Current partition support of bcache is confusing and buggy. It tries to
trace non-continuous device minor numbers by an ida bit string, and
mistakenly mixed bcache device index with minor numbers. This design
generates several negative results,
- Index of bcache device name is not consecutive under /dev/. If there are
  3 bcache devices, they name will be,
  /dev/bcache0, /dev/bcache16, /dev/bcache32
  Only bcache code indexes bcache device name is such an interesting way.
- First minor number of each bcache device is traced by ida bit string.
  One bcache device will occupy 16 bits, this is not a good idea. Indeed
  only one bit is enough.
- Because minor number and bcache device index are mixed, a device index
  is allocated by ida_simple_get(), but an first minor number is sent into
  ida_simple_remove() to release the device. It confused original author
  too.

Root cause of the above errors is, bcache code should not handle device
minor numbers at all! A standard process to support multiple partitions in
Linux kernel is,
- Device driver provides major device number, and indexes multiple device
  instances.
- Device driver does not allocat nor trace device minor number, only
  provides a first minor number of a given device instance, and sets how
  many minor numbers (paritions) the device instance may have.
All rested stuffs are handled by block layer code, most of the details can
be found from block/{genhd, partition-generic}.c files.

This patch re-writes multiple partitions support for bcache. It makes
whole things to be more clear, and uses ida bit string in a more efficeint
way.
- Ida bit string only traces bcache device index, not minor number. For a
  bcache device with 128 partitions, only one bit in ida bit string is
  enough.
- Device minor number and device index are separated in concept. Device
  index is used for /dev node naming, and ida bit string trace. Minor
  number is calculated from device index and only used to initialize
  first_minor of a bcache device.
- It does not follow any standard for 16 partitions on a bcache device.
  This patch sets 128 partitions on single bcache device at max, this is
  the limitation from GPT (GUID Partition Table) and supported by fdisk.

Considering a typical device minor number is 20 bits width, each bcache
device may have 128 partitions (7 bits), there can be 8192 bcache devices
existing on system. For most common deployment for a single server in
now days, it should be enough.

[minor spelling fixes in commit message by Michael Lyle]
Signed-off-by: NColy Li <colyli@suse.de>
Cc: Eric Wheeler <bcache@lists.ewheeler.net>
Cc: Junhui Tang <tang.junhui@zte.com.cn>
Reviewed-by: NMichael Lyle <mlyle@lyle.org>
Signed-off-by: NMichael Lyle <mlyle@lyle.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Code comments in alloc.c:bch_alloc_sectors() mentions a function
name find_data_bucket(), the correct function name should be
pick_data_bucket() indeed. bch_alloc_sectors() is a quite important
function in bcache allocation code, fixing the typo may help
other people to have less confusion.
Signed-off-by: NColy Li <colyli@suse.de>
Reviewed-by: NTang Junhui <tang.junhui@zte.com.cn>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

In bcache code, sysfs entries are created before all resources get
allocated, e.g. allocation thread of a cache set.

There is posibility for NULL pointer deference if a resource is accessed
but which is not initialized yet. Indeed Jorg Bornschein catches one on
cache set allocation thread and gets a kernel oops.

The reason for this bug is, when bch_bucket_alloc() is called during
cache set registration and attaching, ca->alloc_thread is not properly
allocated and initialized yet, call wake_up_process() on ca->alloc_thread
triggers NULL pointer deference failure. A simple and fast fix is, before
waking up ca->alloc_thread, checking whether it is allocated, and only
wake up ca->alloc_thread when it is not NULL.
Signed-off-by: NColy Li <colyli@suse.de>
Reported-by: NJorg Bornschein <jb@capsec.org>
Cc: Kent Overstreet <kent.overstreet@gmail.com>
Cc: stable@vger.kernel.org
Reviewed-by: NMichael Lyle <mlyle@lyle.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Fixes below error with clang:
../drivers/md/bcache/sysfs.c:759:3: error: function definition is not allowed here
                {       return *((uint16_t *) r) - *((uint16_t *) l); }
                ^
../drivers/md/bcache/sysfs.c:789:32: error: use of undeclared identifier 'cmp'
                sort(p, n, sizeof(uint16_t), cmp, NULL);
                                             ^
2 errors generated.

v2:
rename function to __bch_cache_cmp
Signed-off-by: NPeter Foley <pefoley2@pefoley.com>
Reviewed-by: NColy Li <colyli@suse.de>
Reviewed-by: NMichael Lyle <mlyle@lyle.org>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This patch is the followup of the prvious patch:
[writeback: schedule periodic writeback with sysctl].

