Commit Graph

190467 Commits

Author SHA1 Message Date
Philipp Reisner
fc8ce1941d drbd: Fix: Do not detach, if a bio with a barrier fails
Introduced a few days ago:
  commit 45bb912bd5
  Author: Lars Ellenberg <lars.ellenberg@linbit.com>
  Date:   Fri May 14 17:10:48 2010 +0200

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 21:12:00 +02:00
Philipp Reisner
4604d63668 drbd: Ensure to not trigger late-new-UUID creation multiple times
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 21:12:00 +02:00
Philipp Reisner
31a31dccdd drbd: Do not Oops when C_STANDALONE when uuid gets generated
Got introduces with

commit 0c3f34516e
Author: Philipp Reisner <philipp.reisner@linbit.com>
Date:   Mon May 17 16:10:43 2010 +0200

    drbd: Create new current UUID as late as possible

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 21:12:00 +02:00
Jens Axboe
df96e96f76 writeback: fix mixed up arguments to bdi_start_writeback()
The laptop mode timer had the nr_pages and sb_locked arguments
mixed up.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:54 +02:00
Jens Axboe
c2c4986edd writeback: fix problem with !CONFIG_BLOCK compilation
When CONFIG_BLOCK isn't enabled:

mm/page-writeback.c: In function 'laptop_mode_timer_fn':
mm/page-writeback.c:708: error: dereferencing pointer to incomplete type
mm/page-writeback.c:709: error: dereferencing pointer to incomplete type

Fix this by essentially eliminating the laptop sync handlers when
CONFIG_BLOCK isn't set, as most are only used from the block layer code.
The exception is laptop_sync_completion() which is used from sys_sync(),
make that an empty declaration in that case.

Reported-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:03 +02:00
Tejun Heo
b403a98e26 block: improve automatic native capacity unlocking
Currently, native capacity unlocking is initiated only when a
recognized partition extends beyond the end of the disk.  However,
there are several other unhandled cases where truncated capacity can
lead to misdetection of partitions.

* Partition table is fully beyond EOD.

* Partition table is partially beyond EOD (daisy chained ones).

* Recognized partition starts beyond EOD.

This patch updates generic partition check code such that all the
above three cases are handled too.  For the first two, @state tracks
whether low level partition check code tried to read beyond EOD during
partition scan and triggers native capacity unlocking accordingly.
The third is now handled similarly to the original unlocking case.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:03 +02:00
Tejun Heo
1493bf217f block: use struct parsed_partitions *state universally in partition check code
Make the following changes to partition check code.

* Add ->bdev to struct parsed_partitions.

* Introduce read_part_sector() which is a simple wrapper around
  read_dev_sector() which takes struct parsed_partitions *state
  instead of @bdev.

* For functions which used to take @state and @bdev, drop @bdev.  For
  functions which used to take @bdev, replace it with @state.

* While updating, drop superflous checks on NULL state/bdev in ldm.c.

This cleans up the API a bit and enables better handling of IO errors
during partition check as the generic partition check code now has
much better visibility into what went wrong in the low level code
paths.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:02 +02:00
Tejun Heo
c3e33e043f block,ide: simplify bdops->set_capacity() to ->unlock_native_capacity()
bdops->set_capacity() is unnecessarily generic.  All that's required
is a simple one way notification to lower level driver telling it to
try to unlock native capacity.  There's no reason to pass in target
capacity or return the new capacity.  The former is always the
inherent native capacity and the latter can be handled via the usual
device resize / revalidation path.  In fact, the current API is always
used that way.

Replace ->set_capacity() with ->unlock_native_capacity() which take
only @disk and doesn't return anything.  IDE which is the only current
user of the API is converted accordingly.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Ben Hutchings <ben@decadent.org.uk>
Cc: Bartlomiej Zolnierkiewicz <bzolnier@gmail.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:02 +02:00
Tejun Heo
56bca01738 block: restart partition scan after resizing a device
Device resize via ->set_capacity() can reveal new partitions (e.g. in
chained partition table formats such as dos extended parts).  Restart
partition scan from the beginning after resizing a device.  This
change also makes libata always revalidate the disk after resize which
makes lower layer native capacity unlocking implementation simpler and
more robust as resize can be handled in the usual path.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Ben Hutchings <ben@decadent.org.uk>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:02 +02:00
Tejun Heo
fa4b9074cd buffer: make invalidate_bdev() drain all percpu LRU add caches
invalidate_bdev() should release all page cache pages which are clean
and not being used; however, if some pages are still in the percpu LRU
add caches on other cpus, those pages are considered in used and don't
get released.  Fix it by calling lru_add_drain_all() before trying to
invalidate pages.

