linux-toradex.git/drivers/md/dm-thin.c, branch v3.4.96

dm thin: fix discard corruption

2014-06-07T23:02:05+00:00

commit f046f89a99ccfd9408b94c653374ff3065c7edb3 upstream.

Fix a bug in dm_btree_remove that could leave leaf values with incorrect
reference counts.  The effect of this was that removal of a shared block
could result in the space maps thinking the block was no longer used.
More concretely, if you have a thin device and a snapshot of it, sending
a discard to a shared region of the thin could corrupt the snapshot.

Thinp uses a 2-level nested btree to store it's mappings.  This first
level is indexed by thin device, and the second level by logical
block.

Often when we're removing an entry in this mapping tree we need to
rebalance nodes, which can involve shadowing them, possibly creating a
copy if the block is shared.  If we do create a copy then children of
that node need to have their reference counts incremented.  In this
way reference counts percolate down the tree as shared trees diverge.

The rebalance functions were incrementing the children at the
appropriate time, but they were always assuming the children were
internal nodes.  This meant the leaf values (in our case packed
block/flags entries) were not being incremented.

Signed-off-by: Joe Thornber 
Signed-off-by: Alasdair G Kergon 
[bwh: Backported to 3.2: bump target version numbers from 1.0.1 to 1.0.2]
Signed-off-by: Ben Hutchings 
[xr: Backported to 3.4: bump target version numbers to 1.1.1]
Signed-off-by: Rui Xiang 
Signed-off-by: Greg Kroah-Hartman

dm thin: fix dangling bio in process_deferred_bios error path

2014-05-13T12:11:32+00:00

commit fe76cd88e654124d1431bb662a0fc6e99ca811a5 upstream.

If unable to ensure_next_mapping() we must add the current bio, which
was removed from the @bios list via bio_list_pop, back to the
deferred_bios list before all the remaining @bios.

Signed-off-by: Mike Snitzer 
Acked-by: Joe Thornber 
Signed-off-by: Greg Kroah-Hartman

dm: fix truncated status strings

2013-12-08T15:29:43+00:00

commit fd7c092e711ebab55b2688d3859d95dfd0301f73 upstream.

Avoid returning a truncated table or status string instead of setting
the DM_BUFFER_FULL_FLAG when the last target of a table fills the
buffer.

When processing a table or status request, the function retrieve_status
calls ti->type->status. If ti->type->status returns non-zero,
retrieve_status assumes that the buffer overflowed and sets
DM_BUFFER_FULL_FLAG.

However, targets don't return non-zero values from their status method
on overflow. Most targets returns always zero.

If a buffer overflow happens in a target that is not the last in the
table, it gets noticed during the next iteration of the loop in
retrieve_status; but if a buffer overflow happens in the last target, it
goes unnoticed and erroneously truncated data is returned.

In the current code, the targets behave in the following way:
* dm-crypt returns -ENOMEM if there is not enough space to store the
  key, but it returns 0 on all other overflows.
* dm-thin returns errors from the status method if a disk error happened.
  This is incorrect because retrieve_status doesn't check the error
  code, it assumes that all non-zero values mean buffer overflow.
* all the other targets always return 0.

This patch changes the ti->type->status function to return void (because
most targets don't use the return code). Overflow is detected in
retrieve_status: if the status method fills up the remaining space
completely, it is assumed that buffer overflow happened.

Signed-off-by: Mikulas Patocka 
Signed-off-by: Alasdair G Kergon 
Signed-off-by: Greg Kroah-Hartman

dm thin: do not set discard_zeroes_data

2013-05-19T17:54:48+00:00

commit 307615a26e95406c42c95916a66ba50434567e0f upstream.

The dm thin pool target claims to support the zeroing of discarded
data areas.  This turns out to be incorrect when processing discards
that do not exactly cover a complete number of blocks, so the target
must always set discard_zeroes_data_unsupported.

The thin pool target will zero blocks when they are allocated if the
skip_block_zeroing feature is not specified.  The block layer
may send a discard that only partly covers a block.  If a thin pool
block is partially discarded then there is no guarantee that the
discarded data will get zeroed before it is accessed again.
Due to this, thin devices cannot claim discards will always zero data.

Signed-off-by: Mike Snitzer 
Signed-off-by: Joe Thornber 
Signed-off-by: Alasdair G Kergon 
Cc: Libo Chen 
Signed-off-by: Greg Kroah-Hartman

dm thin: fix memory leak in process_prepared_mapping error paths

2012-08-09T15:31:40+00:00

commit 905386f82d08f66726912f303f3e6605248c60a3 upstream.

Fix memory leak in process_prepared_mapping by always freeing
the dm_thin_new_mapping structs from the mapping_pool mempool on
the error paths.

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

dm thin: reduce endio_hook pool size

2012-08-09T15:31:40+00:00

commit 7768ed33ccdc02801c4483fc5682dc66ace14aea upstream.

Reduce the slab size used for the dm_thin_endio_hook mempool.

Allocation has been seen to fail on machines with smaller amounts
of memory due to fragmentation.

  lvm: page allocation failure. order:5, mode:0xd0
  device-mapper: table: 253:38: thin-pool: Error creating pool's endio_hook mempool

Signed-off-by: Alasdair G Kergon 
Signed-off-by: Greg Kroah-Hartman

dm thin: do not send discards to shared blocks

2012-07-29T15:04:20+00:00

commit 650d2a06b4fe1cc1d218c20e256650f68bf0ca31 upstream.

When process_discard receives a partial discard that doesn't cover a
full block, it sends this discard down to that block. Unfortunately, the
block can be shared and the discard would corrupt the other snapshots
sharing this block.

This patch detects block sharing and ends the discard with success when
sending it to the shared block.

The above change means that if the device supports discard it can't be
guaranteed that a discard request zeroes data. Therefore, we set
ti->discard_zeroes_data_unsupported.

Thin target discard support with this bug arrived in commit
104655fd4dcebd50068ef30253a001da72e3a081 (dm thin: support discards).

Signed-off-by: Mikulas Patocka 
Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon 
Signed-off-by: Greg Kroah-Hartman

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