On Wed, Nov 08, 2017 at 08:54:24AM +0800, Qu Wenruo wrote:
> [BUG]
> If we run btrfs with CONFIG_BTRFS_FS_RUN_SANITY_TESTS=y, it will
> instantly cause kernel panic like:
>
> ------
> ...
> assertion failed: 0, file: fs/btrfs/disk-io.c, line: 3853
> ...
> Call Trace:
> btrfs_mark_buffer_dirty+0x187/0x1f0 [btrfs]
> setup_items_for_insert+0x385/0x650 [btrfs]
> __btrfs_drop_extents+0x129a/0x1870 [btrfs]
> ...
> -----
>
> [Cause]
> Btrfs will call btrfs_check_leaf() in btrfs_mark_buffer_dirty() to check
> if the leaf is valid with CONFIG_BTRFS_FS_RUN_SANITY_TESTS=y.
>
> However quite some btrfs_mark_buffer_dirty() callers(*) don't really
> initialize its item data but only initialize its item pointers, leaving
> item data uninitialized.
>
> This makes tree-checker catch uninitialized data as error, causing
> such panic.
>
> *: These callers include but not limited to
> setup_items_for_insert()
> btrfs_split_item()
> btrfs_expand_item()
>
> [Fix]
> Add a new parameter @check_item_data to btrfs_check_leaf().
> With @check_item_data set to false, item data check will be skipped and
> fallback to old btrfs_check_leaf() behavior.
>
> So we can still get early warning if we screw up item pointers, and
> avoid false panic.
>
Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
Thanks,
-liubo
> Cc: Filipe Manana <fdmanana@xxxxxxxxx>
> Reported-by: Lakshmipathi.G <lakshmipathi.g@xxxxxxxxx>
> Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
> ---
> fs/btrfs/disk-io.c | 10 ++++++++--
> fs/btrfs/tree-checker.c | 27 ++++++++++++++++++++++-----
> fs/btrfs/tree-checker.h | 14 +++++++++++++-
> 3 files changed, 43 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index efce9a2fa9be..10a2a579cc7f 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -610,7 +610,7 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
> * that we don't try and read the other copies of this block, just
> * return -EIO.
> */
> - if (found_level == 0 && btrfs_check_leaf(root, eb)) {
> + if (found_level == 0 && btrfs_check_leaf_full(root, eb)) {
> set_bit(EXTENT_BUFFER_CORRUPT, &eb->bflags);
> ret = -EIO;
> }
> @@ -3848,7 +3848,13 @@ void btrfs_mark_buffer_dirty(struct extent_buffer *buf)
> buf->len,
> fs_info->dirty_metadata_batch);
> #ifdef CONFIG_BTRFS_FS_CHECK_INTEGRITY
> - if (btrfs_header_level(buf) == 0 && btrfs_check_leaf(root, buf)) {
> + /*
> + * Since btrfs_mark_buffer_dirty() can be called with item pointer set
> + * but item data not updated.
> + * So here we should only check item pointers, not item data.
> + */
> + if (btrfs_header_level(buf) == 0 &&
> + btrfs_check_leaf_relaxed(root, buf)) {
> btrfs_print_leaf(buf);
> ASSERT(0);
> }
> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
> index 114fc5f0ecc5..ce4ed6ec8f39 100644
> --- a/fs/btrfs/tree-checker.c
> +++ b/fs/btrfs/tree-checker.c
> @@ -242,7 +242,8 @@ static int check_leaf_item(struct btrfs_root *root,
> return ret;
> }
>
> -int btrfs_check_leaf(struct btrfs_root *root, struct extent_buffer *leaf)
> +static int check_leaf(struct btrfs_root *root, struct extent_buffer *leaf,
> + bool check_item_data)
> {
> struct btrfs_fs_info *fs_info = root->fs_info;
> /* No valid key type is 0, so all key should be larger than this key */
> @@ -361,10 +362,15 @@ int btrfs_check_leaf(struct btrfs_root *root, struct extent_buffer *leaf)
> return -EUCLEAN;
> }
>
> - /* Check if the item size and content meet other criteria */
> - ret = check_leaf_item(root, leaf, &key, slot);
> - if (ret < 0)
> - return ret;
> + if (check_item_data) {
> + /*
> + * Check if the item size and content meet other
> + * criteria
> + */
> + ret = check_leaf_item(root, leaf, &key, slot);
> + if (ret < 0)
> + return ret;
> + }
>
> prev_key.objectid = key.objectid;
> prev_key.type = key.type;
> @@ -374,6 +380,17 @@ int btrfs_check_leaf(struct btrfs_root *root, struct extent_buffer *leaf)
> return 0;
> }
>
> +int btrfs_check_leaf_full(struct btrfs_root *root, struct extent_buffer *leaf)
> +{
> + return check_leaf(root, leaf, true);
> +}
> +
> +int btrfs_check_leaf_relaxed(struct btrfs_root *root,
> + struct extent_buffer *leaf)
> +{
> + return check_leaf(root, leaf, false);
> +}
> +
> int btrfs_check_node(struct btrfs_root *root, struct extent_buffer *node)
> {
> unsigned long nr = btrfs_header_nritems(node);
> diff --git a/fs/btrfs/tree-checker.h b/fs/btrfs/tree-checker.h
> index 96c486e95d70..3d53e8d6fda0 100644
> --- a/fs/btrfs/tree-checker.h
> +++ b/fs/btrfs/tree-checker.h
> @@ -20,7 +20,19 @@
> #include "ctree.h"
> #include "extent_io.h"
>
> -int btrfs_check_leaf(struct btrfs_root *root, struct extent_buffer *leaf);
> +/*
> + * Comprehensive leaf checker.
> + * Will check not only the item pointers, but also every possible member
> + * in item data.
> + */
> +int btrfs_check_leaf_full(struct btrfs_root *root, struct extent_buffer *leaf);
> +
> +/*
> + * Less strict leaf checker.
> + * Will only check item pointers, not reading item data.
> + */
> +int btrfs_check_leaf_relaxed(struct btrfs_root *root,
> + struct extent_buffer *leaf);
> int btrfs_check_node(struct btrfs_root *root, struct extent_buffer *node);
>
> #endif
> --
> 2.15.0
>
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