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    Subject[PATCH 4.4 13/51] Btrfs: memset to avoid stale content in btree leaf
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    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>
    ---
    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
    @@ -1726,20 +1726,6 @@ 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
    @@ -3158,6 +3158,21 @@ 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
    @@ -3847,8 +3847,10 @@ 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;

    @@ -3858,15 +3860,21 @@ 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++) {

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