powerpc/thp: Fix crash on mremap
This patch fix the below crash NIP [c00000000004cee4] .__hash_page_thp+0x2a4/0x440 LR [c0000000000439ac] .hash_page+0x18c/0x5e0 ... Call Trace: [c000000736103c40] [00001ffffb000000] 0x1ffffb000000(unreliable) [437908.479693] [c000000736103d50] [c0000000000439ac] .hash_page+0x18c/0x5e0 [437908.479699] [c000000736103e30] [c00000000000924c] .do_hash_page+0x4c/0x58 On ppc64 we use the pgtable for storing the hpte slot information and store address to the pgtable at a constant offset (PTRS_PER_PMD) from pmd. On mremap, when we switch the pmd, we need to withdraw and deposit the pgtable again, so that we find the pgtable at PTRS_PER_PMD offset from new pmd. We also want to move the withdraw and deposit before the set_pmd so that, when page fault find the pmd as trans huge we can be sure that pgtable can be located at the offset. Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com> Acked-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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@ -558,5 +558,19 @@ extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp);
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#define __HAVE_ARCH_PMDP_INVALIDATE
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extern void pmdp_invalidate(struct vm_area_struct *vma, unsigned long address,
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pmd_t *pmdp);
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#define pmd_move_must_withdraw pmd_move_must_withdraw
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typedef struct spinlock spinlock_t;
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static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
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spinlock_t *old_pmd_ptl)
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{
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/*
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* Archs like ppc64 use pgtable to store per pmd
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* specific information. So when we switch the pmd,
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* we should also withdraw and deposit the pgtable
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*/
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return true;
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}
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_POWERPC_PGTABLE_PPC64_H_ */
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@ -558,6 +558,18 @@ static inline pmd_t pmd_read_atomic(pmd_t *pmdp)
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}
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#endif
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#ifndef pmd_move_must_withdraw
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static inline int pmd_move_must_withdraw(spinlock_t *new_pmd_ptl,
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spinlock_t *old_pmd_ptl)
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{
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/*
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* With split pmd lock we also need to move preallocated
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* PTE page table if new_pmd is on different PMD page table.
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*/
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return new_pmd_ptl != old_pmd_ptl;
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}
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#endif
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/*
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* This function is meant to be used by sites walking pagetables with
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* the mmap_sem hold in read mode to protect against MADV_DONTNEED and
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@ -1502,19 +1502,15 @@ int move_huge_pmd(struct vm_area_struct *vma, struct vm_area_struct *new_vma,
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spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING);
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pmd = pmdp_get_and_clear(mm, old_addr, old_pmd);
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VM_BUG_ON(!pmd_none(*new_pmd));
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set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
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if (new_ptl != old_ptl) {
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pgtable_t pgtable;
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/*
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* Move preallocated PTE page table if new_pmd is on
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* different PMD page table.
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*/
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if (pmd_move_must_withdraw(new_ptl, old_ptl)) {
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pgtable_t pgtable;
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pgtable = pgtable_trans_huge_withdraw(mm, old_pmd);
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pgtable_trans_huge_deposit(mm, new_pmd, pgtable);
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spin_unlock(new_ptl);
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}
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set_pmd_at(mm, new_addr, new_pmd, pmd_mksoft_dirty(pmd));
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if (new_ptl != old_ptl)
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spin_unlock(new_ptl);
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spin_unlock(old_ptl);
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}
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out:
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