GFP_ATOMIC was used in reiserfs_get_block to not lose the Bkl so that
nobody can modify the tree in the middle of its work. Now that we
kicked out the bkl, we can use a more friendly flag. We use GFP_NOFS
here because we already hold the reiserfs lock.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>

We had a watchdog in _get_block_create_0() that jumped to a fixup retry
path in case the bkl got relaxed while calling kmap().
This is not necessary anymore since we now have a reiserfs lock that is
not implicitly relaxed while sleeping.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>

The reiserfs ioctl path doesn't need the big kernel lock anymore , now
that the filesystem synchronizes through its own lock.

We can then turn reiserfs_ioctl() into an unlocked_ioctl callback.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>

Reiserfs uses the ioctl callback for its file operations, which means
that its ioctl path is still locked by the bkl, this was synchronizing
with the rest of the filsystem operations. We have changed that by
locking it with the new reiserfs lock but we do that only from the
compat_ioctl callback.

Fix that by locking reiserfs_ioctl() everytime.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>
Cc: Thomas Gleixner <tglx@linutronix.de>

While creating the reiserfs workqueue during the journal
initialization, we are holding the reiserfs lock, but
create_workqueue() also holds the cpu_add_remove_lock, creating
then the following dependency:

- reiserfs lock -> cpu_add_remove_lock

But we also have the following existing dependencies:

- mm->mmap_sem -> reiserfs lock
- cpu_add_remove_lock -> cpu_hotplug.lock -> slub_lock -> sysfs_mutex

The merged dependency chain then becomes:

- mm->mmap_sem -> reiserfs lock -> cpu_add_remove_lock ->
	cpu_hotplug.lock -> slub_lock -> sysfs_mutex

But when we fill a dir entry in sysfs_readir(), we are holding the
sysfs_mutex and we also might fault while copying the directory entry
to the user, leading to the following dependency:

- sysfs_mutex -> mm->mmap_sem

The end result is then a lock inversion between sysfs_mutex and
mm->mmap_sem, as reported in the following lockdep warning:

[ INFO: possible circular locking dependency detected ]
2.6.31-07095-g25a3912 #4
-------------------------------------------------------
udevadm/790 is trying to acquire lock:
 (&mm->mmap_sem){++++++}, at: [<c1098942>] might_fault+0x72/0xc0

but task is already holding lock:
 (sysfs_mutex){+.+.+.}, at: [<c110813c>] sysfs_readdir+0x7c/0x260

which lock already depends on the new lock.

the existing dependency chain (in reverse order) is:

-> #5 (sysfs_mutex){+.+.+.}:
      [...]

-> #4 (slub_lock){+++++.}:
      [...]

-> #3 (cpu_hotplug.lock){+.+.+.}:
      [...]

-> #2 (cpu_add_remove_lock){+.+.+.}:
      [...]

-> #1 (&REISERFS_SB(s)->lock){+.+.+.}:
      [...]

-> #0 (&mm->mmap_sem){++++++}:
      [...]

This can be fixed by relaxing the reiserfs lock while creating the
workqueue.
This is fine to relax the lock here, we just keep it around to pass
through reiserfs lock checks and for paranoid reasons.
Reported-by: NAlexander Beregalov <a.beregalov@gmail.com>
Tested-by: NAlexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>

Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Alexander Beregalov reported the following warning:

	=======================================================
	[ INFO: possible circular locking dependency detected ]
	2.6.31-03149-gdcc030a #1
	-------------------------------------------------------
	udevadm/716 is trying to acquire lock:
	 (&mm->mmap_sem){++++++}, at: [<c107249a>] might_fault+0x4a/0xa0

	but task is already holding lock:
	 (sysfs_mutex){+.+.+.}, at: [<c10cb9aa>] sysfs_readdir+0x5a/0x200

	which lock already depends on the new lock.

	the existing dependency chain (in reverse order) is:

	-> #3 (sysfs_mutex){+.+.+.}:
	       [...]

