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-rw-r--r--mm/mlock.c221
1 files changed, 90 insertions, 131 deletions
diff --git a/mm/mlock.c b/mm/mlock.c
index c83896a72504..8b478350a2a1 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -112,26 +112,49 @@ static void munlock_vma_page(struct page *page)
}
}
-/*
- * mlock a range of pages in the vma.
+/**
+ * __mlock_vma_pages_range() - mlock/munlock a range of pages in the vma.
+ * @vma: target vma
+ * @start: start address
+ * @end: end address
+ * @mlock: 0 indicate munlock, otherwise mlock.
+ *
+ * If @mlock == 0, unlock an mlocked range;
+ * else mlock the range of pages. This takes care of making the pages present ,
+ * too.
*
- * This takes care of making the pages present too.
+ * return 0 on success, negative error code on error.
*
- * vma->vm_mm->mmap_sem must be held for write.
+ * vma->vm_mm->mmap_sem must be held for at least read.
*/
-static int __mlock_vma_pages_range(struct vm_area_struct *vma,
- unsigned long start, unsigned long end)
+static long __mlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ int mlock)
{
struct mm_struct *mm = vma->vm_mm;
unsigned long addr = start;
struct page *pages[16]; /* 16 gives a reasonable batch */
- int write = !!(vma->vm_flags & VM_WRITE);
int nr_pages = (end - start) / PAGE_SIZE;
int ret;
+ int gup_flags = 0;
- VM_BUG_ON(start & ~PAGE_MASK || end & ~PAGE_MASK);
- VM_BUG_ON(start < vma->vm_start || end > vma->vm_end);
- VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem));
+ VM_BUG_ON(start & ~PAGE_MASK);
+ VM_BUG_ON(end & ~PAGE_MASK);
+ VM_BUG_ON(start < vma->vm_start);
+ VM_BUG_ON(end > vma->vm_end);
+ VM_BUG_ON((!rwsem_is_locked(&mm->mmap_sem)) &&
+ (atomic_read(&mm->mm_users) != 0));
+
+ /*
+ * mlock: don't page populate if page has PROT_NONE permission.
+ * munlock: the pages always do munlock althrough
+ * its has PROT_NONE permission.
+ */
+ if (!mlock)
+ gup_flags |= GUP_FLAGS_IGNORE_VMA_PERMISSIONS;
+
+ if (vma->vm_flags & VM_WRITE)
+ gup_flags |= GUP_FLAGS_WRITE;
lru_add_drain_all(); /* push cached pages to LRU */
@@ -146,9 +169,9 @@ static int __mlock_vma_pages_range(struct vm_area_struct *vma,
* disable migration of this page. However, page may
* still be truncated out from under us.
*/
- ret = get_user_pages(current, mm, addr,
+ ret = __get_user_pages(current, mm, addr,
min_t(int, nr_pages, ARRAY_SIZE(pages)),
- write, 0, pages, NULL);
+ gup_flags, pages, NULL);
/*
* This can happen for, e.g., VM_NONLINEAR regions before
* a page has been allocated and mapped at a given offset,
@@ -178,8 +201,12 @@ static int __mlock_vma_pages_range(struct vm_area_struct *vma,
* by the elevated reference, we need only check for
* page truncation (file-cache only).
*/
- if (page->mapping)
- mlock_vma_page(page);
+ if (page->mapping) {
+ if (mlock)
+ mlock_vma_page(page);
+ else
+ munlock_vma_page(page);
+ }
unlock_page(page);
put_page(page); /* ref from get_user_pages() */
@@ -197,125 +224,38 @@ static int __mlock_vma_pages_range(struct vm_area_struct *vma,
return 0; /* count entire vma as locked_vm */
}
-/*
- * private structure for munlock page table walk
- */
-struct munlock_page_walk {
- struct vm_area_struct *vma;
- pmd_t *pmd; /* for migration_entry_wait() */
-};
-
-/*
- * munlock normal pages for present ptes
- */
-static int __munlock_pte_handler(pte_t *ptep, unsigned long addr,
- unsigned long end, struct mm_walk *walk)
-{
- struct munlock_page_walk *mpw = walk->private;
- swp_entry_t entry;
- struct page *page;
- pte_t pte;
-
-retry:
- pte = *ptep;
- /*
- * If it's a swap pte, we might be racing with page migration.
- */
- if (unlikely(!pte_present(pte))) {
- if (!is_swap_pte(pte))
- goto out;
- entry = pte_to_swp_entry(pte);
- if (is_migration_entry(entry)) {
- migration_entry_wait(mpw->vma->vm_mm, mpw->pmd, addr);
- goto retry;
- }
- goto out;
- }
-
- page = vm_normal_page(mpw->vma, addr, pte);
- if (!page)
- goto out;
-
- lock_page(page);
- if (!page->mapping) {
- unlock_page(page);
- goto retry;
- }
- munlock_vma_page(page);
- unlock_page(page);
-
-out:
- return 0;
-}
-
-/*
- * Save pmd for pte handler for waiting on migration entries
- */
-static int __munlock_pmd_handler(pmd_t *pmd, unsigned long addr,
- unsigned long end, struct mm_walk *walk)
-{
- struct munlock_page_walk *mpw = walk->private;
-
- mpw->pmd = pmd;
- return 0;
-}
-
-
-/*
- * munlock a range of pages in the vma using standard page table walk.
- *
- * vma->vm_mm->mmap_sem must be held for write.
