Re: [PATCH v4] f2fs: Use allocate_section_policy to control write priority in multi-devices setups

[Chao Yu <chao@kernel.org>]

On 8/28/2025 4:11 PM, Liao Yuanhong wrote:
> Introduces two new sys nodes: allocate_section_hint and
> allocate_section_policy. The allocate_section_hint identifies the boundary
> between devices, measured in sections; it defaults to the end of the device
> for single storage setups, and the end of the first device for multiple
> storage setups. The allocate_section_policy determines the write strategy,
> with a default value of 0 for normal sequential write strategy. A value of
> 1 prioritizes writes before the allocate_section_hint, while a value of 2
> prioritizes writes after it.
> 
> This strategy addresses the issue where, despite F2FS supporting multiple
> devices, SOC vendors lack multi-devices support (currently only supporting
> zoned devices). As a workaround, multiple storage devices are mapped to a
> single dm device. Both this workaround and the F2FS multi-devices solution
> may require prioritizing writing to certain devices, such as a device with
> better performance or when switching is needed due to performance
> degradation near a device's end. For scenarios with more than two devices,
> sort them at mount time to utilize this feature.
> 
> When using this feature with a single storage device, it has almost no
> impact. However, for configurations where multiple storage devices are
> mapped to the same dm device using F2FS, utilizing this feature can provide
> some optimization benefits. Therefore, I believe it should not be limited
> to just multi-devices usage.
> 
> Signed-off-by: Liao Yuanhong <liaoyuanhong@vivo.com>

Reviewed-by: Chao Yu <chao@kernel.org>

Thanks,