Re: [f2fs-dev] [PATCH 1/1] f2fs-tools: increase overprovision finding speed

[Jaegeuk Kim via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

Applied with limiting 80 columns.

On 05/16, Cherniaev Andrei wrote:
> I think my optimization makes mkfs.f2fs faster in case of invalid volume size. So with the commit user will get err faster.
> Before start I suggest add debug printf() to `f2fs_fs.h` like this:
> ```
> for (; candidate <= end; candidate += diff) {
> 	reserved = get_reserved(sb, candidate);
> 	ovp = (usable_main_segs - reserved) * candidate / 100;
> MSG(0, "ovp=%f usable_main_segs=%u reserved=%u candidate=%f\n", ovp, usable_main_segs, reserved, candidate); //debug printf()
> if (ovp <= 0)
> 		continue;
> 	space = usable_main_segs - max((double)reserved, ovp) -
> 				overprovision_segment_buffer(sb);
> MSG(0, "space=%f max_space=%f\n", space, max_space); //debug printf()
> 	if (max_space < space) {
> 		max_space = space;
> 		max_ovp = candidate;
> 	}
> }
> ```
> 
> Test instruction is based on "boot/grub2/readme.txt" https://gitlab.com/buildroot.org/buildroot/-/blob/master/boot/grub2/readme.txt You can use Ubuntu 24 or similar OS.
> 1. Create a disk image
> ```
> cd /tmp
> dd if=/dev/zero of=disk.img bs=1M count=32
> ```
> 2. Partition it with GPT partitions usinig `cgdisk disk.img` or
> ```
> parted --script disk.img mklabel gpt mkpart primary 1MiB 31MiB
> ```
> 3. Setup loop device and loop partitions
> ```
> loop_dev=$(sudo losetup -f --show disk.img)
> sudo partx -a "$loop_dev"
> ```
> 5. Prepare the root partition
> ```
> sudo mkfs.f2fs -f -l mylable123 -i -O extra_attr,inode_checksum,sb_checksum,compression -e raw -E bin "$loop_dev"
> ```
> 6. Cleanup loop device
> ```
> partx -d "$loop_dev"
> losetup -d "$loop_dev"
> ```
> In log you can see that for ovp==0.0 space calculation looks not necessary...
> ```
> a@Linux:~$ sudo mkfs.f2fs -f -l mylable123 -i -O extra_attr,inode_checksum,sb_checksum,compression -e raw -E bin "$loop_dev"
> 
>     F2FS-tools: mkfs.f2fs Ver: 1.16.0 (2025-05-06)
> 
> Info: Debug level = 0
> Info: Add new cold file extension list
> Info: Add new hot file extension list
> Info: Label = mylable123
> Info: Trim is enabled
> Info: Enable Compression
> Info: Segments per section = 1
> Info: Sections per zone = 1
> Info: sector size = 512
> Info: total sectors = 65536 (32 MB)
> Info: zone aligned segment0 blkaddr: 512
> ovp=429496728.700000 usable_main_segs=8 reserved=17 candidate=10.000000
> space=-429496726.700000 max_space=0.000000
> ovp=644245093.650000 usable_main_segs=8 reserved=13 candidate=15.000000
> space=-644245091.650000 max_space=0.000000
> ovp=858993458.400000 usable_main_segs=8 reserved=12 candidate=20.000000
> space=-858993456.400000 max_space=0.000000
> ovp=1073741823.250000 usable_main_segs=8 reserved=11 candidate=25.000000
> space=-1073741821.250000 max_space=0.000000
> ovp=1288490188.200000 usable_main_segs=8 reserved=10 candidate=30.000000
> space=-1288490186.200000 max_space=0.000000
> ovp=1503238553.250000 usable_main_segs=8 reserved=9 candidate=35.000000
> space=-1503238551.250000 max_space=0.000000
> ovp=1717986918.000000 usable_main_segs=8 reserved=9 candidate=40.000000
> space=-1717986916.000000 max_space=0.000000
> ovp=1932735282.750000 usable_main_segs=8 reserved=9 candidate=45.000000
> space=-1932735280.750000 max_space=0.000000
> ovp=2147483647.500000 usable_main_segs=8 reserved=9 candidate=50.000000
> space=-2147483645.500000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=55.000000
> space=-6.000000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=60.000000
> space=-6.000000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=65.000000
> space=-6.000000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=70.000000
> space=-6.000000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=75.000000
> space=-6.000000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=80.000000
> space=-6.000000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=85.000000
> space=-6.000000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=90.000000
> space=-6.000000 max_space=0.000000
> ovp=0.000000 usable_main_segs=8 reserved=8 candidate=95.000000
> space=-6.000000 max_space=0.000000
> 	Error: Device size is not sufficient for F2FS volume
> 	Error: Failed to prepare a super block!!!
> 	Error: Could not format the device!!!
> ```
> 
> Signed-off-by: Cherniaev Andrei <dungeonlords789@naver.com>
> ---
>  include/f2fs_fs.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/f2fs_fs.h b/include/f2fs_fs.h
> index f7268d1..41755af 100644
> --- a/include/f2fs_fs.h
> +++ b/include/f2fs_fs.h
> @@ -1891,7 +1891,7 @@ static inline double get_best_overprovision(struct f2fs_super_block *sb)
>  	for (; candidate <= end; candidate += diff) {
>  		reserved = get_reserved(sb, candidate);
>  		ovp = (usable_main_segs - reserved) * candidate / 100;
> -		if (ovp < 0)
> +		if (ovp <= 0)
>  			continue;
>  		space = usable_main_segs - max((double)reserved, ovp) -
>  					overprovision_segment_buffer(sb);
> -- 
> 2.45.2


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