linux-ext4 - Re: [PATCH] ext4: fix FS_IOC

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Message-ID: <54c0efff-2b7d-457b-ba31-788d77de14e7@huaweicloud.com>
Date: Tue, 29 Oct 2024 10:20:22 +0800
From: Zhang Yi <yi.zhang@...weicloud.com>
To: Theodore Ts'o <tytso@....edu>
Cc: "Darrick J. Wong" <djwong@...nel.org>,
 Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: fix FS_IOC_GETFSMAP handling

On 2024/10/28 11:59, Theodore Ts'o wrote:
> On Mon, Oct 28, 2024 at 09:47:46AM +0800, Zhang Yi wrote:
>>
>> IIRC, at the moment, fixed metadata does not appear in the middle of
>> the block group.
> 
> The mke2fs from e2fsprogs will not create a file system like that
> normally, no.  *However* it is possible for fixed metadata to be in
> the middle of the block group:
> 
>    * If resize2fs does an off-line file system growth without a resize inode
>      or the reserved blocks in the resize inode has been exhausted
>    * If e2fsck needs to reallocate some fixed metadata blocks as part of
>      repairing a (very badly) corrupted file system.
>    * If there are blocks reported to mke2fs when the file system is created
>    * If a non-standard mkfs.ext4 is used by some other operating system which
>      reimplemented mke2fs for some reason (for example, because they wanted
>      to avoid using GPL'ed code).
> 
> So while these cases are quite uncommon, they *can* happen in the
> wild, and we want GETFSMAP to be able to handle these file systems
> correctly.
> 
> Cheers,
> 

Ha, I see, thank you for the correction.

Cheers,
Yi.