[PATCH 8/8] mm: FOLL flags for GUP flags

Hugh Dickins
2009-09-07T21:41:32Z

__get_user_pages() has been taking its own GUP flags, then processing
them into FOLL flags for follow_page(). Though oddly named, the FOLL
flags are more widely used, so pass them to __get_user_pages() now.
Sorry, VM flags, VM_FAULT flags and FAULT_FLAGs are still distinct.

(The patch to __get_user_pages() looks peculiar, with both gup_flags
and foll_flags: the gup_flags remain constant; but as before there's
an exceptional case, out of scope of the patch, in which foll_flags
per page have FOLL_WRITE masked off.)

Signed-off-by: Hugh Dickins <hugh.dickins@tiscali.co.uk>
---

include/linux/mm.h | 1
mm/internal.h | 6 -----
mm/memory.c | 44 ++++++++++++++++++-------------------------
mm/mlock.c | 4 +--
mm/nommu.c | 16 +++++++--------
5 files changed, 31 insertions(+), 40 deletions(-)

--- mm7/include/linux/mm.h 2009-09-07 13:16:39.000000000 +0100
+++ mm8/include/linux/mm.h 2009-09-07 13:17:07.000000000 +0100
@@ -1248,6 +1248,7 @@ struct page *follow_page(struct vm_area_
#define FOLL_TOUCH 0x02 /* mark page accessed */
#define FOLL_GET 0x04 /* do get_page on page */
#define FOLL_DUMP 0x08 /* give error on hole if it would be zero */
+#define FOLL_FORCE 0x10 /* get_user_pages read/write w/o permission */

typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
void *data);
--- mm7/mm/internal.h 2009-09-07 13:16:39.000000000 +0100
+++ mm8/mm/internal.h 2009-09-07 13:17:07.000000000 +0100
@@ -250,12 +250,8 @@ static inline void mminit_validate_memmo
}
#endif /* CONFIG_SPARSEMEM */

-#define GUP_FLAGS_WRITE 0x01
-#define GUP_FLAGS_FORCE 0x02
-#define GUP_FLAGS_DUMP 0x04
-
int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, int len, int flags,
+ unsigned long start, int len, unsigned int foll_flags,
struct page **pages, struct vm_area_struct **vmas);

#define ZONE_RECLAIM_NOSCAN -2
--- mm7/mm/memory.c 2009-09-07 13:17:01.000000000 +0100
+++ mm8/mm/memory.c 2009-09-07 13:17:07.000000000 +0100
@@ -1209,27 +1209,29 @@ no_page_table:
}

int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, int nr_pages, int flags,
+ unsigned long start, int nr_pages, unsigned int gup_flags,
struct page **pages, struct vm_area_struct **vmas)
{
int i;
- unsigned int vm_flags = 0;
- int write = !!(flags & GUP_FLAGS_WRITE);
- int force = !!(flags & GUP_FLAGS_FORCE);
+ unsigned long vm_flags;

if (nr_pages <= 0)
return 0;
+
+ VM_BUG_ON(!!pages != !!(gup_flags & FOLL_GET));
+
/*
* Require read or write permissions.
- * If 'force' is set, we only require the "MAY" flags.
+ * If FOLL_FORCE is set, we only require the "MAY" flags.
*/
- vm_flags = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
- vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
+ vm_flags = (gup_flags & FOLL_WRITE) ?
+ (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
+ vm_flags &= (gup_flags & FOLL_FORCE) ?
+ (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
i = 0;

do {
struct vm_area_struct *vma;
- unsigned int foll_flags;

vma = find_extend_vma(mm, start);
if (!vma && in_gate_area(tsk, start)) {
@@ -1241,7 +1243,7 @@ int __get_user_pages(struct task_struct
pte_t *pte;

/* user gate pages are read-only */
- if (write)
+ if (gup_flags & FOLL_WRITE)
return i ? : -EFAULT;
if (pg > TASK_SIZE)
pgd = pgd_offset_k(pg);
@@ -1278,22 +1280,15 @@ int __get_user_pages(struct task_struct
!(vm_flags & vma->vm_flags))
return i ? : -EFAULT;

