The patch titled Subject: maple_tree: add GFP_KERNEL to allocations in mas_expected_entries() has been added to the -mm mm-hotfixes-unstable branch. Its filename is maple_tree-add-gfp_kernel-to-allocations-in-mas_expected_entries.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: "Liam R. Howlett" Liam.Howlett@oracle.com Subject: maple_tree: add GFP_KERNEL to allocations in mas_expected_entries() Date: Tue, 10 Oct 2023 10:17:37 -0400

Users complained about OOM errors during fork without triggering compaction. This can be fixed by modifying the flags used in mas_expected_entries() so that the compaction will be triggered in low memory situations. Since mas_expected_entries() is only used during fork, the extra argument does not need to be passed through.

Additionally, the testing in the maple tree fork testing needed to be altered to use the correct locking type so that allocations would not trigger sleeping and thus failures in the testing. The additional locking change requires rwsem support additions to the tools/ directory through the use of pthreads pthread_rwlock_t. With this change test_maple_tree works in userspace, as a module, and in-kernel.

Users may notice that the system gave up early on attempting to start new processes instead of attempting to reclaim memory.

Link: https://lkml.kernel.org/r/20230915093243epcms1p46fa00bbac1ab7b7dca94acb66c44... Link: https://lkml.kernel.org/r/20231010141737.1592866-1-Liam.Howlett@oracle.com Fixes: 54a611b60590 ("Maple Tree: add new data structure") Signed-off-by: Liam R. Howlett Liam.Howlett@oracle.com Cc: jason.sim@samsung.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

lib/maple_tree.c | 2 - lib/test_maple_tree.c | 13 +++++++---- tools/include/linux/rwsem.h | 40 ++++++++++++++++++++++++++++++++++ 3 files changed, 50 insertions(+), 5 deletions(-)

--- a/lib/maple_tree.c~maple_tree-add-gfp_kernel-to-allocations-in-mas_expected_entries +++ a/lib/maple_tree.c @@ -5627,7 +5627,7 @@ int mas_expected_entries(struct ma_state /* Internal nodes */ nr_nodes += DIV_ROUND_UP(nr_nodes, nonleaf_cap); /* Add working room for split (2 nodes) + new parents */ - mas_node_count(mas, nr_nodes + 3); + mas_node_count_gfp(mas, nr_nodes + 3, GFP_KERNEL);

/* Detect if allocations run out */ mas->mas_flags |= MA_STATE_PREALLOC; --- a/lib/test_maple_tree.c~maple_tree-add-gfp_kernel-to-allocations-in-mas_expected_entries +++ a/lib/test_maple_tree.c @@ -9,6 +9,7 @@

#include <linux/maple_tree.h> #include <linux/module.h> +#include <linux/rwsem.h>

#define MTREE_ALLOC_MAX 0x2000000000000Ul #define CONFIG_MAPLE_SEARCH @@ -2616,6 +2617,10 @@ static noinline void __init check_dup_ga void *tmp; MA_STATE(mas, mt, 0, 0); MA_STATE(newmas, &newmt, 0, 0); + struct rw_semaphore newmt_lock; + + init_rwsem(&newmt_lock); + mt_set_external_lock(&newmt, &newmt_lock);

if (!zero_start) i = 1; @@ -2625,9 +2630,9 @@ static noinline void __init check_dup_ga mtree_store_range(mt, i*10, (i+1)*10 - gap, xa_mk_value(i), GFP_KERNEL);

- mt_init_flags(&newmt, MT_FLAGS_ALLOC_RANGE); + mt_init_flags(&newmt, MT_FLAGS_ALLOC_RANGE | MT_FLAGS_LOCK_EXTERN); mt_set_non_kernel(99999); - mas_lock(&newmas); + down_write(&newmt_lock); ret = mas_expected_entries(&newmas, nr_entries); mt_set_non_kernel(0); MT_BUG_ON(mt, ret != 0); @@ -2640,9 +2645,9 @@ static noinline void __init check_dup_ga } rcu_read_unlock(); mas_destroy(&newmas); - mas_unlock(&newmas);

- mtree_destroy(&newmt); + __mt_destroy(&newmt); + up_write(&newmt_lock); }

/* Duplicate many sizes of trees. Mainly to test expected entry values */ --- /dev/null +++ a/tools/include/linux/rwsem.h @@ -0,0 +1,40 @@ +/* SPDX-License-Identifier: GPL-2.0+ */ +#ifndef _TOOLS__RWSEM_H +#define _TOOLS__RWSEM_H + +#include <pthread.h> + +struct rw_semaphore { + pthread_rwlock_t lock; +}; + +static inline int init_rwsem(struct rw_semaphore *sem) +{ + return pthread_rwlock_init(&sem->lock, NULL); +} + +static inline int exit_rwsem(struct rw_semaphore *sem) +{ + return pthread_rwlock_destroy(&sem->lock); +} + +static inline int down_read(struct rw_semaphore *sem) +{ + return pthread_rwlock_rdlock(&sem->lock); +} + +static inline int up_read(struct rw_semaphore *sem) +{ + return pthread_rwlock_unlock(&sem->lock); +} + +static inline int down_write(struct rw_semaphore *sem) +{ + return pthread_rwlock_wrlock(&sem->lock); +} + +static inline int up_write(struct rw_semaphore *sem) +{ + return pthread_rwlock_unlock(&sem->lock); +} +#endif /* _TOOLS_RWSEM_H */ _

Patches currently in -mm which might be from Liam.Howlett@oracle.com are

maple_tree-add-gfp_kernel-to-allocations-in-mas_expected_entries.patch mmap-add-clarifying-comment-to-vma_merge-code.patch radix-tree-test-suite-fix-allocation-calculation-in-kmem_cache_alloc_bulk.patch