linux-stable.git/drivers/md/dm-thin.c, branch linux-3.5.y

dm thin: fix memory leak in process_prepared_mapping error paths

2012-08-09T15:23:11+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

2012-08-09T15:23:11+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

2012-07-20T13:25:05+00:00

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 
Cc: stable@kernel.org
Signed-off-by: Mike Snitzer 
Signed-off-by: Alasdair G Kergon

dm thin: commit metadata before creating metadata snapshot

2012-07-03T11:55:31+00:00

Userland sometimes sees a corrupt metadata block if metadata is changing
rapidly when a metadata snapshot is reserved for userland,  To make the
problem go away, commit before we take the metadata snapshot (which is a
sensible thing to do anyway).

The checksums mean userland spots this corruption immediately so there's
no risk of acting on incorrect data.  No corruption exists from the
kernel's point of view, and thin_check passes after pool shutdown.

I believe this is to do with shared blocks at the first level of the
{device, mapping} btree.  Prior to the metadata-snap support no sharing
at this level was possible, so this patch is only required after commit
cc8394d86f045b86ff303d3c9e4ce47d97148951 ("dm thin: provide userspace
access to pool metadata").

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

dm thin: provide userspace access to pool metadata

2012-06-02T23:30:01+00:00

This patch implements two new messages that can be sent to the thin
pool target allowing it to take a snapshot of the _metadata_.  This,
read-only snapshot can be accessed by userland, concurrently with the
live target.

Only one metadata snapshot can be held at a time.  The pool's status
line will give the block location for the current msnap.

Since version 0.1.5 of the userland thin provisioning tools, the
thin_dump program displays the msnap as follows:

    thin_dump -m  

Available here: https://github.com/jthornber/thin-provisioning-tools

Now that userland can access the metadata we can do various things
that have traditionally been kernel side tasks:

     i) Incremental backups.

     By using metadata snapshots we can work out what blocks have
     changed over time.  Combined with data snapshots we can ensure
     the data doesn't change while we back it up.

     A short proof of concept script can be found here:

     https://github.com/jthornber/thinp-test-suite/blob/master/incremental_backup_example.rb

     ii) Migration of thin devices from one pool to another.

     iii) Merging snapshots back into an external origin.

     iv) Asyncronous replication.

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

dm thin: use slab mempools

2012-06-02T23:30:00+00:00

Use dedicated caches prefixed with a "dm_" name rather than relying on
kmalloc mempools backed by generic slab caches so the memory usage of
thin provisioning (and any leaks) can be accounted for independently.

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

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