There's another issue to fix.
For example,
- When the tunable was set to one hour and is reset to one second, the
  new setting will not take effect for up to one hour.

Kicking the flusher threads immediately fixes it.

Cc: Jens Axboe <axboe@kernel.dk>
Cc: Jan Kara <jack@suse.cz>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NYafang Shao <laoar.shao@gmail.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

This parameter provide an option to disable io scheduler when nullb*
in multi-queue mode.
Signed-off-by: Nweiping zhang <zhangweiping@didichuxing.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

update the range of submits_queues, and correct usage hints.
Signed-off-by: Nweiping zhang <zhangweiping@didichuxing.com>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Christoph correctly points out that this issue is no different
for other block devices, and poking at cross layer internals
is not the right way to solve it.

This reverts commit bb6aa6f0.
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Implement a generic path for sending sync I/O on LightNVM. This allows
to reuse the standard synchronous path trough blk_execute_rq(), instead
of implementing a wait_for_completion on the target side (e.g., pblk).
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Make LightNVM passhtrough commands fail fast. User space will then take
care of re-submitting.

Fixes: 84d4add7 ('lightnvm: add ioctls for vector I/Os')
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

The amount of GC I/O on the write buffer is managed by the rate-limiter,
which is calculated as a function of the number of available free
blocks. When reaching the stable point, we risk having scheduled more
I/Os for GC than are allowed on the write buffer. This would result on
the GC semaphore balancing the outstanding read GC I/Os to be reported
as "hung", though the behavior is normal.

Solve this by allowing to schedule when we detect that the read GC path
is not moving forward.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Cleanup up unused and static functions across the whole codebase.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Lockdep complains about being in atomic context while freeing line
metadata - and rightly so as we take a spinlock and end up calling
vfree that might sleep(in pblk_mfree).

There is no need for holding the line manager free_lock while
freeing line metadata as the pipeline as stopped, so remove the lock.

Fixes: 588726d3 ("lightnvm: pblk: fail gracefully on irrec. error")
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

During garbage collect, lbas being written can end up
being invalidated. Make sure that this is reflected in
the valid lba count.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Finish garbage collect of the lines that are in the gc pipeline
before exiting. Ensure that all lines already in in the pipeline
goes through, from read to write.

Do this by keeping track of how many lines are in the pipeline
and waiting for that number to reach zero before exiting the gc
reader task.

Since we're adding a new gc line counter, change the name of
inflight_gc to read_inflight_gc to make the distinction clear.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Print the CRC of the logical-to-physical mapping during exit and
after recovering the L2P table to facilitate detection of meta
data corruption/recovery issues.

The CRC printed after recovery should match the CRC printed during
the previous exit - if it doesn't this indicates that either the meta
data written to the disk is corrupt or recovery failed.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Shut down the GC workqueues and tasks in the right order.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When recovering lines we need to consider that bad blocks in a line
affect the emeta area size.

Previously it was assumed that the emeta area would grow by the
number of sectors per page * number of bad blocks in the line.

This assumption is not correct - the number of "extra" pages that are
consumed could be both smaller (depending on emeta size) and bigger
(depending on the placement of the bad blocks).

Fix this by calculating the emeta start by iterating backwards
through the line, skipping ppas that map to bad blocks.

Also fix the data types used for ppa indices/counts in
pblk_recov_l2p_from_emeta - we should use u64.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Start GC if needed, directly after init, as we might
need to garbage collect in order to make room for user writes.

Create a helper function that allows to kick GC without exposing the
internals of the GC/rate-limiter interaction.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When rebuilding the L2P table, any full lines (lines without any
valid sectors) will be identified. If these lines are not freed,
we risk not being able to allocate the first data line.

This patch refactors the part of GC that frees empty lines
into a separate function and adds a call to this after the
L2P table has been rebuilt.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When recovering partially written lines, the valid sector
count must be decreased by the number of padded sectors
in the line.

Update line recovery to take all ADDR_EMPTY(padded) sectors
into account.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

GC can be kicked after it has been shut down when closing the last
line during exit, resulting in accesses to freed structures.

