md devices allocate a bio_set and use it for two
distinct purposes.
mddev->bio_set is used to clone bios as part of sending
upper level requests down to lower level devices,
and it is also use for synchronous IO such as superblock
and bitmap updates, and for correcting read errors.

This multiple usage can lead to deadlocks.  It is likely
that cloned bios might be queued for write and to be
waiting for a metadata update before the write can be permitted.
If the cloning exhausted mddev->bio_set, the metadata update
may not be able to proceed.

This scenario has been seen during heavy testing, with lots of IO and
lots of memory pressure.

Address this by adding a new bio_set specifically for synchronous IO.
All synchronous IO goes directly to the underlying device and is not
queued at the md level, so request using entries from the new
mddev->sync_set will complete in a timely fashion.
Requests that use mddev->bio_set will sometimes need to wait
for synchronous IO, but will no longer risk deadlocking that iO.

Also: small simplification in mddev_put(): there is no need to
wait until the spinlock is released before calling bioset_free().
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

The value for spare spot of sb->dev_roles is changed from
MD_DISK_ROLE_FAULTY to MD_DISK_ROLE_SPARE to keep align
with the value when the superblock is firstly created in
userspace.
Signed-off-by: NLidong Zhong <lzhong@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

If mddev_suspend() races with md_write_start() we can deadlock
with mddev_suspend() waiting for the request that is currently
in md_write_start() to complete the ->make_request() call,
and md_write_start() waiting for the metadata to be updated
to mark the array as 'dirty'.
As metadata updates done by md_check_recovery() only happen then
the mddev_lock() can be claimed, and as mddev_suspend() is often
called with the lock held, these threads wait indefinitely for each
other.

We fix this by having md_write_start() abort if mddev_suspend()
is happening, and ->make_request() aborts if md_write_start()
aborted.
md_make_request() can detect this abort, decrease the ->active_io
count, and wait for mddev_suspend().
Reported-by: NNix <nix@esperi.org.uk>
Fix: 68866e42(MD: no sync IO while suspended)
Cc: stable@vger.kernel.org
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

The new per-cpu counter for writes_pending is initialised in
md_alloc(), which is not called by dm-raid.
So dm-raid fails when md_write_start() is called.

Move the initialization to the personality modules
that need it.  This way it is always initialised when needed,
but isn't unnecessarily initialized (requiring memory allocation)
when the personality doesn't use writes_pending.
Reported-by: NHeinz Mauelshagen <heinzm@redhat.com>
Fixes: 4ad23a97 ("MD: use per-cpu counter for writes_pending")
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Commit b685d3d6 "block: treat REQ_FUA and REQ_PREFLUSH as
synchronous" removed REQ_SYNC flag from WRITE_{FUA|PREFLUSH|...}
definitions.  generic_make_request_checks() however strips REQ_FUA and
REQ_PREFLUSH flags from a bio when the storage doesn't report volatile
write cache and thus write effectively becomes asynchronous which can
lead to performance regressions

Fix the problem by making sure all bios which are synchronous are
properly marked with REQ_SYNC.

CC: linux-raid@vger.kernel.org
CC: Shaohua Li <shli@kernel.org>
Fixes: b685d3d6
CC: stable@vger.kernel.org
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NShaohua Li <shli@fb.com>

This essentially reverts commit b5470dc5 ("md: resolve external
metadata handling deadlock in md_allow_write") with some adjustments.

Since commit 6791875e ("md: make reconfig_mutex optional for writes
to md sysfs files.") changing array_state to 'active' does not use
mddev_lock() and will not cause a deadlock with md_allow_write(). This
revert simplifies userspace tools that write to sysfs attributes like
"stripe_cache_size" or "consistency_policy" because it removes the need
for special handling for external metadata arrays, checking for EAGAIN
and retrying the write.
Signed-off-by: NArtur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: NShaohua Li <shli@fb.com>

1/ If an array has any read-only devices when it is started,
   the array itself must be read-only
2/ A read-only device cannot be added to an array after it is
   started.
3/ Setting an array to read-write should not succeed
   if any member devices are read-only
Reported-and-Tested-by: NNanda Kishore Chinnaram <Nanda_Kishore_Chinna@dell.com>
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

md allows a new array device to be created by simply
opening a device file.  This make it difficult to
remove the device and udev is likely to open the device file
as part of processing the REMOVE event.

