On 10/17/2016 06:42 PM, Qu Wenruo wrote:


At 10/18/2016 08:35 AM, Divya Indi wrote:
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).

I didn't think it's good to add a new subcommand just for that.

Why not output such relocation sugguestion for you previous bg-analyze subcommand?
(It's better to make it a parameter to trigger such output)

Thanks,
Qu
Or maybe as an option to btrfs balance start?
Eg: btrfs balance start --check-only <path>

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,




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