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btrfs-progs: check: supplement extent backref list with rbtree

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For the pathlogical case, like xfstests generic/297 that creates a
large file consisting of one, repeating reflinked extent, fsck can
take hours.  The root cause is that calling find_data_backref while
iterating the extent records is an O(n^2) algorithm.  For my
example test run, n was 2*2^20 and fsck was at 8 hours and counting.

This patch supplements the list with an rbtree and drops the runtime
of that testcase to about 20 seconds.

A previous version of this patch introduced a regression that would
have corrupted file systems during repair.  It was traced to the
compare algorithm honoring ->bytes regardless of whether the
reference had been found and a failure to reinsert nodes after
the target reference was found.

Signed-off-by: Jeff Mahoney <jeffm@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Jeff Mahoney 2017-07-25 16:51:32 -04:00 committed by David Sterba
parent 530ca51307
commit 756105181e
1 changed files with 180 additions and 4 deletions
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184
cmds-check.c
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@ -86,6 +86,7 @@ static enum btrfs_check_mode check_mode = CHECK_MODE_DEFAULT;
struct extent_backref {
struct list_head list;
struct rb_node node;
unsigned int is_data:1;
unsigned int found_extent_tree:1;
unsigned int full_backref:1;
@ -98,6 +99,11 @@ static inline struct extent_backref* to_extent_backref(struct list_head *entry)
return list_entry(entry, struct extent_backref, list);
}
static inline struct extent_backref* rb_node_to_extent_backref(struct rb_node *node)
{
return rb_entry(node, struct extent_backref, node);
}
struct data_backref {
struct extent_backref node;
union {
@ -136,6 +142,51 @@ static inline struct data_backref* to_data_backref(struct extent_backref *back)
return container_of(back, struct data_backref, node);
}
static int compare_data_backref(struct rb_node *node1, struct rb_node *node2)
{
struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
struct extent_backref *ext2 = rb_node_to_extent_backref(node2);
struct data_backref *back1 = to_data_backref(ext1);
struct data_backref *back2 = to_data_backref(ext2);
WARN_ON(!ext1->is_data);
WARN_ON(!ext2->is_data);
/* parent and root are a union, so this covers both */
if (back1->parent > back2->parent)
return 1;
if (back1->parent < back2->parent)
return -1;
/* This is a full backref and the parents match. */
if (back1->node.full_backref)
return 0;
if (back1->owner > back2->owner)
return 1;
if (back1->owner < back2->owner)
return -1;
if (back1->offset > back2->offset)
return 1;
if (back1->offset < back2->offset)
return -1;
if (back1->found_ref && back2->found_ref) {
if (back1->disk_bytenr > back2->disk_bytenr)
return 1;
if (back1->disk_bytenr < back2->disk_bytenr)
return -1;
if (back1->bytes > back2->bytes)
return 1;
if (back1->bytes < back2->bytes)
return -1;
}
return 0;
}
/*
* Much like data_backref, just removed the undetermined members
* and change it to use list_head.
@ -164,12 +215,54 @@ static inline struct tree_backref* to_tree_backref(struct extent_backref *back)
return container_of(back, struct tree_backref, node);
}
static int compare_tree_backref(struct rb_node *node1, struct rb_node *node2)
{
struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
struct extent_backref *ext2 = rb_node_to_extent_backref(node2);
struct tree_backref *back1 = to_tree_backref(ext1);
struct tree_backref *back2 = to_tree_backref(ext2);
WARN_ON(ext1->is_data);
WARN_ON(ext2->is_data);
/* parent and root are a union, so this covers both */
if (back1->parent > back2->parent)
return 1;
if (back1->parent < back2->parent)
return -1;
return 0;
}
static int compare_extent_backref(struct rb_node *node1, struct rb_node *node2)
{
struct extent_backref *ext1 = rb_node_to_extent_backref(node1);
struct extent_backref *ext2 = rb_node_to_extent_backref(node2);
if (ext1->is_data > ext2->is_data)
return 1;
if (ext1->is_data < ext2->is_data)
return -1;
if (ext1->full_backref > ext2->full_backref)
return 1;
if (ext1->full_backref < ext2->full_backref)
return -1;
if (ext1->is_data)
return compare_data_backref(node1, node2);
else
return compare_tree_backref(node1, node2);
}
/* Explicit initialization for extent_record::flag_block_full_backref */
enum { FLAG_UNSET = 2 };
struct extent_record {
struct list_head backrefs;
struct list_head dups;
struct rb_root backref_tree;
struct list_head list;
struct cache_extent cache;
struct btrfs_disk_key parent_key;
@ -5067,6 +5160,65 @@ out:
return ret;
}
static struct tree_backref *find_tree_backref(struct extent_record *rec,
u64 parent, u64 root)
{
struct rb_node *node;
struct tree_backref *back = NULL;
struct tree_backref match = {
.node = {
.is_data = 0,
},
};
if (parent) {
match.parent = parent;
match.node.full_backref = 1;
} else {
match.root = root;
}
node = rb_search(&rec->backref_tree, &match.node.node,
(rb_compare_keys)compare_extent_backref, NULL);
if (node)
back = to_tree_backref(rb_node_to_extent_backref(node));
return back;
}
static struct data_backref *find_data_backref(struct extent_record *rec,
u64 parent, u64 root,
u64 owner, u64 offset,
int found_ref,
u64 disk_bytenr, u64 bytes)
{
struct rb_node *node;
struct data_backref *back = NULL;
struct data_backref match = {
.node = {
.is_data = 1,
},
.owner = owner,
.offset = offset,
.bytes = bytes,
.found_ref = found_ref,
.disk_bytenr = disk_bytenr,
};
if (parent) {
match.parent = parent;
match.node.full_backref = 1;
} else {
match.root = root;
}
node = rb_search(&rec->backref_tree, &match.node.node,
(rb_compare_keys)compare_extent_backref, NULL);
if (node)
back = to_data_backref(rb_node_to_extent_backref(node));
return back;
}
/*
* Iterate all item on the tree and call check_inode_item() to check.
*
@ -5347,7 +5499,7 @@ static int all_backpointers_checked(struct extent_record *rec, int print_errs)
goto out;
if (back->is_data) {
dback = to_data_backref(back);
fprintf(stderr, "Backref %llu %s %llu"
fprintf(stderr, "Data backref %llu %s %llu"
" owner %llu offset %llu num_refs %lu"
" not found in extent tree\n",
(unsigned long long)rec->start,
@ -5361,7 +5513,7 @@ static int all_backpointers_checked(struct extent_record *rec, int print_errs)
(unsigned long)dback->num_refs);
} else {
tback = to_tree_backref(back);
fprintf(stderr, "Backref %llu parent %llu"
fprintf(stderr, "Tree backref %llu parent %llu"
" root %llu not found in extent tree\n",
(unsigned long long)rec->start,
(unsigned long long)tback->parent,
@ -5919,6 +6071,7 @@ static int check_block(struct btrfs_root *root,
return ret;
}
#if 0
static struct tree_backref *find_tree_backref(struct extent_record *rec,
u64 parent, u64 root)
{
@ -5946,6 +6099,7 @@ static struct tree_backref *find_tree_backref(struct extent_record *rec,
}
return NULL;
}
#endif
static struct tree_backref *alloc_tree_backref(struct extent_record *rec,
u64 parent, u64 root)
@ -5967,6 +6121,7 @@ static struct tree_backref *alloc_tree_backref(struct extent_record *rec,
return ref;
}
#if 0
static struct data_backref *find_data_backref(struct extent_record *rec,
u64 parent, u64 root,
u64 owner, u64 offset,
@ -6003,6 +6158,7 @@ static struct data_backref *find_data_backref(struct extent_record *rec,
}
return NULL;
}
#endif
static struct data_backref *alloc_data_backref(struct extent_record *rec,
u64 parent, u64 root,
@ -6119,6 +6275,7 @@ static int add_extent_rec_nolookup(struct cache_tree *extent_cache,
INIT_LIST_HEAD(&rec->backrefs);
INIT_LIST_HEAD(&rec->dups);
INIT_LIST_HEAD(&rec->list);
rec->backref_tree = RB_ROOT;
memcpy(&rec->parent_key, &tmpl->parent_key, sizeof(tmpl->parent_key));
rec->cache.start = tmpl->start;
rec->cache.size = tmpl->nr;
@ -6251,6 +6408,7 @@ static int add_tree_backref(struct cache_tree *extent_cache, u64 bytenr,
struct tree_backref *back;
struct cache_extent *cache;
int ret;
bool insert = false;
cache = lookup_cache_extent(extent_cache, bytenr, 1);
if (!cache) {
@ -6285,6 +6443,7 @@ static int add_tree_backref(struct cache_tree *extent_cache, u64 bytenr,
back = alloc_tree_backref(rec, parent, root);
if (!back)
return -ENOMEM;
insert = true;
}
if (found_ref) {
@ -6306,6 +6465,9 @@ static int add_tree_backref(struct cache_tree *extent_cache, u64 bytenr,
}
back->node.found_extent_tree = 1;
}
if (insert)
WARN_ON(rb_insert(&rec->backref_tree, &back->node.node,
compare_extent_backref));
check_extent_type(rec);
maybe_free_extent_rec(extent_cache, rec);
return 0;
@ -6319,6 +6481,7 @@ static int add_data_backref(struct cache_tree *extent_cache, u64 bytenr,
struct data_backref *back;
struct cache_extent *cache;
int ret;
bool insert = false;
cache = lookup_cache_extent(extent_cache, bytenr, 1);
if (!cache) {
@ -6358,6 +6521,7 @@ static int add_data_backref(struct cache_tree *extent_cache, u64 bytenr,
back = alloc_data_backref(rec, parent, root, owner, offset,
max_size);
BUG_ON(!back);
insert = true;
}
if (found_ref) {
@ -6366,8 +6530,16 @@ static int add_data_backref(struct cache_tree *extent_cache, u64 bytenr,
BUG_ON(back->bytes != max_size);
back->node.found_ref = 1;
back->found_ref += 1;
back->bytes = max_size;
back->disk_bytenr = bytenr;
if (back->bytes != max_size || back->disk_bytenr != bytenr) {
back->bytes = max_size;
back->disk_bytenr = bytenr;
/* Need to reinsert if not already in the tree */
if (!insert) {
rb_erase(&back->node.node, &rec->backref_tree);
insert = true;
}
}
rec->refs += 1;
rec->content_checked = 1;
rec->owner_ref_checked = 1;
@ -6386,6 +6558,10 @@ static int add_data_backref(struct cache_tree *extent_cache, u64 bytenr,
back->num_refs = num_refs;
back->node.found_extent_tree = 1;
}
if (insert)
WARN_ON(rb_insert(&rec->backref_tree, &back->node.node,
compare_extent_backref));
maybe_free_extent_rec(extent_cache, rec);
return 0;
}