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Subject: Re: [HELP] What are the allocated blocks on a newly created ext4 fs ?
From:   Artem Blagodarenko <artem.blagodarenko@gmail.com>
In-Reply-To: <b64110a4-8112-a230-2179-5095aa943af9@gmail.com>
Date:   Thu, 6 Jun 2019 15:32:44 +0300
Cc:     linux-ext4@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca
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Message-Id: <7FD3148B-1E27-4BFA-965C-9FDC7FC8FD96@gmail.com>
References: <b64110a4-8112-a230-2179-5095aa943af9@gmail.com>
To:     Jianchao Wang <jianchao.wan9@gmail.com>
Sender: linux-ext4-owner@vger.kernel.org
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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@gmail.com> =
wrote:
>=20
> Dear all
>=20
> After I newly created a ext4 fs and check the mb_group,
>=20
>       #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     ]
>=20
> There are some bgs that have 1024 blocks allocated. What are they for =
?
>=20
BTW, I don=E2=80=99t see from mb_group output why 1024 blocks allocated =
in group #1
> Many thanks in advance
> Jianchao

Best regards,
Artem Blagodarenko.