• Forrest Liu's avatar
    Btrfs: fix find_free_dev_extent() malfunction in case device tree has hole · 1b984508
    Forrest Liu authored
    If device tree has hole, find_free_dev_extent() cannot find available
    address properly.
    
    The problem can be reproduce by following script.
    
        mntpath=/btrfs
        loopdev=/dev/loop0
        filepath=/home/forrest/image
    
        umount $mntpath
        losetup -d $loopdev
        truncate --size 100g $filepath
        losetup $loopdev $filepath
        mkfs.btrfs -f $loopdev
        mount $loopdev $mntpath
    
        # make device tree with one big hole
        for i in `seq 1 1 100`; do
            fallocate -l 1g $mntpath/$i
        done
        sync
        for i in `seq 1 1 95`; do
            rm $mntpath/$i
        done
        sync
    
        # wait cleaner thread remove unused block group
        sleep 300
    
        fallocate -l 1g $mntpath/aaa
    
        # failed to allocate new chunk
        fallocate -l 1g $mntpath/bbb
    
    Above script will make device tree with one big hole, and can only allocate
    just one chunk in a transaction, so failed to allocate new chunk for $mntpath/bbb
    
        item 8 key (1 DEV_EXTENT 2185232384) itemoff 15859 itemsize 48
            dev extent chunk_tree 3
            chunk objectid 256 chunk offset 106292051968 length 1073741824
        item 9 key (1 DEV_EXTENT 104190705664) itemoff 15811 itemsize 48
            dev extent chunk_tree 3
            chunk objectid 256 chunk offset 103108575232 length 1073741824
    Signed-off-by: default avatarForrest Liu <forrestl@synology.com>
    Reviewed-by: default avatarLiu Bo <bo.li.liu@oracle.com>
    Signed-off-by: default avatarChris Mason <clm@fb.com>
    1b984508
volumes.c 173 KB