dm: get rid of GFP_NOIO workarounds for __vmalloc and kvmalloc

In the past, the function __vmalloc didn't respect the GFP flags - it
allocated memory with the provided gfp flags, but it allocated page tables
with GFP_KERNEL. This was fixed in commit 451769e ("mm/vmalloc:
alloc GFP_NO{FS,IO} for vmalloc") so the memalloc_noio_{save,restore}
workaround is no longer needed.

The function kvmalloc didn't like flags different from GFP_KERNEL. This
was fixed in commit a421ef3 ("mm: allow !GFP_KERNEL allocations
for kvmalloc"), so kvmalloc can now be called with GFP_NOIO.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>

drivers/md/dm-bufio.c

@@ -1157,23 +1157,6 @@ static void *alloc_buffer_data(struct dm_bufio_client *c, gfp_t gfp_mask,
 
 	*data_mode = DATA_MODE_VMALLOC;
 
-	/*
-	 * __vmalloc allocates the data pages and auxiliary structures with
-	 * gfp_flags that were specified, but pagetables are always allocated
-	 * with GFP_KERNEL, no matter what was specified as gfp_mask.
-	 *
-	 * Consequently, we must set per-process flag PF_MEMALLOC_NOIO so that
-	 * all allocations done by this process (including pagetables) are done
-	 * as if GFP_NOIO was specified.
-	 */
-	if (gfp_mask & __GFP_NORETRY) {
-		unsigned int noio_flag = memalloc_noio_save();
-		void *ptr = __vmalloc(c->block_size, gfp_mask);
-
-		memalloc_noio_restore(noio_flag);
-		return ptr;
-	}
-
 	return __vmalloc(c->block_size, gfp_mask);
 }
 

drivers/md/dm-ioctl.c

@@ -1932,7 +1932,6 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
 	struct dm_ioctl *dmi;
 	int secure_data;
 	const size_t minimum_data_size = offsetof(struct dm_ioctl, data);
-	unsigned int noio_flag;
 
 	/* check_version() already copied version from userspace, avoid TOCTOU */
 	if (copy_from_user((char *)param_kernel + sizeof(param_kernel->version),
@@ -1962,9 +1961,7 @@ static int copy_params(struct dm_ioctl __user *user, struct dm_ioctl *param_kern
 	 * Use kmalloc() rather than vmalloc() when we can.
 	 */
 	dmi = NULL;
-	noio_flag = memalloc_noio_save();
-	dmi = kvmalloc(param_kernel->data_size, GFP_KERNEL | __GFP_HIGH);
-	memalloc_noio_restore(noio_flag);
+	dmi = kvmalloc(param_kernel->data_size, GFP_NOIO | __GFP_HIGH);
 
 	if (!dmi) {
 		if (secure_data && clear_user(user, param_kernel->data_size))