wireguard-linux/fs/btrfs/sysfs.c, branch update-toolchain

btrfs: introduce new "rescue=ignoresuperflags" mount option

2024-07-11T13:33:30Z

This new mount option allows the kernel to skip the super flags check, it's mostly to allow the kernel to do a rescue mount of an interrupted checksum conversion. Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: introduce new "rescue=ignoremetacsums" mount option

2024-07-11T13:33:29Z

Introduce "rescue=ignoremetacsums" to ignore metadata csums, all the other metadata sanity checks are still kept as is. This new mount option is mostly to allow the kernel to mount an interrupted checksum conversion (at the metadata csum overwrite stage). And since the main part of metadata sanity checks is inside tree-checker, we shouldn't lose much safety, and the new mount option is rescue mount option it requires full read-only mount. Reviewed-by: Josef Bacik Signed-off-by: Qu Wenruo Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: periodic block_group reclaim

2024-07-11T13:33:27Z

We currently employ a edge-triggered block group reclaim strategy which marks block groups for reclaim as they free down past a threshold. With a dynamic threshold, this is worse than doing it in a level-triggered fashion periodically. That is because the reclaim itself happens periodically, so the threshold at that point in time is what really matters, not the threshold at freeing time. If we mark the reclaim in a big pass, then sort by usage and do reclaim, we also benefit from a negative feedback loop preventing unnecessary reclaims as we crunch through the "best" candidates. Since this is quite a different model, it requires some additional support. The edge triggered reclaim has a good heuristic for not reclaiming fresh block groups, so we need to replace that with a typical GC sweep mark which skips block groups that have seen an allocation since the last sweep. Reviewed-by: Josef Bacik Signed-off-by: Boris Burkov Signed-off-by: David Sterba

btrfs: dynamic block_group reclaim threshold

2024-07-11T13:33:27Z

We can currently recover allocated block_groups by: - explicitly starting balance operations - "auto reclaim" via bg_reclaim_threshold The latter works by checking against a fixed threshold on frees. If we pass from above the threshold to below, relocation triggers and the block group will get reclaimed by the cleaner thread (assuming it is still eligible) Picking a threshold is challenging. Too high, and you end up trying to reclaim very full block_groups which is quite costly, and you don't do reclaim on block_groups that don't get quite THAT full, but could still be quite fragmented and stranding a lot of space. Too low, and you similarly miss out on reclaim even if you badly need it to avoid running out of unallocated space, if you have heavily fragmented block groups living above the threshold. No matter the threshold, it suffers from a workload that happens to bounce around that threshold, which can introduce arbitrary amounts of reclaim waste. To improve this situation, introduce a dynamic threshold. The basic idea behind this threshold is that it should be very lax when there is plenty of unallocated space, and increasingly aggressive as we approach zero unallocated space. To that end, it sets a target for unallocated space (10 chunks) and then linearly increases the threshold as the amount of space short of the target we are increases. The formula is: (target - unalloc) / target I tested this by running it on three interesting workloads: 1. bounce allocations around X% full. 2. fill up all the way and introduce full fragmentation. 3. write in a fragmented way until the filesystem is just about full. 1. and 2. attack the weaknesses of a fixed threshold; fixed either works perfectly or fully falls apart, depending on the threshold. Dynamic always handles these cases well. 3. attacks dynamic by checking whether it is too zealous to reclaim in conditions with low unallocated and low unused. It tends to claw back 1GiB of unallocated fairly aggressively, but not much more. Early versions of dynamic threshold struggled on this test. Additional work could be done to intelligently ratchet up the urgency of reclaim in very low unallocated conditions. Existing mechanisms are already useless in that case anyway. Reviewed-by: Josef Bacik Signed-off-by: Boris Burkov Signed-off-by: David Sterba

btrfs: report reclaim stats in sysfs

2024-07-11T13:33:27Z

When evaluating various reclaim strategies/thresholds against each other, it is useful to collect data about the amount of reclaim happening. Expose a count, error count, and byte count via sysfs per space_info. Note that this is only for automatic reclaim, not manually invoked balances or other codepaths that use "relocate_block_group" Reviewed-by: Josef Bacik Reviewed-by: Johannes Thumshirn Signed-off-by: Boris Burkov Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: use btrfs_is_testing() everywhere

2024-05-07T19:31:07Z

There are open coded tests of BTRFS_FS_STATE_DUMMY_FS_INFO and we have a wrapper for that that's a compile-time constant when self-tests are not built in. As this is only for development we can save some bytes and conditions on release configs by using the helper in the remaining cases. Reviewed-by: Josef Bacik Signed-off-by: David Sterba

btrfs: introduce offload_csum_mode to tweak checksum offloading behavior

2024-03-04T15:24:52Z

We disable offloading checksum to workqueues and do it synchronously when the checksum algorithm is fast. However, as reported in the link below, RAID0 with multiple devices may suffer from the sync checksum, because "fast checksum" is still not fast enough to catch up with RAID0 writing. We don't have an effective way to determine whether to offload or not, for now add a sysfs knob so this can be debugged. This is intentionally under CONFIG_BTRFS_DEBUG so ti's not exposed to users as it may be removed in the future agin. Introduce fs_devices->offload_csum_mode, so that a btrfs developer can change the behavior by writing to /sys/fs/btrfs//offload_csum. The default is "auto" which is the same as the previous behavior. Or, you can set "on" or "off" (or "y" or "n" whatever kstrtobool() accepts) to always/never offload checksum. More benchmark need to be collected with this knob to implement a proper criteria to enable/disable checksum offloading. Link: https://lore.kernel.org/linux-btrfs/20230731152223.4EFB.409509F4@e16-tech.com/ Link: https://lore.kernel.org/linux-btrfs/p3vo3g7pqn664mhmdhlotu5dzcna6vjtcoc2hb2lsgo2fwct7k@xzaxclba5tae/ Reviewed-by: Johannes Thumshirn Signed-off-by: Naohiro Aota Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: sysfs: drop unnecessary double logical negation in acl_show()

2024-03-04T15:24:52Z

The IS_ENABLED() macro already guarantees the result will be a suitable boolean return value ("1" for enabled, and "0" for disabled). Thus, it seems that the "!!" used right before is unnecessary to force the 0/1 values. Reviewed-by: Anand Jain Signed-off-by: Neal Gompa Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: use READ/WRITE_ONCE for fs_devices->read_policy

2024-03-04T15:24:47Z

Since we can read/modify the value from the sysfs interface concurrently, it would be better to protect it from compiler optimizations. Currently, there is only one read policy BTRFS_READ_POLICY_PID available, so no actual problem can happen now. This is a preparation for the future expansion. Reviewed-by: Anand Jain Signed-off-by: Naohiro Aota Reviewed-by: David Sterba Signed-off-by: David Sterba

btrfs: sysfs: validate scrub_speed_max value

2023-12-15T22:01:04Z

The value set as scrub_speed_max accepts size with suffixes (k/m/g/t/p/e) but we should still validate it for trailing characters, similar to what we do with chunk_size_store. CC: stable@vger.kernel.org # 5.15+ Signed-off-by: David Disseldorp Reviewed-by: David Sterba Signed-off-by: David Sterba