On 2019/8/28 上午7:26, Anand Jain wrote:
> On 27/8/19 10:05 PM, Qu Wenruo wrote:
>> Btrfs doesn't reuse devid, thus if we add and delete device in a loop,
>> we can increase devid to higher value, triggering tree checker to give a
>> false alert.
>>
>> Furthermore, we have dev extent verification already (after
>> tree-checker, at mount time).
>> So even if user had bitflip on some dev items, we can still detect it
>> and refuse to mount.
>>
>> Reported-by: Anand Jain <anand.j...@oracle.com>
>> Fixes: ab4ba2e13346 ("btrfs: tree-checker: Verify dev item")
>> Signed-off-by: Qu Wenruo <w...@suse.com>
>> ---
>> Changelog:
>> v2:
>> - Remove devid check completely
>> As we already have verify_one_dev_extent().
>> ---
>> fs/btrfs/tree-checker.c | 8 --------
>> 1 file changed, 8 deletions(-)
>>
>> diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
>> index 43e488f5d063..076d5b8014fb 100644
>> --- a/fs/btrfs/tree-checker.c
>> +++ b/fs/btrfs/tree-checker.c
>> @@ -686,9 +686,7 @@ static void dev_item_err(const struct
>> extent_buffer *eb, int slot,
>> static int check_dev_item(struct extent_buffer *leaf,
>> struct btrfs_key *key, int slot)
>> {
>> - struct btrfs_fs_info *fs_info = leaf->fs_info;
>> struct btrfs_dev_item *ditem;
>> - u64 max_devid = max(BTRFS_MAX_DEVS(fs_info),
>> BTRFS_MAX_DEVS_SYS_CHUNK);
>> if (key->objectid != BTRFS_DEV_ITEMS_OBJECTID) {
>> dev_item_err(leaf, slot,
>> @@ -696,12 +694,6 @@ static int check_dev_item(struct extent_buffer
>> *leaf,
>> key->objectid, BTRFS_DEV_ITEMS_OBJECTID);
>> return -EUCLEAN;
>> }
>> - if (key->offset > max_devid) {
>> - dev_item_err(leaf, slot,
>> - "invalid devid: has=%llu expect=[0, %llu]",
>> - key->offset, max_devid);
>> - return -EUCLEAN;
>> - }
>> ditem = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item);
>> if (btrfs_device_id(leaf, ditem) != key->offset) {
>> dev_item_err(leaf, slot,
>>
>
> Though ab4ba2e13346 didn't add BTRFS_MAX_DEVS_SYS_CHUNK,
> BTRFS_MAX_DEVS_SYS_CHUNK is unused now, can be deleted.
Nope, they are still used to determine if we're at the max device limit.
So they are still needed.
Thanks,
Qu
>
> The reproducer script and logs should rather be in this change log.
>
> Thanks, Anand
>
