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authorChristoph Hellwig <hch@lst.de>2020-06-11 04:42:10 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2020-06-11 05:14:18 +0300
commit37c54f9bd48663f7657a9178fe08c47e4f5b537b (patch)
treeba38e9216da172c16c4beafa97a882fc85f86068 /drivers/vhost
parentf5678e7f2ac31c270334b936352f0ef2fe7dd2b3 (diff)
downloadlinux-37c54f9bd48663f7657a9178fe08c47e4f5b537b.tar.xz
kernel: set USER_DS in kthread_use_mm
Some architectures like arm64 and s390 require USER_DS to be set for kernel threads to access user address space, which is the whole purpose of kthread_use_mm, but other like x86 don't. That has lead to a huge mess where some callers are fixed up once they are tested on said architectures, while others linger around and yet other like io_uring try to do "clever" optimizations for what usually is just a trivial asignment to a member in the thread_struct for most architectures. Make kthread_use_mm set USER_DS, and kthread_unuse_mm restore to the previous value instead. Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Tested-by: Jens Axboe <axboe@kernel.dk> Reviewed-by: Jens Axboe <axboe@kernel.dk> Acked-by: Michael S. Tsirkin <mst@redhat.com> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Felipe Balbi <balbi@kernel.org> Cc: Felix Kuehling <Felix.Kuehling@amd.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: Zhi Wang <zhi.a.wang@intel.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Link: http://lkml.kernel.org/r/20200404094101.672954-7-hch@lst.de Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/vhost')
-rw-r--r--drivers/vhost/vhost.c3
1 files changed, 0 insertions, 3 deletions
diff --git a/drivers/vhost/vhost.c b/drivers/vhost/vhost.c
index 1ad3d10c121a..421710c53f6a 100644
--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -329,9 +329,7 @@ static int vhost_worker(void *data)
struct vhost_dev *dev = data;
struct vhost_work *work, *work_next;
struct llist_node *node;
- mm_segment_t oldfs = get_fs();
- set_fs(USER_DS);
kthread_use_mm(dev->mm);
for (;;) {
@@ -361,7 +359,6 @@ static int vhost_worker(void *data)
}
}
kthread_unuse_mm(dev->mm);
- set_fs(oldfs);
return 0;
}