Re: [f2fs-dev] [PATCH v5] f2fs: support dynamic reserve/release for device aliasing

[Chao Yu <chao@kernel.org>]

On 7/24/26 04:20, Daeho Jeong wrote:
> From: Daeho Jeong <daehojeong@google.com>
> 
> This patch adds a dynamic management feature to the existing device
> aliasing functionality. It allows users to dynamically reserve or
> release specific devices from the filesystem's free pool at runtime
> through new ioctls.
> 
> To support this, three new ioctls are introduced:
> - F2FS_IOC_RESERVE_DEV_ALIAS: This reclaims the space occupied by a
>   device aliasing file. It first performs a capacity check, resets GC
>   victim information for the target range, marks the segments as in-use
>   to prevent new allocations, and then triggers GC to migrate existing
>   valid data out of the range. Finally, it reserves these blocks in the
>   SIT to effectively exclude the device from the usable capacity.
> 
> - F2FS_IOC_RELEASE_DEV_ALIAS: This releases the reserved space of a
>   previously reserved device aliasing file. It truncates the blocks
>   associated with the file, which makes them available for general
>   filesystem allocation again.
> 
> - F2FS_IOC_GET_DEV_ALIAS_STATUS: This retrieves the current aliasing
>   status of a device aliasing file, returning whether the file is
>   released (inactive alias) or reserved (active alias, with blocks
>   fully allocated on the device).

Hi Daeho,

BTW, could you please consider to do some coverage test to prevent from
suffering potential corruption.

e.g.:
1. call ioctls in low storage environment
2. race w/ checkpoint={disable,enable}
3. injecting faults in new ioctls + random shutdown

To verify if filesystem or device alias file is corrupted, it needs to
call fsck after the testcase, and find a way to verify whether device alias
status is as expected or not.

Please sharing your thoughts about this. :)

Thanks,