Commit Graph

138 Commits

Author SHA1 Message Date
Mike Snitzer
615d1eb9ca dm snapshot: create function for chunk_is_tracked wait
Move the __chunk_is_tracked() loop into a separate function as we will
also need to call it from the write path in the rare case of conflicting
writes to the same chunk.

Originally introduced in commit a8d41b59f3
("dm snapshot: fix race during exception creation").

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:29 +00:00
Mikulas Patocka
9eaae8ffbc dm snapshot: make bio optional in __origin_write
To support the merging of snapshots back into their origin we need
to trigger exceptions in other snapshots not being merged without
any incoming bio on the origin device.  The bio parameter to
__origin_write() becomes optional and the sector needs supplying
separately.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:28 +00:00
Mike Snitzer
c1f0c183f6 dm snapshot: allow live exception store handover between tables
Permit in-use snapshot exception data to be 'handed over' from one
snapshot instance to another.  This is a pre-requisite for patches
that allow the changes made in a snapshot device to be merged back into
its origin device and also allows device resizing.

The basic call sequence is:

  dmsetup load new_snapshot (referencing the existing in-use cow device)
     - the ctr code detects that the cow is already in use and allows the
       two snapshot target instances to be linked together
  dmsetup suspend original_snapshot
  dmsetup resume new_snapshot
     - the new_snapshot becomes live, and if anything now tries to access
       the original one it will receive -EIO
  dmsetup remove original_snapshot

(There can only be two snapshot targets referencing the same cow device
simultaneously.)

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:24 +00:00
Mike Snitzer
c26655ca3c dm snapshot: track suspended state in target
Keep track of whether or not the device is suspended within the snapshot
target module, the same as we do in dm-raid1.

We will use this later to enforce the correct sequence of ioctls to
transfer the in-core exceptions from a snapshot target instance in
one table to a replacement one capable of merging them back
into the origin.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:12 +00:00
Mike Snitzer
fc56f6fbcc dm snapshot: move cow ref from exception store to snap core
Store the reference to the snapshot cow device in the core snapshot
code instead of each exception store.  It can be accessed through the
new function dm_snap_cow().  Exception stores should each now maintain a
reference to their parent snapshot struct.

This is cleaner and makes part of the forthcoming snapshot merge code simpler.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Reviewed-by: Jonathan Brassow <jbrassow@redhat.com>
Cc: Mikulas Patocka <mpatocka@redhat.com>
2009-12-10 23:52:12 +00:00
Mike Snitzer
985903bb3a dm snapshot: add allocated metadata to snapshot status
Add number of sectors used by metadata to the end of the snapshot's status
line.

Renamed dm_exception_store_type's 'fraction_full' to 'usage'.  Renamed
arguments to be clearer about what is being returned.  Also added
'metadata_sectors'.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:11 +00:00
Jon Brassow
3510cb94ff dm snapshot: rename exception functions
Rename exception functions.  Preparing to pull them out of
dm-snap.c for broader use.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:11 +00:00
Jon Brassow
191437a53c dm snapshot: rename exception_table to dm_exception_table
Rename exception_table for broader use outside dm-snap.c

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:10 +00:00
Jon Brassow
1d4989c858 dm snapshot: rename dm_snap_exception to dm_exception
The exception structure is not necessarily just a snapshot
element (especially after we pull it out of dm-snap.c).

Renaming appropriately.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:10 +00:00
Jon Brassow
d32a6ea65f dm snapshot: consolidate insert exception functions
Consolidate the insert_*exception functions.  'insert_completed_exception'
already contains all the logic to handle 'insert_exception' (via
check for a hash_shift of 0), so remove redundant function.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:09 +00:00
Mikulas Patocka
7e201b3513 dm snapshot: abstract minimum_chunk_size fn
The origin needs to find minimum chunksize of all snapshots.  This logic is
moved to a separate function because it will be used at another place in
the snapshot merge patches.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:52:08 +00:00
Mikulas Patocka
8e87b9b81b dm snapshot: cope with chunk size larger than origin
Under some special conditions the snapshot hash_size is calculated as zero.
This patch instead sets a minimum value of 64, the same as for the
pending exception table.

rounddown_pow_of_two(0) is an undefined operation (it expands to shift
by -1).  init_exception_table with an argument of 0 would fail with -ENOMEM.

