Hi everyone, Over in this thread: https://lore.kernel.org/linux-xfs/20240724131825.GA12250@xxxxxx/ I originally proposed turning on background xfs_scrub by default in Debian. Christoph wondered if it was such a good idea to unleash this upon hoards of debian sid users, considering that the introduction of e2scrub by default didn't go entirely smoothly. Debian policy is to enable packaged services at installation time, which is reasonable for httpd but perhaps not so much for experimental services. I proposed modifying xfsprogs so that for Debian builds, it would spit out a separate "xfsprogs-self-healing" package containing only the files needed to activate the background scrub services by default. People would have to opt-in to installing it... insofar as one can configure apt to pull in Suggests: and Recommends: packages. Christoph suggested adding a compat flag to the superblock so that sysadmins can mark filesystems for (or against) background online repair. Therefore, I'm proposing adding such a flag. Before I start any work on that, I thought I'd sketch out what I'd add to make that happen: On Disk Format Changes ====================== Add a new COMPAT flag XFS_SB_FEAT_COMPAT_SELF_HEALING. If set, the background xfs_scrub_all service can periodically scan the filesystem and initiate repairs. If not set, then background repairs are not allowed. Note that administrator-initated scans (e.g. invoking xfs_scrub from the CLI) would not be blocked by this flag. Question: Should this compat flag control background scrubs as well? Userspace ABI Changes ===================== The first thing is adding a new CLI option to mkfs.xfs to set the value of the flag: # mkfs.xfs -m self_healing=1 Question: If rmap and parent pointers are turned on, should we turn on self healing by default? Question: If self healing is turned on, should we turn on rmap and parent pointers as well? For xfs_scrub_all, we'd need a way to query the status of the self healing bit; this could be snuck into the xfs geometry ioctl as a new feature bit XFS_FSOP_GEOM_FLAGS_SELF_HEALING. # xfs_info /dev/sdf meta-data=/dev/sdf isize=512 agcount=1, agsize=268435455 blks = sectsz=512 attr=2, projid32bit=1 = crc=1 finobt=1, sparse=1, rmapbt=1 = reflink=1 bigtime=1 inobtcount=1 nrext64=1 = exchange=0 metadir=0 self_healing=1 data = bsize=4096 blocks=5192704, imaxpct=25 = sunit=0 swidth=0 blks naming =version 2 bsize=4096 ascii-ci=0, ftype=1, parent=0 log =internal log bsize=4096 blocks=16384, version=2 = sectsz=512 sunit=0 blks, lazy-count=1 realtime =none extsz=4096 blocks=0, rtextents=0 = rgcount=0 rgsize=0 extents I think we also want to enable sysadmins to change this on the fly. For mounted filesystems, this could be done through an administrative ioctl or mount options. Offline, this would become another xfs_admin command. # xfs_spaceman -c 'self_healing on' /usr # xfs_spaceman -c 'self_healing off' /tmp/extraspace # xfs_admin --self-healing=on /dev/sda1 # xfs_admin --self-healing=off /dev/sda2 # mount /dev/sda2 /mnt -o self_healing Thoughts? Flames? --D
