linux-stable.git/drivers/block/null_blk.h, branch v5.10

null_blk: Fix scheduling in atomic with zoned mode

2020-11-06T16:36:42+00:00

Commit aa1c09cb65e2 ("null_blk: Fix locking in zoned mode") changed
zone locking to using the potentially sleeping wait_on_bit_io()
function. This is acceptable when memory backing is enabled as the
device queue is in that case marked as blocking, but this triggers a
scheduling while in atomic context with memory backing disabled.

Fix this by relying solely on the device zone spinlock for zone
information protection without temporarily releasing this lock around
null_process_cmd() execution in null_zone_write(). This is OK to do
since when memory backing is disabled, command processing does not
block and the memory backing lock nullb->lock is unused. This solution
avoids the overhead of having to mark a zoned null_blk device queue as
blocking when memory backing is unused.

This patch also adds comments to the zone locking code to explain the
unusual locking scheme.

Fixes: aa1c09cb65e2 ("null_blk: Fix locking in zoned mode")
Reported-by: kernel test robot 
Signed-off-by: Damien Le Moal 
Reviewed-by: Christoph Hellwig 
Cc: stable@vger.kernel.org
Signed-off-by: Jens Axboe

null_blk: Fix locking in zoned mode

2020-10-29T13:27:30+00:00

When the zoned mode is enabled in null_blk, Serializing read, write
and zone management operations for each zone is necessary to protect
device level information for managing zone resources (zone open and
closed counters) as well as each zone condition and write pointer
position. Commit 35bc10b2eafb ("null_blk: synchronization fix for
zoned device") introduced a spinlock to implement this serialization.
However, when memory backing is also enabled, GFP_NOIO memory
allocations are executed under the spinlock, resulting in might_sleep()
warnings. Furthermore, the zone_lock spinlock is locked/unlocked using
spin_lock_irq/spin_unlock_irq, similarly to the memory backing code with
the nullb->lock spinlock. This nested use of irq locks wrecks the irq
enabled/disabled state.

Fix all this by introducing a bitmap for per-zone lock, with locking
implemented using wait_on_bit_lock_io() and clear_and_wake_up_bit().
This locking mechanism allows keeping a zone locked while executing
null_process_cmd(), serializing all operations to the zone while
allowing to sleep during memory backing allocation with GFP_NOIO.
Device level zone resource management information is protected using
a spinlock which is not held while executing null_process_cmd();

Fixes: 35bc10b2eafb ("null_blk: synchronization fix for zoned device")
Signed-off-by: Damien Le Moal 
Signed-off-by: Jens Axboe

null_blk: synchronization fix for zoned device

2020-10-28T02:40:42+00:00

Parallel write,read,zone-mgmt operations accessing/altering zone state
and write-pointer may get into race. Avoid the situation by using a new
spinlock for zoned device.
Concurrent zone-appends (on a zone) returning same write-pointer issue
is also avoided using this lock.

Cc: stable@vger.kernel.org
Fixes: e0489ed5daeb ("null_blk: Support REQ_OP_ZONE_APPEND")
Signed-off-by: Kanchan Joshi 
Reviewed-by: Damien Le Moal 
Signed-off-by: Jens Axboe

null_blk: add support for max open/active zone limit for zoned devices

2020-09-29T14:12:48+00:00

Add support for user space to set a max open zone and a max active zone
limit via configfs. By default, the default values are 0 == no limit.

Call the block layer API functions used for exposing the configured
limits to sysfs.

Add accounting in null_blk_zoned so that these new limits are respected.
Performing an operation that would exceed these limits results in a
standard I/O error.

A max open zone limit exists in the ZBC standard.
While null_blk_zoned is used to test the Zoned Block Device model in
Linux, when it comes to differences between ZBC and ZNS, null_blk_zoned
mostly follows ZBC.

Therefore, implement the manage open zone resources function from ZBC,
but additionally add support for max active zones.
This enables user space not only to test against a device with an open
zone limit, but also to test against a device with an active zone limit.