The way to trigger the problem is to create a snapshot with a chunk size
that is larger than the origin device.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:51:54 +00:00
Mikulas Patocka
94e76572b5 dm snapshot: only take lock for statustype info not table
Take snapshot lock only for STATUSTYPE_INFO, not STATUSTYPE_TABLE.

Commit 4c6fff445d
(dm-snapshot-lock-snapshot-while-supplying-status.patch)
introduced this use of the lock, but userspace applications using
libdevmapper have been found to request STATUSTYPE_TABLE while the device
is suspended and the lock is already held, leading to deadlock.  Since
the lock is not necessary in this case, don't try to take it.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-12-10 23:51:53 +00:00
Mikulas Patocka
df96eee679 dm snapshot: use unsigned integer chunk size
Use unsigned integer chunk size.

Maximum chunk size is 512kB, there won't ever be need to use 4GB chunk size,
so the number can be 32-bit. This fixes compiler failure on 32-bit systems
with large block devices.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Reviewed-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16 23:18:17 +01:00
Mikulas Patocka
4c6fff445d dm snapshot: lock snapshot while supplying status
This patch locks the snapshot when returning status.  It fixes a race
when it could return an invalid number of free chunks if someone
was simultaneously modifying it.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16 23:18:16 +01:00
Mikulas Patocka
3f2412dc85 dm snapshot: require non zero chunk size by end of ctr
If we are creating snapshot with memory-stored exception store, fail if
the user didn't specify chunk size. Zero chunk size would probably crash
a lot of places in the rest of snapshot code.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Jonathan Brassow <jbrassow@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16 23:18:16 +01:00
Jonathan Brassow
034a186d29 dm snapshot: free exception store on init failure
While initializing the snapshot module, if we fail to register
the snapshot target then we must back-out the exception store
module initialization.

Cc: stable@kernel.org
Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Reviewed-by: Mikulas Patocka <mpatocka@redhat.com>
Reviewed-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16 23:18:14 +01:00
Mikulas Patocka
6d45d93ead dm snapshot: sort by chunk size to fix race
Avoid a race causing corruption when snapshots of the same origin have
different chunk sizes by sorting the internal list of snapshots by chunk
size, largest first.
  https://bugzilla.redhat.com/show_bug.cgi?id=182659

For example, let's have two snapshots with different chunk sizes. The
first snapshot (1) has small chunk size and the second snapshot (2) has
large chunk size.  Let's have chunks A, B, C in these snapshots:
snapshot1: ====A====   ====B====
snapshot2: ==========C==========

(Chunk size is a power of 2. Chunks are aligned.)

A write to the origin at a position within A and C comes along. It
triggers reallocation of A, then reallocation of C and links them
together using A as the 'primary' exception.

Then another write to the origin comes along at a position within B and
C.  It creates pending exception for B.  C already has a reallocation in
progress and it already has a primary exception (A), so nothing is done
to it: B and C are not linked.

If the reallocation of B finishes before the reallocation of C, because
there is no link with the pending exception for C it does not know to
wait for it and, the second write is dispatched to the origin and causes
data corruption in the chunk C in snapshot2.

To avoid this situation, we maintain snapshots sorted in descending
order of chunk size.  This leads to a guaranteed ordering on the links
between the pending exceptions and avoids the problem explained above -
both A and B now get linked to C.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-10-16 23:18:14 +01:00
Mike Snitzer
8811f46c1f dm snapshot: implement iterate devices
Implement the .iterate_devices for the origin and snapshot targets.
dm-snapshot's lack of .iterate_devices resulted in the inability to
properly establish queue_limits for both targets.

With 4K sector drives: an unfortunate side-effect of not establishing
proper limits in either targets' DM device was that IO to the devices
would fail even though both had been created without error.

Commit af4874e03e ("dm target:s introduce
iterate devices fn") in 2.6.31-rc1 should have implemented .iterate_devices
for dm-snap.c's origin and snapshot targets.

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-09-04 20:40:19 +01:00
Mikulas Patocka
494b3ee7d4 dm snapshot: support barriers
Flush support for dm-snapshot target.

This patch just forwards the flush request to either the origin or the snapshot
device.  (It doesn't flush exception store metadata.)

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-06-22 10:12:25 +01:00
Christoph Hellwig
8f3d8ba20e block: move bio list helpers into bio.h
It's used by DM and MD and generally useful, so move the bio list
helpers into bio.h.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2009-04-15 08:28:09 +02:00
Jonathan Brassow
1e302a929e dm snapshot: move status to exception store
Let the exception store types print out their status through
the new API, rather than having the snapshot code do it.

