@@ -437,6 +437,106 @@ out:
return ret;
}
+/* return 0 if balance remove data a block group, return 1 if it does not */
+static int search_data_bgs(const char *path)
+{
+ struct btrfs_ioctl_search_args_v2 *args;
+ struct btrfs_ioctl_search_key *sk;
+ struct btrfs_ioctl_search_header *header;
+ struct btrfs_block_group_item *bg;
+ DIR *dirstream = NULL;
+ int e;
+ int args_size = 65536;
+ int fd;
+ int i;
+ char buf[args_size];
+ 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;
+ char *p;
+
+ fd = btrfs_open_dir(path, &dirstream, 1);
+ if (fd < 0)
+ return 1;
+
+ memset(buf, 0, args_size);
+ args = (struct btrfs_ioctl_search_args_v2 *)buf;
+ sk = &(args->key);
+
+ sk->tree_id = BTRFS_EXTENT_TREE_OBJECTID;
+ sk->min_objectid = sk->min_offset = sk->min_transid = 0;
+ sk->max_objectid = sk->max_offset = sk->max_transid = (u64)-1;
+ sk->max_type = sk->min_type = BTRFS_BLOCK_GROUP_ITEM_KEY;
+ sk->nr_items = 65536;
+ args->buf_size = args_size - sizeof(struct btrfs_ioctl_search_args_v2);
+
+ while (1) {
+ ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH_V2, args);
+ e = errno;
+ if (ret != 0) {
+ fprintf(stderr, "ret %d error '%s'\n", ret, strerror(e));
+ return ret;
+ }
+
+ // it should not happen.
+ if (sk->nr_items == 0)
+ break;
+
+ /*
+ * BTRFS_IOC_TREE_SEARCH_V2: args->buf is in fact __u64 buf[0]
+ * instead of char buf[0]
+ */
+ p = (char *)args->buf;
+
+ for (i = 0; i < sk->nr_items; i++) {
+ header = (struct btrfs_ioctl_search_header *)p;
+
+ p += sizeof(*header);
+ if (header->type == BTRFS_BLOCK_GROUP_ITEM_KEY) {
+ bg = (struct btrfs_block_group_item *)p;
+ flags = btrfs_block_group_flags(bg);
+ used = btrfs_block_group_used(bg);
+ if (flags & BTRFS_BLOCK_GROUP_DATA) {
+ printf("block_group %15llu (len %11llu used %11llu)\n",
+ header->objectid, header->offset,
+ btrfs_block_group_used(bg));
+ total_free += header->offset - used;
+ if (min_used >= used) {
+ min_used = used;
+ free_of_min_used = header->offset - used;
+ bg_of_min_used = header->objectid;
+ }
+ }
+ }
+
+ p += header->len;
+ sk->min_objectid = header->objectid;
+ }
+
+ if (sk->min_objectid < sk->max_objectid)
+ sk->min_objectid += 1;
+ else
+ break;
+ }
+
+ printf("total_free %llu min_used bg %llu has (min_used %llu free %llu)\n",
+ total_free, bg_of_min_used, min_used, free_of_min_used);
+ if (total_free - free_of_min_used > min_used) {
+ printf("run 'btrfs balance start -dvrange=%llu..%llu your_mnt'\n",
+ bg_of_min_used, bg_of_min_used + 1);
+ ret = 0;
+ } else {
+ printf("Please do not balance data block groups, it won't work\n");
+ ret = 1;
+ }
+
+ return ret;
+}
+
static const char * const cmd_balance_start_usage[] = {
"btrfs balance start [options] <path>",
"Balance chunks across the devices",
@@ -450,6 +550,7 @@ static const char * const cmd_balance_start_usage[] = {
"-m[filters] act on metadata chunks",
"-s[filters] act on system chunks (only under -f)",
"-v be verbose",
+ "-c only check if balance would make sense, not doing real job",
"-f force reducing of metadata integrity",
NULL
};
@@ -462,6 +563,7 @@ static int cmd_balance_start(int argc, char **argv)
int force = 0;
int verbose = 0;
int nofilters = 1;
+ int check_data_bgs = 0;
int i;
memset(&args, 0, sizeof(args));
@@ -473,11 +575,12 @@ static int cmd_balance_start(int argc, char **argv)
{ "metadata", optional_argument, NULL, 'm' },
{ "system", optional_argument, NULL, 's' },
{ "force", no_argument, NULL, 'f' },
+ { "check-only", no_argument, NULL, 'c' },
{ "verbose", no_argument, NULL, 'v' },
{ NULL, 0, NULL, 0 }
};
- int opt = getopt_long(argc, argv, "d::s::m::fv", longopts, NULL);
+ int opt = getopt_long(argc, argv, "d::s::m::fvc", longopts, NULL);
if (opt < 0)
break;
@@ -509,6 +612,9 @@ static int cmd_balance_start(int argc, char **argv)
case 'v':
verbose = 1;
break;
+ case 'c':
+ check_data_bgs = 1;
+ break;
default:
usage(cmd_balance_start_usage);
}
@@ -517,6 +623,14 @@ static int cmd_balance_start(int argc, char **argv)
if (check_argc_exact(argc - optind, 1))
usage(cmd_balance_start_usage);
+ if (check_data_bgs) {
+ if (verbose)
+ dump_ioctl_balance_args(&args);
+
+ printf("Checking data block group...\n");
+ return search_data_bgs(argv[optind]);
+ }
+
/*
* allow -s only under --force, otherwise do with system chunks
* the same thing we were ordered to do with meta chunks
Previously I did the same thing to btrfs-debugfs, it works good, but since it's python script, and if your system doesn't have python installed, then you need a binary. This aims to decide whether a balance can reduce the number of data block groups and if it is, this shows the '-dvrange' block group's objectid. With this, you can run 'btrfs balance start -c mnt' or 'btrfs balance start --check-only mnt' -------------------------------------------------------------- $ btrfs balance start -c /mnt/btrfs Checking data block group... block_group 12582912 (len 8388608 used 786432) block_group 1103101952 (len 1073741824 used 536870912) block_group 2176843776 (len 1073741824 used 1073741824) total_free 544473088 min_used bg 12582912 has (min_used 786432 free 7602176) run btrfs balance start -dvrange=12582912..12582913 your_mnt $ btrfs balance start -dvrange=12582912..12582913 /mnt/btrfs Done, had to relocate 1 out of 5 chunks $ btrfs balance start -c /mnt/btrfs Checking data block group... block_group 1103101952 (len 1073741824 used 537395200) block_group 2176843776 (len 1073741824 used 1073741824) total_free 536346624 min_used bg 1103101952 has (min_used 537395200 free 536346624) -------------------------------------------------------------- So you now know how to babysit your btrfs in a smart way. Signed-off-by: Liu Bo <bo.li.liu@oracle.com> --- cmds-balance.c | 116 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++- 1 file changed, 115 insertions(+), 1 deletion(-)