The patch titled
Subject: mm/mremap: retry if either pte_offset_map_*lock() fails
has been added to the -mm mm-unstable branch. Its filename is
mm-mremap-retry-if-either-pte_offset_map_lock-fails.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-mremap-retry-if-either-pte_offset_map_lock-fails.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: Hugh Dickins <hughd@xxxxxxxxxx>
Subject: mm/mremap: retry if either pte_offset_map_*lock() fails
Date: Thu, 8 Jun 2023 18:32:47 -0700 (PDT)
move_ptes() return -EAGAIN if pte_offset_map_lock() of old fails, or if
pte_offset_map_nolock() of new fails: move_page_tables() retry if so.
But that does need a pmd_none() check inside, to stop endless loop when
huge shmem is truncated (thank you to syzbot); and move_huge_pmd() must
tolerate that a page table might have been allocated there just before (of
course it would be more satisfying to remove the empty page table, but
this is not a path worth optimizing).
Link: https://lkml.kernel.org/r/65e5e84a-f04-947-23f2-b97d3462e1e@xxxxxxxxxx
Signed-off-by: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
Cc: Axel Rasmussen <axelrasmussen@xxxxxxxxxx>
Cc: Christophe Leroy <christophe.leroy@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: "Huang, Ying" <ying.huang@xxxxxxxxx>
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Kirill A. Shutemov <kirill.shutemov@xxxxxxxxxxxxxxx>
Cc: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Miaohe Lin <linmiaohe@xxxxxxxxxx>
Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
Cc: Mike Rapoport (IBM) <rppt@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Naoya Horiguchi <naoya.horiguchi@xxxxxxx>
Cc: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Cc: Peter Xu <peterx@xxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Qi Zheng <zhengqi.arch@xxxxxxxxxxxxx>
Cc: Ralph Campbell <rcampbell@xxxxxxxxxx>
Cc: Ryan Roberts <ryan.roberts@xxxxxxx>
Cc: SeongJae Park <sj@xxxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Steven Price <steven.price@xxxxxxx>
Cc: Suren Baghdasaryan <surenb@xxxxxxxxxx>
Cc: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
Cc: Will Deacon <will@xxxxxxxxxx>
Cc: Yang Shi <shy828301@xxxxxxxxx>
Cc: Yu Zhao <yuzhao@xxxxxxxxxx>
Cc: Zack Rusin <zackr@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/huge_memory.c | 5 +++--
mm/mremap.c | 28 ++++++++++++++++++++--------
2 files changed, 23 insertions(+), 10 deletions(-)
--- a/mm/huge_memory.c~mm-mremap-retry-if-either-pte_offset_map_lock-fails
+++ a/mm/huge_memory.c
@@ -1760,9 +1760,10 @@ bool move_huge_pmd(struct vm_area_struct
/*
* The destination pmd shouldn't be established, free_pgtables()
- * should have release it.
+ * should have released it; but move_page_tables() might have already
+ * inserted a page table, if racing against shmem/file collapse.
*/
- if (WARN_ON(!pmd_none(*new_pmd))) {
+ if (!pmd_none(*new_pmd)) {
VM_BUG_ON(pmd_trans_huge(*new_pmd));
return false;
}
--- a/mm/mremap.c~mm-mremap-retry-if-either-pte_offset_map_lock-fails
+++ a/mm/mremap.c
@@ -133,7 +133,7 @@ static pte_t move_soft_dirty_pte(pte_t p
return pte;
}
-static void move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
+static int move_ptes(struct vm_area_struct *vma, pmd_t *old_pmd,
unsigned long old_addr, unsigned long old_end,
struct vm_area_struct *new_vma, pmd_t *new_pmd,
unsigned long new_addr, bool need_rmap_locks)
@@ -143,6 +143,7 @@ static void move_ptes(struct vm_area_str
spinlock_t *old_ptl, *new_ptl;
bool force_flush = false;
unsigned long len = old_end - old_addr;
+ int err = 0;
/*
* When need_rmap_locks is true, we take the i_mmap_rwsem and anon_vma
@@ -170,8 +171,16 @@ static void move_ptes(struct vm_area_str
* pte locks because exclusive mmap_lock prevents deadlock.