- */
-static void __munlock_vma_pages_range(struct vm_area_struct *vma,
- unsigned long start, unsigned long end)
-{
- struct mm_struct *mm = vma->vm_mm;
- struct munlock_page_walk mpw = {
- .vma = vma,
- };
- struct mm_walk munlock_page_walk = {
- .pmd_entry = __munlock_pmd_handler,
- .pte_entry = __munlock_pte_handler,
- .private = &mpw,
- .mm = mm,
- };
-
- VM_BUG_ON(start & ~PAGE_MASK || end & ~PAGE_MASK);
- VM_BUG_ON(!rwsem_is_locked(&vma->vm_mm->mmap_sem));
- VM_BUG_ON(start < vma->vm_start);
- VM_BUG_ON(end > vma->vm_end);
-
- lru_add_drain_all(); /* push cached pages to LRU */
- walk_page_range(start, end, &munlock_page_walk);
- lru_add_drain_all(); /* to update stats */
-}
-
#else /* CONFIG_UNEVICTABLE_LRU */
/*
* Just make pages present if VM_LOCKED. No-op if unlocking.
*/
-static int __mlock_vma_pages_range(struct vm_area_struct *vma,
- unsigned long start, unsigned long end)
+static long __mlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end,
+ int mlock)
{
- if (vma->vm_flags & VM_LOCKED)
+ if (mlock && (vma->vm_flags & VM_LOCKED))
make_pages_present(start, end);
return 0;
}
-
-/*
- * munlock a range of pages in the vma -- no-op.
- */
-static void __munlock_vma_pages_range(struct vm_area_struct *vma,
- unsigned long start, unsigned long end)
-{
-}
#endif /* CONFIG_UNEVICTABLE_LRU */
-/*
- * mlock all pages in this vma range. For mmap()/mremap()/...
+/**
+ * mlock_vma_pages_range() - mlock pages in specified vma range.
+ * @vma - the vma containing the specfied address range
+ * @start - starting address in @vma to mlock
+ * @end - end address [+1] in @vma to mlock
+ *
+ * For mmap()/mremap()/expansion of mlocked vma.
+ *
+ * return 0 on success for "normal" vmas.
+ *
+ * return number of pages [> 0] to be removed from locked_vm on success
+ * of "special" vmas.
+ *
+ * return negative error if vma spanning @start-@range disappears while
+ * mmap semaphore is dropped. Unlikely?
*/
-int mlock_vma_pages_range(struct vm_area_struct *vma,
+long mlock_vma_pages_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end)
{
struct mm_struct *mm = vma->vm_mm;
@@ -331,8 +271,10 @@ int mlock_vma_pages_range(struct vm_area_struct *vma,
if (!((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
is_vm_hugetlb_page(vma) ||
vma == get_gate_vma(current))) {
+ long error;
downgrade_write(&mm->mmap_sem);
- nr_pages = __mlock_vma_pages_range(vma, start, end);
+
+ error = __mlock_vma_pages_range(vma, start, end, 1);
up_read(&mm->mmap_sem);
/* vma can change or disappear */
@@ -340,8 +282,9 @@ int mlock_vma_pages_range(struct vm_area_struct *vma,
vma = find_vma(mm, start);
/* non-NULL vma must contain @start, but need to check @end */
if (!vma || end > vma->vm_end)
- return -EAGAIN;
- return nr_pages;
+ return -ENOMEM;
+
+ return 0; /* hide other errors from mmap(), et al */
}
/*
@@ -356,17 +299,33 @@ int mlock_vma_pages_range(struct vm_area_struct *vma,
no_mlock:
vma->vm_flags &= ~VM_LOCKED; /* and don't come back! */
- return nr_pages; /* pages NOT mlocked */
+ return nr_pages; /* error or pages NOT mlocked */
}
/*
- * munlock all pages in vma. For munmap() and exit().
+ * munlock_vma_pages_range() - munlock all pages in the vma range.'
+ * @vma - vma containing range to be munlock()ed.
+ * @start - start address in @vma of the range
+ * @end - end of range in @vma.
+ *
+ * For mremap(), munmap() and exit().
+ *
+ * Called with @vma VM_LOCKED.
+ *
+ * Returns with VM_LOCKED cleared. Callers must be prepared to
+ * deal with this.
+ *
+ * We don't save and restore VM_LOCKED here because pages are
+ * still on lru. In unmap path, pages might be scanned by reclaim
+ * and re-mlocked by try_to_{munlock|unmap} before we unmap and
+ * free them. This will result in freeing mlocked pages.
*/
-void munlock_vma_pages_all(struct vm_area_struct *vma)
+void munlock_vma_pages_range(struct vm_area_struct *vma,
+ unsigned long start, unsigned long end)
{
vma->vm_flags &= ~VM_LOCKED;
- __munlock_vma_pages_range(vma, vma->vm_start, vma->vm_end);
+ __mlock_vma_pages_range(vma, start, end, 0);
}
/*
@@ -443,7 +402,7 @@ success:
*/
downgrade_write(&mm->mmap_sem);
- ret = __mlock_vma_pages_range(vma, start, end);
+ ret = __mlock_vma_pages_range(vma, start, end, 1);
if (ret > 0) {
mm->locked_vm -= ret;
ret = 0;
@@ -460,7 +419,7 @@ success:
*prev = find_vma(mm, start);
/* non-NULL *prev must contain @start, but need to check @end */
if (!(*prev) || end > (*prev)->vm_end)
- ret = -EAGAIN;
+ ret = -ENOMEM;
} else {
/*
* TODO: for unlocking, pages will already be resident, so
@@ -469,7 +428,7 @@ success:
* while. Should we downgrade the semaphore for both lock
* AND unlock ?
*/
- __munlock_vma_pages_range(vma, start, end);
+ __mlock_vma_pages_range(vma, start, end, 0);
}
out: