Add new subcommand to btrfs inspect-internal

btrfs inspect-internal balance_check <path>
Checks whether 'btrfs balance' can help creating more space (Only
considers data block groups).

Signed-off-by: Divya Indi <divya.i...@oracle.com>
Reviewed-by: Ashish Samant <ashish.sam...@oracle.com>
Reviewed-by: Liu Bo <bo.li....@oracle.com>
---
 cmds-inspect.c |  147 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 147 insertions(+), 0 deletions(-)

diff --git a/cmds-inspect.c b/cmds-inspect.c
index 0e2f15a..5baaa49 100644
--- a/cmds-inspect.c
+++ b/cmds-inspect.c
@@ -267,6 +267,151 @@ static const char * const 
cmd_inspect_inode_resolve_usage[] = {
        NULL
 };
 
+static const char * const cmd_inspect_balance_check_usage[] = {
+       "btrfs inspect-internal balance_check <path>",
+       "To check whether 'btrfs balance' can help creating more space",
+       "",
+       "",
+       NULL
+};
+
+static int cmd_inspect_balance_check(int argc, char **argv)
+{
+       struct btrfs_ioctl_search_args args;
+       struct btrfs_ioctl_search_args bg_args;
+       struct btrfs_ioctl_search_key *sk;
+       struct btrfs_ioctl_search_key *bg_sk;
+       struct btrfs_ioctl_search_header *header;
+       struct btrfs_ioctl_search_header *bg_header;
+       struct btrfs_block_group_item *bg;
+       struct btrfs_chunk *chunk;
+       unsigned long off = 0;
+       unsigned long bg_off = 0;
+       DIR *dirstream = NULL;
+       int fd;
+       int i;
+       u64 total_free = 0;
+       u64 min_used = (u64)-1;
+       u64 free_of_min_used = 0;
+       u64 bg_of_min_used = 0;
+       u64 flags;
+       u64 used;
+       int ret = 0;
+       int nr_data_bgs = 0;
+
+       if (check_argc_exact(argc, 2))
+               usage(cmd_inspect_balance_check_usage);
+
+       fd = btrfs_open_dir(argv[optind], &dirstream, 1);
+       if (fd < 0)
+               return 1;
+
+       memset(&args, 0, sizeof(args));
+       sk = &args.key;
+       sk->min_offset = sk->min_transid = 0;
+       sk->max_offset = sk->max_transid = (u64)-1;
+
+       printf("%20s%20s%20s\n", "Start", "Len", "Used");
+       while (1) {
+               ret = get_chunks(fd, &args);
+               if (ret < 0)
+                       goto out;
+
+               /*
+                * it should not happen.
+                */
+               if (sk->nr_items == 0)
+                       break;
+
+               off = 0;
+               memset(&bg_args, 0, sizeof(bg_args));
+               bg_sk = &bg_args.key;
+
+               /* For every chunk, look up 1 exact match for block group in
+                * the extent tree. */
+               bg_sk->tree_id = BTRFS_EXTENT_TREE_OBJECTID;
+               bg_sk->min_type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+               bg_sk->max_type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+               bg_sk->min_transid =  0;
+               bg_sk->max_transid = (u64)-1;
+
+               for (i = 0; i < sk->nr_items; i++) {
+                       header = (struct btrfs_ioctl_search_header *)(args.buf
+                                                                     + off);
+                       off += sizeof(*header);
+                       if (header->type == BTRFS_CHUNK_ITEM_KEY) {
+                               chunk = (struct btrfs_chunk *)
+                                       (args.buf + off);
+                               ret = get_bg_info(fd, &bg_args, header->offset,
+                                                 chunk->length);
+                               if (ret < 0)
+                                       goto out;
+
+                               /*
+                                * it should not happen.
+                                */
+                               if (bg_sk->nr_items == 0)
+                                       continue;
+
+                               bg_off = 0;
+                               bg_header = (struct btrfs_ioctl_search_header *)
+                                           (bg_args.buf + bg_off);
+                               bg_off += sizeof(*bg_header);
+                               bg = (struct btrfs_block_group_item *)
+                                    (bg_args.buf + bg_off);
+
+                               flags = btrfs_block_group_flags(bg);
+                               if (flags & BTRFS_BLOCK_GROUP_DATA) {
+                                       used = btrfs_block_group_used(bg);
+                                       nr_data_bgs++;
+                                       printf("%20llu%20s%20s\n",
+                                               bg_header->objectid,
+                                               pretty_size(bg_header->offset),
+                                               pretty_size(used));
+                                       total_free += bg_header->offset - used;
+                                       if (min_used >= used) {
+                                               min_used = used;
+                                               free_of_min_used =
+                                                       bg_header->offset - 
used;
+                                               bg_of_min_used =
+                                                       bg_header->objectid;
+                                       }
+                               }
+                       }
+
+                       off += header->len;
+                       sk->min_offset = header->offset + header->len;
+               }
+               sk->nr_items = 4096;
+
+       }
+
+       if (nr_data_bgs <= 1) {
+               printf("Data block groups in fs = %d, no need to do balance.\n",
+                               nr_data_bgs);
+               ret = 1;
+               goto out;
+       }
+
+       printf("Total data bgs: %d\nTotal free space: %s\n"
+              "For min used bg %llu used = %s free = %s\n",
+               nr_data_bgs, pretty_size(total_free), bg_of_min_used,
+               pretty_size(min_used), pretty_size(free_of_min_used));
+
+       if (total_free - free_of_min_used > min_used) {
+               printf("run 'btrfs balance start -dvrange=%llu..%llu 
<mountpoint>'\n",
+                               bg_of_min_used, bg_of_min_used + 1);
+               ret = 0;
+       } else {
+               printf("Please don't balance data block groups, no free 
space\n");
+               ret = 1;
+       }
+
+out:
+       close_file_or_dir(fd, dirstream);
+       return ret;
+}
+
 static int cmd_inspect_inode_resolve(int argc, char **argv)
 {
        int fd;
@@ -816,6 +961,8 @@ const struct cmd_group inspect_cmd_group = {
                        cmd_inspect_min_dev_size_usage, NULL, 0 },
                { "bg_analysis", cmd_inspect_bg_analysis,
                        cmd_inspect_bg_analysis_usage, NULL, 0 },
+               { "balance_check", cmd_inspect_balance_check,
+                       cmd_inspect_balance_check_usage, NULL, 0 },
                { "dump-tree", cmd_inspect_dump_tree,
                                cmd_inspect_dump_tree_usage, NULL, 0 },
                { "dump-super", cmd_inspect_dump_super,
-- 
1.7.1

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