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

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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: ba76149f47d8 ("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>
[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;
TLB flushing was refactored between 4.19 and 5.4;
pmd collapse for PTE-mapped THP was only added in 5.4;
ugly hack for s390 in <=4.19 and arm]
Signed-off-by: Jann Horn <jannh@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Jann Horn 2022-11-25 22:37:13 +01:00 committed by Greg Kroah-Hartman
parent 4b605cd1fb
commit 588be4a04b
3 changed files with 26 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
include/asm-generic/tlb.h
View File

@ -60,6 +60,12 @@ struct mmu_table_batch {
extern void tlb_table_flush(struct mmu_gather *tlb);
extern void tlb_remove_table(struct mmu_gather *tlb, void *table);
void tlb_remove_table_sync_one(void);
#else
static inline void tlb_remove_table_sync_one(void) { }
#endif
/*

15
mm/khugepaged.c
View File

@ -20,6 +20,19 @@
#include <asm/pgalloc.h>
#include "internal.h"
/* gross hack for <=4.19 stable */
#if defined(CONFIG_S390) || defined(CONFIG_ARM)
static void tlb_remove_table_smp_sync(void *arg)
{
/* Simply deliver the interrupt */
}
static void tlb_remove_table_sync_one(void)
{
smp_call_function(tlb_remove_table_smp_sync, NULL, 1);
}
#endif
enum scan_result {
SCAN_FAIL,
SCAN_SUCCEED,
@ -1044,6 +1057,7 @@ 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(mm, mmun_start, mmun_end);
tlb_remove_table_sync_one();
spin_lock(pte_ptl);
isolated = __collapse_huge_page_isolate(vma, address, pte);
@ -1293,6 +1307,7 @@ static void retract_page_tables(struct address_space *mapping, pgoff_t pgoff)
_pmd = pmdp_collapse_flush(vma, addr, pmd);
spin_unlock(ptl);
atomic_long_dec(&mm->nr_ptes);
tlb_remove_table_sync_one();
pte_free(mm, pmd_pgtable(_pmd));
}
up_write(&mm->mmap_sem);

5
mm/memory.c
View File

@ -349,6 +349,11 @@ 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)
{
/*