Hi Anand,
1) so let's say I have a subvolume and a snapshot of this subvolume.
So in this case, I will see "Sole space = 0" for both of them,
correct? Because all extents (except inline ones) are shared.
2) How is this in terms of responsiveness? On a huge subvolume, we
need to iterate all the EXTENT_DATAs and then lookup their
EXTENT_ITEMs.
3) So it's kind of poor man's replacement for quota groups, correct?
I like that it's so easy to check for exclusive data, though:)
Alex.
On Fri, Sep 13, 2013 at 6:44 PM, Wang Shilong <wangshilong1991@xxxxxxxxx> wrote:
>
> Hello Anand,
>
>> (This patch is for review and comments only)
>>
>> This patch provides a way to know how much space can be
>> relinquished if when subvol /snapshot is deleted. With
>> this sys admin can make better judgments in managing the
>> filesystem when fs is near full.
>>
>
> I think this is really *helpful* since users can not really know how much
> space(Exclusive) in a subvolume .
>
> Thanks,
> Wang
>
>> as shown below the parameter 'sole space' indicates the size
>> which is freed when subvol is deleted. (any other better
>> term for this?, pls suggest).
>> ---------------------
>> btrfs su show /btrfs/sv1
>> /btrfs/sv1
>> Name: sv1
>> uuid: b078ba48-d4a5-2f49-ac03-9bd1d56cc768
>> Parent uuid: -
>> Creation time: 2013-09-13 18:17:32
>> Object ID: 257
>> Generation (Gen): 18
>> Gen at creation: 17
>> Parent: 5
>> Top Level: 5
>> Flags: -
>> Sole space: 1.56MiB <----
>> Snapshot(s):
>>
>> btrfs su snap /btrfs/sv1 /btrfs/ss2
>> Create a snapshot of '/btrfs/sv1' in '/btrfs/ss2'
>>
>> btrfs su show /btrfs/sv1
>> /btrfs/sv1
>> Name: sv1
>> uuid: b078ba48-d4a5-2f49-ac03-9bd1d56cc768
>> Parent uuid: -
>> Creation time: 2013-09-13 18:17:32
>> Object ID: 257
>> Generation (Gen): 19
>> Gen at creation: 17
>> Parent: 5
>> Top Level: 5
>> Flags: -
>> Sole space: 0.00 <-----
>> Snapshot(s):
>> ss2
>> ---------------------
>>
>> Signed-off-by: Anand Jain <anand.jain@xxxxxxxxxx>
>> ---
>> cmds-subvolume.c | 5 ++
>> utils.c | 154 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> utils.h | 1 +
>> 3 files changed, 160 insertions(+)
>>
>> diff --git a/cmds-subvolume.c b/cmds-subvolume.c
>> index de246ab..2b02d66 100644
>> --- a/cmds-subvolume.c
>> +++ b/cmds-subvolume.c
>> @@ -809,6 +809,7 @@ static int cmd_subvol_show(int argc, char **argv)
>> int fd = -1, mntfd = -1;
>> int ret = 1;
>> DIR *dirstream1 = NULL, *dirstream2 = NULL;
>> + u64 freeable_bytes;
>>
>> if (check_argc_exact(argc, 2))
>> usage(cmd_subvol_show_usage);
>> @@ -878,6 +879,8 @@ static int cmd_subvol_show(int argc, char **argv)
>> goto out;
>> }
>>
>> + freeable_bytes = get_subvol_freeable_bytes(fd);
>> +
>> ret = 0;
>> /* print the info */
>> printf("%s\n", fullpath);
>> @@ -915,6 +918,8 @@ static int cmd_subvol_show(int argc, char **argv)
>> else
>> printf("\tFlags: \t\t\t-\n");
>>
>> + printf("\tSole space: \t\t%s\n",
>> + pretty_size(freeable_bytes));
>> /* print the snapshots of the given subvol if any*/
>> printf("\tSnapshot(s):\n");
>> filter_set = btrfs_list_alloc_filter_set();
>> diff --git a/utils.c b/utils.c
>> index 22c3310..f01d580 100644
>> --- a/utils.c
>> +++ b/utils.c
>> @@ -2019,3 +2019,157 @@ int is_dev_excl_op_free(int fd)
>> ret = ioctl(fd, BTRFS_IOC_CHECK_DEV_EXCL_OPS, NULL);
>> return ret > 0 ? ret : -errno;
>> }
>> +
>> +/* gets the ref count for given extent
>> + * 0 = didn't find the item
>> + * n = number of references
>> +*/
>> +u64 get_extent_refcnt(int fd, u64 disk_blk)
>> +{
>> + int ret = 0, i, e;
>> + struct btrfs_ioctl_search_args args;
>> + struct btrfs_ioctl_search_key *sk = &args.key;
>> + struct btrfs_ioctl_search_header sh;
>> + unsigned long off = 0;
>> +
>> + memset(&args, 0, sizeof(args));
>> +
>> + sk->tree_id = BTRFS_EXTENT_TREE_OBJECTID;
