The image is dumped by modifying kernel to sleep long enough before
merging relocation trees, so we can just copy the whole image to other
place before kernel begins to merge reloc trees.
And the base image is created by the following script to bump metadata
size:
------
dev=~/test.img
mnt=/mnt/btrfs
umount $mnt &> /dev/null
fallocate -l 128M $dev
mkfs.btrfs -f -n 4k -m single -d single $dev
mount $dev $mnt -o nospace_cache,max_inline=2048
btrfs subvolume create $mnt/src
for i in $(seq -w 0 128); do
xfs_io -f -c "pwrite 0 2k" $mnt/src/file_$i > /dev/null
done
for i in $(seq -w 0 64); do
btrfs subvolume snapshot $mnt/src/ $mnt/snapshot_$i
touch $mnt/snapshot_$i/new
done
sync
------
The image triggers several corner cases that the old lowmem mode didn't
consider.
Like metadata backref with FULL_BACKREF flag and only SHARED_BLOCK_REF
backrefs for metadata. And several tree reloc trees with shared
leaves/nodes to confuse old lowmem mode.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Qu Wenruo