Adjust the buffer position to allow for the preceding DMEMIT in the
arguments to type->status().

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:35 +01:00
Jonathan Brassow
fee1998e9c dm snapshot: move ctr parsing to exception store
First step of having the exception stores parse their own arguments -
generalizing the interface.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:34 +01:00
Jonathan Brassow
2e4a31df2b dm snapshot: use DMEMIT macro for status
Use DMEMIT in place of snprintf.  This makes it easier later when
other modules are helping to populate our status output.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:34 +01:00
Jonathan Brassow
ccc45ea8ae dm snapshot: remove dm_snap header
Move some of the last bits from dm-snap.h into dm-snap.c where they
belong and remove dm-snap.h.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:34 +01:00
Jonathan Brassow
71fab00a6b dm snapshot: remove dm_snap header use
Move useful functions out of dm-snap.h and stop using dm-snap.h.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:33 +01:00
Jonathan Brassow
49beb2b87a dm exception store: move cow pointer
Move COW device from snapshot to exception store.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:33 +01:00
Jonathan Brassow
d021684951 dm exception store: move chunk_fields
Move chunk fields from snapshot to exception store.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:32 +01:00
Jonathan Brassow
0cea9c7827 dm exception store: move dm_target pointer
Move target pointer from snapshot to exception store.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:32 +01:00
Jonathan Brassow
493df71c64 dm exception store: introduce registry
Move exception stores into a registry.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:31 +01:00
Jonathan Brassow
b2a1146529 dm exception store: separate type from instance
Introduce struct dm_exception_store_type.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:30 +01:00
Mikulas Patocka
35bf659b00 dm snapshot: avoid having two exceptions for the same chunk
We need to check if the exception was completed after dropping the lock.

After regaining the lock, __find_pending_exception checks if the exception
was already placed into &s->pending hash.

But we don't check if the exception was already completed and placed into
&s->complete hash. If the process waiting in alloc_pending_exception was
delayed at this point because of a scheduling latency and the exception
was meanwhile completed, we'd miss that and allocate another pending
exception for already completed chunk.

It would lead to a situation where two records for the same chunk exist
and potential data corruption because multiple snapshot I/Os to the
affected chunk could be redirected to different locations in the
snapshot.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:26 +01:00
Mikulas Patocka
c66213921c dm snapshot: avoid dropping lock in __find_pending_exception
It is uncommon and bug-prone to drop a lock in a function that is called with
the lock held, so this is moved to the caller.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:25 +01:00
Mikulas Patocka
2913808eb5 dm snapshot: refactor __find_pending_exception
Move looking-up of a pending exception from __find_pending_exception to another
function.

Cc: stable@kernel.org
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-04-02 19:55:25 +01:00
Jonathan Brassow
a159c1ac5f dm snapshot: extend exception store functions
Supply dm_add_exception as a callback to the read_metadata function.
Add a status function ready for a later patch and name the functions
consistently.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-01-06 03:05:19 +00:00
Alasdair G Kergon
4db6bfe02b dm snapshot: split out exception store implementations
Move the existing snapshot exception store implementations out into
separate files.  Later patches will place these behind a new
interface in preparation for alternative implementations.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-01-06 03:05:17 +00:00
Jonathan Brassow
aea53d92f7 dm snapshot: separate out exception store interface
Pull structures that bridge the gap between snapshot and
exception store out of dm-snap.h and put them in a new
.h file - dm-exception-store.h.  This file will define the
API for new exception stores.

Ultimately, dm-snap.h is unnecessary, since only dm-snap.c
should be using it.

Signed-off-by: Jonathan Brassow <jbrassow@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-01-06 03:05:15 +00:00
Mikulas Patocka
10d3bd09a3 dm: consolidate target deregistration error handling
Change dm_unregister_target to return void and use BUG() for error
reporting.

dm_unregister_target can only fail because of programming bug in the
target driver. It can't fail because of user's behavior or disk errors.

This patch changes unregister_target to return void and use BUG if
someone tries to unregister non-registered target or unregister target
that is in use.

