[2/2] vfs: Avoid softlockups with sendfile(2)
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Message ID 1448280591-27867-2-git-send-email-jack@suse.cz
State New
Headers show

Commit Message

Jan Kara Nov. 23, 2015, 12:09 p.m. UTC
The following test program from Dmitry can cause softlockups or RCU
stalls as it copies 1GB from tmpfs into eventfd and we don't have any
scheduling point at that path in sendfile(2) implementation:

        int r1 = eventfd(0, 0);
        int r2 = memfd_create("", 0);
        unsigned long n = 1<<30;
        fallocate(r2, 0, 0, n);
        sendfile(r1, r2, 0, n);

Add cond_resched() into __splice_from_pipe() to fix the problem.

CC: Dmitry Vyukov <dvyukov@google.com>
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
---
 fs/splice.c | 1 +
 1 file changed, 1 insertion(+)

Comments

Dmitry Vyukov Nov. 23, 2015, 7:42 p.m. UTC | #1
Fixed the issue for me.

Tested-by: Dmitry Vyukov <dvyukov@google.com>

On Mon, Nov 23, 2015 at 1:09 PM, Jan Kara <jack@suse.cz> wrote:
> The following test program from Dmitry can cause softlockups or RCU
> stalls as it copies 1GB from tmpfs into eventfd and we don't have any
> scheduling point at that path in sendfile(2) implementation:
>
>         int r1 = eventfd(0, 0);
>         int r2 = memfd_create("", 0);
>         unsigned long n = 1<<30;
>         fallocate(r2, 0, 0, n);
>         sendfile(r1, r2, 0, n);
>
> Add cond_resched() into __splice_from_pipe() to fix the problem.
>
> CC: Dmitry Vyukov <dvyukov@google.com>
> CC: stable@vger.kernel.org
> Signed-off-by: Jan Kara <jack@suse.cz>
> ---
>  fs/splice.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/fs/splice.c b/fs/splice.c
> index 22adbbe51e52..4cf700d50b40 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -891,6 +891,7 @@ ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
>
>         splice_from_pipe_begin(sd);
>         do {
> +               cond_resched();
>                 ret = splice_from_pipe_next(pipe, sd);
>                 if (ret > 0)
>                         ret = splice_from_pipe_feed(pipe, sd, actor);
> --
> 2.1.4
>
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Patch
diff mbox

diff --git a/fs/splice.c b/fs/splice.c
index 22adbbe51e52..4cf700d50b40 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -891,6 +891,7 @@  ssize_t __splice_from_pipe(struct pipe_inode_info *pipe, struct splice_desc *sd,
 
 	splice_from_pipe_begin(sd);
 	do {
+		cond_resched();
 		ret = splice_from_pipe_next(pipe, sd);
 		if (ret > 0)
 			ret = splice_from_pipe_feed(pipe, sd, actor);