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mm/khugepaged: fix GUP-fast interaction by sending IPI 

Since commit 70cbc3cc78 ("mm: gup: fix the fast GUP race against THP
collapse"), the lockless_pages_from_mm() fastpath rechecks the pmd_t to
ensure that the page table was not removed by khugepaged in between.

However, lockless_pages_from_mm() still requires that the page table is
not concurrently freed.  Fix it by sending IPIs (if the architecture uses
semi-RCU-style page table freeing) before freeing/reusing page tables.

Link: https://lkml.kernel.org/r/20221129154730.2274278-2-jannh@google.com
Link: https://lkml.kernel.org/r/20221128180252.1684965-2-jannh@google.com
Link: https://lkml.kernel.org/r/20221125213714.4115729-2-jannh@google.com
Fixes: ba76149f47 ("thp: khugepaged")
Signed-off-by: Jann Horn <jannh@google.com>
Reviewed-by: Yang Shi <shy828301@gmail.com>
Acked-by: David Hildenbrand <david@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jann Horn 2022-11-25 22:37:13 +01:00 committed by Andrew Morton
parent 8d3c106e19
commit 2ba99c5e08
3 changed files with 7 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
include/asm-generic/tlb.h
View File

@ -222,12 +222,16 @@ extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
#define tlb_needs_table_invalidate() (true)
#endif
void tlb_remove_table_sync_one(void);
#else
#ifdef tlb_needs_table_invalidate
#error tlb_needs_table_invalidate() requires MMU_GATHER_RCU_TABLE_FREE
#endif
static inline void tlb_remove_table_sync_one(void) { }
#endif /* CONFIG_MMU_GATHER_RCU_TABLE_FREE */

2
mm/khugepaged.c
View File

@ -1051,6 +1051,7 @@ static int collapse_huge_page(struct mm_struct *mm, unsigned long address,
_pmd = pmdp_collapse_flush(vma, address, pmd);
spin_unlock(pmd_ptl);
mmu_notifier_invalidate_range_end(&range);
tlb_remove_table_sync_one();
spin_lock(pte_ptl);
result = __collapse_huge_page_isolate(vma, address, pte, cc,
@ -1410,6 +1411,7 @@ static void collapse_and_free_pmd(struct mm_struct *mm, struct vm_area_struct *v
lockdep_assert_held_write(&vma->anon_vma->root->rwsem);
pmd = pmdp_collapse_flush(vma, addr, pmdp);
tlb_remove_table_sync_one();
mm_dec_nr_ptes(mm);
page_table_check_pte_clear_range(mm, addr, pmd);
pte_free(mm, pmd_pgtable(pmd));

4
mm/mmu_gather.c
View File

@ -153,7 +153,7 @@ static void tlb_remove_table_smp_sync(void *arg)
/* Simply deliver the interrupt */
}
static void tlb_remove_table_sync_one(void)
void tlb_remove_table_sync_one(void)
{
/*
* This isn't an RCU grace period and hence the page-tables cannot be
@ -177,8 +177,6 @@ static void tlb_remove_table_free(struct mmu_table_batch *batch)
#else /* !CONFIG_MMU_GATHER_RCU_TABLE_FREE */
static void tlb_remove_table_sync_one(void) { }
static void tlb_remove_table_free(struct mmu_table_batch *batch)
{
__tlb_remove_table_free(batch);