Commit Graph

33 Commits

Author SHA1 Message Date
Shaohua Li 16a43f6a65 raid5-cache: handle journal hotadd in quiesce
Handle journal hotadd in quiesce to avoid creating duplicated threads.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2016-01-14 11:49:43 +11:00
Shaohua Li a62ab49eb5 md: set MD_HAS_JOURNAL in correct places
Set MD_HAS_JOURNAL when a array is loaded or journal is initialized.
This is to avoid the flags set too early in journal disk hotadd.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2016-01-14 11:49:43 +11:00
Christoph Hellwig 5036c39020 raid5: allow r5l_io_unit allocations to fail
And propagate the error up the stack so we can add the stripe
to no_stripes_list and retry our log operation later.  This avoids
blocking raid5d due to reclaim, an it allows to get rid of the
deadlock-prone GFP_NOFAIL allocation.

shli: add missing mempool_destroy()

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: NeilBrown <neilb@suse.com>
2016-01-06 11:40:12 +11:00
Christoph Hellwig e8deb63810 raid5-cache: use a mempool for the metadata block
We only have a limited number in flight, so use a page based mempool.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: NeilBrown <neilb@suse.com>
2016-01-06 11:40:08 +11:00
Christoph Hellwig c38d29b33b raid5-cache: use a bio_set
This allows us to make guaranteed forward progress.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: NeilBrown <neilb@suse.com>
2016-01-06 11:40:04 +11:00
Shaohua Li f6b6ec5cfa raid5-cache: add journal hot add/remove support
Add support for journal disk hot add/remove. Mostly trival checks in md
part. The raid5 part is a little tricky. For hot-remove, we can't wait
pending write as it's called from raid5d. The wait will cause deadlock.
We simplily fail the hot-remove. A hot-remove retry can success
eventually since if journal disk is faulty all pending write will be
failed and finish. For hot-add, since an array supporting journal but
without journal disk will be marked read-only, we are safe to hot add
journal without stopping IO (should be read IO, while journal only
handles write IO).

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2016-01-06 11:39:57 +11:00
Christoph Hellwig ad66d445ee raid5-cache: free meta_page earlier
Once the I/O completed we don't need the meta page anymore.  As the iounits
can live on for a long time this reduces memory pressure a bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2016-01-06 11:39:43 +11:00
Christoph Hellwig 3848c0bcb0 raid5-cache: simplify r5l_move_io_unit_list
It's only used for one kind of move, so make that explicit.  Also clean
up the code a bit by using list_for_each_safe.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2016-01-06 11:39:34 +11:00
Shaohua Li 7dde2ad3c5 raid5-cache: start raid5 readonly if journal is missing
If raid array is expected to have journal (eg, journal is set in MD
superblock feature map) and the array is started without journal disk,
start the array readonly.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:29 +11:00
Shaohua Li 6e74a9cfb5 raid5-cache: IO error handling
There are 3 places the raid5-cache dispatches IO. The discard IO error
doesn't matter, so we ignore it. The superblock write IO error can be
handled in MD core. The remaining are log write and flush. When the IO
error happens, we mark log disk faulty and fail all write IO. Read IO is
still allowed to run. Userspace will get a notification too and
corresponding daemon can choose setting raid array readonly for example.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:29 +11:00
Shaohua Li 4b482044d2 raid5-cache: add trim support for log
Since superblock is updated infrequently, we do a simple trim of log
disk (a synchronous trim)

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:29 +11:00
Christoph Hellwig 6143e2cecb raid5-cache: use bio chaining
Simplify the bio completion handler by using bio chaining and submitting
bios as soon as they are full.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:28 +11:00
Christoph Hellwig 2b8ef16ec4 raid5-cache: small log->seq cleanup
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:28 +11:00
Christoph Hellwig c1b9919849 raid5-cache: new helper: r5_reserve_log_entry
Factor out code to reserve log space.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:28 +11:00
Christoph Hellwig 51039cd066 raid5-cache: inline r5l_alloc_io_unit into r5l_new_meta
This is the only user, and keeping all code initializing the io_unit
structure together improves readbility.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:28 +11:00
Christoph Hellwig 1e932a37cc raid5-cache: take rdev->data_offset into account early on
Set up bi_sector properly when we allocate an bio instead of updating it
at submission time.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:28 +11:00
Christoph Hellwig b349feb36c raid5-cache: refactor bio allocation
Split out a helper to allocate a bio for log writes.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:28 +11:00
Christoph Hellwig 22581f58ed raid5-cache: clean up r5l_get_meta
Remove the only partially used local 'io' variable to simplify the code
flow.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:28 +11:00
Christoph Hellwig 56fef7c6e0 raid5-cache: simplify state machine when caches flushes are not needed
For devices without a volatile write cache we don't need to send a FLUSH
command to ensure writes are stable on disk, and thus can avoid the whole
step of batching up bios for processing by the MD thread.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:28 +11:00
Christoph Hellwig d8858f4321 raid5-cache: factor out a helper to run all stripes for an I/O unit
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:27 +11:00
Christoph Hellwig 04732f741d raid5-cache: rename flushed_ios to finished_ios
After this series we won't nessecarily have flushed the cache for these
I/Os, so give the list a more neutral name.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:27 +11:00
Christoph Hellwig 170364619a raid5-cache: free I/O units earlier
There is no good reason to keep the I/O unit structures around after the
stripe has been written back to the RAID array.  The only information
we need is the log sequence number, and the checkpoint offset of the
highest successfull writeback.  Store those in the log structure, and
free the IO units from __r5l_stripe_write_finished.

