diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/pgtable.h | 103 |
1 files changed, 7 insertions, 96 deletions
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h index 3fabbb018557..a1326e61d7ee 100644 --- a/include/linux/pgtable.h +++ b/include/linux/pgtable.h @@ -599,6 +599,10 @@ extern void pgtable_trans_huge_deposit(struct mm_struct *mm, pmd_t *pmdp, extern pgtable_t pgtable_trans_huge_withdraw(struct mm_struct *mm, pmd_t *pmdp); #endif +#ifndef arch_needs_pgtable_deposit +#define arch_needs_pgtable_deposit() (false) +#endif + #ifdef CONFIG_TRANSPARENT_HUGEPAGE /* * This is an implementation of pmdp_establish() that is only suitable for an @@ -1300,9 +1304,10 @@ static inline int pud_trans_huge(pud_t pud) } #endif -/* See pmd_none_or_trans_huge_or_clear_bad for discussion. */ -static inline int pud_none_or_trans_huge_or_dev_or_clear_bad(pud_t *pud) +static inline int pud_trans_unstable(pud_t *pud) { +#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \ + defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) pud_t pudval = READ_ONCE(*pud); if (pud_none(pudval) || pud_trans_huge(pudval) || pud_devmap(pudval)) @@ -1311,104 +1316,10 @@ static inline int pud_none_or_trans_huge_or_dev_or_clear_bad(pud_t *pud) pud_clear_bad(pud); return 1; } - return 0; -} - -/* See pmd_trans_unstable for discussion. */ -static inline int pud_trans_unstable(pud_t *pud) -{ -#if defined(CONFIG_TRANSPARENT_HUGEPAGE) && \ - defined(CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD) - return pud_none_or_trans_huge_or_dev_or_clear_bad(pud); -#else - return 0; #endif -} - -#ifndef arch_needs_pgtable_deposit -#define arch_needs_pgtable_deposit() (false) -#endif -/* - * This function is meant to be used by sites walking pagetables with - * the mmap_lock held in read mode to protect against MADV_DONTNEED and - * transhuge page faults. MADV_DONTNEED can convert a transhuge pmd - * into a null pmd and the transhuge page fault can convert a null pmd - * into an hugepmd or into a regular pmd (if the hugepage allocation - * fails). While holding the mmap_lock in read mode the pmd becomes - * stable and stops changing under us only if it's not null and not a - * transhuge pmd. When those races occurs and this function makes a - * difference vs the standard pmd_none_or_clear_bad, the result is - * undefined so behaving like if the pmd was none is safe (because it - * can return none anyway). The compiler level barrier() is critically - * important to compute the two checks atomically on the same pmdval. - * - * For 32bit kernels with a 64bit large pmd_t this automatically takes - * care of reading the pmd atomically to avoid SMP race conditions - * against pmd_populate() when the mmap_lock is hold for reading by the - * caller (a special atomic read not done by "gcc" as in the generic - * version above, is also needed when THP is disabled because the page - * fault can populate the pmd from under us). - */ -static inline int pmd_none_or_trans_huge_or_clear_bad(pmd_t *pmd) -{ - pmd_t pmdval = pmdp_get_lockless(pmd); - /* - * !pmd_present() checks for pmd migration entries - * - * The complete check uses is_pmd_migration_entry() in linux/swapops.h - * But using that requires moving current function and pmd_trans_unstable() - * to linux/swapops.h to resolve dependency, which is too much code move. - * - * !pmd_present() is equivalent to is_pmd_migration_entry() currently, - * because !pmd_present() pages can only be under migration not swapped - * out. - * - * pmd_none() is preserved for future condition checks on pmd migration - * entries and not confusing with this function name, although it is - * redundant with !pmd_present(). - */ - if (pmd_none(pmdval) || pmd_trans_huge(pmdval) || - (IS_ENABLED(CONFIG_ARCH_ENABLE_THP_MIGRATION) && !pmd_present(pmdval))) - return 1; - if (unlikely(pmd_bad(pmdval))) { - pmd_clear_bad(pmd); - return 1; - } return 0; } -/* - * This is a noop if Transparent Hugepage Support is not built into - * the kernel. Otherwise it is equivalent to - * pmd_none_or_trans_huge_or_clear_bad(), and shall only be called in - * places that already verified the pmd is not none and they want to - * walk ptes while holding the mmap sem in read mode (write mode don't - * need this). If THP is not enabled, the pmd can't go away under the - * code even if MADV_DONTNEED runs, but if THP is enabled we need to - * run a pmd_trans_unstable before walking the ptes after - * split_huge_pmd returns (because it may have run when the pmd become - * null, but then a page fault can map in a THP and not a regular page). - */ -static inline int pmd_trans_unstable(pmd_t *pmd) -{ -#ifdef CONFIG_TRANSPARENT_HUGEPAGE - return pmd_none_or_trans_huge_or_clear_bad(pmd); -#else - return 0; -#endif -} - -/* - * the ordering of these checks is important for pmds with _page_devmap set. - * if we check pmd_trans_unstable() first we will trip the bad_pmd() check - * inside of pmd_none_or_trans_huge_or_clear_bad(). this will end up correctly - * returning 1 but not before it spams dmesg with the pmd_clear_bad() output. - */ -static inline int pmd_devmap_trans_unstable(pmd_t *pmd) -{ - return pmd_devmap(*pmd) || pmd_trans_unstable(pmd); -} - #ifndef CONFIG_NUMA_BALANCING /* * Technically a PTE can be PROTNONE even when not doing NUMA balancing but |