CIFS: use the correct length when pinning memory for direct I/O for write

Message ID 20181216231704.16761-1-longli@linuxonhyperv.com
State New
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Series
  • CIFS: use the correct length when pinning memory for direct I/O for write
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Commit Message

Long Li Dec. 16, 2018, 11:17 p.m.
From: Long Li <longli@microsoft.com>

The current code attempts to pin memory using the largest possible wsize
based on the currect SMB credits. This doesn't cause kernel oops but this is
not optimal as we may pin more pages then actually needed.

Fix this by only pinning what are needed for doing this write I/O.

Signed-off-by: Long Li <longli@microsoft.com>
Cc: stable@vger.kernel.org
---
 fs/cifs/file.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

Comments

Joey Pabalinas Dec. 17, 2018, 1:10 a.m. | #1
On Sun, Dec 16, 2018 at 11:17:04PM +0000, Long Li wrote:
> From: Long Li <longli@microsoft.com>
> 
> The current code attempts to pin memory using the largest possible wsize
> based on the currect SMB credits. This doesn't cause kernel oops but this is
> not optimal as we may pin more pages then actually needed.
> 
> Fix this by only pinning what are needed for doing this write I/O.
> 
> Signed-off-by: Long Li <longli@microsoft.com>
> Cc: stable@vger.kernel.org

Looks sane to me.

Reviewed-by: Joey Pabalinas <joeypabalinas@gmail.com>

> ---
>  fs/cifs/file.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 3467351..c23bf9d 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2617,11 +2617,13 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
>  		if (rc)
>  			break;
>  
> +		cur_len = min_t(const size_t, len, wsize);
> +
>  		if (ctx->direct_io) {
>  			ssize_t result;
>  
>  			result = iov_iter_get_pages_alloc(
> -				from, &pagevec, wsize, &start);
> +				from, &pagevec, cur_len, &start);
>  			if (result < 0) {
>  				cifs_dbg(VFS,
>  					"direct_writev couldn't get user pages "
> -- 
> 2.7.4
>
Steve French Dec. 18, 2018, 5:05 a.m. | #2
merged into cifs-2.6.git for-next

On Sun, Dec 16, 2018 at 5:18 PM Long Li <longli@linuxonhyperv.com> wrote:
>
> From: Long Li <longli@microsoft.com>
>
> The current code attempts to pin memory using the largest possible wsize
> based on the currect SMB credits. This doesn't cause kernel oops but this is
> not optimal as we may pin more pages then actually needed.
>
> Fix this by only pinning what are needed for doing this write I/O.
>
> Signed-off-by: Long Li <longli@microsoft.com>
> Cc: stable@vger.kernel.org
> ---
>  fs/cifs/file.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 3467351..c23bf9d 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2617,11 +2617,13 @@ cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
>                 if (rc)
>                         break;
>
> +               cur_len = min_t(const size_t, len, wsize);
> +
>                 if (ctx->direct_io) {
>                         ssize_t result;
>
>                         result = iov_iter_get_pages_alloc(
> -                               from, &pagevec, wsize, &start);
> +                               from, &pagevec, cur_len, &start);
>                         if (result < 0) {
>                                 cifs_dbg(VFS,
>                                         "direct_writev couldn't get user pages "
> --
> 2.7.4
>

Patch

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 3467351..c23bf9d 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2617,11 +2617,13 @@  cifs_write_from_iter(loff_t offset, size_t len, struct iov_iter *from,
 		if (rc)
 			break;
 
+		cur_len = min_t(const size_t, len, wsize);
+
 		if (ctx->direct_io) {
 			ssize_t result;
 
 			result = iov_iter_get_pages_alloc(
-				from, &pagevec, wsize, &start);
+				from, &pagevec, cur_len, &start);
 			if (result < 0) {
 				cifs_dbg(VFS,
 					"direct_writev couldn't get user pages "