Besides simplifying the code this also avoid having to keep the allocation
for the I/O unit around for a potentially long time as superblock updates
that checkpoint the log do not happen very often.

This also fixes the previously incorrect calculation of 'free' in
r5l_do_reclaim as a side effect: previous if took the last unit which
isn't checkpointed into account.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:27 +11:00
Shaohua Li e6c033f79a raid5-cache: move reclaim stop to quiesce
Move reclaim stop to quiesce handling, where is safer for this stuff.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:27 +11:00
Shaohua Li 253f9fd41a raid5-cache: don't delay stripe captured in log
There is a case a stripe gets delayed forever.
1. a stripe finishes construction
2. a new bio hits the stripe
3. handle_stripe runs for the stripe. The stripe gets DELAYED bit set
since construction can't run for new bio (the stripe is locked since
step 1)

Without log, handle_stripe will call ops_run_io. After IO finishes, the
stripe gets unlocked and the stripe will restart and run construction
for the new bio. With log, ops_run_io need to run two times. If the
DELAYED bit set, the stripe can't enter into the handle_list, so the
second ops_run_io doesn't run, which leaves the stripe stalled.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:27 +11:00
Shaohua Li 85f2f9a4f4 raid5-cache: check stripe finish out of order
stripes could finish out of order. Hence r5l_move_io_unit_list() of
__r5l_stripe_write_finished might not move any entry and leave
stripe_end_ios list empty.

This applies on top of http://marc.info/?l=linux-raid&m=144122700510667

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:26 +11:00
Shaohua Li 828cbe989e raid5-cache: optimize FLUSH IO with log enabled
With log enabled, bio is written to raid disks after the bio is settled
down in log disk. The recovery guarantees we can recovery the bio data
from log disk, so we we skip FLUSH IO.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:26 +11:00
Christoph Hellwig 509ffec708 raid5-cache: move functionality out of __r5l_set_io_unit_state
Just keep __r5l_set_io_unit_state as a small set the state wrapper, and
remove r5l_set_io_unit_state entirely after moving the real
functionality to the two callers that need it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:26 +11:00
Shaohua Li 0fd22b45b2 raid5-cache: fix a user-after-free bug
r5l_compress_stripe_end_list() can free an io_unit. This breaks the
assumption only reclaimer can free io_unit. We can add a reference count
based io_unit free, but since only reclaim can wait io_unit becoming to
STRIPE_END state, we use a simple global wait queue here.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:26 +11:00
Shaohua Li a8c34f9159 raid5-cache: switching to state machine for log disk cache flush
Before we write stripe data to raid disks, we must guarantee stripe data
is settled down in log disk. To do this, we flush log disk cache and
wait the flush finish. That wait introduces sleep time in raid5d thread
and impact performance. This patch moves the log disk cache flush
process to the stripe handling state machine, which can remove the wait
in raid5d.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-11-01 13:48:26 +11:00
Shaohua Li 5cb2fbd6ea raid5-cache: use crc32c checksum
crc32c has lower overhead with cpu acceleration. It's a shame I didn't
use it in first post, sorry. This changes disk format, but we are still
ok in current stage.

V2: delete unnecessary type conversion as pointed out by Bart

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
2015-11-01 13:45:39 +11:00
Shaohua Li 355810d12a raid5: log recovery
This is the log recovery support. The process is quite straightforward.
We scan the log and read all valid meta/data/parity into memory. If a
stripe's data/parity checksum is correct, the stripe will be recoveried.
Otherwise, it's discarded and we don't scan the log further. The reclaim
process guarantees stripe which starts to be flushed raid disks has
completed data/parity and has correct checksum. To recovery a stripe, we
just copy its data/parity to corresponding raid disks.