This problem was discovered while testing block automatic native
capacity unlocking.  Null pages which were read before automatic
unlocking didn't get released by invalidate_bdev() and ended up
interfering with partition scan after unlocking.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:02 +02:00
Paul E. McKenney
f1ac2502e1 block: remove all rcu head initializations
Remove all rcu head inits. We don't care about the RCU head state before passing
it to call_rcu() anyway. Only leave the "on_stack" variants so debugobjects can
keep track of objects on stack.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:01:02 +02:00
Jens Axboe
6423104b6a writeback: fixups for !dirty_writeback_centisecs
Commit 69b62d01 fixed up most of the places where we would enter
busy schedule() spins when disabling the periodic background
writeback. This fixes up the sb timer so that it doesn't get
hammered on with the delay disabled, and ensures that it gets
rearmed if needed when /proc/sys/vm/dirty_writeback_centisecs
gets modified.

bdi_forker_task() also needs to check for !dirty_writeback_centisecs
and use schedule() appropriately, fix that up too.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:00:35 +02:00
Jens Axboe
f9eadbbd42 writeback: bdi_writeback_task() must set task state before calling schedule()
Calling schedule without setting the task state to non-running will
return immediately, so ensure that we set it properly and check our
sleep conditions after doing so.

This is a fixup for commit 69b62d01.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:00:25 +02:00
Jens Axboe
7c8a3554c6 writeback: ensure that WB_SYNC_NONE writeback with sb pinned is sync
Even if the writeout itself isn't a data integrity operation, we need
to ensure that the caller doesn't drop the sb umount sem before we
have actually done the writeback.

This is a fixup for commit e913fc82.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-21 20:00:25 +02:00
Julia Lawall
2db4e42eac drivers/block/drbd: Use kzalloc
Use kzalloc rather than the combination of kmalloc and memset.

The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression x,size,flags;
statement S;
@@

-x = kmalloc(size,flags);
+x = kzalloc(size,flags);
 if (x == NULL) S
-memset(x, 0, size);
// </smpl>

Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 02:04:10 +02:00
Philipp Reisner
0c3f34516e drbd: Create new current UUID as late as possible
The choice was to either delay creation of the new UUID until
IO got thawed or to delay it until the first IO request.

Both are correct, the later is more friendly to users of
dual-primary setups, that actually only write on one side.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 02:03:49 +02:00
Philipp Reisner
9a25a04c80 drbd: If we detect late that IO got frozen, retry after we thawed.
If we detect late (= after grabing mdev->req_lock) that IO got frozen, we
return 1 to generic_make_request(), which simply will retry to make a
request for that bio.

In the subsequent call of generic_make_request() into drbd_make_request_26()
we sleep in inc_ap_bio().

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 02:03:32 +02:00
Lars Ellenberg
a1c88d0d7a drbd: always use_bmbv, ignore setting
Now that the peer may handle multi-bio EEs,
we can ignore the peer's limit,
and concentrate on the limits of the local IO stack.

