab+0x170/0x660 [ 1240.304601] shrink_node+0x7f7/0x1df0 [ 1240.305515] balance_pgdat+0x766/0xf50 [ 1240.306657] kswapd+0x5bd/0xd20 [ 1240.307551] kthread+0x34f/0x460 [ 1240.308346] ret_from_fork+0x22/0x30 [ 1240.309247] [ 1240.309247] other info that might help us debug this: [ 1240.309247] [ 1240.310944] Possible unsafe locking scenario: [ 1240.310944] [ 1240.312379] CPU0 CPU1 [ 1240.313363] ---- ---- [ 1240.314433] lock(fs_reclaim); [ 1240.315107] lock((work_completion)(&gc->work)); [ 1240.316828] lock(fs_reclaim); [ 1240.318088] lock((work_completion)(&gc->work)); [ 1240.319203] [ 1240.319203] *** DEADLOCK *** ... [ 2438.431081] Workqueue: xfs-inodegc/sda xfs_inodegc_worker [ 2438.432089] Call Trace: [ 2438.432562] __schedule+0xa94/0x1d20 [ 2438.435787] schedule+0xbf/0x270 [ 2438.436397] schedule_timeout+0x6f8/0x8b0 [ 2438.445126] wait_for_completion+0x163/0x260 [ 2438.448610] __flush_work+0x4c4/0xa40 [ 2438.455011] xfs_inode_mark_reclaimable+0x6ef/0xda0 [ 2438.456695] destroy_inode+0xc6/0x1b0 [ 2438.457375] dispose_list+0xe1/0x1d0 [ 2438.458834] prune_icache_sb+0xe8/0x150 [ 2438.461181] super_cache_scan+0x2b3/0x470 [ 2438.461950] do_shrink_slab+0x3cf/0xa50 [ 2438.462687] shrink_slab+0x17d/0x660 [ 2438.466392] shrink_node+0x87e/0x1d40 [ 2438.467894] do_try_to_free_pages+0x364/0x1300 [ 2438.471188] try_to_free_pages+0x26c/0x5b0 [ 2438.473567] __alloc_pages_slowpath.constprop.136+0x7aa/0x2100 [ 2438.482577] __alloc_pages+0x5db/0x710 [ 2438.485231] alloc_pages+0x100/0x200 [ 2438.485923] allocate_slab+0x2c0/0x380 [ 2438.486623] ___slab_alloc+0x41f/0x690 [ 2438.490254] __slab_alloc+0x54/0x70 [ 2438.491692] kmem_cache_alloc+0x23e/0x270 [ 2438.492437] xfs_trans_alloc+0x88/0x880 [ 2438.493168] xfs_inactive_ifree+0xe2/0x4e0 [ 2438.496419] xfs_inactive+0x4eb/0x8b0 [ 2438.497123] xfs_inodegc_worker+0x16b/0x5e0 [ 2438.497918] process_one_work+0xbf7/0x1a20 [ 2438.500316] worker_thread+0x8c/0x1060 [ 2438.504938] ret_from_fork+0x22/0x30 When the memory is insufficient, xfs_inonodegc_worker will trigger memory reclamation when memory is allocated, then flush_work() may be called to wait for the work to complete. This causes a deadlock. So use memalloc_nofs_save() to avoid triggering memory reclamation in xfs_inodegc_worker. Signed-off-by: Wu Guanghao <wuguanghao3@huawei.com> --- v2: - use memalloc_nofs_save() to avoid triggering memory reclamation fs/xfs/xfs_icache.c | 10 ++++++++++ 1 file changed, 10 insertions(+) -- 2.27.0