Signed-off-by: Niklas Cassel 
Reviewed-by: Damien Le Moal 
Reviewed-by: Johannes Thumshirn 
Signed-off-by: Jens Axboe

null_blk: introduce zone capacity for zoned device

2020-07-08T14:16:19+00:00

Allow emulation of a zoned device with a per zone capacity smaller than
the zone size as as defined in the Zoned Namespace (ZNS) Command Set
specification. The zone capacity defaults to the zone size if not
specified and must be smaller than the zone size otherwise.

Reviewed-by: Matias Bjørling 
Reviewed-by: Chaitanya Kulkarni 
Reviewed-by: Himanshu Madhani 
Reviewed-by: Martin K. Petersen 
Reviewed-by: Hannes Reinecke 
Reviewed-by: Johannes Thumshirn 
Reviewed-by: Daniel Wagner 
Signed-off-by: Aravind Ramesh 
Signed-off-by: Christoph Hellwig

null_blk: Cleanup zoned device initialization

2020-04-23T15:35:09+00:00

Move all zoned mode related code from null_blk_main.c to
null_blk_zoned.c, avoiding an ugly #ifdef in the process.
Rename null_zone_init() into null_init_zoned_dev(), null_zone_exit()
into null_free_zoned_dev() and add the new function
null_register_zoned_dev() to finalize the zoned dev setup before
add_disk().

Signed-off-by: Damien Le Moal 
Reviewed-by: Christoph Hellwig 
Reviewed-by: Johannes Thumshirn 
Signed-off-by: Jens Axboe

null_blk: Fix zoned command handling

2020-04-23T15:35:09+00:00

For write operations issued to a null_blk device with zoned mode
enabled, the state and write pointer position of the zone targeted by
the command should be checked before badblocks and memory backing
are handled as the write may be first failed due to, for instance, a
sector position not aligned with the zone write pointer. This order of
checking for errors reflects more accuratly the behavior of physical
zoned devices.

Furthermore, the write pointer position of the target zone should be
incremented only and only if no errors are reported by badblocks and
memory backing handling.

To fix this, introduce the small helper function null_process_cmd()
which execute null_handle_badblocks() and null_handle_memory_backed()
and use this function in null_zone_write() to correctly handle write
requests to zoned null devices depending on the type and state of the
write target zone. Also call this function in null_handle_zoned() to
process read requests to zoned null devices.

null_process_cmd() is called directly from null_handle_cmd() for
regular null devices, resulting in no functional change for these type
of devices. To have symmetric names, the function null_handle_zoned()
is renamed to null_process_zoned_cmd().

Signed-off-by: Damien Le Moal 
Reviewed-by: Chaitanya Kulkarni 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Jens Axboe

null_blk: remove unused fields in 'nullb_cmd'

2020-02-25T16:43:29+00:00

'list', 'll_list' and 'csd' are no longer used.

The 'list' is not used since it was introduced by commit f2298c0403b0
("null_blk: multi queue aware block test driver").

The 'll_list' is no longer used since commit 3c395a969acc ("null_blk: set a
separate timer for each command").

The 'csd' is no longer used since commit ce2c350b2cfe ("null_blk: use
blk_complete_request and blk_mq_complete_request").

Reviewed-by: Bart Van Assche 
Signed-off-by: Dongli Zhang 
Signed-off-by: Jens Axboe

block: rework zone reporting

2019-11-13T02:12:07+00:00

Avoid the need to allocate a potentially large array of struct blk_zone
in the block layer by switching the ->report_zones method interface to
a callback model. Now the caller simply supplies a callback that is
executed on each reported zone, and private data for it.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Shin'ichiro Kawasaki 
Signed-off-by: Damien Le Moal 
Reviewed-by: Hannes Reinecke 
Reviewed-by: Mike Snitzer 
Signed-off-by: Jens Axboe

null_blk: clean up report zones

2019-11-13T02:12:01+00:00

Make the instance name match the method name and define the name to NULL
instead of providing an inline stub, which is rather pointless for a
method call.

Signed-off-by: Christoph Hellwig 
Signed-off-by: Damien Le Moal 
Reviewed-by: Hannes Reinecke 
Reviewed-by: Chaitanya Kulkarni 
Signed-off-by: Jens Axboe