	-> #2 (&bdev->bd_mutex){+.+.+.}:
	       [...]

	-> #1 (&REISERFS_SB(s)->lock){+.+.+.}:
	       [...]

	-> #0 (&mm->mmap_sem){++++++}:
	       [...]

On reiserfs mount path, we take the reiserfs lock and while
initializing the journal, we open the device, taking the
bdev->bd_mutex. Then rescan_partition() may signal the change
to sysfs.

We have then the following dependency:

	reiserfs_lock -> bd_mutex -> sysfs_mutex

Later, while entering reiserfs_readpage() after a pagefault in an
mmaped reiserfs file, we are holding the mm->mmap_sem, and we are going
to take the reiserfs lock too.
We have then the following dependency:

	mm->mmap_sem -> reiserfs_lock

which, expanded with the previous dependency gives us:

	mm->mmap_sem -> reiserfs_lock -> bd_mutex -> sysfs_mutex

Now while entering the sysfs readdir path, we are holding the
sysfs_mutex. And when we copy a directory entry to the user buffer, we
might fault and then take the mm->mmap_sem lock. Which leads to the
circular locking dependency reported.

We can fix that by relaxing the reiserfs lock during the call to
journal_init_dev(), which is the place where we open the mounted
device.

This is fine to relax the lock here because we are in the begining of
the reiserfs mount path and there is nothing to protect at this time,
the journal is not intialized.
We just keep this lock around for paranoid reasons.
Reported-by: NAlexander Beregalov <a.beregalov@gmail.com>
Tested-by: NAlexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>

Until now, trying to unlock the reiserfs write lock whereas the current
task doesn't hold it lead to a simple warning.
We should actually warn and panic in this case to avoid the user datas
to reach an unstable state.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>

reiserfs_commit_write() is always called with the write lock held.
Thus the current calls to reiserfs_write_lock() in this function are
acquiring the lock recursively.
We can safely drop them.

This also solves further assumptions for this lock to be really
released while calling reiserfs_write_unlock().
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>

reiserfs_mkdir() acquires the reiserfs lock, assuming it has been called
from the dir inodes callbacks, without the lock held.

But it can also be called from other internal sites such as
reiserfs_xattr_init() which already holds the lock. This recursive
locking leads to further wrong assumptions. For example, later calls
to reiserfs_mutex_lock_safe() won't actually unlock the reiserfs lock
the time we acquire a given mutex, creating unexpected lock inversions.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>

reiserfs_xattr_init is called with the reiserfs write lock held, but
if the ".reiserfs_priv" entry is not created, we take the superblock
root directory inode mutex until .reiserfs_priv is created.

This creates a lock dependency inversion against other sites such as
reiserfs_file_release() which takes an inode mutex and the reiserfs
lock after.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Laurent Riffard <laurent.riffard@free.fr>

When do_balance() balances the tree, a trick is performed to
provide the ability for other tree writers/readers to check whether
do_balance() is executing concurrently (requires CONFIG_REISERFS_CHECK).

This is done to protect concurrent accesses to the tree. The trick
is the following:

When do_balance is called, a unique global variable called cur_tb
takes a pointer to the current tree to be rebalanced.
Once do_balance finishes its work, cur_tb takes the NULL value.

Then, concurrent tree readers/writers just have to check the value
of cur_tb to ensure do_balance isn't executing concurrently.
If it is, then it proves that schedule() occured on do_balance(),
which then relaxed the bkl that protected the tree.

Now that the bkl has be turned into a mutex, this check is still
fine even though do_balance() becomes preemptible: the write lock
will not be automatically released on schedule(), so the tree is
still protected.

But this is only fine if we have a single reiserfs mountpoint.
Indeed, because the bkl is a global lock, it didn't allowed
concurrent executions between a tree reader/writer in a mount point
and a do_balance() on another tree from another mountpoint.

So assuming all these readers/writers weren't supposed to be
reentrant, the current check now sometimes detect false positives with
the current per-superblock mutex which allows this reentrancy.

