Re: [PATCH 01/16] ashmem: switch to ->read_iter

[Al Viro]

On Wed, Aug 30, 2017 at 04:59:52PM +0200, Christoph Hellwig wrote:
> And use the proper VFS helper for using the backing file.

Actually, I wonder if that update of ->f_pos of the underlying file is
correct.  That's unrelated to this patch, but might be worth sorting
out while we are at it.

How about
        mutex_unlock(&ashmem_mutex);
        /*
         * asma and asma->file are used outside the lock here.  We assume
         * once asma->file is set it will never be changed, and will not
         * be destroyed until all references to the file are dropped and
         * ashmem_release is called.
         */
	ret = vfs_iter_read(asma->file, iter, &iocb->ki_pos, 0);
        mutex_lock(&ashmem_mutex);
        if (ret >= 0)
                asma->file->f_pos = *pos;
out_unlock:
        mutex_unlock(&ashmem_mutex);
        return ret;

in there?