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media: vb2: frame_vector.c: replace WARN_ONCE with a comment

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The WARN_ONCE was issued also in cases that had nothing to do with VM_IO
(e.g. if the start address was just a random value and uaccess fails with
-EFAULT).

There are no reports of WARN_ONCE being issued for actual VM_IO cases, so
just drop it and instead add a note to the comment before the function.

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reported-by: Yikebaer Aizezi <yikebaer61@gmail.com>
This commit is contained in:
Hans Verkuil 2023-08-17 12:41:32 +02:00
parent 41ebaa5e0e
commit 735de5caf7
1 changed files with 4 additions and 2 deletions
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6
drivers/media/common/videobuf2/frame_vector.c
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@ -31,6 +31,10 @@
* different type underlying the specified range of virtual addresses. * different type underlying the specified range of virtual addresses.
* When the function isn't able to map a single page, it returns error. * When the function isn't able to map a single page, it returns error.
* *
* Note that get_vaddr_frames() cannot follow VM_IO mappings. It used
* to be able to do that, but that could (racily) return non-refcounted
* pfns.
*
* This function takes care of grabbing mmap_lock as necessary. * This function takes care of grabbing mmap_lock as necessary.
*/ */
int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write, int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write,
@ -59,8 +63,6 @@ int get_vaddr_frames(unsigned long start, unsigned int nr_frames, bool write,
if (likely(ret > 0)) if (likely(ret > 0))
return ret; return ret;
/* This used to (racily) return non-refcounted pfns. Let people know */
WARN_ONCE(1, "get_vaddr_frames() cannot follow VM_IO mapping");
vec->nr_frames = 0; vec->nr_frames = 0;
return ret ? ret : -EFAULT; return ret ? ret : -EFAULT;
} }