This patch removes code duplication (testing of error codes in all dm
targets) and reports bugs in just one place, in dm_unregister_target. In
some target drivers, these return codes were ignored, which could lead
to a situation where bugs could be missed.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-01-06 03:04:58 +00:00
Mikulas Patocka
90fa1527bd dm snapshot: change yield to msleep
Change yield() to msleep(1). If the thread had realtime priority,
yield() doesn't really yield, so the yielding process would loop
indefinitely and cause machine lockup.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2009-01-06 03:04:54 +00:00
Mikulas Patocka
879129d208 dm snapshot: wait for chunks in destructor
If there are several snapshots sharing an origin and one is removed
while the origin is being written to, the snapshot's mempool may get
deleted while elements are still referenced.

Prior to dm-snapshot-use-per-device-mempools.patch the pending
exceptions may still have been referenced after the snapshot was
destroyed, but this was not a problem because the shared mempool
was still there.

This patch fixes the problem by tracking the number of mempool elements
in use.

The scenario:
- You have an origin and two snapshots 1 and 2.
- Someone writes to the origin.
- It creates two exceptions in the snapshots, snapshot 1 will be primary
exception, snapshot 2's pending_exception->primary_pe will point to the
exception in snapshot 1.
- The exceptions are being relocated, relocation of exception 1 finishes
(but it's pending_exception is still allocated, because it is referenced
by an exception from snapshot 2)
- The user lvremoves snapshot 1 --- it calls just suspend (does nothing)
and destructor. md->pending is zero (there is no I/O submitted to the
snapshot by md layer), so it won't help us.
- The destructor waits for kcopyd jobs to finish on snapshot 1 --- but
there are none.
- The destructor on snapshot 1 cleans up everything.
- The relocation of exception on snapshot 2 finishes, it drops reference
on primary_pe. This frees its primary_pe pointer. Primary_pe points to
pending exception created for snapshot 1. So it frees memory into
non-existing mempool.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-30 13:33:16 +00:00
Mikulas Patocka
60c856c8e2 dm snapshot: fix register_snapshot deadlock
register_snapshot() performs a GFP_KERNEL allocation while holding
_origins_lock for write, but that could write out dirty pages onto a
device that attempts to acquire _origins_lock for read, resulting in
deadlock.

So move the allocation up before taking the lock.

This path is not performance-critical, so it doesn't matter that we
allocate memory and free it if we find that we won't need it.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-30 13:33:12 +00:00
Mikulas Patocka
f68d4f3d39 dm snapshot: drop unused last_percent
The last_percent field is unused - remove it.
(It dates from when events were triggered as each X% filled up.)

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-10-21 17:44:53 +01:00
Mikulas Patocka
7c5f78b9d7 dm snapshot: fix primary_pe race
Fix a race condition with primary_pe ref_count handling.

put_pending_exception runs under dm_snapshot->lock, it does atomic_dec_and_test
on primary_pe->ref_count, and later does atomic_read primary_pe->ref_count.

__origin_write does atomic_dec_and_test on primary_pe->ref_count without holding
dm_snapshot->lock.

This opens the following race condition:
Assume two CPUs, CPU1 is executing put_pending_exception (and holding
dm_snapshot->lock). CPU2 is executing __origin_write in parallel.
primary_pe->ref_count == 2.

CPU1:
if (primary_pe && atomic_dec_and_test(&primary_pe->ref_count))
	origin_bios = bio_list_get(&primary_pe->origin_bios);
... decrements primary_pe->ref_count to 1. Doesn't load origin_bios

CPU2:
if (first && atomic_dec_and_test(&primary_pe->ref_count)) {
	flush_bios(bio_list_get(&primary_pe->origin_bios));
	free_pending_exception(primary_pe);
	/* If we got here, pe_queue is necessarily empty. */
	return r;
}
... decrements primary_pe->ref_count to 0, submits pending bios, frees
primary_pe.

CPU1:
if (!primary_pe || primary_pe != pe)
	free_pending_exception(pe);
... this has no effect.
if (primary_pe && !atomic_read(&primary_pe->ref_count))
	free_pending_exception(primary_pe);
... sees ref_count == 0 (written by CPU 2), does double free !!

This bug can happen only if someone is simultaneously writing to both the
origin and the snapshot.

If someone is writing only to the origin, __origin_write will submit kcopyd
request after it decrements primary_pe->ref_count (so it can't happen that the
finished copy races with primary_pe->ref_count decrementation).

If someone is writing only to the snapshot, __origin_write isn't invoked at all
and the race can't happen.

