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[PATCH] tmpfs: shmem_fallocate must return ERESTARTSYS

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  [PATCH] tmpfs: shmem_fallocate must return ERESTARTSYS Maxim Patlasov <mpatlasov@virtuozzo.com> - 2016-03-04 01:40 +0100
    Re: [PATCH] tmpfs: shmem_fallocate must return ERESTARTSYS Mike Kravetz <mike.kravetz@oracle.com> - 2016-03-04 01:50 +0100

#1349728 — [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 <mpatlasov@virtuozzo.com>
---
 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

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#1349729

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 <mpatlasov@virtuozzo.com>
> ---
>  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

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