[PATCH 2/4] mm: rename __mlock_vma_pages_range() to populate_vma_page_range()

Kirill A. Shutemov
2015-02-11T17:12:18Z

__mlock_vma_pages_range() doesn't necessary mlock pages. It depends on
vma flags. The same codepath is used for MAP_POPULATE.

Let's rename __mlock_vma_pages_range() to populate_vma_page_range().

This patch also drops mlock_vma_pages_range() references from
documentation. It has gone in commit cea10a19b797.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Michel Lespinasse <walken@google.com>
---
Documentation/vm/unevictable-lru.txt | 26 ++++++++------------------
mm/internal.h | 2 +-
mm/mlock.c | 12 ++++++------
mm/mmap.c | 4 ++--
4 files changed, 17 insertions(+), 27 deletions(-)

diff --git a/Documentation/vm/unevictable-lru.txt b/Documentation/vm/unevictable-lru.txt
index 744f82f86c58..86cb4624fc5a 100644
--- a/Documentation/vm/unevictable-lru.txt
+++ b/Documentation/vm/unevictable-lru.txt
@@ -317,7 +317,7 @@ If the VMA passes some filtering as described in "Filtering Special Vmas"
below, mlock_fixup() will attempt to merge the VMA with its neighbors or split
off a subset of the VMA if the range does not cover the entire VMA. Once the
VMA has been merged or split or neither, mlock_fixup() will call
-__mlock_vma_pages_range() to fault in the pages via get_user_pages() and to
+populate_vma_page_range() to fault in the pages via get_user_pages() and to
mark the pages as mlocked via mlock_vma_page().

Note that the VMA being mlocked might be mapped with PROT_NONE. In this case,
@@ -327,7 +327,7 @@ fault path or in vmscan.

Also note that a page returned by get_user_pages() could be truncated or
migrated out from under us, while we're trying to mlock it. To detect this,
-__mlock_vma_pages_range() checks page_mapping() after acquiring the page lock.
+populate_vma_page_range() checks page_mapping() after acquiring the page lock.
If the page is still associated with its mapping, we'll go ahead and call
mlock_vma_page(). If the mapping is gone, we just unlock the page and move on.
In the worst case, this will result in a page mapped in a VM_LOCKED VMA
@@ -392,7 +392,7 @@ ignored for munlock.

If the VMA is VM_LOCKED, mlock_fixup() again attempts to merge or split off the
specified range. The range is then munlocked via the function
-__mlock_vma_pages_range() - the same function used to mlock a VMA range -
+populate_vma_page_range() - the same function used to mlock a VMA range -
passing a flag to indicate that munlock() is being performed.

Because the VMA access protections could have been changed to PROT_NONE after
@@ -402,7 +402,7 @@ get_user_pages() was enhanced to accept a flag to ignore the permissions when
fetching the pages - all of which should be resident as a result of previous
mlocking.

-For munlock(), __mlock_vma_pages_range() unlocks individual pages by calling
+For munlock(), populate_vma_page_range() unlocks individual pages by calling
munlock_vma_page(). munlock_vma_page() unconditionally clears the PG_mlocked
flag using TestClearPageMlocked(). As with mlock_vma_page(),
munlock_vma_page() use the Test*PageMlocked() function to handle the case where
@@ -463,21 +463,11 @@ populate the page table.