>> +
>> + sk->min_type = BTRFS_EXTENT_ITEM_KEY;
>> + sk->max_type = BTRFS_EXTENT_ITEM_KEY;
>> +
>> + sk->min_objectid = disk_blk;
>> + sk->max_objectid = disk_blk;
>> +
>> + sk->max_offset = (u64)-1;
>> + sk->max_transid = (u64)-1;
>> +
>> + while (1) {
>> + sk->nr_items = 4096;
>> +
>> + ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
>> + e = errno;
>> + if (ret < 0) {
>> + fprintf(stderr, "ERROR: search failed - %s\n",
>> + strerror(e));
>> + return 0;
>> + }
>> + if (sk->nr_items == 0)
>> + break;
>> +
>> + off = 0;
>> + for (i = 0; i < sk->nr_items; i++) {
>> + struct btrfs_extent_item *ei;
>> + u64 ref;
>> +
>> + memcpy(&sh, args.buf + off, sizeof(sh));
>> + off += sizeof(sh);
>> +
>> + if (sh.type != BTRFS_EXTENT_ITEM_KEY) {
>> + off += sh.len;
>> + continue;
>> + }
>> +
>> + ei = (struct btrfs_extent_item *)(args.buf + off);
>> + ref = btrfs_stack_extent_refs(ei);
>> + return ref;
>> + }
>> + sk->min_objectid = sh.objectid;
>> + sk->min_offset = sh.offset;
>> + sk->min_type = sh.type;
>> + if (sk->min_offset < (u64)-1)
>> + sk->min_offset++;
>> + else if (sk->min_objectid < (u64)-1) {
>> + sk->min_objectid++;
>> + sk->min_offset = 0;
>> + sk->min_type = 0;
>> + } else
>> + break;
>> + }
>> + return 0;
>> +}
>> +
>> +u64 get_subvol_freeable_bytes(int fd)
>> +{
>> + int ret = 0, i, e;
>> + struct btrfs_ioctl_search_args args;
>> + struct btrfs_ioctl_search_key *sk = &args.key;
>> + struct btrfs_ioctl_search_header sh;
>> + unsigned long off = 0;
>> + u64 size_bytes = 0;
>> +
>> + memset(&args, 0, sizeof(args));
>> +
>> + sk->tree_id = 0;
>> +
>> + sk->min_type = BTRFS_EXTENT_DATA_KEY;
>> + sk->max_type = BTRFS_EXTENT_DATA_KEY;
>> +
>> + sk->max_objectid = (u64) -1;
>> + sk->max_offset = (u64)-1;
>> + sk->max_transid = (u64)-1;
>> +
>> + while (1) {
>> + sk->nr_items = 4096;
>> +
>> + ret = ioctl(fd, BTRFS_IOC_TREE_SEARCH, &args);
>> + e = errno;
>> + if (ret < 0) {
>> + fprintf(stderr, "ERROR: search failed - %s\n",
>> + strerror(e));
>> + return 0;
>> + }
>> + if (sk->nr_items == 0)
>> + break;
>> +
>> + off = 0;
>> + for (i = 0; i < sk->nr_items; i++) {
>> + struct btrfs_file_extent_item *efi;
>> + u64 disk_bytenr = 0;
>> + u64 num_bytes = 0;
>> + u64 refcnt;
>> + u8 type;
>> +
>> + memcpy(&sh, args.buf + off, sizeof(sh));
>> + off += sizeof(sh);
>> +
>> + if (sh.type != BTRFS_EXTENT_DATA_KEY) {
>> + off += sh.len;
>> + continue;
>> + }
>> +
>> + efi = (struct btrfs_file_extent_item *)(args.buf + off);
>> + type = btrfs_stack_file_extent_type(efi);
>> +
>> + if (type == BTRFS_FILE_EXTENT_INLINE) {
>> + size_bytes +=
>> + btrfs_stack_file_extent_ram_bytes(efi);
>> + goto skip_extent_data;
>> + }
>> + disk_bytenr = btrfs_stack_file_extent_disk_bytenr(efi);
>> + num_bytes = btrfs_stack_file_extent_num_bytes(efi);
>> +
>> + if (disk_bytenr) {
>> + refcnt = get_extent_refcnt(fd, disk_bytenr);
>> + if (refcnt == 1)
>> + size_bytes += num_bytes;
>> + }
>> +skip_extent_data:
>> + off += sh.len;
>> + }
>> + sk->min_objectid = sh.objectid;
>> + sk->min_offset = sh.offset;
>> + sk->min_type = sh.type;
>> +
>> + if (sk->min_offset < (u64)-1)
>> + sk->min_offset++;
>> + else if (sk->min_objectid < (u64)-1) {
>> + sk->min_objectid++;
>> + sk->min_offset = 0;
>> + sk->min_type = 0;
>> + } else
>> + break;
>> + }
>> + return size_bytes;
>> +}
>> diff --git a/utils.h b/utils.h
>> index 6952d34..0920bb3 100644
>> --- a/utils.h
>> +++ b/utils.h
>> @@ -86,4 +86,5 @@ int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
>> int verify);
>> int get_btrfs_mount(const char *dev, char *mp, size_t mp_size);
>> int is_dev_excl_op_free(int fd);
>> +u64 get_subvol_freeable_bytes(int fd);
>> #endif
>> --
>> 1.8.4.rc4.1.g0d8beaa
>>
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