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 <chrnosphe...@gmail.com>
> Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
> ---
>  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.
> +
> +

For space_cache=v2, clear_cache does immediately destroy the entire free
space tree. Still, this could be useful support to have in btrfsck
anyways.

>  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);
> +             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;
> +}
> diff --git a/free-space-cache.h b/free-space-cache.h
> index 9214077..707fb6d 100644
> --- a/free-space-cache.h
> +++ b/free-space-cache.h
> @@ -59,4 +59,6 @@ void unlink_free_space(struct btrfs_free_space_ctl *ctl,
>                      struct btrfs_free_space *info);
>  int btrfs_add_free_space(struct btrfs_free_space_ctl *ctl, u64 offset,
>                        u64 bytes);
> +int btrfs_clear_free_space_cache(struct btrfs_fs_info *fs_info,
> +                              struct btrfs_block_group_cache *bg);
>  #endif
> -- 
> 2.10.0
> 
> 
> 
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-- 
Omar
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