There is an alternate mechanism for creating arrays
by writing to the new_array module parameter.
When using tools that work with this parameter, it is
best to disable the old semantics.
This new module parameter allows that.
Signed-off-by: NNeilBrown <neilb@suse.com>
Acted-by: NColy Li <colyli@suse.de>
Signed-off-by: NShaohua Li <shli@fb.com>

The intention when creating the "new_array" parameter and the
possibility of having array names line "md_HOME" was to transition
away from the old way of creating arrays and to eventually only use
this new way.

The "old" way of creating array is to create a device node in /dev
and then open it.  The act of opening creates the array.
This is problematic because sometimes the device node can be opened
when we don't want to create an array.  This can easily happen
when some rule triggered by udev looks at a device as it is being
destroyed.  The node in /dev continues to exist for a short period
after an array is stopped, and opening it during this time recreates
the array (as an inactive array).

Unfortunately no clear plan for the transition was created.  It is now
time to fix that.

This patch allows devices with numeric names, like "md999" to be
created by writing to "new_array".  This will only work if the minor
number given is not already in use.  This will allow mdadm to
support the creation of arrays with numbers > 511 (currently not
possible) by writing to new_array.
mdadm can, at some point, use this approach to create *all* arrays,
which will allow the transition to only using the new-way.
Signed-off-by: NNeilBrown <neilb@suse.com>
Acted-by: NColy Li <colyli@suse.de>
Signed-off-by: NShaohua Li <shli@fb.com>

md.c: it needs to release the mddev lock before
the array_size_store() returns.

Fixes: ab5a98b1 ("md-cluster: change array_sectors and update size are not supported")
Signed-off-by: NZhilong Liu <zlliu@suse.com>
Reviewed-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

if called md_set_readonly and set MD_CLOSING bit, the mddev cannot
be opened any more due to the MD_CLOING bit wasn't cleared. Thus it
needs to be cleared in md_ioctl after any call to md_set_readonly()
or do_md_stop().
Signed-off-by: NNeilBrown <neilb@suse.com>
Fixes: af8d8e6f ("md: changes for MD_STILL_CLOSED flag")
Cc: stable@vger.kernel.org (v4.9+)
Signed-off-by: NZhilong Liu <zlliu@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

The 'writes_pending' counter is used to determine when the
array is stable so that it can be marked in the superblock
as "Clean".  Consequently it needs to be updated frequently
but only checked for zero occasionally.  Recent changes to
raid5 cause the count to be updated even more often - once
per 4K rather than once per bio.  This provided
justification for making the updates more efficient.

So we replace the atomic counter a percpu-refcount.
This can be incremented and decremented cheaply most of the
time, and can be switched to "atomic" mode when more
precise counting is needed.  As it is possible for multiple
threads to want a precise count, we introduce a
"sync_checker" counter to count the number of threads
in "set_in_sync()", and only switch the refcount back
to percpu mode when that is zero.

We need to be careful about races between set_in_sync()
setting ->in_sync to 1, and md_write_start() setting it
to zero.  md_write_start() holds the rcu_read_lock()
while checking if the refcount is in percpu mode.  If
it is, then we know a switch to 'atomic' will not happen until
after we call rcu_read_unlock(), in which case set_in_sync()
will see the elevated count, and not set in_sync to 1.
If it is not in percpu mode, we take the mddev->lock to
ensure proper synchronization.

It is no longer possible to quickly check if the count is zero, which
we previously did to update a timer or to schedule the md_thread.
So now we do these every time we decrement that counter, but make
sure they are fast.

mod_timer() already optimizes the case where the timeout value doesn't
actually change.  We leverage that further by always rounding off the
jiffies to the timeout value.  This may delay the marking of 'clean'
slightly, but ensure we only perform atomic operation here when absolutely
needed.

md_wakeup_thread() current always calls wake_up(), even if
THREAD_WAKEUP is already set.  That too can be optimised to avoid
calls to wake_up().
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

If ->in_sync is being set just as md_write_start() is being called,
it is possible that set_in_sync() won't see the elevated
->writes_pending, and md_write_start() won't see the set ->in_sync.

