On Thu, Oct 13, 2016 at 05:22:26PM +0800, Qu Wenruo wrote:
> Kernel clear_cache mount option will only rebuilt free space cache if
> used space of that chunk has changed.
>
> So it won't ensure any corrupted free space cache get cleared.
>
> So add a new option "--clear-space-cache v1|v2" to btrfsck, to
> completely wipe out free space cache.
> So kernel won't complain again.
>
> Reported-by: Ivan P <chrnosphered@xxxxxxxxx>
> Signed-off-by: Qu Wenruo <quwenruo@xxxxxxxxxxxxxx>
> ---
> Documentation/btrfs-check.asciidoc | 9 +++
> cmds-check.c | 63 ++++++++++++++++++-
> free-space-cache.c | 124 +++++++++++++++++++++++++++++++++++++
> free-space-cache.h | 2 +
> 4 files changed, 197 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/btrfs-check.asciidoc b/Documentation/btrfs-check.asciidoc
> index a32e1c7..ef1e464 100644
> --- a/Documentation/btrfs-check.asciidoc
> +++ b/Documentation/btrfs-check.asciidoc
> @@ -78,6 +78,15 @@ respective superblock offset is within the device size
> This can be used to use a different starting point if some of the primary
> superblock is damaged.
>
> +--clear-space-cache v1|v2::
> +completely wipe out all free space cache.
> +Only v1(file based) free space cache is supported yet.
> ++
> +NOTE: Kernel mount option 'clear_cache' is only designed to rebuild free space cache
> +which is modified during the lifetime of that mount option.
> +It doesn't rebuild all free space cache, nor clear them out.
> +
> +
> DANGEROUS OPTIONS
> -----------------
>
> diff --git a/cmds-check.c b/cmds-check.c
> index 670ccd1..f62fc62 100644
> --- a/cmds-check.c
> +++ b/cmds-check.c
> @@ -11206,6 +11206,36 @@ out:
> return bad_roots;
> }
>
> +static int clear_free_space_cache(struct btrfs_fs_info *fs_info)
> +{
> + struct btrfs_trans_handle *trans;
> + struct btrfs_block_group_cache *bg_cache;
> + u64 current = 0;
> + int ret = 0;
> +
> + /* Clear all free space cache inodes and its extent data */
> + while (1) {
> + bg_cache = btrfs_lookup_first_block_group(fs_info, current);
> + if (!bg_cache)
> + break;
> + ret = btrfs_clear_free_space_cache(fs_info, bg_cache);
The function can fail for a lot of reasons, what would be the filesystem
state when we exit here? Some of the inodes could be cleared completely,
the last one partially. The function copes with a missing inode item
but I don't know how many other intermediate states could be left.
> + if (ret < 0)
> + return ret;
> + current = bg_cache->key.objectid + bg_cache->key.offset;
> + }
> +
> + /* Don't forget to set cache_generation to -1 */
> + trans = btrfs_start_transaction(fs_info->tree_root, 0);
> + if (IS_ERR(trans)) {
> + error("failed to update super block cache generation");
> + return PTR_ERR(trans);
> + }
> + btrfs_set_super_cache_generation(fs_info->super_copy, (u64)-1);
> + btrfs_commit_transaction(trans, fs_info->tree_root);
> +
> + return ret;
> +}
> +
> const char * const cmd_check_usage[] = {
> "btrfs check [options] <device>",
> "Check structural integrity of a filesystem (unmounted).",
> @@ -11233,6 +11263,9 @@ const char * const cmd_check_usage[] = {
> "-r|--tree-root <bytenr> use the given bytenr for the tree root",
> "--chunk-root <bytenr> use the given bytenr for the chunk tree root",
> "-p|--progress indicate progress",
> + "--clear-space-cache v1|v2 clear space cache for v1(file based) or ",
> + " v2(tree based).",
> + " Only support v1 yet",
> NULL
> };
>
> @@ -11250,6 +11283,7 @@ int cmd_check(int argc, char **argv)
> u64 num;
> int init_csum_tree = 0;
> int readonly = 0;
> + int clear_space_cache = 0;
> int qgroup_report = 0;
> int qgroups_repaired = 0;
> unsigned ctree_flags = OPEN_CTREE_EXCLUSIVE;
> @@ -11259,7 +11293,7 @@ int cmd_check(int argc, char **argv)
> 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_MODE };
> + GETOPT_VAL_MODE, GETOPT_VAL_CLEAR_SPACE_CACHE };
> static const struct option long_options[] = {
> { "super", required_argument, NULL, 's' },
> { "repair", no_argument, NULL, GETOPT_VAL_REPAIR },
> @@ -11279,6 +11313,8 @@ int cmd_check(int argc, char **argv)
> { "progress", no_argument, NULL, 'p' },
> { "mode", required_argument, NULL,
> GETOPT_VAL_MODE },
> + { "clear-space-cache", required_argument, NULL,
> + GETOPT_VAL_CLEAR_SPACE_CACHE},
> { NULL, 0, NULL, 0}
> };
>
> @@ -11350,6 +11386,14 @@ int cmd_check(int argc, char **argv)
> exit(1);
> }
> break;
> + case GETOPT_VAL_CLEAR_SPACE_CACHE:
> + if (strcmp(optarg, "v1")) {
> + error("only support to clear 'v1' space cache");
> + exit(1);
> + }
> + clear_space_cache = 1;
> + ctree_flags |= OPEN_CTREE_WRITES;
> + break;
> }
> }
>