This patch keeps the concurrent tree accesses check but moves it
per superblock, so that only trees from a same mount point are
checked to be not accessed concurrently.

[ Impact: fix spurious panic while running several reiserfs mount-points ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

While searching a pathname, an inode mutex can be acquired
in do_lookup() which calls reiserfs_lookup() which in turn
acquires the write lock.

On the other side reiserfs_fill_super() can acquire the write_lock
and then call reiserfs_lookup_privroot() which can acquire an
inode mutex (the root of the mount point).

So we theoretically risk an AB - BA lock inversion that could lead
to a deadlock.

As for other lock dependencies found since the bkl to mutex
conversion, the fix is to use reiserfs_mutex_lock_safe() which
drops the lock dependency to the write lock.

[ Impact: fix a possible deadlock with reiserfs ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

search_by_key() is the site which most requires the lock.
This is mostly because it is a very central function and also
because it releases/reaqcuires the write lock at least once each
time it is called.

Such release/reacquire creates a lot of contention in this place and
also opens more the window which let another thread changing the tree.
When it happens, the current path searching over the tree must be
retried from the beggining (the root) which is a wasteful and
time consuming recovery.

This patch factorizes two release/reacquire sequences:

- reading leaf nodes blocks
- reading current block

The latter immediately follows the former.

The whole sequence is safe as a single unlocked section because
we check just after if the tree has changed during these operations.

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

reiserfs_mutex_lock_safe() is a hack to avoid any dependency between
an internal reiserfs mutex and the write lock, it has been proposed
to follow the old bkl logic.

The code does the following:

while (!mutex_trylock(m)) {
	reiserfs_write_unlock(s);
	schedule();
	reiserfs_write_lock(s);
}

It then imitate the implicit behaviour of the lock when it was
a Bkl and hadn't such dependency:

mutex_lock(m) {
	if (fastpath)
		let's go
	else {
		wait_for_mutex() {
			schedule() {
				unlock_kernel()
				reacquire_lock_kernel()
			}
		}
	}
}

The problem is that by using such explicit schedule(), we don't
benefit of the adaptive mutex spinning on owner.

The logic in use now is:

reiserfs_write_unlock(s);
mutex_lock(m); // -> possible adaptive spinning
reiserfs_write_lock(s);

[ Impact: restore the use of adaptive spinning mutexes in reiserfs ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

reiserfs_write_end() is a hot path in reiserfs.
We have two wasteful write lock lock/release inside that can be gathered
without changing the code logic.

This patch factorizes them out in a single protected section, reducing the
number of contentions inside.

[ Impact: reduce lock contention in a reiserfs hotpath ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

search_by_key() is a central function in reiserfs which searches
the patch in the fs tree from the root to a node given its key.

It is the function that is most requesting the write lock
because it's a path very often used.

Also we forget to release the lock while reading the next tree node,
making us holding the lock in a wasteful way.

Then we release the lock while reading the current node and its childs,
all-in-one. It should be safe because we have a reference to these
blocks and even if we read a block that will be concurrently changed,
we have an fs_changed check later that will make us retry the path from
the root.

[ Impact: release the write lock while unused in a hot path ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

The write lock can be acquired recursively in reiserfs_lookup(). But we may
want to *really* release the lock before possible rescheduling from a
reiserfs_lookup() callee.

Hence we want to only acquire the lock once (ie: not recursively).

[ Impact: prevent from possible false unreleased write lock on sleeping ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

reiserfs_get_block() is one of these sites where the write lock might
be acquired recursively.

It's a particular problem because this function is called very often.
It's a hot spot which needs to reschedule() periodically while converting
direct items to indirect ones because it can take some time.

Then if we are applying the write lock release/reacquire pattern on
schedule() here, it may not produce the desired effect since we may have
locked in more than one depth.

The solution is to use reiserfs_write_lock_once() which won't try
to reacquire the lock recursively. Then the lock will be *really*
released before schedule().

Also, we only release the lock if TIF_NEED_RESCHED is set to not
create wasteful numerous contentions.

[ Impact: fix a too long holded lock case in reiserfs_get_block() ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

flush_commit_list() uses ll_rw_block() to commit the pending log blocks.
ll_rw_block() might sleep, and the bkl was released at this point. Then
we can also relax the write lock at this point.

[ Impact: release the reiserfs write lock when it is not needed ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

reiserfs_read_bitmap_block() uses sb_bread() to read the bitmap block. This
helper might sleep.

Then, when the bkl was used, it was released at this point. We can then
relax the write lock too here.

[ Impact: release the reiserfs write lock when it is not needed ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

get_neighbors() is used to get the left and/or right blocks
against a given one in order to balance a tree.

sb_bread() is used to read the buffer of these neighors blocks and
while it waits for this operation, it might sleep.

The bkl was released at this point, and then we can also release
the write lock before calling sb_bread().

This is safe because if the filesystem is changed after this
lock release, the function returns REPEAT_SEARCH (aka SCHEDULE_OCCURRED
in the function header comments) in order to repeat the neighbhor
research.

[ Impact: release the reiserfs write lock when it is not needed ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

prepare_for_delete_or_cut() can process several types of items, including
indirect items, ie: items which contain no file data but pointers to
unformatted nodes scattering the datas of a file.

In this case it has to zero out these pointers to block numbers of
unformatted nodes and release the bitmap from these block numbers.

It can take some time, so a rescheduling() is performed between each
block processed. We can safely release the write lock while
rescheduling(), like the bkl did, because the code checks just after
if the item has moved after sleeping.

[ Impact: release the reiserfs write lock when it is not needed ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

When do_journal_end() copies data to the journal blocks buffers in memory,
it reschedules if needed between each block copied and dirtyfied.

We can also release the write lock at this rescheduling stage,
like did the bkl implicitly.

[ Impact: release the reiserfs write lock when it is not needed ]

Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>

Impact: fix a deadlock

reiserfs_dirty_inode() is the super_operations::dirty_inode() callback
of reiserfs. It can be called from different contexts where the write
lock can be already held.

But this function also grab the write lock (possibly recursively).
Subsequent release of the lock before sleep will actually not release
the lock if the caller of mark_inode_dirty() (which in turn calls
reiserfs_dirty_inode()) already owns the lock.

A typical case:

reiserfs_write_end() {
	acquire_write_lock()
	mark_inode_dirty() {
		reiserfs_dirty_inode() {
			reacquire_write_lock() {
				journal_begin() {
					do_journal_begin_r() {
						/*
						 * fail to release, still
						 * one depth of lock
						 */
						release_write_lock()
						reiserfs_wait_on_write_block() {
							wait_event()

The event is usually provided by something which needs the write lock but
it hasn't been released.

We use reiserfs_write_lock_once() here to ensure we only grab the
write lock in one level.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@texware.it>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Chris Mason <chris.mason@oracle.com>
LKML-Reference: <1239680065-25013-4-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix a deadlock

reiserfs_truncate_file() can be called from multiple context where
the write lock can be already hold or not.

This function also acquire (possibly recursively) the write
lock. Subsequent releases before sleeping will not actually release
the lock because we may be in more than one lock depth degree.

A typical case is:

reiserfs_file_release {
	acquire_the_lock()
	reiserfs_truncate_file()
		reacquire_the_lock()
		journal_begin() {
			do_journal_begin_r() {
				reiserfs_wait_on_write_block() {
					/*
					 * Not released because still one
					 * depth owned
					 */
					release_lock()
					wait_for_event()

At this stage the event never happen because the one which provides
it needs the write lock.

We use reiserfs_write_lock_once() here to ensure that we don't acquire the
write lock recursively.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@texware.it>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Chris Mason <chris.mason@oracle.com>
LKML-Reference: <1239680065-25013-3-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Sometimes we don't want to recursively hold the per superblock write
lock because we want to be sure it is actually released when we come
to sleep.