To close this race, re-test ->writes_pending after setting ->in_sync,
and add memory barriers to ensure the increment of ->writes_pending
will be seen by the time of this second test, or the new ->in_sync
will be seen by md_write_start().

Add a spinlock to array_state_show() to ensure this temporary
instability is never visible from userspace.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Three separate places in md.c check if the number of active
writes is zero and, if so, sets mddev->in_sync.

There are a few differences, but there shouldn't be:
- it is always appropriate to notify the change in
  sysfs_state, and there is no need to do this outside a
  spin-locked region.
- we never need to check ->recovery_cp.  The state of resync
  is not relevant for whether there are any pending writes
  or not (which is what ->in_sync reports).

So create set_in_sync() which does the correct tests and
makes the correct changes, and call this in all three
places.

Any behaviour changes here a minor and cosmetic.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

We use md_write_start() to increase the count of pending writes, and
md_write_end() to decrement the count.  We currently count bios
submitted to md/raid5.  Change it count stripe_heads that a WRITE bio
has been attached to.

So now, raid5_make_request() calls md_write_start() and then
md_write_end() to keep the count elevated during the setup of the
request.

add_stripe_bio() calls md_write_start() for each stripe_head, and the
completion routines always call md_write_end(), instead of only
calling it when raid5_dec_bi_active_stripes() returns 0.
make_discard_request also calls md_write_start/end().

The parallel between md_write_{start,end} and use of bi_phys_segments
can be seen in that:
 Whenever we set bi_phys_segments to 1, we now call md_write_start.
 Whenever we increment it on non-read requests with
   raid5_inc_bi_active_stripes(), we now call md_write_start().
 Whenever we decrement bi_phys_segments on non-read requsts with
    raid5_dec_bi_active_stripes(), we now call md_write_end().

This reduces our dependence on keeping a per-bio count of active
stripes in bi_phys_segments.

md_write_inc() is added which parallels md_write_start(), but requires
that a write has already been started, and is certain never to sleep.
This can be used inside a spinlocked region when adding to a write
request.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Since we have switched to sync way to handle METADATA_UPDATED
msg for md-cluster, then process_metadata_update is depended
on mddev->thread->wqueue.

With the new change, clustered raid could possible hang if
array received a METADATA_UPDATED msg after array unregistered
mddev->thread, so we need to stop clustered raid (bitmap_destroy
-> bitmap_free -> md_cluster_stop) earlier than unregister
thread (mddev_detach -> md_unregister_thread).

And this change should be safe for non-clustered raid since
all writes are stopped before the destroy. Also in md_run,
we activate the personality (pers->run()) before activating
the bitmap (bitmap_create()). So it is pleasingly symmetric
to stop the bitmap (bitmap_destroy()) before stopping the
personality (__md_stop() calls pers->free()), we achieve this
by move bitmap_destroy to the beginning of __md_stop.

But we don't want to break the codes for waiting behind IO as
Shaohua mentioned, so introduce bitmap_wait_behind_writes to
call the codes, and call the new fun in both mddev_detach and
bitmap_destroy, then we will not break original behind IO code
and also fit the new condition well.
Signed-off-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Allow writing to 'consistency_policy' attribute when the array is
active. Add a new function 'change_consistency_policy' to the
md_personality operations structure to handle the change in the
personality code. Values "ppl" and "resync" are accepted and
turn PPL on and off respectively.

When enabling PPL its location and size should first be set using
'ppl_sector' and 'ppl_size' attributes and a valid PPL header should be
written at this location on each member device.

Enabling or disabling PPL is performed under a suspended array.  The
raid5_reset_stripe_cache function frees the stripe cache and allocates
it again in order to allocate or free the ppl_pages for the stripes in
the stripe cache.
Signed-off-by: NArtur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Add 'consistency_policy' attribute for array. It indicates how the array
maintains consistency in case of unexpected shutdown.

Add 'ppl_sector' and 'ppl_size' for rdev, which describe the location
and size of the PPL space on the device. They can't be changed for
active members if the array is started and PPL is enabled, so in the
setter functions only basic checks are performed. More checks are done
in ppl_validate_rdev() when starting the log.

