Hello Jianchao, Not enought input data to give an answer. It depends on mkfs options. For example, if flex_bg option is enabled, then several block groups are tied together as one logical block group; the bitmap spaces and the inode table space in the first block group, so some groups are not totally free just after FS creating. > On 6 Jun 2019, at 13:41, Jianchao Wang <jianchao.wan9@xxxxxxxxx> wrote: > > Dear all > > After I newly created a ext4 fs and check the mb_group, > > #group: free frags first [ 2^0 2^1 2^2 2^3 2^4 2^5 2^6 2^7 2^8 2^9 2^10 2^11 2^12 2^13 ] > #0 : 23513 1 9255 [ 1 0 0 1 1 0 1 1 1 1 0 1 1 2 ] > #1 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] > ^^^^ > #2 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] > #3 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] > #4 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] > #5 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] > #6 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] > #7 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] > #8 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] > #9 : 31743 1 1025 [ 1 1 1 1 1 1 1 1 1 1 0 1 1 3 ] > #10 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] > #11 : 32768 1 0 [ 0 0 0 0 0 0 0 0 0 0 0 0 0 4 ] > > There are some bgs that have 1024 blocks allocated. What are they for ? > BTW, I don’t see from mb_group output why 1024 blocks allocated in group #1 > Many thanks in advance > Jianchao Best regards, Artem Blagodarenko.
