[Devel] [PATCH RHEL COMMIT] tmpfs: shmem_fallocate must return ERESTARTSYS

[Konstantin Khorenko]

The commit is pushed to "branch-rh9-5.14.vz9.1.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after ark-5.14
------>
commit f33430218b2519e64010ee927fa11ce8d2c29c8c
Author: Maxim Patlasov <mpatlasov at virtuozzo.com>
Date:   Fri Oct 1 19:38:37 2021 +0300

    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.
    
    https://jira.sw.ru/browse/PSBM-43399
    
    Signed-off-by: Maxim Patlasov <mpatlasov at virtuozzo.com>
    
    Acked-by: Dmitry Monakhov <dmonakhov at virtuozzo.com>
    
    mpatlasov@: note, shmem_fallocate() doesn't return ERESTARTSYS to userspace.
    It returns ERESTARTSYS to some internal kernel function that restarts syscall
    (I tested this behavior). This is how any other "return -ERESTARTSYS;" works.
    
    (cherry picked from vz7 commit 0011c60ac1fde1f735d2474c967b454b9019461a)
    Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
    
    (cherry-picked from vz8 commit 3eb592c3bd9b ("tmpfs: shmem_fallocate
    must return ERESTARTSYS"))
    
    Signed-off-by: Nikita Yushchenko <nikita.yushchenko at virtuozzo.com>
---
 mm/shmem.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index 4bce39662d70..6ba6b558d7c1 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2728,11 +2728,13 @@ 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