kernel_optimize_test/include
Benjamin Marzinski 86f1152b11 dm: allow active and inactive tables to share dm_devs
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 <bmarzins@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
2014-10-05 20:03:35 -04:00
..
acpi ACPI / scan: not cache _SUN value in struct acpi_device_pnp 2014-09-03 22:41:14 +02:00
asm-generic
clocksource
crypto crypto: drbg - backport "fix maximum value checks on 32 bit systems" 2014-09-05 15:52:28 +08:00
drm
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linux block: add bioset_create_nobvec() 2014-10-03 15:28:18 -06:00
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net Merge tag 'master-2014-09-04' of git://git.kernel.org/pub/scm/linux/kernel/git/linville/wireless 2014-09-07 16:11:10 -07:00
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scsi sd: Honor block layer integrity handling flags 2014-09-30 15:17:35 -06:00
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trace net: treewide: Fix typo found in DocBook/networking.xml 2014-09-05 17:35:28 -07:00
uapi dm: allow active and inactive tables to share dm_devs 2014-10-05 20:03:35 -04:00
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xen xen/arm: introduce XENFEAT_grant_map_identity 2014-09-11 18:11:52 +00:00
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