This patch introduces the necessary tools for that.

reiserfs_write_lock_once() does the same job than reiserfs_write_lock()
except that it won't try to acquire recursively the lock if the current
task already owns it. Also the lock_depth before the call of this function
is returned.

reiserfs_write_unlock_once() unlock only if reiserfs_write_lock_once()
returned a depth equal to -1, ie: only if it actually locked.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@texware.it>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>
Cc: Chris Mason <chris.mason@oracle.com>
LKML-Reference: <1239680065-25013-2-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

Impact: fix a deadlock

The j_flush_mutex is acquired safely in journal.c:
if we can't take it, we free the reiserfs per superblock lock
and wait a bit.

But we have a remaining place in kupdate_transactions() where
j_flush_mutex is still acquired traditionnaly. Thus the following
scenario (warned by lockdep) can happen:

A						B

mutex_lock(&write_lock)			mutex_lock(&write_lock)
	mutex_lock(&j_flush_mutex)	mutex_lock(&j_flush_mutex) //block
	mutex_unlock(&write_lock)
	sleep...
	mutex_lock(&write_lock) //deadlock

Fix this by using reiserfs_mutex_lock_safe() in kupdate_transactions().
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Cc: Alessio Igor Bogani <abogani@texware.it>
Cc: Jeff Mahoney <jeffm@suse.com>
LKML-Reference: <1239660635-12940-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

This patch is an attempt to remove the Bkl based locking scheme from
reiserfs and is intended.

It is a bit inspired from an old attempt by Peter Zijlstra:

   http://lkml.indiana.edu/hypermail/linux/kernel/0704.2/2174.html

The bkl is heavily used in this filesystem to prevent from
concurrent write accesses on the filesystem.

Reiserfs makes a deep use of the specific properties of the Bkl:

- It can be acqquired recursively by a same task
- It is released on the schedule() calls and reacquired when schedule() returns

The two properties above are a roadmap for the reiserfs write locking so it's
very hard to simply replace it with a common mutex.

- We need a recursive-able locking unless we want to restructure several blocks
  of the code.
- We need to identify the sites where the bkl was implictly relaxed
  (schedule, wait, sync, etc...) so that we can in turn release and
  reacquire our new lock explicitly.
  Such implicit releases of the lock are often required to let other
  resources producer/consumer do their job or we can suffer unexpected
  starvations or deadlocks.

So the new lock that replaces the bkl here is a per superblock mutex with a
specific property: it can be acquired recursively by a same task, like the
bkl.

For such purpose, we integrate a lock owner and a lock depth field on the
superblock information structure.

The first axis on this patch is to turn reiserfs_write_(un)lock() function
into a wrapper to manage this mutex. Also some explicit calls to
lock_kernel() have been converted to reiserfs_write_lock() helpers.

The second axis is to find the important blocking sites (schedule...(),
wait_on_buffer(), sync_dirty_buffer(), etc...) and then apply an explicit
release of the write lock on these locations before blocking. Then we can
safely wait for those who can give us resources or those who need some.
Typically this is a fight between the current writer, the reiserfs workqueue
(aka the async commiter) and the pdflush threads.

The third axis is a consequence of the second. The write lock is usually
on top of a lock dependency chain which can include the journal lock, the
flush lock or the commit lock. So it's dangerous to release and trying to
reacquire the write lock while we still hold other locks.

This is fine with the bkl:

      T1                       T2

lock_kernel()
    mutex_lock(A)
    unlock_kernel()
    // do something
                            lock_kernel()
                                mutex_lock(A) -> already locked by T1
                                schedule() (and then unlock_kernel())
    lock_kernel()
    mutex_unlock(A)
    ....

This is not fine with a mutex:

      T1                       T2

mutex_lock(write)
    mutex_lock(A)
    mutex_unlock(write)
    // do something
                           mutex_lock(write)
                              mutex_lock(A) -> already locked by T1
                              schedule()

    mutex_lock(write) -> already locked by T2
    deadlock

The solution in this patch is to provide a helper which releases the write
lock and sleep a bit if we can't lock a mutex that depend on it. It's another
simulation of the bkl behaviour.