- foll_flags = FOLL_TOUCH;
- if (pages)
- foll_flags |= FOLL_GET;
- if (flags & GUP_FLAGS_DUMP)
- foll_flags |= FOLL_DUMP;
- if (write)
- foll_flags |= FOLL_WRITE;
-
if (is_vm_hugetlb_page(vma)) {
i = follow_hugetlb_page(mm, vma, pages, vmas,
- &start, &nr_pages, i, foll_flags);
+ &start, &nr_pages, i, gup_flags);
continue;
}

do {
struct page *page;
+ unsigned int foll_flags = gup_flags;

/*
* If we have a pending SIGKILL, don't keep faulting
@@ -1302,9 +1297,6 @@ int __get_user_pages(struct task_struct
if (unlikely(fatal_signal_pending(current)))
return i ? i : -ERESTARTSYS;

- if (write)
- foll_flags |= FOLL_WRITE;
-
cond_resched();
while (!(page = follow_page(vma, start, foll_flags))) {
int ret;
@@ -1416,12 +1408,14 @@ int get_user_pages(struct task_struct *t
unsigned long start, int nr_pages, int write, int force,
struct page **pages, struct vm_area_struct **vmas)
{
- int flags = 0;
+ int flags = FOLL_TOUCH;

+ if (pages)
+ flags |= FOLL_GET;
if (write)
- flags |= GUP_FLAGS_WRITE;
+ flags |= FOLL_WRITE;
if (force)
- flags |= GUP_FLAGS_FORCE;
+ flags |= FOLL_FORCE;

return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
}
@@ -1448,7 +1442,7 @@ struct page *get_dump_page(unsigned long
struct page *page;

if (__get_user_pages(current, current->mm, addr, 1,
- GUP_FLAGS_FORCE | GUP_FLAGS_DUMP, &page, &vma) < 1)
+ FOLL_FORCE | FOLL_DUMP | FOLL_GET, &page, &vma) < 1)
return NULL;
if (page == ZERO_PAGE(0)) {
page_cache_release(page);
--- mm7/mm/mlock.c 2009-09-07 13:16:15.000000000 +0100
+++ mm8/mm/mlock.c 2009-09-07 13:17:07.000000000 +0100
@@ -166,9 +166,9 @@ static long __mlock_vma_pages_range(stru
VM_BUG_ON(end > vma->vm_end);
VM_BUG_ON(!rwsem_is_locked(&mm->mmap_sem));

- gup_flags = 0;
+ gup_flags = FOLL_TOUCH | FOLL_GET;
if (vma->vm_flags & VM_WRITE)
- gup_flags = GUP_FLAGS_WRITE;
+ gup_flags |= FOLL_WRITE;

while (nr_pages > 0) {
int i;
--- mm7/mm/nommu.c 2009-09-07 13:16:22.000000000 +0100
+++ mm8/mm/nommu.c 2009-09-07 13:17:07.000000000 +0100
@@ -128,20 +128,20 @@ unsigned int kobjsize(const void *objp)
}

int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, int nr_pages, int flags,
+ unsigned long start, int nr_pages, int foll_flags,
struct page **pages, struct vm_area_struct **vmas)
{
struct vm_area_struct *vma;
unsigned long vm_flags;
int i;
- int write = !!(flags & GUP_FLAGS_WRITE);
- int force = !!(flags & GUP_FLAGS_FORCE);

/* calculate required read or write permissions.
- * - if 'force' is set, we only require the "MAY" flags.
+ * If FOLL_FORCE is set, we only require the "MAY" flags.
*/
- vm_flags = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
- vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
+ vm_flags = (foll_flags & FOLL_WRITE) ?
+ (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
+ vm_flags &= (foll_flags & FOLL_FORCE) ?
+ (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);

for (i = 0; i < nr_pages; i++) {
vma = find_vma(mm, start);
@@ -183,9 +183,9 @@ int get_user_pages(struct task_struct *t
int flags = 0;

if (write)
- flags |= GUP_FLAGS_WRITE;
+ flags |= FOLL_WRITE;
if (force)
- flags |= GUP_FLAGS_FORCE;
+ flags |= FOLL_FORCE;

return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
}