The patch titled Subject: mm: memcontrol: fix GFP_NOFS recursion in memory.high enforcement has been added to the -mm mm-hotfixes-unstable branch. Its filename is mm-memcontrol-fix-gfp_nofs-recursion-in-memoryhigh-enforcement.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------ From: Johannes Weiner hannes@cmpxchg.org Subject: mm: memcontrol: fix GFP_NOFS recursion in memory.high enforcement Date: Thu, 14 Sep 2023 11:21:39 -0400

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.

Link: https://lkml.kernel.org/r/20230914152139.100822-1-hannes@cmpxchg.org Fixes: c9afe31ec443 ("memcg: synchronously enforce memory.high for large overcharges") Signed-off-by: Johannes Weiner hannes@cmpxchg.org Reported-by: Breno Leitao leitao@debian.org Reported-by: Josef Bacik josef@toxicpanda.com Cc: Shakeel Butt shakeelb@google.com Cc: Michal Hocko mhocko@suse.com Cc: Roman Gushchin roman.gushchin@linux.dev Cc: Muchun Song songmuchun@bytedance.com Cc: stable@vger.kernel.org [5.17+] Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

include/linux/memcontrol.h | 4 ++-- include/linux/resume_user_mode.h | 2 +- mm/memcontrol.c | 6 +++--- 3 files changed, 6 insertions(+), 6 deletions(-)

--- a/include/linux/memcontrol.h~mm-memcontrol-fix-gfp_nofs-recursion-in-memoryhigh-enforcement +++ a/include/linux/memcontrol.h @@ -920,7 +920,7 @@ unsigned long mem_cgroup_get_zone_lru_si 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_pag rcu_read_unlock(); }

-static inline void mem_cgroup_handle_over_high(void) +static inline void mem_cgroup_handle_over_high(gfp_t gfp_mask) { }

--- a/include/linux/resume_user_mode.h~mm-memcontrol-fix-gfp_nofs-recursion-in-memoryhigh-enforcement +++ a/include/linux/resume_user_mode.h @@ -55,7 +55,7 @@ static inline void resume_user_mode_work } #endif

- mem_cgroup_handle_over_high(); + mem_cgroup_handle_over_high(GFP_KERNEL); blkcg_maybe_throttle_current();

rseq_handle_notify_resume(NULL, regs); --- a/mm/memcontrol.c~mm-memcontrol-fix-gfp_nofs-recursion-in-memoryhigh-enforcement +++ a/mm/memcontrol.c @@ -2555,7 +2555,7 @@ static unsigned long calculate_high_dela * 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 @@ retry_reclaim: */ 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 @@ done_restock: 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; } _

Patches currently in -mm which might be from hannes@cmpxchg.org are

mm-page_alloc-fix-cma-and-highatomic-landing-on-the-wrong-buddy-list.patch mm-memcontrol-fix-gfp_nofs-recursion-in-memoryhigh-enforcement.patch mm-page_alloc-remove-pcppage-migratetype-caching.patch mm-page_alloc-fix-up-block-types-when-merging-compatible-blocks.patch mm-page_alloc-move-free-pages-when-converting-block-during-isolation.patch mm-page_alloc-fix-move_freepages_block-range-error.patch mm-page_alloc-fix-freelist-movement-during-block-conversion.patch mm-page_alloc-consolidate-free-page-accounting.patch