The race happens when someone writes to the snapshot --- this creates
pending_exception with primary_pe == NULL and starts copying. Then, someone
writes to the same chunk in the snapshot, and __origin_write races with
termination of already submitted request in pending_complete (that calls
put_pending_exception).

This race may be reason for bugs:
  http://bugzilla.kernel.org/show_bug.cgi?id=11636
  https://bugzilla.redhat.com/show_bug.cgi?id=465825

The patch fixes the code to make sure that:
1. If atomic_dec_and_test(&primary_pe->ref_count) returns false, the process
must no longer dereference primary_pe (because someone else may free it under
us).
2. If atomic_dec_and_test(&primary_pe->ref_count) returns true, the process
is responsible for freeing primary_pe.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: stable@kernel.org
2008-10-21 17:44:51 +01:00
Mikulas Patocka
92e868122e dm snapshot: use per device mempools
Change snapshot per-module mempool to per-device mempool.

Per-module mempools could cause a deadlock if multiple
snapshot devices are stacked above each other.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-07-21 12:00:35 +01:00
Mikulas Patocka
a8d41b59f3 dm snapshot: fix race during exception creation
Fix a race condition that returns incorrect data when a write causes an
exception to be allocated whilst a read is still in flight.

The race condition happens as follows:
* A read to non-reallocated sector in the snapshot is submitted so that the
  read is routed to the original device.
* A write to the original device is submitted. The write causes an exception
  that reallocates the block.  The write proceeds.
* The original read is dequeued and reads the wrong data.

This race can be triggered with CFQ scheduler and one thread writing and
multiple threads reading simultaneously.

(This patch relies upon the earlier dm-kcopyd-per-device.patch to avoid a
deadlock.)

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-07-21 12:00:34 +01:00
Mikulas Patocka
cd45daffd1 dm snapshot: track snapshot reads
Whenever a snapshot read gets mapped through to the origin, track it in
a per-snapshot hash table indexed by chunk number, using memory allocated
from a new per-snapshot mempool.

We need to track these reads to avoid race conditions which will be fixed
by patches that follow.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-07-21 12:00:32 +01:00
Alasdair G Kergon
a765e20eeb dm: move include files
Publish the dm-io, dm-log and dm-kcopyd headers in include/linux.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-04-25 13:26:55 +01:00
Heinz Mauelshagen
eb69aca5d3 dm kcopyd: clean interface
Clean up the kcopyd interface to prepare for publishing it in include/linux.

Signed-off-by: Heinz Mauelshagen <hjm@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-04-25 13:26:44 +01:00
Heinz Mauelshagen
22a1ceb1e6 dm io: clean interface
Clean up the dm-io interface to prepare for publishing it in include/linux.

Signed-off-by: Heinz Mauelshagen <hjm@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-04-25 13:26:43 +01:00
Mikulas Patocka
72727bad54 dm snapshot: store pointer to target instance
Save pointer to dm_target in dm_snapshot structure.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-04-25 13:26:40 +01:00
Milan Broz
8ee2767a59 dm snapshot: reduce default memory allocation
Limit the amount of memory allocated per snapshot on systems
with a large page size.  (The larger default chunk size on
these systems compensates for the smaller number of pages reserved.)

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-04-25 13:26:35 +01:00
Alasdair G Kergon
4cdc1d1fa5 dm io: write error bits form long not int
write_err is an unsigned long used with set_bit() so should not be passed
around as unsigned int.

http://bugzilla.kernel.org/show_bug.cgi?id=10271

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-03-28 14:45:23 -07:00
Milan Broz
d74f81f8ad dm snapshot: combine consecutive exceptions in memory
Provided sector_t is 64 bits, reduce the in-memory footprint of the
snapshot exception table by the simple method of using unused bits of
the chunk number to combine consecutive entries.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-02-08 02:11:27 +00:00
Robert P. J. Day
8defd83084 dm snapshot: use rounddown_pow_of_two
Since the source file already includes the log2.h header file, it
seems pointless to re-invent the necessary routine.

Signed-off-by: Robert P. J. Day <rpjday@crashcourse.ca>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2008-02-08 02:10:06 +00:00
vignesh babu
6f3c3f0afa dm: use is_power_of_2
Replacing n & (n - 1) for power of 2 check by is_power_of_2(n)

Signed-off-by: vignesh babu <vignesh.babu@wipro.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
2007-10-20 02:01:06 +01:00
NeilBrown
6712ecf8f6 Drop 'size' argument from bio_endio and bi_end_io
As bi_end_io is only called once when the reqeust is complete,
the 'size' argument is now redundant.  Remove it.

