diff mbox

[v2,1/6] mm: get_user_pages: consolidate error handling

Message ID 20180702005654.20369-2-jhubbard@nvidia.com (mailing list archive)
State New, archived
Headers show

Commit Message

john.hubbard@gmail.com July 2, 2018, 12:56 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.

Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
 mm/gup.c | 37 ++++++++++++++++++++++---------------
 1 file changed, 22 insertions(+), 15 deletions(-)

Comments

Jan Kara July 2, 2018, 10:17 a.m. UTC | #1 
On Sun 01-07-18 17:56:49, 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.
> 
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

This looks nice! You can add:

Reviewed-by: Jan Kara <jack@suse.cz>

								Honza

> ---
>  mm/gup.c | 37 ++++++++++++++++++++++---------------
>  1 file changed, 22 insertions(+), 15 deletions(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index b70d7ba7cc13..73f0b3316fa7 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,
> -- 
> 2.18.0
>
John Hubbard July 2, 2018, 9:34 p.m. UTC | #2 
On 07/02/2018 03:17 AM, Jan Kara wrote:
> On Sun 01-07-18 17:56:49, 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.
>>
>> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> 
> This looks nice! You can add:
> 
> Reviewed-by: Jan Kara <jack@suse.cz>
> 

Great, thanks for the review!
diff mbox

Patch

diff --git a/mm/gup.c b/mm/gup.c
index b70d7ba7cc13..73f0b3316fa7 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,