linux-stable.git/drivers/md/dm-thin.c, branch v3.4

dm thin: fix table output when pool target disables discard passdown internally

2012-05-19T00:01:01+00:00

When the thin pool target clears the discard_passdown parameter
internally, it incorrectly changes the table line reported to userspace.
This breaks dumb string comparisons on these table lines in generic
userspace device-mapper library code and leads to tables being reloaded
repeatedly when nothing is actually meant to be changing.

This patch corrects this by no longer changing the table line when
discard passdown was disabled.

We can still tell when discard passdown is overridden by looking for the
message "Discard unsupported by data device (sdX): Disabling discard passdown."

This automatic detection is also moved from the 'load' to the 'resume'
so that it is re-evaluated should the properties of underlying devices
change.

Signed-off-by: Mike Snitzer 
Acked-by: Joe Thornber 
Signed-off-by: Alasdair G Kergon

dm thin: correct module description

2012-05-12T00:43:19+00:00

Remove duplicate copy of string "device-mapper" (DM_NAME) from
MODULE_DESCRIPTION.

Signed-off-by: Alasdair G Kergon

dm thin: fix unprotected use of prepared_discards list

2012-05-12T00:43:16+00:00

Fix two places in commit 104655fd4dce ("dm thin: support discards") that
didn't use pool->lock to protect against concurrent changes to the
prepared_discards list.

Without this fix, thin_endio() can race with process_discard(), leading
to concurrent list_add()s that result in the processes locking up with
an error like the following:

WARNING: at lib/list_debug.c:32 __list_add+0x8f/0xa0()
...
list_add corruption. next->prev should be prev (ffff880323b96140), but was ffff8801d2c48440. (next=ffff8801d2c485c0).
...
Pid: 17205, comm: kworker/u:1 Tainted: G        W  O 3.4.0-rc3.snitm+ #1
Call Trace:
 [] warn_slowpath_common+0x7f/0xc0
 [] warn_slowpath_fmt+0x46/0x50
 [] ? bio_detain+0xc6/0x210 [dm_thin_pool]
 [] __list_add+0x8f/0xa0
 [] process_discard+0x2a2/0x2d0 [dm_thin_pool]
 [] ? remap_and_issue+0x38/0x50 [dm_thin_pool]
 [] process_deferred_bios+0x7b/0x230 [dm_thin_pool]
 [] ? process_deferred_bios+0x230/0x230 [dm_thin_pool]
 [] do_worker+0x52/0x60 [dm_thin_pool]
 [] process_one_work+0x129/0x450
 [] worker_thread+0x17c/0x3c0
 [] ? manage_workers+0x120/0x120
 [] kthread+0x9e/0xb0
 [] kernel_thread_helper+0x4/0x10
 [] ? kthread_freezable_should_stop+0x70/0x70
 [] ? gs_change+0x13/0x13
---[ end trace 7e0a523bc5e52692 ]---

Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm thin: reinstate missing mempool_free in cell_release_singleton

2012-05-12T00:43:12+00:00

Fix a significant memory leak inadvertently introduced during
simplification of cell_release_singleton() in commit
6f94a4c45a6f744383f9f695dde019998db3df55 ("dm thin: fix stacked bi_next
usage").

A cell's hlist_del() must be accompanied by a mempool_free().
Use __cell_release() to do this, like before.

Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm thin: add pool target flags to control discard

2012-03-28T17:41:29+00:00

Add dm thin target arguments to control discard support.

ignore_discard: Disables discard support

no_discard_passdown: Don't pass discards down to the underlying data
device, but just remove the mapping within the thin provisioning target.

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm thin: support discards

2012-03-28T17:41:28+00:00

Support discards in the thin target.

On discard the corresponding mapping(s) are removed from the thin
device.  If the associated block(s) are no longer shared the discard
is passed to the underlying device.

All bios other than discards now have an associated deferred_entry
that is saved to the 'all_io_entry' in endio_hook.  When non-discard
IO completes and associated mappings are quiesced any discards that
were deferred, via ds_add_work() in process_discard(), will be queued
for processing by the worker thread.

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon 

drivers/md/dm-thin.c |  173 ++++++++++++++++++++++++++++++++++++++++++++++----
 drivers/md/dm-thin.c |  172 ++++++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 158 insertions(+), 14 deletions(-)

dm thin: prepare to support discard

2012-03-28T17:41:28+00:00

This patch contains the ground work needed for dm-thin to support discard.

  - Adds endio function that replaces shared_read_endio.

  - Introduce an explicit 'quiesced' flag into the new_mapping structure.
    Before, this was implicitly indicated by m->list being empty.

  - The map_info->ptr remains constant for the duration of a bio's trip
    through the thin target.  Make it easier to reason about it.

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm thin: use dm_target_offset

2012-03-28T17:41:28+00:00

Use dm_target_offset wrapper instead of referencing the awkward ti->begin
explicitly.

Signed-off-by: Alasdair G Kergon

dm thin: support read only external snapshot origins

2012-03-28T17:41:28+00:00

Support the use of an external _read only_ device as an origin for a thin
device.

Any read to an unprovisioned area of the thin device will be passed
through to the origin.  Writes trigger allocation of new blocks as
usual.

One possible use case for this would be VM hosts that want to run
guests on thinly-provisioned volumes but have the base image on another
device (possibly shared between many VMs).

Signed-off-by: Joe Thornber 
Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm thin: relax hard limit on the maximum size of a metadata device

2012-03-28T17:41:28+00:00

The thin metadata format can only make use of a device that is <=
THIN_METADATA_MAX_SECTORS (currently 15.9375 GB).  Therefore, there is no
practical benefit to using a larger device.

However, it may be that other factors impose a certain granularity for
the space that is allocated to a device (E.g. lvm2 can impose a coarse
granularity through the use of large, >= 1 GB, physical extents).

Rather than reject a larger metadata device, during thin-pool device
construction, switch to allowing it but issue a warning if a device
larger than THIN_METADATA_MAX_SECTORS_WARNING (16 GB) is
provided.  Any space over 15.9375 GB will not be used.

Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon