From: Lu Fengqi <lufq.f...@cn.fujitsu.com>
Introduce a new fsck mode: low memory mode.
Old btrfsck is doing a quite efficient but uses some memory for each
extent item.
Old method will ensure extents are only iterated once at extent/chunk
tree check process.
But since it uses a little memory for each extent item, for large fs
with several TB metadata, this can easily eat up memory and cause OOM.
To handle such limitation and improve scalability, the new low-memory
mode will not use any heap memory to record which extent is checked.
Instead it will use extent backref to avoid most of uneeded check on
shared fs/subvolume tree blocks.
And with the use forward and backward reference cross check, we can also
ensure every tree block is at least checked once.
Signed-off-by: Lu Fengqi <lufq.f...@cn.fujitsu.com>
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
Documentation/btrfs-check.asciidoc | 6 +++
cmds-check.c | 80 +++++++++++++++++++++++++++++++++++++-
2 files changed, 84 insertions(+), 2 deletions(-)
diff --git a/Documentation/btrfs-check.asciidoc
b/Documentation/btrfs-check.asciidoc
index 74a2ad2..4e27863 100644
--- a/Documentation/btrfs-check.asciidoc
+++ b/Documentation/btrfs-check.asciidoc
@@ -93,6 +93,12 @@ build the extent tree from scratch
+
NOTE: Do not use unless you know what you're doing.
+--low-memory::
+check fs in low memory usage mode(experimental)
+May takes longer time than normal check.
++
+NOTE: Doesn't work with '--repair' option yet.
+
EXIT STATUS
-----------
*btrfs check* returns a zero exit status if it succeeds. Non zero is
diff --git a/cmds-check.c b/cmds-check.c
index 6a49f07..7a3026c 100644
--- a/cmds-check.c
+++ b/cmds-check.c
@@ -71,6 +71,7 @@ static int repair = 0;
static int no_holes = 0;
static int init_extent_tree = 0;
static int check_data_csum = 0;
+static int low_memory = 0;
static struct btrfs_fs_info *global_info;
static struct task_ctx ctx = { 0 };
static struct cache_tree *roots_info_cache = NULL;
@@ -9795,6 +9796,63 @@ static int traversal_tree_block(struct btrfs_root *root,
return err;
}
+/*
+ * Low memory usage version check_chunks_and_extents.
+ */
+static int check_chunks_and_extents_v2(struct btrfs_root *root)
+{
+ struct btrfs_path path;
+ struct btrfs_key key;
+ struct btrfs_root *root1;
+ struct btrfs_root *cur_root;
+ int err = 0;
+ int ret;
+
+ root1 = root->fs_info->chunk_root;
+ ret = traversal_tree_block(root1, root1->node);
+ err |= ret;
+
+ root1 = root->fs_info->tree_root;
+ ret = traversal_tree_block(root1, root1->node);
+ err |= ret;
+
+ btrfs_init_path(&path);
+ key.objectid = BTRFS_EXTENT_TREE_OBJECTID;
+ key.offset = 0;
+ key.type = BTRFS_ROOT_ITEM_KEY;
+
+ ret = btrfs_search_slot(NULL, root1, &key, &path, 0, 0);
+ if (ret) {
+ error("couldn't find extent_tree_root from tree_root");
+ goto out;
+ }
+
+ while (1) {
+ btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+ if (key.type != BTRFS_ROOT_ITEM_KEY)
+ goto next;
+ key.offset = (u64)-1;
+
+ cur_root = btrfs_read_fs_root(root->fs_info, &key);
+ if (IS_ERR(cur_root) || !cur_root) {
+ error("Fail to read tree: %lld", key.objectid);
+ goto next;
+ }
+
+ ret = traversal_tree_block(cur_root, cur_root->node);
+ err |= ret;
+
+next:
+ ret = btrfs_next_item(root1, &path);
+ if (ret)
+ goto out;
+ }
+
+out:
+ btrfs_release_path(&path);
+ return err;
+}
+
static int btrfs_fsck_reinit_root(struct btrfs_trans_handle *trans,
struct btrfs_root *root, int overwrite)
{
@@ -10911,6 +10969,7 @@ const char * const cmd_check_usage[] = {
"--readonly run in read-only mode (default)",
"--init-csum-tree create a new CRC tree",
"--init-extent-tree create a new extent tree",
+ "--low-memory check in low memory usage
mode(experimental)",
"--check-data-csum verify checksums of data blocks",
"-Q|--qgroup-report print a report on qgroup consistency",
"-E|--subvol-extents <subvolid>",
@@ -10942,7 +11001,8 @@ int cmd_check(int argc, char **argv)
int c;
enum { GETOPT_VAL_REPAIR = 257, GETOPT_VAL_INIT_CSUM,
GETOPT_VAL_INIT_EXTENT, GETOPT_VAL_CHECK_CSUM,
- GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE };
+ GETOPT_VAL_READONLY, GETOPT_VAL_CHUNK_TREE,
+ GETOPT_VAL_LOW_MEMORY };
static const struct option long_options[] = {
{ "super", required_argument, NULL, 's' },
{ "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
@@ -10960,6 +11020,8 @@ int cmd_check(int argc, char **argv)
{ "chunk-root", required_argument, NULL,
GETOPT_VAL_CHUNK_TREE },
{ "progress", no_argument, NULL, 'p' },
+ { "low-memory", no_argument, NULL,
+ GETOPT_VAL_LOW_MEMORY },
{ NULL, 0, NULL, 0}
};
@@ -11024,6 +11086,9 @@ int cmd_check(int argc, char **argv)
case GETOPT_VAL_CHECK_CSUM:
check_data_csum = 1;
break;
+ case GETOPT_VAL_LOW_MEMORY:
+ low_memory = 1;
+ break;
}
}
@@ -11041,6 +11106,14 @@ int cmd_check(int argc, char **argv)
exit(1);
}
+ /*
+ * Not supported yet
+ */
+ if (repair && low_memory) {
+ error("Low memory mode doesn't support repair yet");
+ exit(1);
+ }
+
radix_tree_init();
cache_tree_init(&root_cache);
@@ -11164,7 +11237,10 @@ int cmd_check(int argc, char **argv)
if (!ctx.progress_enabled)
fprintf(stderr, "checking extents\n");
- ret = check_chunks_and_extents(root);
+ if (low_memory)
+ ret = check_chunks_and_extents_v2(root);
+ else
+ ret = check_chunks_and_extents(root);
if (ret)
fprintf(stderr, "Errors found in extent allocation tree or
chunk allocation\n");
--
2.8.2
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