[PATCH 3.16 035/245] Btrfs: memset to avoid stale content in btree leaf

Ben Hutchings
2020-04-23T23:24:50Z

From: Liu Bo <bo.li.liu@oracle.com>

commit 851cd173f06045816528176001cf82948282029c upstream.

This is an additional patch to
"Btrfs: memset to avoid stale content in btree node block".

This uses memset to initialize the unused space in a leaf to avoid
potential stale content, which may be incurred by pushing items
between sibling leaves.

Signed-off-by: Liu Bo <bo.li.liu@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/btrfs/ctree.c | 14 --------------
fs/btrfs/ctree.h | 15 +++++++++++++++
fs/btrfs/extent_io.c | 18 +++++++++++++-----
3 files changed, 28 insertions(+), 19 deletions(-)

--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -1721,20 +1721,6 @@ int btrfs_realloc_node(struct btrfs_tran
return err;
}

-/*
- * The leaf data grows from end-to-front in the node.
- * this returns the address of the start of the last item,
- * which is the stop of the leaf data stack
- */
-static inline unsigned int leaf_data_end(struct btrfs_root *root,
- struct extent_buffer *leaf)
-{
- u32 nr = btrfs_header_nritems(leaf);
- if (nr == 0)
- return BTRFS_LEAF_DATA_SIZE(root);
- return btrfs_item_offset_nr(leaf, nr - 1);
-}
-

/*
* search for key in the extent_buffer. The items start at offset p,
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3036,6 +3036,21 @@ static inline unsigned long btrfs_leaf_d
return offsetof(struct btrfs_leaf, items);
}

+/*
+ * The leaf data grows from end-to-front in the node.
+ * this returns the address of the start of the last item,
+ * which is the stop of the leaf data stack
+ */
+static inline unsigned int leaf_data_end(struct btrfs_root *root,
+ struct extent_buffer *leaf)
+{
+ u32 nr = btrfs_header_nritems(leaf);
+
+ if (nr == 0)
+ return BTRFS_LEAF_DATA_SIZE(root);
+ return btrfs_item_offset_nr(leaf, nr - 1);
+}
+
/* struct btrfs_file_extent_item */
BTRFS_SETGET_FUNCS(file_extent_type, struct btrfs_file_extent_item, type, 8);
BTRFS_SETGET_STACK_FUNCS(stack_file_extent_disk_bytenr,
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -3617,8 +3617,10 @@ static noinline_for_stack int write_one_
struct block_device *bdev = fs_info->fs_devices->latest_bdev;
struct extent_io_tree *tree = &BTRFS_I(fs_info->btree_inode)->io_tree;
u64 offset = eb->start;
+ u32 nritems;
unsigned long i, num_pages;
unsigned long bio_flags = 0;
+ unsigned long start, end;
int rw = (epd->sync_io ? WRITE_SYNC : WRITE) | REQ_META;
int ret = 0;

@@ -3628,15 +3630,21 @@ static noinline_for_stack int write_one_
if (btrfs_header_owner(eb) == BTRFS_TREE_LOG_OBJECTID)
bio_flags = EXTENT_BIO_TREE_LOG;

- /* set btree node beyond nritems with 0 to avoid stale content */
+ /* set btree blocks beyond nritems with 0 to avoid stale content. */
+ nritems = btrfs_header_nritems(eb);
if (btrfs_header_level(eb) > 0) {
- u32 nritems;
- unsigned long end;
-
- nritems = btrfs_header_nritems(eb);
end = btrfs_node_key_ptr_offset(nritems);

memset_extent_buffer(eb, 0, end, eb->len - end);
+ } else {
+ /*
+ * leaf:
+ * header 0 1 2 .. N ... data_N .. data_2 data_1 data_0
+ */
+ start = btrfs_item_nr_offset(nritems);
+ end = btrfs_leaf_data(eb) +
+ leaf_data_end(fs_info->tree_root, eb);
+ memset_extent_buffer(eb, 0, start, end - start);
}

for (i = 0; i < num_pages; i++) {