*/
old_pte = pte_offset_map_lock(mm, old_pmd, old_addr, &old_ptl);
- new_pte = pte_offset_map(new_pmd, new_addr);
- new_ptl = pte_lockptr(mm, new_pmd);
+ if (!old_pte) {
+ err = -EAGAIN;
+ goto out;
+ }
+ new_pte = pte_offset_map_nolock(mm, new_pmd, new_addr, &new_ptl);
+ if (!new_pte) {
+ pte_unmap_unlock(old_pte, old_ptl);
+ err = -EAGAIN;
+ goto out;
+ }
if (new_ptl != old_ptl)
spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
flush_tlb_batched_pending(vma->vm_mm);
@@ -208,8 +217,10 @@ static void move_ptes(struct vm_area_str
spin_unlock(new_ptl);
pte_unmap(new_pte - 1);
pte_unmap_unlock(old_pte - 1, old_ptl);
+out:
if (need_rmap_locks)
drop_rmap_locks(vma);
+ return err;
}
#ifndef arch_supports_page_table_move
@@ -537,6 +548,7 @@ unsigned long move_page_tables(struct vm
new_pmd = alloc_new_pmd(vma->vm_mm, vma, new_addr);
if (!new_pmd)
break;
+again:
if (is_swap_pmd(*old_pmd) || pmd_trans_huge(*old_pmd) ||
pmd_devmap(*old_pmd)) {
if (extent == HPAGE_PMD_SIZE &&
@@ -544,8 +556,6 @@ unsigned long move_page_tables(struct vm
old_pmd, new_pmd, need_rmap_locks))
continue;
split_huge_pmd(vma, old_pmd, old_addr);
- if (pmd_trans_unstable(old_pmd))
- continue;
} else if (IS_ENABLED(CONFIG_HAVE_MOVE_PMD) &&
extent == PMD_SIZE) {
/*
@@ -556,11 +566,13 @@ unsigned long move_page_tables(struct vm
old_pmd, new_pmd, true))
continue;
}
-
+ if (pmd_none(*old_pmd))
+ continue;
if (pte_alloc(new_vma->vm_mm, new_pmd))
break;
- move_ptes(vma, old_pmd, old_addr, old_addr + extent, new_vma,
- new_pmd, new_addr, need_rmap_locks);
+ if (move_ptes(vma, old_pmd, old_addr, old_addr + extent,
+ new_vma, new_pmd, new_addr, need_rmap_locks) < 0)
+ goto again;
}
mmu_notifier_invalidate_range_end(&range);
_
Patches currently in -mm which might be from hughd@xxxxxxxxxx are
arm-allow-pte_offset_map-to-fail.patch
arm64-allow-pte_offset_map-to-fail.patch
arm64-hugetlb-pte_alloc_huge-pte_offset_huge.patch
ia64-hugetlb-pte_alloc_huge-pte_offset_huge.patch
m68k-allow-pte_offset_map-to-fail.patch
microblaze-allow-pte_offset_map-to-fail.patch
mips-update_mmu_cache-can-replace-__update_tlb.patch
mips-update_mmu_cache-can-replace-__update_tlb-fix.patch
parisc-add-pte_unmap-to-balance-get_ptep.patch
parisc-unmap_uncached_pte-use-pte_offset_kernel.patch
parisc-hugetlb-pte_alloc_huge-pte_offset_huge.patch
powerpc-kvmppc_unmap_free_pmd-pte_offset_kernel.patch
powerpc-allow-pte_offset_map-to-fail.patch
powerpc-hugetlb-pte_alloc_huge.patch
riscv-hugetlb-pte_alloc_huge-pte_offset_huge.patch
s390-allow-pte_offset_map_lock-to-fail.patch
s390-gmap-use-pte_unmap_unlock-not-spin_unlock.patch
sh-hugetlb-pte_alloc_huge-pte_offset_huge.patch
sparc-hugetlb-pte_alloc_huge-pte_offset_huge.patch
sparc-allow-pte_offset_map-to-fail.patch
sparc-iounit-and-iommu-use-pte_offset_kernel.patch
x86-allow-get_locked_pte-to-fail.patch
x86-sme_populate_pgd-use-pte_offset_kernel.patch
xtensa-add-pte_unmap-to-balance-pte_offset_map.patch
mm-use-pmdp_get_lockless-without-surplus-barrier.patch
mm-migrate-remove-cruft-from-migration_entry_waits.patch
mm-pgtable-kmap_local_page-instead-of-kmap_atomic.patch
mm-pgtable-allow-pte_offset_map-to-fail.patch
mm-filemap-allow-pte_offset_map_lock-to-fail.patch
mm-page_vma_mapped-delete-bogosity-in-page_vma_mapped_walk.patch
mm-page_vma_mapped-reformat-map_pte-with-less-indentation.patch
mm-page_vma_mapped-pte_offset_map_nolock-not-pte_lockptr.patch
mm-pagewalkers-action_again-if-pte_offset_map_lock-fails.patch
mm-pagewalk-walk_pte_range-allow-for-pte_offset_map.patch
mm-vmwgfx-simplify-pmd-pud-mapping-dirty-helpers.patch
mm-vmalloc-vmalloc_to_page-use-pte_offset_kernel.patch
mm-hmm-retry-if-pte_offset_map-fails.patch
mm-userfaultfd-retry-if-pte_offset_map-fails.patch
mm-userfaultfd-allow-pte_offset_map_lock-to-fail.patch
mm-debug_vm_pgtablepage_table_check-warn-pte-map-fails.patch
mm-various-give-up-if-pte_offset_map-fails.patch
mm-mprotect-delete-pmd_none_or_clear_bad_unless_trans_huge.patch
mm-mremap-retry-if-either-pte_offset_map_lock-fails.patch
mm-madvise-clean-up-pte_offset_map_lock-scans.patch
mm-madvise-clean-up-force_shm_swapin_readahead.patch
mm-swapoff-allow-pte_offset_map-to-fail.patch
mm-mglru-allow-pte_offset_map_nolock-to-fail.patch
mm-migrate_device-allow-pte_offset_map_lock-to-fail.patch
mm-gup-remove-foll_split_pmd-use-of-pmd_trans_unstable.patch
mm-huge_memory-split-huge-pmd-under-one-pte_offset_map.patch
mm-khugepaged-allow-pte_offset_map-to-fail.patch
mm-memory-allow-pte_offset_map-to-fail.patch
mm-memory-handle_pte_fault-use-pte_offset_map_nolock.patch
mm-pgtable-delete-pmd_trans_unstable-and-friends.patch
mm-swap-swap_vma_readahead-do-the-pte_offset_map.patch
perf-core-allow-pte_offset_map-to-fail.patch
