Re: [PATCH 00/15] btrfs: Hot spare and Auto replace

[Austin S Hemmelgarn <ahferroin7@gmail.com>]

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On 2015-11-09 05:56, Anand Jain wrote:
> These set of patches provides btrfs hot spare and auto replace support
> for you review and comments.
>
> First, here below are the simple example steps to configure the same:
>
> Add a spare device:
>      btrfs spare add /dev/sde -f
>
> OR if there is a spare device which is already added before the, just
> run
>
>      btrfs dev scan [/dev/sde]
>
> this will register the spare device to the kernel.
>
>      btrfs fi show
>      Label: none  uuid: 52f170c1-725c-457d-8cfd-d57090460091
> 	Total devices 2 FS bytes used 112.00KiB
> 	devid    1 size 2.00GiB used 417.50MiB path /dev/sdc
> 	devid    2 size 2.00GiB used 417.50MiB path /dev/sdd
>
>      Global spare
> 	device size 3.00GiB path /dev/sde
>
> Thats it.
>
> Auto replace:
>   Replace happens automatically, that is when there is any write
>   failed or flush failed, the device will be marked as failed, which
>   will stop any further IO attempt to that device. And in the next commit
>   thread cycle the auto replace will pick the spare device (/dev/sde is
>   above example) to replace the failed device. And so the btrfs volume is
>   back to a healthy state.
>
>
> Its btrfs Global spare:
>   as of now only global hot spare is supported, that is hot spare(s)
>   are for all the btrfs FS in the system.
>
> No spare when device failed:
>   It would scan for spare device at the rate of transaction commit
>   and will trigger the auto replace when ever spare device is added.
>
> Priority:
>   In some future work there can be some chronological order to pick
>   a spare and the failed device.
>
>
> Patches:
>
> Kernel:
> First, it needs, Qu's per chunk missing device patchset,
> which is part of the set here and also there is a light optimization
> (patch 5/15) which was required as part of this enhancement.
>
> Next patches 7,8/15 brings in support, to manage the transition of
> devices from online (no state) to offline OR failed state dynamically.
> On top of static device state like the current "missing" state.
>
> Patch 9/15 fixes a bug where in we should have blocked the incompatible
> feature at the device scan/add level instead/also at in the mount level.
> This is because we don't have to bring a device into the device list,
> if it is incompatible.
>
> Next patches 10,11,12,13/15 adds support for Spare device. For the
> details on how to add a spare device kindly see further below.
> For kernel with out spare feature supported the spare device
> is kept away. And when the kernel supports the spare device, it will
> inhibit from mounting it. Further these patch set provides helper
> function to pick a spare device and release a spare device back to
> the spare device pool.
>
> Patch 14/15 provides function for auto replace, this is mainly
> from the existing replace code, and in the long run I see opportunity
> to merge these code with the replace code that is triggered from
> the user spare.
>
> Last 15/15, uses all these facilities, picks a failed device and
> triggers a auto replace in a kthread (casualty_kthread())
>
>
> Progs:
> Would need 4 patches as listed below.
>
>
> Known Bug:
>
> As now I see below stale kmem cache during module unload. Which
> I am digging.
> ------
> BUG btrfs_path (Not tainted): Objects remaining in btrfs_path on kmem_cache_close()
> ------
>
> Anand Jain (10):
>    btrfs: optimize btrfs_check_degradable() for calls outside of barrier
>    btrfs: introduce device dynamic state transition to offline or failed
>    btrfs: check device for critical errors and mark failed
>    btrfs: block incompatible optional features at scan
>    btrfs: introduce BTRFS_FEATURE_INCOMPAT_SPARE_DEV
>    btrfs: add check not to mount a spare device
>    btrfs: support btrfs dev scan for spare device
>    btrfs: provide framework to get and put a spare device
>    btrfs: introduce helper functions to perform hot replace
>    btrfs: check for failed device and hot replace
>
> Qu Wenruo (5):
>    btrfs: Introduce a new function to check if all chunks a OK for
>      degraded mount
>    btrfs: Do per-chunk check for mount time check
>    btrfs: Do per-chunk degraded check for remount
>    btrfs: Allow barrier_all_devices to do per-chunk device check
>    btrfs: Cleanup num_tolerated_disk_barrier_failures
>
>   fs/btrfs/ctree.h       |   7 +-
>   fs/btrfs/dev-replace.c | 116 ++++++++++++++++++++
>   fs/btrfs/dev-replace.h |   1 +
>   fs/btrfs/disk-io.c     | 211 +++++++++++++++++++++++-------------
>   fs/btrfs/disk-io.h     |   2 -
>   fs/btrfs/super.c       |  20 +++-
>   fs/btrfs/transaction.c |   3 +-
>   fs/btrfs/volumes.c     | 283 ++++++++++++++++++++++++++++++++++++++++++++++---
>   fs/btrfs/volumes.h     |  27 +++++
>   9 files changed, 571 insertions(+), 99 deletions(-)
>
I've thrown everything I can think of at this over the weekend, and 
nothing broke (at least, nothing broke that had anything to do with 
these patches, I ended up triggering a couple of known bugs that I had 
completely forgotten about), so you can add:
Tested-by: Austin S. Hemmelgarn <ahferroin7@gmail.com>


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