This is safe accross drbd protocol versions,
as our queue_max_sectors() will be adjusted accordingly.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 02:03:05 +02:00
Lars Ellenberg
bb3d000cb9 drbd: allow resync requests to be larger than max_segment_size
this should allow for better background resync performance.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 02:02:36 +02:00
Lars Ellenberg
45bb912bd5 drbd: Allow drbd_epoch_entries to use multiple bios.
This should allow for better performance if the lower level IO stack
of the peers differs in limits exposed either via the queue,
or via some merge_bvec_fn.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 02:01:23 +02:00
Lars Ellenberg
708d740ed8 drbd: reduce sizeof struct drbd_epoch_entry by 8 byte by aligning members
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:28:35 +02:00
Philipp Reisner
162f3ec7f0 drbd: Fixes to the new delay_probes code
* Only send delay_probes with protocol 93 or newer
* drbd_send_delay_probes() is called only from worker context,
  no atomic_t needed for delay_seq

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:28:08 +02:00
Philipp Reisner
a8cdfd8d3b drbd: A fixes to the new resync speed code
* Mention P_DELAY_PROBE in the packet naming array
* Do not corrupt the mdev->data.work list in case the timer goes
  off before delay_probe_work got handled by the worker
* Do not mod_timer() twice for a single delay_probe pair

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:26:51 +02:00
Philipp Reisner
eedf386ae9 drbd: Proc bits of new resync speed stuff
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:26:27 +02:00
Philipp Reisner
cdd67a7460 drbd: Control the actual resync rate based on the queuing delay of data packets
In a setup with a high bandwidth and high latency network, eventually
involving deep queues in routers, it is beneficial to only fill those
queues up to an limited extend with resync data.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:25:47 +02:00
Philipp Reisner
bd26bfc5b4 drbd: Actually send delay probes
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:25:28 +02:00
Philipp Reisner
67c7ddd055 drbd: Four new configuration settings for resync speed control
To reasonably control resync speed over drbd-proxy connections,
drbd has to measure the current delay of packets transmitted over
the (possibly congested) data socket vs the meta-data socket.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:25:00 +02:00
Philipp Reisner
7237bc430f drbd: Sending of delay_probes
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:22:46 +02:00
Philipp Reisner
0ced55a3be drbd: Receiving of delay_probes
Delay_probes are new packets in the DRBD protocol, which allow
DRBD to know the current delay packets have on the data socket.
(relative to the meta data socket)

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:22:11 +02:00
Philipp Reisner
5223671bb0 drbd: Fixed bitmap in case of online-grow without resync
The "surplus" bits of the old (smaller) bitmap must be clean
in case of online-grow without resync.

Note: Reverted 67ae8b80d4a116ab3b7094eb3723506b20c06dff as
well, since the lines added by this patch are redundant. The
bits get set by the bm_set_surplus(b) call before that.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:20:33 +02:00
Philipp Reisner
6b4388ac1f drbd: Added transmission faults to the fault injection code
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:19:51 +02:00
Philipp Reisner
087c24925c drbd: bugfix: Make resize work, if remote's size was limiting and increased in the meantime
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:18:22 +02:00
Philipp Reisner
6495d2c6d0 drbd: Implemented the --assume-clean option for drbdsetup resize
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:17:47 +02:00
Philipp Reisner
b4ee79dac3 drbd: Added some missing statics
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:17:11 +02:00
Philipp Reisner
fd76438c24 drbd: Make sure to resync all of the new storage upon online resize
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:16:20 +02:00
Philipp Reisner
e89b591c3a drbd: Implemented flags for the resize packet
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:15:44 +02:00
Philipp Reisner
02d9a94bbb drbd: Implemented the set_new_bits parameter for drbd_bm_resize()
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:14:43 +02:00
Philipp Reisner
d845030f21 drbd: made determin_dev_size's parameter an flag enum
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:14:04 +02:00
Adam Gandelman
3a11a48789 drbd: New handler: initial-split-brain
Some wish to be notified of all instances of split brain, not just those that
go unresolved.  The initial-split-brain handler is called to notify someone
upon  detection of all split brain conditions even if auto-recovery policies
are configured.

Signed-off-by: Adam Gandelman <adam.gandelman@linbit.com>
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:13:33 +02:00
Lars Ellenberg
979f5c7f1f drbd: fail_requests_early: remove incorrect and unnecessary optimization
The condition does not fit the commend (I may well be Primary,
even if I lost the disk earlier and now the connection).

