2016-03-04 00:30:40

by Maxim Patlasov

Subject: [PATCH] tmpfs: shmem_fallocate must return ERESTARTSYS

shmem_fallocate() is restartable, so it can return ERESTARTSYS if
signal_pending(). Although fallocate(2) manpage permits EINTR,
the more places use ERESTARTSYS the better.

Signed-off-by: Maxim Patlasov <[email protected]>
---
mm/shmem.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 440e2a7..60e9c8a 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2229,11 +2229,13 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
struct page *page;

/*
- * Good, the fallocate(2) manpage permits EINTR: we may have
- * been interrupted because we are using up too much memory.
+ * Although fallocate(2) manpage permits EINTR, the more
+ * places use ERESTARTSYS the better. If we have been
+ * interrupted because we are using up too much memory,
+ * oom-killer used fatal signal and we will die anyway.
*/
if (signal_pending(current))
- error = -EINTR;
+ error = -ERESTARTSYS;
else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
error = -ENOMEM;
else

2016-03-04 00:45:06

by Mike Kravetz

Subject: Re: [PATCH] tmpfs: shmem_fallocate must return ERESTARTSYS

On 03/03/2016 04:30 PM, Maxim Patlasov wrote:
> shmem_fallocate() is restartable, so it can return ERESTARTSYS if
> signal_pending(). Although fallocate(2) manpage permits EINTR,
> the more places use ERESTARTSYS the better.
>
> Signed-off-by: Maxim Patlasov <[email protected]>
> ---
> mm/shmem.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 440e2a7..60e9c8a 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -2229,11 +2229,13 @@ static long shmem_fallocate(struct file *file, int mode, loff_t offset,
> struct page *page;
>
> /*
> - * Good, the fallocate(2) manpage permits EINTR: we may have
> - * been interrupted because we are using up too much memory.
> + * Although fallocate(2) manpage permits EINTR, the more
> + * places use ERESTARTSYS the better. If we have been
> + * interrupted because we are using up too much memory,
> + * oom-killer used fatal signal and we will die anyway.
> */
> if (signal_pending(current))
> - error = -EINTR;
> + error = -ERESTARTSYS;
> else if (shmem_falloc.nr_unswapped > shmem_falloc.nr_falloced)
> error = -ENOMEM;
> else

I used the shmem fallocate code as a basis for hugetlbfs fallocate.
See, hugetlbfs_fallocate(). Specifically:

/*
* fallocate(2) manpage permits EINTR; we may have been
* interrupted because we are using up too much memory.
*/
if (signal_pending(current)) {
error = -EINTR;
break;
}

I don't know much about the advantages of changing to ERESTARTSYS. But,
if it is changed for shmem it should be changed for hugetlbfs as well.

--
Mike Kravetz