dm resume: don't return EINVAL when signalled

If the dm_resume method is called on a device that is not suspended, the
method will suspend the device briefly, before resuming it (so that the
table will be swapped).

However, there was a bug that the return value of dm_suspended_md was not
checked. dm_suspended_md may return an error when it is interrupted by a
signal. In this case, do_resume would call dm_swap_table, which would
return -EINVAL.

This commit fixes the logic, so that error returned by dm_suspend is
checked and the resume operation is undone.

Signed-off-by: Mikulas Patocka <[e-mail]>
Signed-off-by: Khazhismel Kumykov <[e-mail]>
Cc: [e-mail]

drivers/md/dm-ioctl.c

···
 			suspend_flags &= ~DM_SUSPEND_LOCKFS_FLAG;
 		if (param->flags & DM_NOFLUSH_FLAG)
 			suspend_flags |= DM_SUSPEND_NOFLUSH_FLAG;
-		if (!dm_suspended_md(md))
-			dm_suspend(md, suspend_flags);
+		if (!dm_suspended_md(md)) {
+			r = dm_suspend(md, suspend_flags);
+			if (r) {
+				down_write(&_hash_lock);
+				hc = dm_get_mdptr(md);
+				if (hc && !hc->new_map) {
+					hc->new_map = new_map;
+					new_map = NULL;
+				} else {
+					r = -ENXIO;
+				}
+				up_write(&_hash_lock);
+				if (new_map) {
+					dm_sync_table(md);
+					dm_table_destroy(new_map);
+				}
+				dm_put(md);
+				return r;
+			}
+		}
 
 		old_size = dm_get_size(md);
 		old_map = dm_swap_table(md, new_map);