Btrfs devel - Sep 2012 - [PATCH V3 4/7] Btrfs-progs: fix wrong way to check if the root item contains otime and uuid

Now we check if the root item contains otime and uuid or not by comparing
->generation_v2 and ->generation of the btrfs_root_item structure, it is
wrong because it is possbile that ->generation may equal to the first
variant of the next item. We fix this problem by comparing the size of
btrfs_root_item because the size is different between the old and new ones.
we needn''t worry the case that the new filesystem is mounted on the old
kernel.
because the otime and uuid are not changed on the old kernel, we can get the
correct result even on the kernel.

Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
---
Changelog v1 -> v3:
- new patch
---
 btrfs-list.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/btrfs-list.c b/btrfs-list.c
index ef621f0..2101695 100644
--- a/btrfs-list.c
+++ b/btrfs-list.c
@@ -737,7 +737,7 @@ again:
 			} else if (get_gen && sh->type == BTRFS_ROOT_ITEM_KEY) {
 				ri = (struct btrfs_root_item *)(args.buf + off);
 				gen = btrfs_root_generation(ri);
-				if(ri->generation == ri->generation_v2) {
+				if(sh->len == sizeof(struct btrfs_root_item)) {
 					t = ri->otime.sec;
 					memcpy(uuid, ri->uuid, BTRFS_UUID_SIZE);
 				} else {
@@ -844,7 +844,7 @@ static int __list_snapshot_search(int fd, struct root_lookup
*root_lookup)
 			off += sizeof(*sh);
 			if (sh->type == BTRFS_ROOT_ITEM_KEY && sh->offset) {
 				item = (struct btrfs_root_item *)(args.buf + off);
-				if(item->generation == item->generation_v2) {
+				if(sh->len == sizeof(struct btrfs_root_item)) {
 					t = item->otime.sec;
 					memcpy(uuid, item->uuid, BTRFS_UUID_SIZE);
 				} else {
-- 
1.7.6.5
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> -				if(ri->generation == ri->generation_v2) {
> +				if(sh->len == sizeof(struct btrfs_root_item)) {
>   					t = ri->otime.sec;
  This looks fine now but should this work when we
  move to v3 and still have access to v2 introduced
  members.?

  ker cli
  v3  v2  v2 introduced members are unnecessarily blocked
  v2  v3  --as above--

Thanks, Anand
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On Tue, 18 Sep 2012 13:56:44 +0800, Anand Jain wrote:
> 
> 
>> -                if(ri->generation == ri->generation_v2) {
>> +                if(sh->len == sizeof(struct btrfs_root_item)) {
>>                       t = ri->otime.sec;
> 
>  This looks fine now but should this work when we
>  move to v3 and still have access to v2 introduced
>  members.?
> 
>  ker cli
>  v3  v2  v2 introduced members are unnecessarily blocked
>  v2  v3  --as above--
No.

I will update my patch to fix this problem.

Thanks
Miao
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