Make sure that GC is not triggered while it is not operational.
Also make sure that GC won't be re-activated during exit when
running on another processor by using timer_del_sync.
Signed-off-by: NHans Holmberg <hans.holmberg@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

If pblk_core_init fails lets destroy all global caches.
Signed-off-by: NRakesh Pandit <rakesh@tuxera.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

We already pass the structure pointer so no need to pass the member.
Signed-off-by: NRakesh Pandit <rakesh@tuxera.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Not all exported symbols are being used outside core and there were
some stale entries in lightnvm.h
Signed-off-by: NRakesh Pandit <rakesh@tuxera.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

vblk isn't being used anyway and if we ever have a usecase we can
introduce this again.  This makes the logic easier and removes
unnecessary checks.
Signed-off-by: NRakesh Pandit <rakesh@tuxera.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Signed-off-by: NRakesh Pandit <rakesh@tuxera.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

pblk_line_gc_list seems to had a bug since the introduction of pblk in
getting GC list for a line. In b20ba1bc while redesigning the GC
algorithm, the naming for the GC thresholds was altered, but the
values for high_thrs and mid_thrs were not. The result is that when
moving to the GC lists, the mid threshold is never evaluated.

Fixes: a4bd217b("lightnvm: physical block device (pblk) target")
Signed-off-by: NRakesh Pandit <rakesh@tuxera.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Make sure that the variable controlling block threshold for allocating
extra metadata sectors in case of a line with bad blocks does not get a
negative value. Otherwise, the line will be marked as corrupted and
wasted.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Metadata I/Os are scheduled to minimize their impact on user data I/Os.
When there are enough LUNs instantiated (i.e., enough bandwidth), it is
easy to interleave metadata and data one after the other so that
metadata I/Os are the ones being blocked and not vice-versa.

We do this by calculating the distance between the I/Os in terms of the
LUNs that are not in used, and selecting a free LUN that satisfies a
the simple heuristic that metadata is scheduled behind. The per-LUN
semaphores guarantee consistency. This works fine on >1 LUN
configuration. However, when a single LUN is instantiated, this design
leads to a deadlock, where metadata waits to be scheduled on a free LUN.

This patch implements the 1 LUN case by simply scheduling the metadada
I/O after the data I/O. In the process, we refactor the way a line is
replaced to ensure that metadata writes are submitted after data writes
in order to guarantee block sequentiality. Note that, since there is
only one LUN, both I/Os will block each other by design. However, such
configuration only pursues tight read latencies, not write bandwidth.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

pblk schedules user I/O, metadata I/O and erases on the write path in
order to minimize collisions at the media level. Until now, there has
been a dependency between user and metadata I/Os that could lead to a
deadlock as both take the per-LUN semaphore to schedule submission.

This path removes this dependency and guarantees forward progress at a
per I/O granurality.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

A partial read I/O in pblk is an I/O where some sectors reside in the
write buffer in main memory and some are persisted on the device. Such
an I/O must at least contain 2 lbas, therefore checking for the case
where a single lba is mapped is not necessary.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

When a line is recycled during garbage collection, reads can still be
issued to the line. If the line is freed in the middle of this process,
data corruption might occur.

This patch guarantees that lines are not freed in the middle of reads
that target them (lines). Specifically, we use the existing line
reference to decide when a line is eligible for being freed after the
recycle process.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

As part of pblk's recovery scheme, we store the lba mapped to each
physical sector on the device's out-of-bound (OOB) area.

On the read path, we can use this information to validate that the data
being delivered to the upper layers corresponds to the lba being
requested. The cost of this check is an extra copy on the DMA region on
the device and an extra comparison in the host, given that (i) the OOB
area is being read together with the data in the media, and (ii) the DMA
region allocated for the ppa list can be reused for the metadata stored
on the OOB area.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

For consistency with the rest of pblk, use rqd->end_io to point to the
function taking care of ending the request on the completion path.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Refactor the rqd allocation and free functions so that all I/O types can
use these helper functions.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Each request type sent to the LightNVM subsystem requires different
metadata. Until now, we have tailored this metadata based on write, read
and erase commands. However, pblk uses different metadata for internal
writes that do not hit the write buffer. Instead of abusing the metadata
for reads, create a new request type - internal write to improve
code readability.

In the process, create internal values for each I/O type instead of
abusing the READ/WRITE macros, as suggested by Christoph.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Wait until we know the exact number of ppas to be sent to the device,
before allocating the bio.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

On REQ_PREFLUSH, directly tag the I/O context flags to signal a flush in
the write to cache path, instead of finding the correct entry context
and imposing a memory barrier. This simplifies the code and might
potentially prevent race conditions when adding functionality to the
write path.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>

Simplify put bio by doing it on bio end_io instead of manually putting
it on the completion path.
Signed-off-by: NJavier González <javier@cnexlabs.com>
Signed-off-by: NMatias Bjørling <m@bjorling.me>
Signed-off-by: NJens Axboe <axboe@kernel.dk>