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SubjectRe: [PATCH] staging: android: ashmem: lseek failed due to no FMODE_LSEEK.
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On 04/06/2017 10:08 AM, Greg KH wrote:
> On Thu, Apr 06, 2017 at 08:30:40AM -0700, Greg Hackmann wrote:
>> On 04/06/2017 07:30 AM, zhangshuxiaomi@gmail.com wrote:
>>> From: zhangshuxiao <zhangshuxiao@xiaomi.com>
>>>
>>> vfs_llseek will check whether the file mode has
>>> FMODE_LSEEK, no return failure. But ashmem can be
>>> lseek, so add FMODE_LSEEK to ashmem file.
>>>
>>> Signed-off-by: Shuxiao Zhang <zhangshuxiao@xiaomi.com>
>>> Tested-by: Greg Hackmann <ghackmann@google.com>
>>> ---
>>> drivers/staging/android/ashmem.c | 1 +
>>> 1 file changed, 1 insertion(+)
>>>
>>> diff --git a/drivers/staging/android/ashmem.c b/drivers/staging/android/ashmem.c
>>> index 3f11332..e4530ac 100644
>>> --- a/drivers/staging/android/ashmem.c
>>> +++ b/drivers/staging/android/ashmem.c
>>> @@ -392,6 +392,7 @@ static int ashmem_mmap(struct file *file, struct vm_area_struct *vma)
>>> ret = PTR_ERR(vmfile);
>>> goto out;
>>> }
>>> + vmfile->f_mode |= FMODE_LSEEK;
>>> asma->file = vmfile;
>>> }
>>> get_file(asma->file);
>>>
>>
>> This commit message is missing some important context.
>>
>> ashmem_llseek() passes the llseek() call through to the backing shmem file.
>> 91360b02ab48 ("ashmem: use vfs_llseek()") changed this from directly calling
>> the file's llseek() op into a VFS layer call. This also adds a check for
>> the FMODE_LSEEK bit, so without that bit ashmem_llseek() now always fails
>> with -ESPIPE.
>>
>> I've tested that this patch fixes the regression on both hikey running AOSP
>> and User Mode Linux running Debian.
>
> Thanks for letting me know, I'll update the changelog a bit. How far
> back does this patch need to go in stable kernel releases?
>
> thanks,
>
> greg k-h
>

3.18 and later.

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