io_uring: rsrc: delegate VMA file-backed check to GUP

Now that the GUP explicitly checks FOLL_LONGTERM pin_user_pages() for
broken file-backed mappings in "mm/gup: disallow FOLL_LONGTERM GUP-nonfast
writing to file-backed mappings", there is no need to explicitly check VMAs
for this condition, so simply remove this logic from io_uring altogether.

Link: https://lkml.kernel.org/r/e4a4efbda9cd12df71e0ed81796dc630231a1ef2.1684350871.git.lstoakes@gmail.comSigned-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: David Hildenbrand <david@redhat.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christian König <christian.koenig@amd.com>
Cc: Dennis Dalessandro <dennis.dalessandro@cornelisnetworks.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jarkko Sakkinen <jarkko@kernel.org>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

io_uring/rsrc.c

@@ -1030,9 +1030,8 @@ static int io_buffer_account_pin(struct io_ring_ctx *ctx, struct page **pages,
 struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages)
 {
 	unsigned long start, end, nr_pages;
-	struct vm_area_struct **vmas = NULL;
 	struct page **pages = NULL;
-	int i, pret, ret = -ENOMEM;
+	int pret, ret = -ENOMEM;
 
 	end = (ubuf + len + PAGE_SIZE - 1) >> PAGE_SHIFT;
 	start = ubuf >> PAGE_SHIFT;
@@ -1042,45 +1041,24 @@ struct page **io_pin_pages(unsigned long ubuf, unsigned long len, int *npages)
 	if (!pages)
 		goto done;
 
-	vmas = kvmalloc_array(nr_pages, sizeof(struct vm_area_struct *),
-			      GFP_KERNEL);
-	if (!vmas)
-		goto done;
-
 	ret = 0;
 	mmap_read_lock(current->mm);
 	pret = pin_user_pages(ubuf, nr_pages, FOLL_WRITE | FOLL_LONGTERM,
-			      pages, vmas);
-	if (pret == nr_pages) {
-		/* don't support file backed memory */
-		for (i = 0; i < nr_pages; i++) {
-			struct vm_area_struct *vma = vmas[i];
-
-			if (vma_is_shmem(vma))
-				continue;
-			if (vma->vm_file &&
-			    !is_file_hugepages(vma->vm_file)) {
-				ret = -EOPNOTSUPP;
-				break;
-			}
-		}
+			      pages, NULL);
+	if (pret == nr_pages)
 		*npages = nr_pages;
-	} else {
+	else
 		ret = pret < 0 ? pret : -EFAULT;
-	}
+
 	mmap_read_unlock(current->mm);
 	if (ret) {
-		/*
-		 * if we did partial map, or found file backed vmas,
-		 * release any pages we did get
-		 */
+		/* if we did partial map, release any pages we did get */
 		if (pret > 0)
 			unpin_user_pages(pages, pret);
 		goto done;
 	}
 	ret = 0;
 done:
-	kvfree(vmas);
 	if (ret < 0) {
 		kvfree(pages);
 		pages = ERR_PTR(ret);