> @@ -11401,6 +11445,23 @@ int cmd_check(int argc, char **argv)
>
> global_info = info;
> root = info->fs_root;
> + if (clear_space_cache) {
> + if (btrfs_fs_compat_ro(info,
> + BTRFS_FEATURE_COMPAT_RO_FREE_SPACE_TREE)) {
> + error("doesn't support free space cache v2(tree based) yet");
> + ret = 1;
> + goto close_out;
> + }
> + printf("Clearing free space cache\n");
> + ret = clear_free_space_cache(info);
> + if (ret) {
> + error("failed to clear free space cache");
> + ret = 1;
> + } else {
> + printf("Free space cache cleared\n");
> + }
> + goto close_out;
> + }
>
> /*
> * repair mode will force us to commit transaction which
> diff --git a/free-space-cache.c b/free-space-cache.c
> index 1919d90..88a1013 100644
> --- a/free-space-cache.c
> +++ b/free-space-cache.c
> @@ -25,6 +25,7 @@
> #include "crc32c.h"
> #include "bitops.h"
> #include "internal.h"
> +#include "utils.h"
>
> /*
> * Kernel always uses PAGE_CACHE_SIZE for sectorsize, but we don't have
> @@ -877,3 +878,126 @@ next:
> prev = e;
> }
> }
> +
> +int btrfs_clear_free_space_cache(struct btrfs_fs_info *fs_info,
> + struct btrfs_block_group_cache *bg)
> +{
> + struct btrfs_trans_handle *trans;
> + struct btrfs_root *tree_root = fs_info->tree_root;
> + struct btrfs_path path;
> + struct btrfs_key key;
> + struct btrfs_disk_key location;
> + struct btrfs_free_space_header *sc_header;
> + struct extent_buffer *node;
> + u64 ino;
> + int slot;
> + int ret;
> +
> + trans = btrfs_start_transaction(tree_root, 1);
> + if (IS_ERR(trans))
> + return PTR_ERR(trans);
> +
> + btrfs_init_path(&path);
> +
> + key.objectid = BTRFS_FREE_SPACE_OBJECTID;
> + key.type = 0;
> + key.offset = bg->key.objectid;
> +
> + ret = btrfs_search_slot(trans, tree_root, &key, &path, -1, 1);
> + if (ret > 0) {
> + ret = 0;
> + goto out;
> + }
> + if (ret < 0)
> + goto out;
> +
> + node = path.nodes[0];
> + slot = path.slots[0];
> + sc_header = btrfs_item_ptr(node, slot, struct btrfs_free_space_header);
> + btrfs_free_space_key(node, sc_header, &location);
> + ino = location.objectid;
> +
> + /* Delete the free space header, as we have the ino to continue */
> + ret = btrfs_del_item(trans, tree_root, &path);
> + if (ret < 0) {
> + error("failed to remove free space header for block group %llu",
> + bg->key.objectid);
> + goto out;
> + }
> + btrfs_release_path(&path);
> +
> + /* Iterate from the end of the free space cache inode */
> + key.objectid = ino;
> + key.type = BTRFS_EXTENT_DATA_KEY;
> + key.offset = (u64)-1;
> + ret = btrfs_search_slot(trans, tree_root, &key, &path, -1, 1);
> + if (ret < 0) {
> + error("failed to locate free space cache extent for block group %llu",
> + bg->key.objectid);
> + goto out;
> + }
> + while (1) {
> + struct btrfs_file_extent_item *fi;
> + u64 disk_bytenr;
> + u64 disk_num_bytes;
> +
> +
> + ret = btrfs_previous_item(tree_root, &path, ino,
> + BTRFS_EXTENT_DATA_KEY);
> + if (ret > 0) {
> + ret = 0;
> + break;
> + }
> + if (ret < 0) {
> + error("failed to locate free space cache extent for block group %llu",
> + bg->key.objectid);
> + goto out;
> + }
> + node = path.nodes[0];
> + slot = path.slots[0];
> + btrfs_item_key_to_cpu(node, &key, slot);
> + fi = btrfs_item_ptr(node, slot, struct btrfs_file_extent_item);
> + disk_bytenr = btrfs_file_extent_disk_bytenr(node, fi);
> + disk_num_bytes = btrfs_file_extent_disk_num_bytes(node, fi);
> +
> + ret = btrfs_free_extent(trans, tree_root, disk_bytenr,
> + disk_num_bytes, 0, tree_root->objectid,
> + ino, key.offset);
> + if (ret < 0) {
> + error("failed to remove backref for disk bytenr %llu",
> + disk_bytenr);
> + goto out;
> + }
> + ret = btrfs_del_item(trans, tree_root, &path);
> + if (ret < 0) {
> + error("failed to remove free space extent data for ino %llu offset %llu",
> + ino, key.offset);
> + goto out;
> + }
> + }
> + btrfs_release_path(&path);
> +
> + /* Now delete free space cache inode item */
> + key.objectid = ino;
> + key.type = BTRFS_INODE_ITEM_KEY;
> + key.offset = 0;
> +
> + ret = btrfs_search_slot(trans, tree_root, &key, &path, -1, 1);
> + if (ret > 0)
> + warning("free space inode %llu not found, ignore", ino);
> + if (ret < 0) {
> + error("failed to locate free space cache inode %llu for block group %llu",
> + ino, bg->key.objectid);
> + goto out;
> + }
> + ret = btrfs_del_item(trans, tree_root, &path);
> + if (ret < 0) {
> + error("failed to delete free space cache inode %llu for block group %llu",
> + ino, bg->key.objectid);
> + }
> +out:
> + btrfs_release_path(&path);
> + if (!ret)
> + btrfs_commit_transaction(trans, tree_root);
> + return ret;
> +}
--
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