Messages in this thread Patch in this message | | | Subject | [PATCH 05/10] mm: mincore: clean up hugetlbfs handling (part 1) | From | Dave Hansen <> | Date | Mon, 02 Jun 2014 14:36:51 -0700 |
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From: Dave Hansen <dave.hansen@linux.intel.com>
The page walker functions are only called _via_ the page walker. I don't see this changing any time soon. The page walker only calls walk->hugetlb_entry() under an #ifdef CONFIG_HUGETLB_PAGE.
With this in place, I think putting BUG()s in the ->hugetlb_entry handlers is a bit like wearing a belt and suspenders.
This axes the BUG() from the mincore ->hugetlb_entry along with the #ifdef. The compiler is more than smart enough to do the right thing when it sees:
if (1) return; // unreachable
The only downside here is that we now need some header stubs for huge_pte_none() / huge_pte_get().
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> ---
b/include/linux/hugetlb.h | 10 ++++++++++ b/mm/mincore.c | 9 +++++---- 2 files changed, 15 insertions(+), 4 deletions(-)
diff -puN include/linux/hugetlb.h~cleanup-hugetlbfs-mincore-1 include/linux/hugetlb.h --- a/include/linux/hugetlb.h~cleanup-hugetlbfs-mincore-1 2014-06-02 14:20:20.144845525 -0700 +++ b/include/linux/hugetlb.h 2014-06-02 14:20:20.149845750 -0700 @@ -458,6 +458,16 @@ static inline spinlock_t *huge_pte_lockp { return &mm->page_table_lock; } +static inline int huge_pte_none(pte_t pte) +{ + WARN_ONCE(1, "%s() called when hugetlbfs disabled", __func__); + return 1; +} +static inline pte_t huge_ptep_get(pte_t *pte) +{ + WARN_ONCE(1, "%s() called when hugetlbfs disabled", __func__); + return __pte(0); +} #endif /* CONFIG_HUGETLB_PAGE */ static inline spinlock_t *huge_pte_lock(struct hstate *h, diff -puN mm/mincore.c~cleanup-hugetlbfs-mincore-1 mm/mincore.c --- a/mm/mincore.c~cleanup-hugetlbfs-mincore-1 2014-06-02 14:20:20.146845615 -0700 +++ b/mm/mincore.c 2014-06-02 14:20:20.149845750 -0700 @@ -23,8 +23,12 @@ static int mincore_hugetlb_page_range(pt unsigned long addr, unsigned long end, struct mm_walk *walk) { -#ifdef CONFIG_HUGETLB_PAGE unsigned char *vec = walk->private; + + /* This is as good as an explicit ifdef */ + if (!is_vm_hugetlb_page(walk->vma)) + return 0; + while (1) { int present = !huge_pte_none(huge_ptep_get(ptep)); while (1) { @@ -38,9 +42,6 @@ static int mincore_hugetlb_page_range(pt break; } } -#else - BUG(); -#endif return 0; } _
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