linux-toradex.git/fs/btrfs/locking.c, branch v5.0

btrfs: replace waitqueue_actvie with cond_wake_up

2018-05-28T16:23:09+00:00

Use the wrappers and reduce the amount of low-level details about the
waitqueue management.

Reviewed-by: Nikolay Borisov 
Signed-off-by: David Sterba

btrfs: replace GPL boilerplate by SPDX -- sources

2018-04-12T14:29:51+00:00

Remove GPL boilerplate text (long, short, one-line) and keep the rest,
ie. personal, company or original source copyright statements. Add the
SPDX header.

Signed-off-by: David Sterba

btrfs: Relax memory barrier in btrfs_tree_unlock

2018-03-30T23:26:51+00:00

When performing an unlock on an extent buffer we'd like to order the
decrement of extent_buffer::blocking_writers with waking up any
waiters. In such situations it's sufficient to use smp_mb__after_atomic
rather than the heavy smp_mb. On architectures where atomic operations
are fully ordered (such as x86 or s390) unconditionally executing
a heavyweight smp_mb instruction causes a severe hit to performance
while bringin no improvements in terms of correctness.

The better thing is to use the appropriate smp_mb__after_atomic routine
which will do the correct thing (invoke a full smp_mb or in the case
of ordered atomics insert a compiler barrier). Put another way,
an RMW atomic op + smp_load__after_atomic equals, in terms of
semantics, to a full smp_mb. This ensures that none of the problems
described in the accompanying comment of waitqueue_active occur.
No functional changes.

Signed-off-by: Nikolay Borisov 
Reviewed-by: David Sterba 
Signed-off-by: David Sterba

btrfs: cleanup, remove stray return statements

2016-01-07T13:30:52+00:00

Signed-off-by: David Sterba

btrfs: comment the rest of implicit barriers before waitqueue_active

2015-10-10T16:42:00+00:00

There are atomic operations that imply the barrier for waitqueue_active
mixed in an if-condition.

Signed-off-by: David Sterba

btrfs: add comments to barriers before waitqueue_active

2015-10-10T16:40:04+00:00

Reduce number of undocumented barriers out there.

Signed-off-by: David Sterba

btrfs: Add WARN_ON() for double lock in btrfs_tree_lock()

2015-08-09T14:07:14+00:00

When a task trying to double lock a extent buffer, there are no
lockdep warning about it because this lock may be in "blocking_lock"
state, and make us hard to debug.

This patch add a WARN_ON() for above condition, it can not report
all deadlock cases(as lock between tasks), but at least helps us
some.

Signed-off-by: Zhao Lei 
Signed-off-by: Chris Mason

btrfs: fix lockups from btrfs_clear_path_blocking

2014-11-19T18:34:35+00:00

The fair reader/writer locks mean that btrfs_clear_path_blocking needs
to strictly follow lock ordering rules even when we already have
blocking locks on a given path.

Before we can clear a blocking lock on the path, we need to make sure
all of the locks have been converted to blocking.  This will remove lock
inversions against anyone spinning in write_lock() against the buffers
we're trying to get read locks on.  These inversions didn't exist before
the fair read/writer locks, but now we need to be more careful.

We papered over this deadlock in the past by changing
btrfs_try_read_lock() to be a true trylock against both the spinlock and
the blocking lock.  This was slower, and not sufficient to fix all the
deadlocks.  This patch adds a btrfs_tree_read_lock_atomic(), which
basically means get the spinlock but trylock on the blocking lock.

Signed-off-by: Chris Mason 
Signed-off-by: Josef Bacik 
Reported-by: Patrick Schmid 
cc: stable@vger.kernel.org #v3.15+

Btrfs: fix deadlocks with trylock on tree nodes

2014-06-19T21:19:55+00:00

The Btrfs tree trylock function is poorly named.  It always takes
the spinlock and backs off if the blocking lock is held.  This
can lead to surprising lockups because people expect it to really be a
trylock.

This commit makes it a pure trylock, both for the spinlock and the
blocking lock.  It also reworks the nested lock handling slightly to
avoid taking the read lock while a spinning write lock might be held.

Signed-off-by: Chris Mason

btrfs: make static code static & remove dead code

2013-05-06T19:55:23+00:00

Big patch, but all it does is add statics to functions which
are in fact static, then remove the associated dead-code fallout.

removed functions:

btrfs_iref_to_path()
__btrfs_lookup_delayed_deletion_item()
__btrfs_search_delayed_insertion_item()
__btrfs_search_delayed_deletion_item()
find_eb_for_page()
btrfs_find_block_group()
range_straddles_pages()
extent_range_uptodate()
btrfs_file_extent_length()
btrfs_scrub_cancel_devid()
btrfs_start_transaction_lflush()

btrfs_print_tree() is left because it is used for debugging.
btrfs_start_transaction_lflush() and btrfs_reada_detach() are
left for symmetry.

ulist.c functions are left, another patch will take care of those.

Signed-off-by: Eric Sandeen 
Signed-off-by: Josef Bacik