On 2018/9/20 下午1:26, anand.jain@xxxxxxxxxx wrote:
>
>
> Test script [1] tries to punch hole on a full FS and it works fine as
> long as the hole size and the offset is aligned with the sectorsize and
> the extent, so that it could just drop the relevant extent to create the
> hole.
>
> The reason why this test fails for non aligned hole size and offset is
> because, as it rightfully tries to truncate the non aligned extent at
> the front and back of the hole, it tries to create new extent which ends
> up with ENOSPC.
This is what btrfs should do, I don't see any problem though.
>
> Any idea, how do we solve this?
I don't really think this is a problem though.
As long as we need to do data COW, such ENOSPC would happen.
>
> xfs is fine.
Of course xfs is fine, XFS defaults to do NODATACOW, in contrast to
btrfs' default DATACOW.
Have you tried to do the same when the file is reflinked?
Thanks,
Qu
>
> [1]
> cat ./punch-hole-on-full-fs
> ------------------------
> cleanup()
> {
> umount /dev/sdb > /dev/null 2>&1
> btrfs_reload
> }
>
> full_fs_setup()
> {
> btrfs-dyndbg disable
> mkfs.$fs -b 200M -fq $mkfs_options /dev/sdb || exit
> mount $mount_options /dev/sdb /mnt/scratch || exit
> dd status=none if=/dev/zero of=/mnt/scratch/filler bs=512 >
> /dev/null 2>&1
> }
>
> test()
> {
> cleanup
> full_fs_setup
>
> btrfs-dyndbg enable
> echo "---- fallocate -p -o 0 -l $punch_hole_size /mnt/scratch/filler
> ----"
> fallocate -p -o 0 -l $punch_hole_size /mnt/scratch/filler
> }
>
> fs=btrfs; mkfs_options=""; mount_options="";
> [[ $1 ]] || { echo "usage: $0 <hole-len>"; exit; }
> punch_hole_size=$1 && test
> ------------------------
>
> ./punch-hole-on-full-fs 512
> -- fallocate -p -o 0 -l 512 /mnt/scratch/filler --
> fallocate: /mnt/scratch/filler: fallocate failed: No space left on device
>
> ./punch-hole-on-full-fs 8000
> -- fallocate -p -o 0 -l 8000 /mnt/scratch/filler --
> fallocate: /mnt/scratch/filler: fallocate failed: No space left on device
>
>
> Thanks, Anand
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