kernel/git/stable/linux.git/drivers/md/dm.h, branch linux-3.18.y

dm: allow active and inactive tables to share dm_devs

2014-10-06T00:03:35+00:00

Until this change, when loading a new DM table, DM core would re-open all of the devices in the DM table. Now, DM core will avoid redundant device opens (and closes when destroying the old table) if the old table already has a device open using the same mode. This is achieved by managing reference counts on the table_devices that DM core now stores in the mapped_device structure (rather than in the dm_table structure). So a mapped_device's active and inactive dm_tables' dm_dev lists now just point to the dm_devs stored in the mapped_device's table_devices list. This improvement in DM core's device reference counting has the side-effect of fixing a long-standing limitation of the multipath target: a DM multipath table couldn't include any paths that were unusable (failed). For example: if all paths have failed and you add a new, working, path to the table; you can't use it since the table load would fail due to it still containing failed paths. Now a re-load of a multipath table can include failed devices and when those devices become active again they can be used instantly. The device list code in dm.c isn't a straight copy/paste from the code in dm-table.c, but it's very close (aside from some variable renames). One subtle difference is that find_table_device for the tables_devices list will only match devices with the same name and mode. This is because we don't want to upgrade a device's mode in the active table when an inactive table is loaded. Access to the mapped_device structure's tables_devices list requires a mutex (tables_devices_lock), so that tables cannot be created and destroyed concurrently. Signed-off-by: Benjamin Marzinski Signed-off-by: Mike Snitzer

dm table: make dm_table_supports_discards static

2014-08-01T16:30:34+00:00

The function dm_table_supports_discards is only called from dm-table.c:dm_table_set_restrictions(). So move it above dm_table_set_restrictions and make it static. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm table: add dm_table_run_md_queue_async

2014-03-27T20:56:24+00:00

Introduce dm_table_run_md_queue_async() to run the request_queue of the mapped_device associated with a request-based DM table. Also add dm_md_get_queue() wrapper to extract the request_queue from a mapped_device. Signed-off-by: Mike Snitzer Signed-off-by: Hannes Reinecke Reviewed-by: Jun'ichi Nomura

dm: make dm_table_alloc_md_mempools static

2014-03-27T20:56:23+00:00

Make the function dm_table_alloc_md_mempools static because it is not called from another file. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer

dm sysfs: fix a module unload race

2014-01-15T04:23:04+00:00

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 Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org

dm: wait until embedded kobject is released before destroying a device

2014-01-08T02:01:43+00:00

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 Signed-off-by: Mike Snitzer Cc: stable@vger.kernel.org

dm: allow remove to be deferred

2013-11-09T23:20:22+00:00

This patch allows the removal of an open device to be deferred until it is closed. (Previously such a removal attempt would fail.) The deferred remove functionality is enabled by setting the flag DM_DEFERRED_REMOVE in the ioctl structure on DM_DEV_REMOVE or DM_REMOVE_ALL ioctl. On return from DM_DEV_REMOVE, the flag DM_DEFERRED_REMOVE indicates if the device was removed immediately or flagged to be removed on close - if the flag is clear, the device was removed. On return from DM_DEV_STATUS and other ioctls, the flag DM_DEFERRED_REMOVE is set if the device is scheduled to be removed on closure. A device that is scheduled to be deleted can be revived using the message "@cancel_deferred_remove". This message clears the DMF_DEFERRED_REMOVE flag so that the device won't be deleted on close. Signed-off-by: Mikulas Patocka Signed-off-by: Alasdair G Kergon Signed-off-by: Mike Snitzer

dm: add reserved_bio_based_ios module parameter

2013-09-23T14:42:24+00:00

Allow user to change the number of IOs that are reserved by bio-based DM's mempools by writing to this file: /sys/module/dm_mod/parameters/reserved_bio_based_ios The default value is RESERVED_BIO_BASED_IOS (16). The maximum allowed value is RESERVED_MAX_IOS (1024). Export dm_get_reserved_bio_based_ios() for use by DM targets and core code. Switch to sizing dm-io's mempool and bioset using DM core's configurable 'reserved_bio_based_ios'. Signed-off-by: Mike Snitzer Signed-off-by: Frank Mayhar

dm: add reserved_rq_based_ios module parameter

2013-09-23T14:42:24+00:00

Allow user to change the number of IOs that are reserved by request-based DM's mempools by writing to this file: /sys/module/dm_mod/parameters/reserved_rq_based_ios The default value is RESERVED_REQUEST_BASED_IOS (256). The maximum allowed value is RESERVED_MAX_IOS (1024). Export dm_get_reserved_rq_based_ios() for use by DM targets and core code. Switch to sizing dm-mpath's mempool using DM core's configurable 'reserved_rq_based_ios'. Signed-off-by: Mike Snitzer Signed-off-by: Frank Mayhar Acked-by: Mikulas Patocka

dm: add statistics support

2013-09-06T00:46:06+00:00

Support the collection of I/O statistics on user-defined regions of a DM device. If no regions are defined no statistics are collected so there isn't any performance impact. Only bio-based DM devices are currently supported. Each user-defined region specifies a starting sector, length and step. Individual statistics will be collected for each step-sized area within the range specified. The I/O statistics counters for each step-sized area of a region are in the same format as /sys/block/*/stat or /proc/diskstats but extra counters (12 and 13) are provided: total time spent reading and writing in milliseconds. All these counters may be accessed by sending the @stats_print message to the appropriate DM device via dmsetup. The creation of DM statistics will allocate memory via kmalloc or fallback to using vmalloc space. At most, 1/4 of the overall system memory may be allocated by DM statistics. The admin can see how much memory is used by reading /sys/module/dm_mod/parameters/stats_current_allocated_bytes See Documentation/device-mapper/statistics.txt for more details. Signed-off-by: Mikulas Patocka Signed-off-by: Mike Snitzer Signed-off-by: Alasdair G Kergon