On Wed, 28 Jun 2017 13:43:29 +0800 Qu Wenruo <quwen...@cn.fujitsu.com> wrote:
> The patchset can be fetched from my github repo: > https://github.com/adam900710/linux/tree/degradable > > The patchset is based on David's for-4.13-part1 branch. > > Btrfs currently uses num_tolerated_disk_barrier_failures to do global > check for tolerated missing device. > > Although the one-size-fit-all solution is quite safe, it's too strict > if data and metadata has different duplication level. > > For example, if one use Single data and RAID1 metadata for 2 disks, it > means any missing device will make the fs unable to be degraded > mounted. > > But in fact, some times all single chunks may be in the existing > device and in that case, we should allow it to be rw degraded mounted. > > Such case can be easily reproduced using the following script: > # mkfs.btrfs -f -m raid1 -d sing /dev/sdb /dev/sdc > # wipefs -f /dev/sdc > # mount /dev/sdb -o degraded,rw > > If using btrfs-debug-tree to check /dev/sdb, one should find that the > data chunk is only in sdb, so in fact it should allow degraded mount. > > This patchset will introduce a new per-chunk degradable check for > btrfs, allow above case to succeed, and it's quite small anyway. > > And enhance kernel error message for missing device, at least user > can know what's making mount failed, other than meaningless > "failed to read system chunk/chunk tree -5". > > v2: > Update after almost 2 years. > Add the last patch to enhance the kernel output, so user can know > it's missing devices that prevents btrfs to be mounted. > v3: > Remove one duplicated missing device output > Use the advice from Anand Jain, not to add new members in > btrfs_device, but use a new structure extra_rw_degrade_errors, to > record error when sending down/waiting device. > v3.1: > Reduce the critical section in btrfs_check_rw_degradable(), follow > other caller to only acquire the lock when searching, as extent_map > has refcount to avoid concurrency already. > The modification itself won't affect the behavior, so tested-by > tags are added to each patch. > v4: > Thanks Anand for this dev flush work, which makes us more easier to > detect flush error in previous transaction. > Now this patchset won't need to alloc memory, and can just use > btrfs_device->last_flush_error to check if last flush finished > correctly. > New rebase, so old tested by tags are all removed, sorry guys. > > Qu Wenruo (6): > btrfs: Introduce a function to check if all chunks a OK for degraded > rw mount > btrfs: Do chunk level rw degrade check at mount time > btrfs: Do chunk level degradation check for remount > btrfs: Allow barrier_all_devices to do chunk level device check > btrfs: Cleanup num_tolerated_disk_barrier_failures > btrfs: Enhance missing device kernel message > > fs/btrfs/ctree.h | 2 -- > fs/btrfs/disk-io.c | 81 ++++---------------------------------------- > fs/btrfs/disk-io.h | 2 -- > fs/btrfs/super.c | 3 +- > fs/btrfs/volumes.c | 99 > +++++++++++++++++++++++++++++++++++++++++------------- > fs/btrfs/volumes.h | 3 ++ 6 files changed, 85 insertions(+), 105 > deletions(-) > Tested on top of current mainline master (commit af3c8d98508d37541d4bf57f13a984a7f73a328c). Didn't find any regressions. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
