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ext4srv: fix meta csum producing garbage

A block was never cleared before setting the field.
This would result in garbage and wrong checksums.

Also enable checksum verification now that it actually
works.

--- a/sys/src/cmd/ext4srv/ext4_dir.c

+++ b/sys/src/cmd/ext4srv/ext4_dir.c

@@ -58,14 +58,16 @@

 		t = ext4_dir_get_tail(inode_ref, dirent);

 		if (!t) {

 			/* There is no space to hold the checksum */

+			werrstr("no space for checksum");

 			return false;

 		}

 		intptr diff = (char *)t - (char *)dirent;

 		u32int csum = ext4_dir_csum(inode_ref, dirent, diff);

-		if (t->checksum != to_le32(csum))

+		if (t->checksum != to_le32(csum)) {

+			werrstr("checksum does not match");

 			return false;

-

+		}

 	}

 	return true;

 }

@@ -92,8 +94,7 @@

 		}

 		intptr diff = (char *)t - (char *)dirent;

-		u32int csum = ext4_dir_csum(inode_ref, dirent, diff);

-		t->checksum = to_le32(csum);

+		t->checksum = to_le32(ext4_dir_csum(inode_ref, dirent, diff));

 	}

 }

@@ -305,9 +306,8 @@

 			/* Needed to clear dir index flag if corrupted */

 			ext4_inode_clear_flag(parent->inode, EXT4_INODE_FLAG_INDEX);

 			parent->dirty = true;

-		} else if (r == 0) {

-			return 0;

 		}

+		return r;

 	}

 	/* Linear algorithm */

@@ -377,8 +377,7 @@

 		ext4_dir_write_entry(sb, blk_en, el, child, name, name_len);

 		ext4_dir_init_entry_tail(EXT4_DIRENT_TAIL(b.data, block_size));

 	} else {

-		ext4_dir_write_entry(sb, blk_en, block_size, child, name,

-				name_len);

+		ext4_dir_write_entry(sb, blk_en, block_size, child, name, name_len);

 	}

 	ext4_dir_set_csum(parent, (void *)b.data);

@@ -408,9 +407,8 @@

 			/* Needed to clear dir index flag if corrupted */

 			ext4_inode_clear_flag(parent->inode, EXT4_INODE_FLAG_INDEX);

 			parent->dirty = true;

-		} else if (r == 0) {

-			return 0;

 		}

+		return r;

 	}

 	/* Linear algorithm */

--- a/sys/src/cmd/ext4srv/ext4_dir_idx.c

+++ b/sys/src/cmd/ext4srv/ext4_dir_idx.c

@@ -232,10 +232,6 @@

 	return (struct ext4_dir_idx_climit *)(((char *)dirent) + count_offset);

 }

-/*

- * BIG FAT NOTES:

- *       Currently we do not verify the checksum of HTree node.

- */

 static bool ext4_dir_dx_csum_verify(struct ext4_inode_ref *inode_ref,

 				    struct ext4_dir_en *de)

 {

@@ -262,7 +258,7 @@

 		u32int c = to_le32(ext4_dir_dx_checksum(inode_ref, de, coff, cnt, t));

 		if (t->checksum != c)

-			return true; // FIXME lwext4 does not set correct checksums sometimes

+			return false;

 	}

 	return true;

 }

@@ -292,8 +288,7 @@

 		}

 		t = (void *)(((struct ext4_dir_idx_entry *)climit) + limit);

-		t->checksum = to_le32(ext4_dir_dx_checksum(inode_ref, dirent,

-					coff, count, t));

+		t->checksum = to_le32(ext4_dir_dx_checksum(inode_ref, dirent, coff, count, t));

 	}

 }

@@ -388,6 +383,7 @@

 	if (ext4_sb_feature_ro_com(sb, EXT4_FRO_COM_METADATA_CSUM)) {

 		int len = block_size - sizeof(struct ext4_dir_entry_tail);

+		memset(be, 0, len);

 		ext4_dir_en_set_entry_len(be, len);

 		ext4_dir_en_set_name_len(sb, be, 0);

 		ext4_dir_en_set_inode_type(sb, be, EXT4_DE_UNKNOWN);

@@ -1211,6 +1207,8 @@

 			 "Block: %ud\n",

 			 parent->index,

 			 (u32int)0);

+		werrstr("htree root checksum mismatch");

+		return EXT4_ERR_BAD_DX_DIR;

 	}

 	/* Initialize hinfo structure (mainly compute hash) */

@@ -1263,6 +1261,9 @@

 				"Block: %ud\n",

 				parent->index,

 				leaf_block_idx);

+		r = -1;

+		werrstr("htree leaf block checksum mismatch");

+		goto release_index;

 	}

 	/* Check if insert operation passed */