From 2996e1f8bcadf0436cc67b63af01523f6cf5d43f Mon Sep 17 00:00:00 2001
From: Johannes Thumshirn <jthumshirn@suse.de>
Date: Mon, 25 Feb 2019 14:24:15 +0100
Patch-mainline: v5.1
Git-commit: 2996e1f8bcadf0436cc67b63af01523f6cf5d43f
References: bsc#1168273
Subject: [PATCH] btrfs: factor our read/write stage off csum_tree_block into
 its callers

Currently csum_tree_block() does two things, first it as it's name
suggests it calculates the checksum for a tree-block. But it also writes
this checksum to disk or reads an extent_buffer from disk and compares the
checksum with the calculated checksum, depending on the verify argument.

Furthermore one of the two callers passes in '1' for the verify argument,
the other one passes in '0'.

For clarity and less layering violations, factor out the second stage in
csum_tree_block()'s callers.

Suggested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 fs/btrfs/disk-io.c |   55 +++++++++++++++++++++++++++--------------------------
 1 file changed, 29 insertions(+), 26 deletions(-)

--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -277,15 +277,12 @@ void btrfs_csum_final(u32 crc, u8 *resul
 }
 
 /*
- * compute the csum for a btree block, and either verify it or write it
- * into the csum field of the block.
+ * Compute the csum of a btree block and store the result to provided buffer.
+ *
+ * Returns error if the extent buffer cannot be mapped.
  */
-static int csum_tree_block(struct btrfs_fs_info *fs_info,
-			   struct extent_buffer *buf,
-			   int verify)
+static int csum_tree_block(struct extent_buffer *buf, u8 *result)
 {
-	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
-	char result[BTRFS_CSUM_SIZE];
 	unsigned long len;
 	unsigned long cur_len;
 	unsigned long offset = BTRFS_CSUM_SIZE;
@@ -311,23 +308,6 @@ static int csum_tree_block(struct btrfs_
 
 	btrfs_csum_final(crc, result);
 
-	if (verify) {
-		if (memcmp_extent_buffer(buf, result, 0, csum_size)) {
-			u32 val;
-			u32 found = 0;
-			memcpy(&found, result, csum_size);
-
-			read_extent_buffer(buf, &val, 0, csum_size);
-			btrfs_warn_rl(fs_info,
-				"%s checksum verify failed on %llu wanted %X found %X level %d",
-				fs_info->sb->s_id, buf->start,
-				val, found, btrfs_header_level(buf));
-			return -EUCLEAN;
-		}
-	} else {
-		write_extent_buffer(buf, result, 0, csum_size);
-	}
-
 	return 0;
 }
 
@@ -544,6 +524,8 @@ static int csum_dirty_buffer(struct btrf
 {
 	u64 start = page_offset(page);
 	u64 found_start;
+	u8 result[BTRFS_CSUM_SIZE];
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 	struct extent_buffer *eb;
 
 	eb = (struct extent_buffer *)page->private;
@@ -563,7 +545,11 @@ static int csum_dirty_buffer(struct btrf
 	ASSERT(memcmp_extent_buffer(eb, fs_info->fsid,
 			btrfs_header_fsid(), BTRFS_FSID_SIZE) == 0);
 
-	return csum_tree_block(fs_info, eb, 0);
+	if (csum_tree_block(eb, result))
+		return -EINVAL;
+
+	write_extent_buffer(eb, result, 0, csum_size);
+	return 0;
 }
 
 static int check_tree_block_fsid(struct btrfs_fs_info *fs_info,
@@ -593,7 +579,9 @@ static int btree_readpage_end_io_hook(st
 	struct extent_buffer *eb;
 	struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 	int ret = 0;
+	u8 result[BTRFS_CSUM_SIZE];
 	int reads_done;
 
 	if (!page->private)
@@ -640,10 +628,25 @@ static int btree_readpage_end_io_hook(st
 	btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb),
 				       eb, found_level);
 
-	ret = csum_tree_block(fs_info, eb, 1);
+	ret = csum_tree_block(eb, result);
 	if (ret)
 		goto err;
 
+	if (memcmp_extent_buffer(eb, result, 0, csum_size)) {
+		u32 val;
+		u32 found = 0;
+
+		memcpy(&found, result, csum_size);
+
+		read_extent_buffer(eb, &val, 0, csum_size);
+		btrfs_warn_rl(fs_info,
+		"%s checksum verify failed on %llu wanted %x found %x level %d",
+			      fs_info->sb->s_id, eb->start,
+			      val, found, btrfs_header_level(eb));
+		ret = -EUCLEAN;
+		goto err;
+	}
+
 	/*
 	 * If this is a leaf block and it is corrupt, set the corrupt bit so
 	 * that we don't try and read the other copies of this block, just