These attributes are writable to allow enabling PPL for external
metadata arrays and (later) to enable/disable PPL for a running array.
Signed-off-by: NArtur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Include information about PPL location and size into mdp_superblock_1
and copy it to/from rdev. Because PPL is mutually exclusive with bitmap,
put it in place of 'bitmap_offset'. Add a new flag MD_FEATURE_PPL for
'feature_map', analogically to MD_FEATURE_BITMAP_OFFSET. Add MD_HAS_PPL
to mddev->flags to indicate that PPL is enabled on an array.
Signed-off-by: NArtur Paszkiewicz <artur.paszkiewicz@intel.com>
Signed-off-by: NShaohua Li <shli@fb.com>

To update size for cluster raid, we need to make
sure all nodes can perform the change successfully.
However, it is possible that some of them can't do
it due to failure (bitmap_resize could fail). So
we need to consider the issue before we set the
capacity unconditionally, and we use below steps
to perform sanity check.

1. A change the size, then broadcast METADATA_UPDATED
   msg.
2. B and C receive METADATA_UPDATED change the size
   excepts call set_capacity, sync_size is not update
   if the change failed. Also call bitmap_update_sb
   to sync sb to disk.
3. A checks other node's sync_size, if sync_size has
   been updated in all nodes, then send CHANGE_CAPACITY
   msg otherwise send msg to revert previous change.
4. B and C call set_capacity if receive CHANGE_CAPACITY
   msg, otherwise pers->resize will be called to restore
   the old value.
Reviewed-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Previously, when node received METADATA_UPDATED msg, it just
need to wakeup mddev->thread, then md_reload_sb will be called
eventually.

We taken the asynchronous way to avoid a deadlock issue, the
deadlock issue could happen when one node is receiving the
METADATA_UPDATED msg (wants reconfig_mutex) and trying to run
the path:

md_check_recovery -> mddev_trylock(hold reconfig_mutex)
                  -> md_update_sb-metadata_update_start
		     (want EX on token however token is
		      got by the sending node)

Since we will support resizing for clustered raid, and we
need the metadata update handling to be synchronous so that
the initiating node can detect failure, so we need to change
the way for handling METADATA_UPDATED msg.

But, we obviously need to avoid above deadlock with the
sync way. To make this happen, we considered to not hold
reconfig_mutex to call md_reload_sb, if some other thread
has already taken reconfig_mutex and waiting for the 'token',
then process_recvd_msg() can safely call md_reload_sb()
without taking the mutex. This is because we can be certain
that no other thread will take the mutex, and we also certain
that the actions performed by md_reload_sb() won't interfere
with anything that the other thread is in the middle of.

To make this more concrete, we added a new cinfo->state bit
        MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD

Which is set in lock_token() just before dlm_lock_sync() is
called, and cleared just after. As lock_token() is always
called with reconfig_mutex() held (the specific case is the
resync_info_update which is distinguished well in previous
patch), if process_recvd_msg() finds that the new bit is set,
then the mutex must be held by some other thread, and it will
keep waiting.

So process_metadata_update() can call md_reload_sb() if either
mddev_trylock() succeeds, or if MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD
is set. The tricky bit is what to do if neither of these apply.
We need to wait. Fortunately mddev_unlock() always calls wake_up()
on mddev->thread->wqueue. So we can get lock_token() to call
wake_up() on that when it sets the bit.

There are also some related changes inside this commit:
1. remove RELOAD_SB related codes since there are not valid anymore.
2. mddev is added into md_cluster_info then we can get mddev inside
   lock_token.
3. add new parameter for lock_token to distinguish reconfig_mutex
   is held or not.