And this is catched below anyways, where it also gets logged.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:10:31 +02:00
Lars Ellenberg
6666032ade drbd: check for corrupt or malicous sector addresses when receiving data
Even if it should never happen if the peer does behave, we need to
double check, and not even attempt access beyond end of device.
It usually would be caught by lower layers, resulting in "IO error",
but may also end up in the internal meta data area.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:09:57 +02:00
Philipp Reisner
c3fe30b0e7 drbd: cleanup: This code path to trigger a resync is no longer needed
Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:09:13 +02:00
Lars Ellenberg
8d4ce82b3c drbd: don't start a resync without access to up-to-date Data
In case both nodes are "inconsistent", invalidate would
have started a resync anyways, without a chance to ever
succeed, just filling the logs with warning messages.

Simply disallow that state change,
re-using the SS_NO_UP_TO_DATE_DISK return value.

This also changes the corresponding error string to
"Need access to UpToDate Data" -- I found the
"Refusing to be Primary without at least one UpToDate disk"
answer misleading in some situations anyways.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:08:18 +02:00
Lars Ellenberg
c3470cde57 drbd: fix potential protocol error
Don't forget to drain the digest in case we cannot satisfy a
checksum based resync or online-verify request.

It would additionally cause a protocoll error,
dropping the connection.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:07:38 +02:00
Lars Ellenberg
8d1894ebe4 drbd: remove bogus ASSERT
block_id may be ID_SYNCER,
as well as checksum based resync request magic, or online verify magic.

Let's just drop that ASSERT.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:06:59 +02:00
Lars Ellenberg
e0f83012dc drbd: fix regression: attach while connected failed
commit e4f925e12e
Author: Philipp Reisner <philipp.reisner@linbit.com>
Date:   Wed Mar 17 14:18:41 2010 +0100

    drbd: Do not upgrade state to Outdated if already Inconsistent

prevented the necessary state transition for attaching while connected
(Diskless -> Consistent respectively Outdated).
This is the fix for the fix.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:06:07 +02:00
Philipp Reisner
e4f925e12e drbd: Do not upgrade state to Outdated if already Inconsistent [Bugz 277]
There was a race condition:
  In a situation with a SyncSource+Primary and a SyncTarget+Secondary node,
  and a resync dependency to some other device. After both nodes decided
  to do the resync, the other device finishes its resync process.
  At that time SyncSource already sent the P_SYNC_UUID packet, and
  already updated its peer disk state to Inconsistent.
  The SyncTarget node waits for the P_SYNC_UUID and sends a state packet
  to report the resync dependency change. That packet still carries
  a disk state of Outdated.

Impact:
  If application writes come in, during that time on the Primary node,
  those do not get replicated, and the out-of-sync counter gets increased.
  => The completion of resync is not detected on the primary node.
  => stalled.
  Those blocks get resync'ed with the next resync, since the are get
  marked as out-of-sync in the bitmap.

In order to fix this, we filter out that wrong state change in the
sanitize_state() function.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 01:01:05 +02:00
Lars Ellenberg
8c484ee491 drbd: use proc_create_data with explicit NULL argument
To document that we know about deprecation of proc_create,
even though we are not affected, as we don't use the ->data member,
open code proc_create_data(..., NULL);

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
2010-05-18 00:59:00 +02:00
Dmitry Monakhov
5547e8aac6 writeback: Update dirty flags in two steps
Filesystems with delalloc support may dirty inode during writepages.
As result inode will have dirty metadata flags even after write_inode.
In fact we have two dedicated functions for proper data and metadata
writeback. It is reasonable to separate flags updates in two stages.

https://bugzilla.kernel.org/show_bug.cgi?id=15906

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-17 13:00:41 +02:00
Jens Axboe
e913fc825d writeback: fix WB_SYNC_NONE writeback from umount
When umount calls sync_filesystem(), we first do a WB_SYNC_NONE
writeback to kick off writeback of pending dirty inodes, then follow
that up with a WB_SYNC_ALL to wait for it. Since umount already holds
the sb s_umount mutex, WB_SYNC_NONE ends up doing nothing and all
writeback happens as WB_SYNC_ALL. This can greatly slow down umount,
since WB_SYNC_ALL writeback is a data integrity operation and thus
a bigger hammer than simple WB_SYNC_NONE. For barrier aware file systems
it's a lot slower.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
2010-05-17 12:55:07 +02:00