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Message-Id: <1245923935.31755.104.camel@twins>
Date: Thu, 25 Jun 2009 11:58:55 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: "Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Linus Torvalds <torvalds@...ux-foundation.org>,
LKML <linux-kernel@...r.kernel.org>, Ingo Molnar <mingo@...e.hu>,
Darren Hart <dvhltc@...ibm.com>
Subject: [PATCH] clarify get_user_pages() prototype
On Thu, 2009-06-25 at 10:43 +0800, Zhang, Yanmin wrote:
> > +static int fault_in_user_writeable(u32 __user *uaddr)
> > +{
> > + int ret = get_user_pages(current, current->mm, (unsigned long)uaddr,
> > + sizeof(*uaddr), 1, 0, NULL, NULL);
> The 4th parameter of get_user_pages means page number. sizeof(*uaddr) is equal to
> 4, so you want 4 pages?
crap... that's what you get for only looking at the prototype :/
---
Subject: clarify get_user_pages() prototype
Currently the 4th parameter of get_user_pages() is called len, but its
in pages, not bytes. Rename the thing to nr_pages to avoid future
confusion.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
include/linux/mm.h | 2 +-
mm/memory.c | 26 ++++++++++++--------------
mm/nommu.c | 12 +++++-------
3 files changed, 18 insertions(+), 22 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index d006e93..ba3a7cb 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -826,7 +826,7 @@ extern int make_pages_present(unsigned long addr, unsigned long end);
extern int access_process_vm(struct task_struct *tsk, unsigned long addr, void *buf, int len, int write);
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, int len, int write, int force,
+ unsigned long start, int nr_pages, int write, int force,
struct page **pages, struct vm_area_struct **vmas);
int get_user_pages_fast(unsigned long start, int nr_pages, int write,
struct page **pages);
diff --git a/mm/memory.c b/mm/memory.c
index f46ac18..6521619 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1207,8 +1207,8 @@ static inline int use_zero_page(struct vm_area_struct *vma)
int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, int len, int flags,
- struct page **pages, struct vm_area_struct **vmas)
+ unsigned long start, int nr_pages, int flags,
+ struct page **pages, struct vm_area_struct **vmas)
{
int i;
unsigned int vm_flags = 0;
@@ -1217,7 +1217,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
int ignore = !!(flags & GUP_FLAGS_IGNORE_VMA_PERMISSIONS);
int ignore_sigkill = !!(flags & GUP_FLAGS_IGNORE_SIGKILL);
- if (len <= 0)
+ if (nr_pages <= 0)
return 0;
/*
* Require read or write permissions.
@@ -1269,7 +1269,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
vmas[i] = gate_vma;
i++;
start += PAGE_SIZE;
- len--;
+ nr_pages--;
continue;
}
@@ -1280,7 +1280,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
if (is_vm_hugetlb_page(vma)) {
i = follow_hugetlb_page(mm, vma, pages, vmas,
- &start, &len, i, write);
+ &start, &nr_pages, i, write);
continue;
}
@@ -1357,9 +1357,9 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
vmas[i] = vma;
i++;
start += PAGE_SIZE;
- len--;
- } while (len && start < vma->vm_end);
- } while (len);
+ nr_pages--;
+ } while (nr_pages && start < vma->vm_end);
+ } while (nr_pages);
return i;
}
@@ -1368,7 +1368,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
* @tsk: task_struct of target task
* @mm: mm_struct of target mm
* @start: starting user address
- * @len: number of pages from start to pin
+ * @nr_pages: number of pages from start to pin
* @write: whether pages will be written to by the caller
* @force: whether to force write access even if user mapping is
* readonly. This will result in the page being COWed even
@@ -1380,7 +1380,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
* Or NULL if the caller does not require them.
*
* Returns number of pages pinned. This may be fewer than the number
- * requested. If len is 0 or negative, returns 0. If no pages
+ * requested. If nr_pages is 0 or negative, returns 0. If no pages
* were pinned, returns -errno. Each page returned must be released
* with a put_page() call when it is finished with. vmas will only
* remain valid while mmap_sem is held.
@@ -1414,7 +1414,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
* See also get_user_pages_fast, for performance critical applications.
*/
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, int len, int write, int force,
+ unsigned long start, int nr_pages, int write, int force,
struct page **pages, struct vm_area_struct **vmas)
{
int flags = 0;
@@ -1424,9 +1424,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
if (force)
flags |= GUP_FLAGS_FORCE;
- return __get_user_pages(tsk, mm,
- start, len, flags,
- pages, vmas);
+ return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
}
EXPORT_SYMBOL(get_user_pages);
diff --git a/mm/nommu.c b/mm/nommu.c
index 2fd2ad5..bf0cc76 100644
--- a/mm/nommu.c
+++ b/mm/nommu.c
@@ -173,8 +173,8 @@ unsigned int kobjsize(const void *objp)
}
int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, int len, int flags,
- struct page **pages, struct vm_area_struct **vmas)
+ unsigned long start, int nr_pages, int flags,
+ struct page **pages, struct vm_area_struct **vmas)
{
struct vm_area_struct *vma;
unsigned long vm_flags;
@@ -189,7 +189,7 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
vm_flags = write ? (VM_WRITE | VM_MAYWRITE) : (VM_READ | VM_MAYREAD);
vm_flags &= force ? (VM_MAYREAD | VM_MAYWRITE) : (VM_READ | VM_WRITE);
- for (i = 0; i < len; i++) {
+ for (i = 0; i < nr_pages; i++) {
vma = find_vma(mm, start);
if (!vma)
goto finish_or_fault;
@@ -224,7 +224,7 @@ finish_or_fault:
* - don't permit access to VMAs that don't support it, such as I/O mappings
*/
int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
- unsigned long start, int len, int write, int force,
+ unsigned long start, int nr_pages, int write, int force,
struct page **pages, struct vm_area_struct **vmas)
{
int flags = 0;
@@ -234,9 +234,7 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
if (force)
flags |= GUP_FLAGS_FORCE;
- return __get_user_pages(tsk, mm,
- start, len, flags,
- pages, vmas);
+ return __get_user_pages(tsk, mm, start, nr_pages, flags, pages, vmas);
}
EXPORT_SYMBOL(get_user_pages);
--
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