diff mbox series

[1/6] mm: get_user_pages: consolidate error handling

Message ID 20181012060014.10242-2-jhubbard@nvidia.com (mailing list archive)
State New, archived
Headers show
Series RFC: gup+dma: tracking dma-pinned pages | expand

Commit Message

john.hubbard@gmail.com Oct. 12, 2018, 6 a.m. UTC 
From: John Hubbard <jhubbard@nvidia.com>

An upcoming patch requires a way to operate on each page that
any of the get_user_pages_*() variants returns.

In preparation for that, consolidate the error handling for
__get_user_pages(). This provides a single location (the "out:" label)
for operating on the collected set of pages that are about to be returned.

As long every use of the "ret" variable is being edited, rename
"ret" --> "err", so that its name matches its true role.
This also gets rid of two shadowed variable declarations, as a
tiny beneficial a side effect.

Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 mm/gup.c | 37 ++++++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 15 deletions(-)

Comments

Education Directorate Oct. 12, 2018, 6:30 a.m. UTC | #1 
On Thu, Oct 11, 2018 at 11:00:09PM -0700, john.hubbard@gmail.com wrote:
> From: John Hubbard <jhubbard@nvidia.com>
> 
> An upcoming patch requires a way to operate on each page that
> any of the get_user_pages_*() variants returns.
> 
> In preparation for that, consolidate the error handling for
> __get_user_pages(). This provides a single location (the "out:" label)
> for operating on the collected set of pages that are about to be returned.
> 
> As long every use of the "ret" variable is being edited, rename
> "ret" --> "err", so that its name matches its true role.
> This also gets rid of two shadowed variable declarations, as a
> tiny beneficial a side effect.
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> ---

Looks good, might not be needed but
Reviewed-by: Balbir Singh <bsingharora@gmail.com>
John Hubbard Oct. 12, 2018, 10:45 p.m. UTC | #2 
On 10/11/18 11:30 PM, Balbir Singh wrote:
> On Thu, Oct 11, 2018 at 11:00:09PM -0700, john.hubbard@gmail.com wrote:
>> From: John Hubbard <jhubbard@nvidia.com>
>>
>> An upcoming patch requires a way to operate on each page that
>> any of the get_user_pages_*() variants returns.
>>
>> In preparation for that, consolidate the error handling for
>> __get_user_pages(). This provides a single location (the "out:" label)
>> for operating on the collected set of pages that are about to be returned.
>>
>> As long every use of the "ret" variable is being edited, rename
>> "ret" --> "err", so that its name matches its true role.
>> This also gets rid of two shadowed variable declarations, as a
>> tiny beneficial a side effect.
>>
>> Reviewed-by: Jan Kara <jack@suse.cz>
>> Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
>> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
>> ---
> 
> Looks good, might not be needed but
> Reviewed-by: Balbir Singh <bsingharora@gmail.com>
> 

Thanks for the review, very good to have another set of eyes on
this one.
diff mbox series

Patch

diff --git a/mm/gup.c b/mm/gup.c
index 1abc8b4afff6..05ee7c18e59a 100644
--- a/mm/gup.c
+++ b/mm/gup.c
@@ -660,6 +660,7 @@  static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 		struct vm_area_struct **vmas, int *nonblocking)
 {
 	long i = 0;
+	int err = 0;
 	unsigned int page_mask;
 	struct vm_area_struct *vma = NULL;
 
@@ -685,18 +686,19 @@  static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 		if (!vma || start >= vma->vm_end) {
 			vma = find_extend_vma(mm, start);
 			if (!vma && in_gate_area(mm, start)) {
-				int ret;
-				ret = get_gate_page(mm, start & PAGE_MASK,
+				err = get_gate_page(mm, start & PAGE_MASK,
 						gup_flags, &vma,
 						pages ? &pages[i] : NULL);
-				if (ret)
-					return i ? : ret;
+				if (err)
+					goto out;
 				page_mask = 0;
 				goto next_page;
 			}
 
-			if (!vma || check_vma_flags(vma, gup_flags))
-				return i ? : -EFAULT;
+			if (!vma || check_vma_flags(vma, gup_flags)) {
+				err = -EFAULT;
+				goto out;
+			}
 			if (is_vm_hugetlb_page(vma)) {
 				i = follow_hugetlb_page(mm, vma, pages, vmas,
 						&start, &nr_pages, i,
@@ -709,23 +711,25 @@  static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 		 * If we have a pending SIGKILL, don't keep faulting pages and
 		 * potentially allocating memory.
 		 */
-		if (unlikely(fatal_signal_pending(current)))
-			return i ? i : -ERESTARTSYS;
+		if (unlikely(fatal_signal_pending(current))) {
+			err = -ERESTARTSYS;
+			goto out;
+		}
 		cond_resched();
 		page = follow_page_mask(vma, start, foll_flags, &page_mask);
 		if (!page) {
-			int ret;
-			ret = faultin_page(tsk, vma, start, &foll_flags,
+			err = faultin_page(tsk, vma, start, &foll_flags,
 					nonblocking);
-			switch (ret) {
+			switch (err) {
 			case 0:
 				goto retry;
 			case -EFAULT:
 			case -ENOMEM:
 			case -EHWPOISON:
-				return i ? i : ret;
+				goto out;
 			case -EBUSY:
-				return i;
+				err = 0;
+				goto out;
 			case -ENOENT:
 				goto next_page;
 			}
@@ -737,7 +741,8 @@  static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 			 */
 			goto next_page;
 		} else if (IS_ERR(page)) {
-			return i ? i : PTR_ERR(page);
+			err = PTR_ERR(page);
+			goto out;
 		}
 		if (pages) {
 			pages[i] = page;
@@ -757,7 +762,9 @@  static long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
 		start += page_increm * PAGE_SIZE;
 		nr_pages -= page_increm;
 	} while (nr_pages);
-	return i;
+
+out:
+	return i ? i : err;
 }
 
 static bool vma_permits_fault(struct vm_area_struct *vma,