Now there is no need for bio_endio to subtract the size completed
from bi_size.  So don't do that either.

While we are at it, change bi_end_io to return void.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2007-10-10 09:25:57 +02:00
Stefan Bader
07a83c47cf dm: disable barriers
This patch causes device-mapper to reject any barrier requests.  This is done
since most of the targets won't handle this correctly anyway.  So until the
situation improves it is better to reject these requests at the first place.
Since barrier requests won't get to the targets, the checks there can be
removed.

Cc: stable@kernel.org
Signed-off-by: Stefan Bader <shbader@de.ibm.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-12 15:01:08 -07:00
Milan Broz
0764147b11 dm snapshot: permit invalid activation
Allow invalid snapshots to be activated instead of failing.

This allows userspace to reinstate any given snapshot state - for
example after an unscheduled reboot - and clean up the invalid snapshot
at its leisure.

Cc: stable@kernel.org
Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-12 15:01:08 -07:00
Alasdair G Kergon
028867ac28 dm: use kmem_cache macro
Use new KMEM_CACHE() macro and make the newly-exposed structure names more
meaningful.  Also remove some superfluous casts and inlines (let a modern
compiler be the judge).

Acked-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2007-07-12 15:01:08 -07:00
Adrian Bunk
c642f9e03b [PATCH] make drivers/md/dm-snap.c:ksnapd static
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Acked-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:29:09 -08:00
Milan Broz
31c93a0c29 [PATCH] dm: snapshot: abstract memory release
Move the code that releases memory used by a snapshot into a separate function.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:29:09 -08:00
Kiyoshi Ueda
d2a7ad29a8 [PATCH] dm: map and endio symbolic return codes
Update existing targets to use the new symbols for return values from target
map and end_io functions.

There is no effect on behaviour.

Test results:
Done build test without errors.

Signed-off-by: Kiyoshi Ueda <k-ueda@ct.jp.nec.com>
Signed-off-by: Jun'ichi Nomura <j-nomura@ce.jp.nec.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: dm-devel@redhat.com
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-08 08:29:09 -08:00
Christoph Lameter
e18b890bb0 [PATCH] slab: remove kmem_cache_t
Replace all uses of kmem_cache_t with struct kmem_cache.

The patch was generated using the following script:

	#!/bin/sh
	#
	# Replace one string by another in all the kernel sources.
	#

	set -e

	for file in `find * -name "*.c" -o -name "*.h"|xargs grep -l $1`; do
		quilt add $file
		sed -e "1,\$s/$1/$2/g" $file >/tmp/$$
		mv /tmp/$$ $file
		quilt refresh
	done

The script was run like this

	sh replace kmem_cache_t "struct kmem_cache"

Signed-off-by: Christoph Lameter <clameter@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-12-07 08:39:25 -08:00
David Howells
c4028958b6 WorkStruct: make allyesconfig
Fix up for make allyesconfig.

Signed-Off-By: David Howells <dhowells@redhat.com>
2006-11-22 14:57:56 +00:00
Alasdair G Kergon
695368ac33 [PATCH] dm snapshot: fix freeing pending exception
If a snapshot became invalid while there are outstanding pending_exceptions,
when pending_complete() processes each one it forgets to remove the
corresponding exception from its exception table before freeing it.

Fix this by moving the 'out:' label up one statement so that
remove_exception() is always called.  Then __invalidate_exception() no longer
needs to call it and its 'pe' argument become superfluous.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:15 -07:00
Alasdair G Kergon
4b832e8de2 [PATCH] dm snapshot: tidy pe ref counting
Rename sibling_count to ref_count and introduce get and put functions.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:14 -07:00
Alasdair G Kergon
ca3a931fd3 [PATCH] dm snapshot: add workqueue
Add a workqueue so that I/O can be queued up to be flushed from a separate
thread (e.g.  if local interrupts are disabled).

A new per-snapshot spinlock pe_lock is introduced to protect queued_bios.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:14 -07:00
Alasdair G Kergon
9d493fa8c9 [PATCH] dm snapshot: tidy pending_complete
This patch rearranges the pending_complete() code so that the functional
changes in subsequent patches are clearer.

