Merge tag 'for-4.18-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux

Pull btrfs fixes from David Sterba:
 "Three regression fixes. They're few-liners and fixing some corner
  cases missed in the origial patches"

* tag 'for-4.18-rc5-tag' of git://git.kernel.org/pub/scm/linux/kernel/git/kdave/linux:
  btrfs: scrub: Don't use inode page cache in scrub_handle_errored_block()
  btrfs: fix use-after-free of cmp workspace pages
  btrfs: restore uuid_mutex in btrfs_open_devices

fs/btrfs/ioctl.c

@@ -3327,11 +3327,13 @@ static void btrfs_cmp_data_free(struct cmp_pages *cmp)
 		if (pg) {
 			unlock_page(pg);
 			put_page(pg);
+			cmp->src_pages[i] = NULL;
 		}
 		pg = cmp->dst_pages[i];
 		if (pg) {
 			unlock_page(pg);
 			put_page(pg);
+			cmp->dst_pages[i] = NULL;
 		}
 	}
 }

fs/btrfs/scrub.c

@@ -1151,11 +1151,6 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
 		return ret;
 	}
 
-	if (sctx->is_dev_replace && !is_metadata && !have_csum) {
-		sblocks_for_recheck = NULL;
-		goto nodatasum_case;
-	}
-
 	/*
 	 * read all mirrors one after the other. This includes to
 	 * re-read the extent or metadata block that failed (that was
@@ -1268,13 +1263,19 @@ static int scrub_handle_errored_block(struct scrub_block *sblock_to_check)
 		goto out;
 	}
 
-	if (!is_metadata && !have_csum) {
+	/*
+	 * NOTE: Even for nodatasum case, it's still possible that it's a
+	 * compressed data extent, thus scrub_fixup_nodatasum(), which write
+	 * inode page cache onto disk, could cause serious data corruption.
+	 *
+	 * So here we could only read from disk, and hope our recovery could
+	 * reach disk before the newer write.
+	 */
+	if (0 && !is_metadata && !have_csum) {
 		struct scrub_fixup_nodatasum *fixup_nodatasum;
 
 		WARN_ON(sctx->is_dev_replace);
 
-nodatasum_case:
-
 		/*
 		 * !is_metadata and !have_csum, this means that the data
 		 * might not be COWed, that it might be modified

fs/btrfs/volumes.c

@@ -1146,6 +1146,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 {
 	int ret;
 
+	mutex_lock(&uuid_mutex);
 	mutex_lock(&fs_devices->device_list_mutex);
 	if (fs_devices->opened) {
 		fs_devices->opened++;
@@ -1155,6 +1156,7 @@ int btrfs_open_devices(struct btrfs_fs_devices *fs_devices,
 		ret = open_fs_devices(fs_devices, flags, holder);
 	}
 	mutex_unlock(&fs_devices->device_list_mutex);
+	mutex_unlock(&uuid_mutex);
 
 	return ret;
 }