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Commit 48b00ceb authored by Jann Horn's avatar Jann Horn Committed by Greg Kroah-Hartman
Browse files

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

commit 2ba99c5e08812494bc57f319fb562f527d9bacd8 upstream.

Since commit 70cbc3cc78a99 ("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: ba76149f ("thp: khugepaged")
Signed-off-by: default avatarJann Horn <jannh@google.com>
Reviewed-by: default avatarYang Shi <shy828301@gmail.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
[manual backport: two of the three places in khugepaged that can free
ptes were refactored into a common helper between 5.15 and 6.0;
TLB flushing was refactored between 5.4 and 5.10]
Signed-off-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarSasha Levin <sashal@kernel.org>
parent 324abbd8

include/asm-generic/tlb.h

+4 −0
Original line number Diff line number Diff line
@@ -190,12 +190,16 @@ 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 HAVE_RCU_TABLE_FREE

#endif



static inline void tlb_remove_table_sync_one(void) { }



#endif /* CONFIG_HAVE_RCU_TABLE_FREE */

mm/khugepaged.c

+3 −0
Original line number Diff line number Diff line
@@ -1060,6 +1060,7 @@ static void collapse_huge_page(struct mm_struct *mm, 
	_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);

	isolated = __collapse_huge_page_isolate(vma, address, pte);
@@ -1407,6 +1408,7 @@ void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr) 
	/* step 4: collapse pmd */

	_pmd = pmdp_collapse_flush(vma, haddr, pmd);

	mm_dec_nr_ptes(mm);

	tlb_remove_table_sync_one();

	pte_free(mm, pmd_pgtable(_pmd));



	i_mmap_unlock_write(vma->vm_file->f_mapping);
@@ -1494,6 +1496,7 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff) 
				/* assume page table is clear */

				_pmd = pmdp_collapse_flush(vma, addr, pmd);

				mm_dec_nr_ptes(mm);

				tlb_remove_table_sync_one();

				pte_free(mm, pmd_pgtable(_pmd));

			}

			up_write(&mm->mmap_sem);

mm/mmu_gather.c

+5 −0
Original line number Diff line number Diff line
@@ -117,6 +117,11 @@ static void tlb_remove_table_smp_sync(void *arg) 
	/* Simply deliver the interrupt */

}



void tlb_remove_table_sync_one(void)

{

	smp_call_function(tlb_remove_table_smp_sync, NULL, 1);

}



static void tlb_remove_table_one(void *table)

{

	/*