By consolidating the error and the non-error paths, we can move
error_snapshot_bios() and __flush_bios() in line.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:14 -07:00
Alasdair G Kergon
ba40a2aa6e [PATCH] dm snapshot: tidy snapshot_map
This patch rearranges the snapshot_map code so that the functional changes in
subsequent patches are clearer.

The only functional change is to replace the existing read lock with a write
lock which the next patch needs.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:14 -07:00
Mark McLoughlin
f9cea4f707 [PATCH] dm snapshot: fix metadata error handling
Fix the error handling when store.read_metadata is called: the error should be
returned immediately.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:14 -07:00
Mark McLoughlin
4c7e3bf44d [PATCH] dm snapshot: allow zero chunk_size
The chunk size of snapshots cannot be changed so it is redundant to require it
as a parameter when activating an existing snapshot.  Allow a value of zero in
this case and ignore it.  For a new snapshot, use a default value if zero is
specified.

Signed-off-by: Mark McLoughlin <markmc@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:14 -07:00
Milan Broz
92c060a692 [PATCH] dm snapshot: fix invalidation ENOMEM
Fix ENOMEM error sign.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-10-03 08:04:14 -07:00
Jörn Engel
6ab3d5624e Remove obsolete #include <linux/config.h>
Signed-off-by: Jörn Engel <joern@wohnheim.fh-wedel.de>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
2006-06-30 19:25:36 +02:00
Alasdair G Kergon
72d9486169 [PATCH] dm: improve error message consistency
Tidy device-mapper error messages to include context information
automatically.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 09:58:36 -07:00
Alasdair G Kergon
c51c275249 [PATCH] dm snapshot: unify chunk_size
Persistent snapshots currently store a private copy of the chunk size.
Userspace also supplies the chunk size when loading a snapshot.  Ensure
consistency by only storing the chunk_size in one place instead of two.

Currently the two sizes will differ if the chunk size supplied by userspace
does not match the chunk size an existing snapshot actually uses.  Amongst
other problems, this causes an incorrect 'percentage full' to be reported.

The patch ensures consistency by only storing the chunk_size in one place,
removing it from struct pstore.  Some initialisation is delayed until the
correct chunk_size is known.  If read_header() discovers that the wrong chunk
size was supplied, the 'area' buffer (which the header already got read into)
is reinitialised to the correct size.

[akpm: too late for 2.6.17 - suitable for 2.6.17.x after it has settled]

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: <stable@kernel.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-06-26 09:58:34 -07:00
Alasdair G Kergon
138728dc96 [PATCH] dm snapshot: fix kcopyd destructor
Before removing a snapshot, wait for the completion of any kcopyd jobs using
it.

Do this by maintaining a count (nr_jobs) of how many outstanding jobs each
kcopyd_client has.

The snapshot destructor first unregisters the snapshot so that no new kcopyd
jobs (created by writes to the origin) will reference that particular
snapshot.  kcopyd_client_destroy() is now run next to wait for the completion
of any outstanding jobs before the snapshot exception structures (that those
jobs reference) are freed.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:59 -08:00
Andrew Morton
4ee218cd67 [PATCH] dm: remove SECTOR_FORMAT
We don't know what type sector_t has.  Sometimes it's unsigned long, sometimes
it's unsigned long long.  For example on ppc64 it's unsigned long with
CONFIG_LBD=n and on x86_64 it's unsigned long long with CONFIG_LBD=n.

The way to handle all of this is to always use unsigned long long and to
always typecast the sector_t when printing it.

Acked-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:58 -08:00
Alasdair G Kergon
76df1c651b [PATCH] device-mapper snapshot: fix invalidation
When a snapshot becomes invalid, s->valid is set to 0.  In this state, a
snapshot can no longer be accessed.

When s->lock is acquired, before doing anything else, s->valid must be checked
to ensure the snapshot remains valid.

This patch eliminates some races (that may cause panics) by adding some
missing checks.  At the same time, some unnecessary levels of indentation are
removed and snapshot invalidation is moved into a single function that always
generates a device-mapper event.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:58 -08:00
Alasdair G Kergon
b4b610f684 [PATCH] device-mapper snapshot: replace sibling list
The siblings "list" is used unsafely at the moment.

Firstly, only the element on the list being changed gets locked (via the
snapshot lock), not the next and previous elements which have pointers that
are also being changed.

