linux-kernel - Re: [PATCH v4] f2fs: modify f2fs_is_checkpoint_ready logic to allow more data to be written with the CP disable

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Message-ID: <b0760a9b-0973-453c-af18-3e384f85a9f5@kernel.org>
Date: Mon, 28 Oct 2024 17:34:47 +0800
From: Chao Yu <chao@...nel.org>
To: Qi Han <hanqi@...o.com>, jaegeuk@...nel.org
Cc: Chao Yu <chao@...nel.org>, niuzhiguo84@...il.com,
 linux-f2fs-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4] f2fs: modify f2fs_is_checkpoint_ready logic to allow
 more data to be written with the CP disable

On 2024/10/25 17:18, Qi Han wrote:
> When the free segment is used up during CP disable, many write or
> ioctl operations will get ENOSPC error codes, even if there are
> still many blocks available. We can reproduce it in the following
> steps:
> 
> dd if=/dev/zero of=f2fs.img bs=1M count=65
> mkfs.f2fs -f f2fs.img
> mount f2fs.img f2fs_dir -o checkpoint=disable:10%
> cd f2fs_dir
> i=1 ; while [[ $i -lt 50 ]] ; do (file_name=./2M_file$i ; dd \
> if=/dev/random of=$file_name bs=1M count=2); i=$((i+1)); done
> sync
> i=1 ; while [[ $i -lt 50 ]] ; do (file_name=./2M_file$i ; truncate \
> -s 1K $file_name); i=$((i+1)); done
> sync
> dd if=/dev/zero of=./file bs=1M count=20
> 
> In f2fs_need_SSR() function, it is allowed to use SSR to allocate
> blocks when CP is disabled, so in f2fs_is_checkpoint_ready function,
> can we judge the number of invalid blocks when free segment is not
> enough, and return ENOSPC only if the number of invalid blocks is
> also not enough.
> 
> Signed-off-by: Qi Han <hanqi@...o.com>

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

Thanks,