And, we need to set MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD in below:
1. set it before unregister thread, otherwise a deadlock could
   appear if stop a resyncing array.
   This is because md_unregister_thread(&cinfo->recv_thread) is
   blocked by recv_daemon -> process_recvd_msg
			  -> process_metadata_update.
   To resolve the issue, MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD is
   also need to be set before unregister thread.
2. set it in metadata_update_start to fix another deadlock.
	a. Node A sends METADATA_UPDATED msg (held Token lock).
	b. Node B wants to do resync, and is blocked since it can't
	   get Token lock, but MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD is
	   not set since the callchain
	   (md_do_sync -> sync_request
        	       -> resync_info_update
		       -> sendmsg
		       -> lock_comm -> lock_token)
	   doesn't hold reconfig_mutex.
	c. Node B trys to update sb (held reconfig_mutex), but stopped
	   at wait_event() in metadata_update_start since we have set
	   MD_CLUSTER_SEND_LOCK flag in lock_comm (step 2).
	d. Then Node B receives METADATA_UPDATED msg from A, of course
	   recv_daemon is blocked forever.
   Since metadata_update_start always calls lock_token with reconfig_mutex,
   we need to set MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD here as well, and
   lock_token don't need to set it twice unless lock_token is invoked from
   lock_comm.

Finally, thanks to Neil for his great idea and help!
Reviewed-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

The sb->layout is of type __le32, so we shoud use le32_to_cpu.
Signed-off-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NShaohua Li <shli@fb.com>

The sb->super_offset should be big-endian, but the rdev->sb_start is in
host byte order, so fix this by adding cpu_to_le64.
Signed-off-by: NJason Yan <yanaijie@huawei.com>
Signed-off-by: NShaohua Li <shli@fb.com>

These arrays, created with "mdadm --build" don't benefit from a limit.
The default will be used, which is '0' and is interpreted as "don't
impose a limit".

Reported-by: ian_bruce@mail.ru
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

raid1_resize and raid5_resize should also check the
mddev->queue if run underneath dm-raid.

And both set_capacity and revalidate_disk are used in
pers->resize such as raid1, raid10 and raid5. So
move them from personality file to common code.
Reviewed-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Nobody is using mddev_check_plugged(), so delete the dead code
Signed-off-by: NShaohua Li <shli@fb.com>

We are going to split <linux/sched/signal.h> out of <linux/sched.h>, which
will have to be picked up from other headers and a couple of .c files.

Create a trivial placeholder <linux/sched/signal.h> file that just
maps to <linux/sched.h> to make this patch obviously correct and
bisectable.

Include the new header in the files that are going to need it.
Acked-by: NLinus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: NIngo Molnar <mingo@kernel.org>

Firstly bio_clone_mddev() is used in raid normal I/O and isn't
in resync I/O path.

Secondly all the direct access to bvec table in raid happens on
resync I/O except for write behind of raid1, in which we still
use bio_clone() for allocating new bvec table.

So this patch replaces bio_clone() with bio_clone_fast()
in bio_clone_mddev().

Also kill bio_clone_mddev() and call bio_clone_fast() directly, as
suggested by Christoph Hellwig.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NShaohua Li <shli@fb.com>

mddev is never NULL and neither is ->bio_set, so
remove the check.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NShaohua Li <shli@fb.com>

The current behaviour is to fall back to allocate
bio from 'fs_bio_set', that isn't a correct way
because it might cause deadlock.

So this patch simply return failure if mddev->bio_set
can't be created.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NMing Lei <tom.leiming@gmail.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Commit: cbd19983 ("md: Fix unfortunate interaction with evms")
change mddev_put() so that it would not destroy an md device while
->ctime was non-zero.

Unfortunately, we didn't make sure to clear ->ctime when unloading
the module, so it is possible for an md device to remain after
module unload.  An attempt to open such a device will trigger
an invalid memory reference in:
  get_gendisk -> kobj_lookup -> exact_lock -> get_disk

when tring to access disk->fops, which was in the module that has
been removed.

So ensure we clear ->ctime in md_exit(), and explain how that is useful,
as it isn't immediately obvious when looking at the code.

Fixes: cbd19983 ("md: Fix unfortunate interaction with evms")
Tested-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

We will want to have struct backing_dev_info allocated separately from
struct request_queue. As the first step add pointer to backing_dev_info
to request_queue and convert all users touching it. No functional
changes in this patch.
Reviewed-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NJens Axboe <axboe@fb.com>

For safer operation, all arrays start in write-through mode, which has been
better tested and is more mature. And actually the write-through/write-mode
isn't persistent after array restarted, so we always start array in
write-through mode. However, if recovery found data-only stripes before the
shutdown (from previous write-back mode), it is not safe to start the array in
write-through mode, as write-through mode can not handle stripes with data in
write-back cache. To solve this problem, we flush all data-only stripes in
r5l_recovery_log(). When r5l_recovery_log() returns, the array starts with
empty cache in write-through mode.

