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path: root/drivers/md/dm-sysfs.c
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2015-04-15dm: add 'use_blk_mq' module param and expose in per-device ro sysfs attrMike Snitzer
Request-based DM's blk-mq support defaults to off; but a user can easily change the default using the dm_mod.use_blk_mq module/boot option. Also, you can check what mode a given request-based DM device is using with: cat /sys/block/dm-X/dm/use_blk_mq This change enabled further cleanup and reduced work (e.g. the md->io_pool and md->rq_pool isn't created if using blk-mq). Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-04-15dm: impose configurable deadline for dm_request_fn's merge heuristicMike Snitzer
Otherwise, for sequential workloads, the dm_request_fn can allow excessive request merging at the expense of increased service time. Add a per-device sysfs attribute to allow the user to control how long a request, that is a reasonable merge candidate, can be queued on the request queue. The resolution of this request dispatch deadline is in microseconds (ranging from 1 to 100000 usecs), to set a 20us deadline: echo 20 > /sys/block/dm-7/dm/rq_based_seq_io_merge_deadline The dm_request_fn's merge heuristic and associated extra accounting is disabled by default (rq_based_seq_io_merge_deadline is 0). This sysfs attribute is not applicable to bio-based DM devices so it will only ever report 0 for them. By allowing a request to remain on the queue it will block others requests on the queue. But introducing a short dequeue delay has proven very effective at enabling certain sequential IO workloads on really fast, yet IOPS constrained, devices to build up slightly larger IOs -- yielding 90+% throughput improvements. Having precise control over the time taken to wait for larger requests to build affords control beyond that of waiting for certain IO sizes to accumulate (which would require a deadline anyway). This knob will only ever make sense with sequential IO workloads and the particular value used is storage configuration specific. Given the expected niche use-case for when this knob is useful it has been deemed acceptable to expose this relatively crude method for crafting optimal IO on specific storage -- especially given the solution is simple yet effective. In the context of DM multipath, it is advisable to tune this sysfs attribute to a value that offers the best performance for the common case (e.g. if 4 paths are expected active, tune for that; if paths fail then performance may be slightly reduced). Alternatives were explored to have request-based DM autotune this value (e.g. if/when paths fail) but they were quickly deemed too fragile and complex to warrant further design and development time. If this problem proves more common as faster storage emerges we'll have to look at elevating a generic solution into the block core. Tested-by: Shiva Krishna Merla <shivakrishna.merla@netapp.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2015-04-15dm sysfs: introduce ability to add writable attributesMike Snitzer
Add DM_ATTR_RW() macro and establish .store method in dm_sysfs_ops. Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2014-01-15dm sysfs: fix a module unload raceMikulas Patocka
This reverts commit be35f48610 ("dm: wait until embedded kobject is released before destroying a device") and provides an improved fix. The kobject release code that calls the completion must be placed in a non-module file, otherwise there is a module unload race (if the process calling dm_kobject_release is preempted and the DM module unloaded after the completion is triggered, but before dm_kobject_release returns). To fix this race, this patch moves the completion code to dm-builtin.c which is always compiled directly into the kernel if BLK_DEV_DM is selected. The patch introduces a new dm_kobject_holder structure, its purpose is to keep the completion and kobject in one place, so that it can be accessed from non-module code without the need to export the layout of struct mapped_device to that code. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
2014-01-08dm: wait until embedded kobject is released before destroying a deviceMikulas Patocka
There may be other parts of the kernel holding a reference on the dm kobject. We must wait until all references are dropped before deallocating the mapped_device structure. The dm_kobject_release method signals that all references are dropped via completion. But dm_kobject_release doesn't free the kobject (which is embedded in the mapped_device structure). This is the sequence of operations: * when destroying a DM device, call kobject_put from dm_sysfs_exit * wait until all users stop using the kobject, when it happens the release method is called * the release method signals the completion and should return without delay * the dm device removal code that waits on the completion continues * the dm device removal code drops the dm_mod reference the device had * the dm device removal code frees the mapped_device structure that contains the kobject Using kobject this way should avoid the module unload race that was mentioned at the beginning of this thread: https://lkml.org/lkml/2014/1/4/83 Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com> Cc: stable@vger.kernel.org
2010-03-08Driver core: Constify struct sysfs_ops in struct kobj_typeEmese Revfy
Constify struct sysfs_ops. This is part of the ops structure constification effort started by Arjan van de Ven et al. Benefits of this constification: * prevents modification of data that is shared (referenced) by many other structure instances at runtime * detects/prevents accidental (but not intentional) modification attempts on archs that enforce read-only kernel data at runtime * potentially better optimized code as the compiler can assume that the const data cannot be changed * the compiler/linker move const data into .rodata and therefore exclude them from false sharing Signed-off-by: Emese Revfy <re.emese@gmail.com> Acked-by: David Teigland <teigland@redhat.com> Acked-by: Matt Domsch <Matt_Domsch@dell.com> Acked-by: Maciej Sosnowski <maciej.sosnowski@intel.com> Acked-by: Hans J. Koch <hjk@linutronix.de> Acked-by: Pekka Enberg <penberg@cs.helsinki.fi> Acked-by: Jens Axboe <jens.axboe@oracle.com> Acked-by: Stephen Hemminger <shemminger@vyatta.com> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
2010-02-16dm: sysfs revert add empty release function to avoid debug warningAlasdair G Kergon
Revert commit d2bb7df8cac647b92f51fb84ae735771e7adbfa7 at Greg's request. Author: Milan Broz <mbroz@redhat.com> Date: Thu Dec 10 23:51:53 2009 +0000 dm: sysfs add empty release function to avoid debug warning This patch just removes an unnecessary warning: kobject: 'dm': does not have a release() function, it is broken and must be fixed. The kobject is embedded in mapped device struct, so code does not need to release memory explicitly here. Cc: Greg KH <gregkh@suse.de> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10dm: rename dm_suspended to dm_suspended_mdKiyoshi Ueda
This patch renames dm_suspended() to dm_suspended_md() and keeps it internal to dm. No functional change. Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com> Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com> Cc: Mike Anderson <andmike@linux.vnet.ibm.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10dm: sysfs add empty release function to avoid debug warningMilan Broz
This patch just removes an unnecessary warning: kobject: 'dm': does not have a release() function, it is broken and must be fixed. The kobject is embedded in mapped device struct, so code does not need to release memory explicitly here. Cc: stable@kernel.org Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-06-22dm: sysfs add suspended attributePeter Rajnoha
Add a file named 'suspended' to each device-mapper device directory in sysfs. It holds the value 1 while the device is suspended. Otherwise it holds 0. Signed-off-by: Peter Rajnoha <prajnoha@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-01-06dm: add name and uuid to sysfsMilan Broz
Implement simple read-only sysfs entry for device-mapper block device. This patch adds a simple sysfs directory named "dm" under block device properties and implements - name attribute (string containing mapped device name) - uuid attribute (string containing UUID, or empty string if not set) The kobject is embedded in mapped_device struct, so no additional memory allocation is needed for initializing sysfs entry. During the processing of sysfs attribute we need to lock mapped device which is done by a new function dm_get_from_kobj, which returns the md associated with kobject and increases the usage count. Each 'show attribute' function is responsible for its own locking. Signed-off-by: Milan Broz <mbroz@redhat.com> Signed-off-by: Alasdair G Kergon <agk@redhat.com>