The last axis is to locate the fs callbacks that are called with the bkl held,
according to Documentation/filesystem/Locking.

Those are:

- reiserfs_remount
- reiserfs_fill_super
- reiserfs_put_super

Reiserfs didn't need to explicitly lock because of the context of these callbacks.
But now we must take care of that with the new locking.

After this patch, reiserfs suffers from a slight performance regression (for now).
On UP, a high volume write with dd reports an average of 27 MB/s instead
of 30 MB/s without the patch applied.
Signed-off-by: NFrederic Weisbecker <fweisbec@gmail.com>
Reviewed-by: NIngo Molnar <mingo@elte.hu>
Cc: Jeff Mahoney <jeffm@suse.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Bron Gondwana <brong@fastmail.fm>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
LKML-Reference: <1239070789-13354-1-git-send-email-fweisbec@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

* Remove smp_lock.h from files which don't need it (including some headers!)
* Add smp_lock.h to files which do need it
* Make smp_lock.h include conditional in hardirq.h
  It's needed only for one kernel_locked() usage which is under CONFIG_PREEMPT

  This will make hardirq.h inclusion cheaper for every PREEMPT=n config
  (which includes allmodconfig/allyesconfig, BTW)
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

Commit 1faa16d2 accidentally broke
the bdi congestion wait queue logic, causing us to wait on congestion
for WRITE (== 1) when we really wanted BLK_RW_ASYNC (== 0) instead.
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>

Fix various silly problems wrt mnt_namespace.h:

 - exit_mnt_ns() isn't used, remove it
 - done that, sched.h and nsproxy.h inclusions aren't needed
 - mount.h inclusion was need for vfsmount_lock, but no longer
 - remove mnt_namespace.h inclusion from files which don't use anything
   from mnt_namespace.h
Signed-off-by: NAlexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

helpers: get_cached_acl(inode, type), set_cached_acl(inode, type, acl),
forget_cached_acl(inode, type).

ubifs/xattr.c needed includes reordered, the rest is a plain switchover.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

reiserfs uses NULL as "unknown" and ERR_PTR(-ENODATA) as "no ACL";
several codepaths store the former instead of the latter.

All those codepaths go through iset_acl() and all cases when it's
called with NULL acl are for the second variety, so the minimal
fix is to teach iset_acl() to deal with that.

Proper fix is to switch to more usual conventions and avoid back
and forth between internally used ERR_PTR(-ENODATA) and NULL
expected by the rest of the kernel.
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Reiserfs doesn't use lock_super anywhere internally, and ->remount_fs
which calls reiserfs_resize does have it currently but also expects it
to be held on return, so there's no business for the unlock_super here.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked by Edward Shishkin <edward.shishkin@gmail.com>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Several code paths in reiserfs have a construct like:

 if (is_direntry_le_ih(ih = B_N_PITEM_HEAD(src, item_num))) ...

which, in addition to being ugly, end up causing compiler warnings with
gcc 4.4.0.  Previous compilers didn't issue a warning.

fs/reiserfs/do_balan.c:1273: warning: operation on `aux_ih' may be undefined
fs/reiserfs/lbalance.c:393: warning: operation on `ih' may be undefined
fs/reiserfs/lbalance.c:421: warning: operation on `ih' may be undefined
fs/reiserfs/lbalance.c:777: warning: operation on `ih' may be undefined

I believe this is due to the ih being passed to macros which evaluate the
argument more than once.  This is old code and we haven't seen any
problems with it, but this patch eliminates the warnings.

It converts the multiple evaluation macros to static inlines and does a
preassignment for the cases that were causing the warnings because that
code is just ugly.
Reported-by: NChris Mason <mason@oracle.com>
Signed-off-by: NJeff Mahoney <jeffm@suse.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

[xfs, btrfs, capifs, shmem don't need BKL, exempt]
Signed-off-by: NAlessio Igor Bogani <abogani@texware.it>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>