This logic is implemented in r5c_recovery_flush_data_only_stripes():

1. enable write back cache
2. flush all stripes
3. wake up conf->mddev->thread
4. wait for all stripes get flushed (reuse wait_for_quiescent)
5. disable write back cache

The wait in 4 will be waked up in release_inactive_stripe_list()
when conf->active_stripes reaches 0.

It is safe to wake up mddev->thread here because all the resource
required for the thread has been initialized.
Signed-off-by: NSong Liu <songliubraving@fb.com>
Signed-off-by: NShaohua Li <shli@fb.com>

The mddev->flags are used for different purposes. There are a lot of
places we check/change the flags without masking unrelated flags, we
could check/change unrelated flags. These usage are most for superblock
write, so spearate superblock related flags. This should make the code
clearer and also fix real bugs.
Reviewed-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

Fixes: 90f5f7ad("md: Wait for md_check_recovery before attempting device
removal.")
Reviewed-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

md_open() gets a counted reference on an mddev using mddev_find().
If it ends up returning an error, it must drop this reference.

There are two error paths where the reference is not dropped.
One only happens if the process is signalled and an awkward time,
which is quite unlikely.
The other was introduced recently in commit af8d8e6f.

Change the code to ensure the drop the reference when returning an error,
and make it harded to re-introduce this sort of bug in the future.
Reported-by: NMarc Smith <marc.smith@mcc.edu>
Fixes: af8d8e6f ("md: changes for MD_STILL_CLOSED flag")
Signed-off-by: NNeilBrown <neilb@suse.com>
Acked-by: NGuoqing Jiang <gqjiang@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

__md_stop_writes currently doesn't stop raid5-cache reclaim thread. It's
possible the reclaim thread is still running and doing write, which
doesn't match what __md_stop_writes should do. The extra ->quiesce()
call should not harm any raid types. For raid5-cache, this will
guarantee we reclaim all caches before we update superblock.
Signed-off-by: NShaohua Li <shli@fb.com>
Reviewed-by: NNeilBrown <neilb@suse.de>
Cc: Song Liu <songliubraving@fb.com>

There is mechanism to suspend a kernel thread. Use it instead of playing
create/destroy game.
Signed-off-by: NShaohua Li <shli@fb.com>
Reviewed-by: NNeilBrown <neilb@suse.de>
Cc: Song Liu <songliubraving@fb.com>

This can only be supported on personalities which ensure
that md_error() never causes an array to enter the 'failed'
state.  i.e. if marking a device Faulty would cause some
data to be inaccessible, the device is status is left as
non-Faulty.  This is true for RAID1 and RAID10.

If we get a failure writing metadata but the device doesn't
fail, it must be the last device so we re-write without
FAILFAST to improve chance of success.  We also flag the
device as LastDev so that future metadata updates don't
waste time on failfast writes.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>

This patch just adds a 'failfast' per-device flag which can be stored
in v0.90 or v1.x metadata.
The flag is not used yet but the intent is that it can be used for
mirrored (raid1/raid10) arrays where low latency is more important
than keeping all devices on-line.

Setting the flag for a device effectively gives permission for that
device to be marked as Faulty and excluded from the array on the first
error.  The underlying driver will be directed not to retry requests
that result in failures.  There is a proviso that the device must not
be marked faulty if that would cause the array as a whole to fail, it
may only be marked Faulty if the array remains functional, but is
degraded.

Failures on read requests will cause the device to be marked
as Faulty immediately so that further reads will avoid that
device.  No attempt will be made to correct read errors by
over-writing with the correct data.

It is expected that if transient errors, such as cable unplug, are
possible, then something in user-space will revalidate failed
devices and re-add them when they appear to be working again.
Signed-off-by: NNeilBrown <neilb@suse.com>
Signed-off-by: NShaohua Li <shli@fb.com>