When we convert bch_btree_insert() to bch_btree_map_leaf_nodes(), we
won't be passing struct btree_op to bch_btree_insert() anymore - so we
need a different way of returning whether there was a collision (really,
a replace collision).
Signed-off-by: NKent Overstreet <kmo@daterainc.com>

This is prep work for converting bch_btree_insert to
bch_btree_map_leaf_nodes() - we have to convert all its arguments to
actual arguments. Bunch of churn, but should be straightforward.
Signed-off-by: NKent Overstreet <kmo@daterainc.com>

This isn't used for waiting asynchronously anymore - so this is a fairly
trivial refactoring.
Signed-off-by: NKent Overstreet <kmo@daterainc.com>

Eventual goal is for struct btree_op to contain only what is necessary
for traversing the btree.
Signed-off-by: NKent Overstreet <kmo@daterainc.com>

This is a fairly straightforward conversion, mostly reshuffling -
op->lookup_done goes away, replaced by MAP_DONE/MAP_CONTINUE. And the
code for handling cache hits and misses wasn't really btree code, so it
gets moved to request.c.
Signed-off-by: NKent Overstreet <kmo@daterainc.com>

Slowly working on pruning struct btree_op - the aim is for it to only
contain things that are actually necessary for traversing the btree.
Signed-off-by: NKent Overstreet <kmo@daterainc.com>

Making things less asynchronous that don't need to be - bch_journal()
only has to block when the journal or journal entry is full, which is
emphatically not a fast path. So make it a normal function that just
returns when it finishes, to make the code and control flow easier to
follow.
Signed-off-by: NKent Overstreet <kmo@daterainc.com>

The tracepoints were reworked to be more sensible, and fixed a null
pointer deref in one of the tracepoints.

Converted some of the pr_debug()s to tracepoints - this is partly a
performance optimization; it used to be that with DEBUG or
CONFIG_DYNAMIC_DEBUG pr_debug() was an empty macro; but at some point it
was changed to an empty inline function.

Some of the pr_debug() statements had rather expensive function calls as
part of the arguments, so this code was getting run unnecessarily even
on non debug kernels - in some fast paths, too.
Signed-off-by: NKent Overstreet <koverstreet@google.com>

Does writethrough and writeback caching, handles unclean shutdown, and
has a bunch of other nifty features motivated by real world usage.

See the wiki at http://bcache.evilpiepirate.org for more.
Signed-off-by: NKent Overstreet <koverstreet@google.com>