Secondly, if you have two or more snapshots and write to the same chunk a
second time before every snapshot has finished making its private copy of the
data, if you're unlucky, _origin_write() could attempt its list_merge() and
dereference a 'last' pointer to a pending_exception structure that has just
been freed.

Analysis reveals that the list is actually only there for reference counting.
If 5 pending_exceptions are needed in origin_write, then the 5 are joined
together into a 5-element list - without a separate list head because there's
nowhere suitable to store it.  As the pending_exceptions complete, they are
removed from the list one-by-one and any contents of origin_bios get moved
across to one of the remaining pending_exceptions on the list.  Whichever one
is last is detected because list_empty() is then true and the origin_bios get
submitted.

The fix proposed here uses an alternative reference counting mechanism by
choosing one of the pending_exceptions as primary and maintaining an atomic
counter there.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:58 -08:00
Alasdair G Kergon
eccf081799 [PATCH] device-mapper snapshot: fix origin_write pending_exception submission
Say you have several snapshots of the same origin and then you issue a write
to some place in the origin for the first time.

Before the device-mapper snapshot target lets the write go through to the
underlying device, it needs to make a copy of the data that is about to be
overwritten.  Each snapshot is independent, so it makes one copy for each
snapshot.

__origin_write() loops through each snapshot and checks to see whether a copy
is needed for that snapshot.  (A copy is only needed the first time that data
changes.)

If a copy is needed, the code allocates a 'pending_exception' structure
holding the details.  It links these together for all the snapshots, then
works its way through this list and submits the copying requests to the kcopyd
thread by calling start_copy().  When each request is completed, the original
pending_exception structure gets freed in pending_complete().

If you're very unlucky, this structure can get freed *before* the submission
process has finished walking the list.

This patch:

  1) Creates a new temporary list pe_queue to hold the pending exception
     structures;

  2) Does all the bookkeeping up-front, then walks through the new list
     safely and calls start_copy() for each pending_exception that needed it;

  3) Avoids attempting to add pe->siblings to the list if it's already
     connected.

[NB This does not fix all the races in this code.  More patches will follow.]

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-27 08:44:58 -08:00
Matthew Dobson
93d2341c75 [PATCH] mempool: use mempool_create_slab_pool()
Modify well over a dozen mempool users to call mempool_create_slab_pool()
rather than calling mempool_create() with extra arguments, saving about 30
lines of code and increasing readability.

Signed-off-by: Matthew Dobson <colpatch@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-03-26 08:57:00 -08:00
Alasdair G Kergon
4aac0a63fe [PATCH] device-mapper snapshot: barriers not supported
The snapshot and origin targets are incapable of handling barriers and need to
indicate this.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-01 08:53:11 -08:00
Alasdair G Kergon
aa14edeb99 [PATCH] device-mapper snapshot: load metadata on creation
Move snapshot metadata loading to happen when the table is created instead of
when the device is resumed.  Writes to the origin device don't trigger
exceptions until each snapshot table becomes active when resume() is called on
each snapshot.

If you're using lvm2, for this patch to work properly you should update to
lvm2 version 2.02.01 or later and device-mapper version 1.02.02 or later.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-02-01 08:53:10 -08:00
Arjan van de Ven
858119e159 [PATCH] Unlinline a bunch of other functions
Remove the "inline" keyword from a bunch of big functions in the kernel with
the goal of shrinking it by 30kb to 40kb

Signed-off-by: Arjan van de Ven <arjan@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Acked-by: Jeff Garzik <jgarzik@pobox.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-14 18:27:06 -08:00
Alasdair G Kergon
2d38fe2044 [PATCH] device-mapper snapshot: metadata reading separation
More snapshot metadata reading into separate function, to prepare for changing
the place it gets called from.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2006-01-06 08:34:00 -08:00
Alasdair G Kergon
d5e404c10a [PATCH] device-mapper snapshots: Handle origin extension
Handle writes to a snapshot-origin device that has been extended since the
snapshot was taken.

Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-07-12 16:19:11 -07:00
Alasdair G Kergon
f6a80ea8ed [PATCH] device-mapper multipath: Barriers not supported
dm multipath will report barriers as not supported with this patch.

Signed-off-by: Lars Marowsky-Bree <lmb@suse.de>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
2005-07-12 16:19:10 -07:00
Linus Torvalds
1da177e4c3 Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!
2005-04-16 15:20:36 -07:00