To mlock a range of memory under the unevictable/mlock infrastructure, the
mmap() handler and task address space expansion functions call
-mlock_vma_pages_range() specifying the vma and the address range to mlock.
-mlock_vma_pages_range() filters VMAs like mlock_fixup(), as described above in
-"Filtering Special VMAs". It will clear the VM_LOCKED flag, which will have
-already been set by the caller, in filtered VMAs. Thus these VMA's need not be
-visited for munlock when the region is unmapped.
-
-For "normal" VMAs, mlock_vma_pages_range() calls __mlock_vma_pages_range() to
-fault/allocate the pages and mlock them. Again, like mlock_fixup(),
-mlock_vma_pages_range() downgrades the mmap semaphore to read mode before
-attempting to fault/allocate and mlock the pages and "upgrades" the semaphore
-back to write mode before returning.
-
-The callers of mlock_vma_pages_range() will have already added the memory range
+populate_vma_page_range() specifying the vma and the address range to mlock.
+
+The callers of populate_vma_page_range() will have already added the memory range
to be mlocked to the task's "locked_vm". To account for filtered VMAs,
-mlock_vma_pages_range() returns the number of pages NOT mlocked. All of the
+populate_vma_page_range() returns the number of pages NOT mlocked. All of the
callers then subtract a non-negative return value from the task's locked_vm. A
negative return value represent an error - for example, from get_user_pages()
attempting to fault in a VMA with PROT_NONE access. In this case, we leave the
diff --git a/mm/internal.h b/mm/internal.h
index c4d6c9b43491..5445860bfc08 100644
--- a/mm/internal.h
+++ b/mm/internal.h
@@ -240,7 +240,7 @@ void __vma_link_list(struct mm_struct *mm, struct vm_area_struct *vma,
struct vm_area_struct *prev, struct rb_node *rb_parent);

#ifdef CONFIG_MMU
-extern long __mlock_vma_pages_range(struct vm_area_struct *vma,
+extern long populate_vma_page_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end, int *nonblocking);
extern void munlock_vma_pages_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end);
diff --git a/mm/mlock.c b/mm/mlock.c
index 7712d8ab6fe5..c3ea18323034 100644
--- a/mm/mlock.c
+++ b/mm/mlock.c
@@ -206,13 +206,13 @@ out:
}

/**
- * __mlock_vma_pages_range() - mlock a range of pages in the vma.
+ * populate_vma_page_range() - populate a range of pages in the vma.
* @vma: target vma
* @start: start address
* @end: end address
* @nonblocking:
*
- * This takes care of making the pages present too.
+ * This takes care of mlocking the pages too if VM_LOCKED is set.
*
* return 0 on success, negative error code on error.
*
@@ -224,7 +224,7 @@ out:
* If @nonblocking is non-NULL, it must held for read only and may be
* released. If it's released, *@nonblocking will be set to 0.
*/
-long __mlock_vma_pages_range(struct vm_area_struct *vma,
+long populate_vma_page_range(struct vm_area_struct *vma,
unsigned long start, unsigned long end, int *nonblocking)
{
struct mm_struct *mm = vma->vm_mm;
@@ -596,7 +596,7 @@ success:
/*
* vm_flags is protected by the mmap_sem held in write mode.
* It's okay if try_to_unmap_one unmaps a page just after we
- * set VM_LOCKED, __mlock_vma_pages_range will bring it back.
+ * set VM_LOCKED, populate_vma_page_range will bring it back.
*/

if (lock)
@@ -702,11 +702,11 @@ int __mm_populate(unsigned long start, unsigned long len, int ignore_errors)
if (nstart < vma->vm_start)
nstart = vma->vm_start;
/*
- * Now fault in a range of pages. __mlock_vma_pages_range()
+ * Now fault in a range of pages. populate_vma_page_range()
* double checks the vma flags, so that it won't mlock pages
* if the vma was already munlocked.
*/
- ret = __mlock_vma_pages_range(vma, nstart, nend, &locked);
+ ret = populate_vma_page_range(vma, nstart, nend, &locked);
if (ret < 0) {
if (ignore_errors) {
ret = 0;
diff --git a/mm/mmap.c b/mm/mmap.c
index da9990acc08b..943c6ad18b1d 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2318,7 +2318,7 @@ find_extend_vma(struct mm_struct *mm, unsigned long addr)
if (!prev || expand_stack(prev, addr))
return NULL;
if (prev->vm_flags & VM_LOCKED)
- __mlock_vma_pages_range(prev, addr, prev->vm_end, NULL);
+ populate_vma_page_range(prev, addr, prev->vm_end, NULL);
return prev;
}
#else
@@ -2353,7 +2353,7 @@ find_extend_vma(struct mm_struct *mm, unsigned long addr)
if (expand_stack(vma, addr))
return NULL;
if (vma->vm_flags & VM_LOCKED)
- __mlock_vma_pages_range(vma, addr, start, NULL);
+ populate_vma_page_range(vma, addr, start, NULL);
return vma;
}
#endif
--
2.1.4