[PATCH] mm: memcontrol: fix GFP_NOFS recursion in memory.high enforcement
From: Johannes Weiner
Date: Thu Sep 14 2023 - 11:21:43 EST
Breno and Josef report a deadlock scenario from cgroup reclaim
re-entering the filesystem:
[ 361.546690] ======================================================
[ 361.559210] WARNING: possible circular locking dependency detected
[ 361.571703] 6.5.0-0_fbk700_debug_rc0_kbuilder_13159_gbf787a128001 #1 Tainted: G S E
[ 361.589704] ------------------------------------------------------
[ 361.602277] find/9315 is trying to acquire lock:
[ 361.611625] ffff88837ba140c0 (&delayed_node->mutex){+.+.}-{4:4}, at: __btrfs_release_delayed_node+0x68/0x4f0
[ 361.631437]
[ 361.631437] but task is already holding lock:
[ 361.643243] ffff8881765b8678 (btrfs-tree-01){++++}-{4:4}, at: btrfs_tree_read_lock+0x1e/0x40
[ 362.904457] mutex_lock_nested+0x1c/0x30
[ 362.912414] __btrfs_release_delayed_node+0x68/0x4f0
[ 362.922460] btrfs_evict_inode+0x301/0x770
[ 362.982726] evict+0x17c/0x380
[ 362.988944] prune_icache_sb+0x100/0x1d0
[ 363.005559] super_cache_scan+0x1f8/0x260
[ 363.013695] do_shrink_slab+0x2a2/0x540
[ 363.021489] shrink_slab_memcg+0x237/0x3d0
[ 363.050606] shrink_slab+0xa7/0x240
[ 363.083382] shrink_node_memcgs+0x262/0x3b0
[ 363.091870] shrink_node+0x1a4/0x720
[ 363.099150] shrink_zones+0x1f6/0x5d0
[ 363.148798] do_try_to_free_pages+0x19b/0x5e0
[ 363.157633] try_to_free_mem_cgroup_pages+0x266/0x370
[ 363.190575] reclaim_high+0x16f/0x1f0
[ 363.208409] mem_cgroup_handle_over_high+0x10b/0x270
[ 363.246678] try_charge_memcg+0xaf2/0xc70
[ 363.304151] charge_memcg+0xf0/0x350
[ 363.320070] __mem_cgroup_charge+0x28/0x40
[ 363.328371] __filemap_add_folio+0x870/0xd50
[ 363.371303] filemap_add_folio+0xdd/0x310
[ 363.399696] __filemap_get_folio+0x2fc/0x7d0
[ 363.419086] pagecache_get_page+0xe/0x30
[ 363.427048] alloc_extent_buffer+0x1cd/0x6a0
[ 363.435704] read_tree_block+0x43/0xc0
[ 363.443316] read_block_for_search+0x361/0x510
[ 363.466690] btrfs_search_slot+0xc8c/0x1520
This is caused by the mem_cgroup_handle_over_high() not respecting the
gfp_mask of the allocation context. We used to only call this function
on resume to userspace, where no locks were held. But c9afe31ec443
("memcg: synchronously enforce memory.high for large overcharges")
added a call from the allocation context without considering the gfp.
Reported-by: Breno Leitao <leitao@xxxxxxxxxx>
Reported-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Fixes: c9afe31ec443 ("memcg: synchronously enforce memory.high for large overcharges")
Cc: stable@xxxxxxxxxxxxxxx # 5.17+
Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
---
include/linux/memcontrol.h | 4 ++--
include/linux/resume_user_mode.h | 2 +-
mm/memcontrol.c | 6 +++---
3 files changed, 6 insertions(+), 6 deletions(-)
diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
index ab94ad4597d0..e4e24da16d2c 100644
--- a/include/linux/memcontrol.h
+++ b/include/linux/memcontrol.h
@@ -920,7 +920,7 @@ unsigned long mem_cgroup_get_zone_lru_size(struct lruvec *lruvec,
return READ_ONCE(mz->lru_zone_size[zone_idx][lru]);
}
-void mem_cgroup_handle_over_high(void);
+void mem_cgroup_handle_over_high(gfp_t gfp_mask);
unsigned long mem_cgroup_get_max(struct mem_cgroup *memcg);
@@ -1458,7 +1458,7 @@ static inline void mem_cgroup_unlock_pages(void)
rcu_read_unlock();
}
-static inline void mem_cgroup_handle_over_high(void)
+static inline void mem_cgroup_handle_over_high(gfp_t gfp_mask)
{
}
diff --git a/include/linux/resume_user_mode.h b/include/linux/resume_user_mode.h
index 285189454449..f8f3e958e9cf 100644
--- a/include/linux/resume_user_mode.h
+++ b/include/linux/resume_user_mode.h
@@ -55,7 +55,7 @@ static inline void resume_user_mode_work(struct pt_regs *regs)
}
#endif
- mem_cgroup_handle_over_high();
+ mem_cgroup_handle_over_high(GFP_KERNEL);
blkcg_maybe_throttle_current();
rseq_handle_notify_resume(NULL, regs);
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index a4d3282493b6..d13dde2f8b56 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2555,7 +2555,7 @@ static unsigned long calculate_high_delay(struct mem_cgroup *memcg,
* Scheduled by try_charge() to be executed from the userland return path
* and reclaims memory over the high limit.
*/
-void mem_cgroup_handle_over_high(void)
+void mem_cgroup_handle_over_high(gfp_t gfp_mask)
{
unsigned long penalty_jiffies;
unsigned long pflags;
@@ -2583,7 +2583,7 @@ void mem_cgroup_handle_over_high(void)
*/
nr_reclaimed = reclaim_high(memcg,
in_retry ? SWAP_CLUSTER_MAX : nr_pages,
- GFP_KERNEL);
+ gfp_mask);
/*
* memory.high is breached and reclaim is unable to keep up. Throttle
@@ -2819,7 +2819,7 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask,
if (current->memcg_nr_pages_over_high > MEMCG_CHARGE_BATCH &&
!(current->flags & PF_MEMALLOC) &&
gfpflags_allow_blocking(gfp_mask)) {
- mem_cgroup_handle_over_high();
+ mem_cgroup_handle_over_high(gfp_mask);
}
return 0;
}
--
2.42.0