mm: khugepaged: make khugepaged_enter() void function

The most callers of khugepaged_enter() don't care about the return value.
Only dup_mmap(), anonymous THP page fault and MADV_HUGEPAGE handle the
error by returning -ENOMEM.  Actually it is not harmful for them to ignore
the error case either.  It also sounds overkilling to fail fork() and page
fault early due to khugepaged_enter() error, and MADV_HUGEPAGE does set
VM_HUGEPAGE flag regardless of the error.

Link: https://lkml.kernel.org/r/20220510203222.24246-6-shy828301@gmail.com
Signed-off-by: Yang Shi <shy828301@gmail.com>
Acked-by: Song Liu <song@kernel.org>
Acked-by: Vlastmil Babka <vbabka@suse.cz>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Rik van Riel <riel@surriel.com>
Cc: Song Liu <songliubraving@fb.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h
index 2fcc018..0423d36 100644 (file)
--- a/include/linux/khugepaged.h
+++ b/include/linux/khugepaged.h
@@ -12,10 +12,10 @@ extern struct attribute_group khugepaged_attr_group;
 extern int khugepaged_init(void);
 extern void khugepaged_destroy(void);
 extern int start_stop_khugepaged(void);
-extern int __khugepaged_enter(struct mm_struct *mm);
+extern void __khugepaged_enter(struct mm_struct *mm);
 extern void __khugepaged_exit(struct mm_struct *mm);
-extern int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
-                                     unsigned long vm_flags);
+extern void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
+                                      unsigned long vm_flags);
 extern void khugepaged_min_free_kbytes_update(void);
 #ifdef CONFIG_SHMEM
 extern void collapse_pte_mapped_thp(struct mm_struct *mm, unsigned long addr);
@@ -40,11 +40,10 @@ static inline void collapse_pte_mapped_thp(struct mm_struct *mm,
        (transparent_hugepage_flags &                           \
         (1<<TRANSPARENT_HUGEPAGE_DEFRAG_KHUGEPAGED_FLAG))
 
-static inline int khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
+static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 {
        if (test_bit(MMF_VM_HUGEPAGE, &oldmm->flags))
-               return __khugepaged_enter(mm);
-       return 0;
+               __khugepaged_enter(mm);
 }
 
 static inline void khugepaged_exit(struct mm_struct *mm)
@@ -53,7 +52,7 @@ static inline void khugepaged_exit(struct mm_struct *mm)
                __khugepaged_exit(mm);
 }
 
-static inline int khugepaged_enter(struct vm_area_struct *vma,
+static inline void khugepaged_enter(struct vm_area_struct *vma,
                                   unsigned long vm_flags)
 {
        if (!test_bit(MMF_VM_HUGEPAGE, &vma->vm_mm->flags))
@@ -62,27 +61,22 @@ static inline int khugepaged_enter(struct vm_area_struct *vma,
                     (khugepaged_req_madv() && (vm_flags & VM_HUGEPAGE))) &&
                    !(vm_flags & VM_NOHUGEPAGE) &&
                    !test_bit(MMF_DISABLE_THP, &vma->vm_mm->flags))
-                       if (__khugepaged_enter(vma->vm_mm))
-                               return -ENOMEM;
-       return 0;
+                       __khugepaged_enter(vma->vm_mm);
 }
 #else /* CONFIG_TRANSPARENT_HUGEPAGE */
-static inline int khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
+static inline void khugepaged_fork(struct mm_struct *mm, struct mm_struct *oldmm)
 {
-       return 0;
 }
 static inline void khugepaged_exit(struct mm_struct *mm)
 {
 }
-static inline int khugepaged_enter(struct vm_area_struct *vma,
-                                  unsigned long vm_flags)
+static inline void khugepaged_enter(struct vm_area_struct *vma,
+                                   unsigned long vm_flags)
 {
-       return 0;
 }
-static inline int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
-                                            unsigned long vm_flags)
+static inline void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
+                                             unsigned long vm_flags)
 {
-       return 0;
 }
 static inline void collapse_pte_mapped_thp(struct mm_struct *mm,
                                           unsigned long addr)

diff --git a/kernel/fork.c b/kernel/fork.c
index 9796897..0d13baf 100644 (file)
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -612,9 +612,7 @@ static __latent_entropy int dup_mmap(struct mm_struct *mm,
        retval = ksm_fork(mm, oldmm);
        if (retval)
                goto out;
-       retval = khugepaged_fork(mm, oldmm);
-       if (retval)
-               goto out;
+       khugepaged_fork(mm, oldmm);
 
        prev = NULL;
        for (mpnt = oldmm->mmap; mpnt; mpnt = mpnt->vm_next) {

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 1a00bdf..efd06af 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -726,8 +726,8 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_fault *vmf)
                return VM_FAULT_FALLBACK;
        if (unlikely(anon_vma_prepare(vma)))
                return VM_FAULT_OOM;
-       if (unlikely(khugepaged_enter(vma, vma->vm_flags)))
-               return VM_FAULT_OOM;
+       khugepaged_enter(vma, vma->vm_flags);
+
        if (!(vmf->flags & FAULT_FLAG_WRITE) &&
                        !mm_forbids_zeropage(vma->vm_mm) &&
                        transparent_hugepage_use_zero_page()) {

diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index 1f4822d..b43b294 100644 (file)
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -365,8 +365,7 @@ int hugepage_madvise(struct vm_area_struct *vma,
                 * register it here without waiting a page fault that
                 * may not happen any time soon.
                 */
-               if (khugepaged_enter_vma_merge(vma, *vm_flags))
-                       return -ENOMEM;
+               khugepaged_enter_vma_merge(vma, *vm_flags);
                break;
        case MADV_NOHUGEPAGE:
                *vm_flags &= ~VM_HUGEPAGE;
@@ -475,20 +474,20 @@ static bool hugepage_vma_check(struct vm_area_struct *vma,
        return true;
 }
 
-int __khugepaged_enter(struct mm_struct *mm)
+void __khugepaged_enter(struct mm_struct *mm)
 {
        struct mm_slot *mm_slot;
        int wakeup;
 
        mm_slot = alloc_mm_slot();
        if (!mm_slot)
-               return -ENOMEM;
+               return;
 
        /* __khugepaged_exit() must not run from under us */
        VM_BUG_ON_MM(khugepaged_test_exit(mm), mm);
        if (unlikely(test_and_set_bit(MMF_VM_HUGEPAGE, &mm->flags))) {
                free_mm_slot(mm_slot);
-               return 0;
+               return;
        }
 
        spin_lock(&khugepaged_mm_lock);
@@ -504,11 +503,9 @@ int __khugepaged_enter(struct mm_struct *mm)
        mmgrab(mm);
        if (wakeup)
                wake_up_interruptible(&khugepaged_wait);
-
-       return 0;
 }
 
-int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
+void khugepaged_enter_vma_merge(struct vm_area_struct *vma,
                               unsigned long vm_flags)
 {
        unsigned long hstart, hend;
@@ -519,13 +516,12 @@ int khugepaged_enter_vma_merge(struct vm_area_struct *vma,
         * file-private shmem THP is not supported.
         */
        if (!hugepage_vma_check(vma, vm_flags))
-               return 0;
+               return;
 
        hstart = (vma->vm_start + ~HPAGE_PMD_MASK) & HPAGE_PMD_MASK;
        hend = vma->vm_end & HPAGE_PMD_MASK;
        if (hstart < hend)
-               return khugepaged_enter(vma, vm_flags);
-       return 0;
+               khugepaged_enter(vma, vm_flags);
 }
 
 void __khugepaged_exit(struct mm_struct *mm)