The trick thing is superblock update after recovery. we can't let
superblock point to last valid meta block. The log might look like:
| meta 1| meta 2| meta 3|
meta 1 is valid, meta 2 is invalid. meta 3 could be valid. If superblock
points to meta 1, we write a new valid meta 2n.  If crash happens again,
new recovery will start from meta 1. Since meta 2n is valid, recovery
will think meta 3 is valid, which is wrong.  The solution is we create a
new meta in meta2 with its seq == meta 1's seq + 10 and let superblock
points to meta2.  recovery will not think meta 3 is a valid meta,
because its seq is wrong

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-10-24 17:16:19 +11:00
Shaohua Li 0576b1c618 raid5: log reclaim support
This is the reclaim support for raid5 log. A stripe write will have
following steps:

1. reconstruct the stripe, read data/calculate parity. ops_run_io
prepares to write data/parity to raid disks
2. hijack ops_run_io. stripe data/parity is appending to log disk
3. flush log disk cache
4. ops_run_io run again and do normal operation. stripe data/parity is
written in raid array disks. raid core can return io to upper layer.
5. flush cache of all raid array disks
6. update super block
7. log disk space used by the stripe can be reused

In practice, several stripes consist of an io_unit and we will batch
several io_unit in different steps, but the whole process doesn't
change.

It's possible io return just after data/parity hit log disk, but then
read IO will need read from log disk. For simplicity, IO return happens
at step 4, where read IO can directly read from raid disks.

Currently reclaim run if there is specific reclaimable space (1/4 disk
size or 10G) or we are out of space. Reclaim is just to free log disk
spaces, it doesn't impact data consistency. The size based force reclaim
is to make sure log isn't too big, so recovery doesn't scan log too
much.

Recovery make sure raid disks and log disk have the same data of a
stripe. If crash happens before 4, recovery might/might not recovery
stripe's data/parity depending on if data/parity and its checksum
matches. In either case, this doesn't change the syntax of an IO write.
After step 3, stripe is guaranteed recoverable, because stripe's
data/parity is persistent in log disk. In some cases, log disk content
and raid disks content of a stripe are the same, but recovery will still
copy log disk content to raid disks, this doesn't impact data
consistency. space reuse happens after superblock update and cache
flush.

There is one situation we want to avoid. A broken meta in the middle of
a log causes recovery can't find meta at the head of log. If operations
require meta at the head persistent in log, we must make sure meta
before it persistent in log too. The case is stripe data/parity is in
log and we start write stripe to raid disks (before step 4). stripe
data/parity must be persistent in log before we do the write to raid
disks. The solution is we restrictly maintain io_unit list order. In
this case, we only write stripes of an io_unit to raid disks till the
io_unit is the first one whose data/parity is in log.

The io_unit list order is important for other cases too. For example,
some io_unit are reclaimable and others not. They can be mixed in the
list, we shouldn't reuse space of an unreclaimable io_unit.

Includes fixes to problems which were...
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-10-24 17:16:19 +11:00
Shaohua Li f6bed0ef0a raid5: add basic stripe log
This introduces a simple log for raid5. Data/parity writing to raid
array first writes to the log, then write to raid array disks. If
crash happens, we can recovery data from the log. This can speed up
raid resync and fix write hole issue.

The log structure is pretty simple. Data/meta data is stored in block
unit, which is 4k generally. It has only one type of meta data block.
The meta data block can track 3 types of data, stripe data, stripe
parity and flush block. MD superblock will point to the last valid
meta data block. Each meta data block has checksum/seq number, so
recovery can scan the log correctly. We store a checksum of stripe
data/parity to the metadata block, so meta data and stripe data/parity
can be written to log disk together. otherwise, meta data write must
wait till stripe data/parity is finished.

For stripe data, meta data block will record stripe data sector and
size. Currently the size is always 4k. This meta data record can be made
simpler if we just fix write hole (eg, we can record data of a stripe's
different disks together), but this format can be extended to support
caching in the future, which must record data address/size.

For stripe parity, meta data block will record stripe sector. It's
size should be 4k (for raid5) or 8k (for raid6). We always store p
parity first. This format should work for caching too.

flush block indicates a stripe is in raid array disks. Fixing write
hole doesn't need this type of meta data, it's for caching extension.

Signed-off-by: Shaohua Li <shli@fb.com>
Signed-off-by: NeilBrown <neilb@suse.com>
2015-10-24 17:16:19 +11:00