The patch titled
Subject: mm/mmap: remove preallocation from do_mas_align_munmap()
has been added to the -mm mm-unstable branch. Its filename is
mm-mmap-remove-preallocation-from-do_mas_align_munmap.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mmap-remove-preallocation-from-do_mas_align_munmap.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: "Liam R. Howlett" <Liam.Howlett@xxxxxxxxxx>
Subject: mm/mmap: remove preallocation from do_mas_align_munmap()
Date: Fri, 20 Jan 2023 11:26:12 -0500
In preparation of passing the vma state through split, the pre-allocation
that occurs before the split has to be moved to after. Since the
preallocation would then live right next to the store, just call store
instead of preallocating. This effectively restores the potential error
path of splitting and not munmap'ing which pre-dates the maple tree.
Link: https://lkml.kernel.org/r/20230120162650.984577-12-Liam.Howlett@xxxxxxxxxx
Signed-off-by: Liam R. Howlett <Liam.Howlett@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/mm/mmap.c~mm-mmap-remove-preallocation-from-do_mas_align_munmap
+++ a/mm/mmap.c
@@ -2329,9 +2329,6 @@ do_mas_align_munmap(struct ma_state *mas
mt_init_flags(&mt_detach, MT_FLAGS_LOCK_EXTERN);
mt_set_external_lock(&mt_detach, &mm->mmap_lock);
- if (mas_preallocate(mas, GFP_KERNEL))
- return -ENOMEM;
-
mas->last = end - 1;
/*
* If we need to split any vma, do it now to save pain later.
@@ -2422,8 +2419,6 @@ do_mas_align_munmap(struct ma_state *mas
goto userfaultfd_error;
}
- /* Point of no return */
- mas_set_range(mas, start, end - 1);
#if defined(CONFIG_DEBUG_VM_MAPLE_TREE)
/* Make sure no VMAs are about to be lost. */
{
@@ -2431,6 +2426,7 @@ do_mas_align_munmap(struct ma_state *mas
struct vm_area_struct *vma_mas, *vma_test;
int test_count = 0;
+ mas_set_range(mas, start, end - 1);
rcu_read_lock();
vma_test = mas_find(&test, end - 1);
mas_for_each(mas, vma_mas, end - 1) {
@@ -2440,10 +2436,13 @@ do_mas_align_munmap(struct ma_state *mas
}
rcu_read_unlock();
BUG_ON(count != test_count);
- mas_set_range(mas, start, end - 1);
}
#endif
- mas_store_prealloc(mas, NULL);
+ /* Point of no return */
+ mas_set_range(mas, start, end - 1);
+ if (mas_store_gfp(mas, NULL, GFP_KERNEL))
+ return -ENOMEM;
+
mm->map_count -= count;
/*
* Do not downgrade mmap_lock if we are next to VM_GROWSDOWN or
@@ -2475,7 +2474,6 @@ end_split_failed:
__mt_destroy(&mt_detach);
start_split_failed:
map_count_exceeded:
- mas_destroy(mas);
return error;
}
_
Patches currently in -mm which might be from Liam.Howlett@xxxxxxxxxx are
maple_tree-add-mas_init-function.patch
maple_tree-fix-potential-rcu-issue.patch
maple_tree-reduce-user-error-potential.patch
test_maple_tree-test-modifications-while-iterating.patch
mm-expand-vma-iterator-interface.patch
mm-mmap-convert-brk-to-use-vma-iterator.patch
kernel-fork-convert-forking-to-using-the-vmi-iterator.patch
mmap-convert-vma_link-vma-iterator.patch
mm-mmap-remove-preallocation-from-do_mas_align_munmap.patch
mmap-change-do_mas_munmap-and-do_mas_aligned_munmap-to-use-vma-iterator.patch
mmap-convert-vma_expand-to-use-vma-iterator.patch
mm-add-temporary-vma-iterator-versions-of-vma_merge-split_vma-and-__split_vma.patch
ipc-shm-use-the-vma-iterator-for-munmap-calls.patch
userfaultfd-use-vma-iterator.patch
mm-change-mprotect_fixup-to-vma-iterator.patch
mlock-convert-mlock-to-vma-iterator.patch
coredump-convert-to-vma-iterator.patch
mempolicy-convert-to-vma-iterator.patch
task_mmu-convert-to-vma-iterator.patch
sched-convert-to-vma-iterator.patch
madvise-use-vmi-iterator-for-__split_vma-and-vma_merge.patch
mmap-pass-through-vmi-iterator-to-__split_vma.patch
mmap-use-vmi-version-of-vma_merge.patch
mm-mremap-use-vmi-version-of-vma_merge.patch
nommu-convert-nommu-to-using-the-vma-iterator.patch
mm-switch-vma_merge-split_vma-and-__split_vma-to-vma-iterator.patch
mmap-convert-__vma_adjust-to-use-vma-iterator.patch
mm-pass-through-vma-iterator-to-__vma_adjust.patch
madvise-use-split_vma-instead-of-__split_vma.patch
mm-remove-unnecessary-write-to-vma-iterator-in-__vma_adjust.patch
mm-pass-vma-iterator-through-to-__vma_adjust.patch
mm-add-vma-iterator-to-vma_adjust-arguments.patch
mmap-clean-up-mmap_region-unrolling.patch
mm-change-munmap-splitting-order-and-move_vma.patch
mm-mmap-move-anon_vma-setting-in-__vma_adjust.patch
mm-mmap-refactor-locking-out-of-__vma_adjust.patch
mm-mmap-use-vma_prepare-and-vma_complete-in-vma_expand.patch
mm-mmap-introduce-init_vma_prep-and-init_multi_vma_prep.patch
mm-dont-use-__vma_adjust-in-__split_vma.patch
mm-mmap-dont-use-__vma_adjust-in-shift_arg_pages.patch
mm-mmap-introduce-dup_vma_anon-helper.patch
mm-mmap-convert-do_brk_flags-to-use-vma_prepare-and-vma_complete.patch
mm-mmap-remove-__vma_adjust.patch
vma_merge-set-vma-iterator-to-correct-position.patch
