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btrfs-progs: check: introduce function to check tree block backref in extent tree 

Introduce function check_tree_block_ref() to check whether a tree block
has correct backref in extent tree.

Unlike old extent tree check method, we only use search_slot() to search
reference, no extra structure will be allocated in heap to record what we
have checked.

This method may cause a little more IO, but should work for super large
fs without triggering OOM.

Signed-off-by: Lu Fengqi <lufq.fnst@cn.fujitsu.com>
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Reviewed-by: Josef Bacik <jbacik@fb.com>
Signed-off-by: David Sterba <dsterba@suse.com>
master
Lu Fengqi 2016-04-23 14:40:37 +08:00 committed by David Sterba
parent a13bfba3e2
commit ae60006cee
1 changed files with 165 additions and 0 deletions
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165
cmds-check.c
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@ -434,6 +434,15 @@ struct root_item_info {
struct cache_extent cache_extent;
};
/*
* Error bit for low memory mode check.
*
* Currently no caller cares about it yet. Just internal use for error
* classification.
*/
#define BACKREF_MISSING (1 << 0) /* Backref missing in extent tree */
#define BACKREF_MISMATCH (1 << 1) /* Backref exists but does not match */
static void *print_status_check(void *p)
{
struct task_ctx *priv = p;
@ -8539,6 +8548,162 @@ loop:
goto again;
}
/*
* Check backrefs of a tree block given by @bytenr or @eb.
*
* @root: the root containing the @bytenr or @eb
* @eb: tree block extent buffer, can be NULL
* @bytenr: bytenr of the tree block to search
* @level: tree level of the tree block
* @owner: owner of the tree block
*
* Return >0 for any error found and output error message
* Return 0 for no error found
*/
static int check_tree_block_ref(struct btrfs_root *root,
struct extent_buffer *eb, u64 bytenr,
int level, u64 owner)
{
struct btrfs_key key;
struct btrfs_root *extent_root = root->fs_info->extent_root;
struct btrfs_path path;
struct btrfs_extent_item *ei;
struct btrfs_extent_inline_ref *iref;
struct extent_buffer *leaf;
unsigned long end;
unsigned long ptr;
int slot;
int skinny_level;
int type;
u32 nodesize = root->nodesize;
u32 item_size;
u64 offset;
int found_ref = 0;
int err = 0;
int ret;
btrfs_init_path(&path);
key.objectid = bytenr;
if (btrfs_fs_incompat(root->fs_info,
BTRFS_FEATURE_INCOMPAT_SKINNY_METADATA))
key.type = BTRFS_METADATA_ITEM_KEY;
else
key.type = BTRFS_EXTENT_ITEM_KEY;
key.offset = (u64)-1;
/* Search for the backref in extent tree */
ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
if (ret < 0) {
err |= BACKREF_MISSING;
goto out;
}
ret = btrfs_previous_extent_item(extent_root, &path, bytenr);
if (ret) {
err |= BACKREF_MISSING;
goto out;
}
leaf = path.nodes[0];
slot = path.slots[0];
btrfs_item_key_to_cpu(leaf, &key, slot);
ei = btrfs_item_ptr(leaf, slot, struct btrfs_extent_item);
if (key.type == BTRFS_METADATA_ITEM_KEY) {
skinny_level = (int)key.offset;
iref = (struct btrfs_extent_inline_ref *)(ei + 1);
} else {
struct btrfs_tree_block_info *info;
info = (struct btrfs_tree_block_info *)(ei + 1);
skinny_level = btrfs_tree_block_level(leaf, info);
iref = (struct btrfs_extent_inline_ref *)(info + 1);
}
if (eb) {
u64 header_gen;
u64 extent_gen;
if (!(btrfs_extent_flags(leaf, ei) &
BTRFS_EXTENT_FLAG_TREE_BLOCK)) {
error(
"extent[%llu %u] backref type mismatch, missing bit: %llx",
key.objectid, nodesize,
BTRFS_EXTENT_FLAG_TREE_BLOCK);
err = BACKREF_MISMATCH;
}
header_gen = btrfs_header_generation(eb);
extent_gen = btrfs_extent_generation(leaf, ei);
if (header_gen != extent_gen) {
error(
"extent[%llu %u] backref generation mismatch, wanted: %llu, have: %llu",
key.objectid, nodesize, header_gen,
extent_gen);
err = BACKREF_MISMATCH;
}
if (level != skinny_level) {
error(
"extent[%llu %u] level mismatch, wanted: %u, have: %u",
key.objectid, nodesize, level, skinny_level);
err = BACKREF_MISMATCH;
}
if (!is_fstree(owner) && btrfs_extent_refs(leaf, ei) != 1) {
error(
"extent[%llu %u] is referred by other roots than %llu",
key.objectid, nodesize, root->objectid);
err = BACKREF_MISMATCH;
}
}
/*
* Iterate the extent/metadata item to find the exact backref
*/
item_size = btrfs_item_size_nr(leaf, slot);
ptr = (unsigned long)iref;
end = (unsigned long)ei + item_size;
while (ptr < end) {
iref = (struct btrfs_extent_inline_ref *)ptr;
type = btrfs_extent_inline_ref_type(leaf, iref);
offset = btrfs_extent_inline_ref_offset(leaf, iref);
if (type == BTRFS_TREE_BLOCK_REF_KEY &&
(offset == root->objectid || offset == owner)) {
found_ref = 1;
} else if (type == BTRFS_SHARED_BLOCK_REF_KEY) {
/* Check if the backref points to valid referencer */
found_ref = !check_tree_block_ref(root, NULL, offset,
level + 1, owner);
}
if (found_ref)
break;
ptr += btrfs_extent_inline_ref_size(type);
}
/*
* Inlined extent item doesn't have what we need, check
* TREE_BLOCK_REF_KEY
*/
if (!found_ref) {
btrfs_release_path(&path);
key.objectid = bytenr;
key.type = BTRFS_TREE_BLOCK_REF_KEY;
key.offset = root->objectid;
ret = btrfs_search_slot(NULL, extent_root, &key, &path, 0, 0);
if (!ret)
found_ref = 1;
}
if (!found_ref)
err |= BACKREF_MISSING;
out:
btrfs_release_path(&path);
if (eb && (err & BACKREF_MISSING))
error("extent[%llu %u] backref lost (owner: %llu, level: %u)",
bytenr, nodesize, owner, level);
return err;
}
static int btrfs_fsck_reinit_root(struct btrfs_trans_handle *trans,
struct btrfs_root *root, int overwrite)
{