| Message ID | 3-v4-0de2f6c78ed0+9d1-iommufd_jgg@nvidia.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | IOMMUFD Generic interface | expand |
Hi Jason, On 11/8/22 01:48, Jason Gunthorpe wrote: > The span iterator travels over the indexes of the interval_tree, not the > nodes, and classifies spans of indexes as either 'used' or 'hole'. > > 'used' spans are fully covered by nodes in the tree and 'hole' spans have > no node intersecting the span. > > This is done greedily such that spans are maximally sized and every > iteration step switches between used/hole. > > As an example a trivial allocator can be written as: > > for (interval_tree_span_iter_first(&span, itree, 0, ULONG_MAX); > !interval_tree_span_iter_done(&span); > interval_tree_span_iter_next(&span)) > if (span.is_hole && > span.last_hole - span.start_hole >= allocation_size - 1) > return span.start_hole; > > With all the tricky boundary conditions handled by the library code. > > The following iommufd patches have several algorithms for its overlapping > node interval trees that are significantly simplified with this kind of > iteration primitive. As it seems generally useful, put it into lib/. > > Tested-by: Nicolin Chen <nicolinc@nvidia.com> > Reviewed-by: Kevin Tian <kevin.tian@intel.com> > Signed-off-by: Jason Gunthorpe <jgg@nvidia.com> > --- > .clang-format | 1 + > include/linux/interval_tree.h | 58 +++++++++++++++ > lib/Kconfig | 4 ++ > lib/interval_tree.c | 132 ++++++++++++++++++++++++++++++++++ > 4 files changed, 195 insertions(+) > > diff --git a/.clang-format b/.clang-format > index 1247d54f9e49fa..96d07786dcfb46 100644 > --- a/.clang-format > +++ b/.clang-format > @@ -440,6 +440,7 @@ ForEachMacros: > - 'inet_lhash2_for_each_icsk' > - 'inet_lhash2_for_each_icsk_continue' > - 'inet_lhash2_for_each_icsk_rcu' > + - 'interval_tree_for_each_span' > - 'intlist__for_each_entry' > - 'intlist__for_each_entry_safe' > - 'kcore_copy__for_each_phdr' > diff --git a/include/linux/interval_tree.h b/include/linux/interval_tree.h > index 288c26f50732d7..2b8026a3990645 100644 > --- a/include/linux/interval_tree.h > +++ b/include/linux/interval_tree.h > @@ -27,4 +27,62 @@ extern struct interval_tree_node * > interval_tree_iter_next(struct interval_tree_node *node, > unsigned long start, unsigned long last); > > +/** > + * struct interval_tree_span_iter - Find used and unused spans. > + * @start_hole: Start of an interval for a hole when is_hole == 1 > + * @last_hole: Inclusive end of an interval for a hole when is_hole == 1 > + * @start_used: Start of a used interval when is_hole == 0 > + * @last_used: Inclusive end of a used interval when is_hole == 0 > + * @is_hole: 0 == used, 1 == is_hole, -1 == done iteration > + * > + * This iterator travels over spans in an interval tree. It does not return > + * nodes but classifies each span as either a hole, where no nodes intersect, or > + * a used, which is fully covered by nodes. Each iteration step toggles between > + * hole and used until the entire range is covered. The returned spans always > + * fully cover the requested range. > + * > + * The iterator is greedy, it always returns the largest hole or used possible, > + * consolidating all consecutive nodes. > + * > + * Use interval_tree_span_iter_done() to detect end of iteration. > + */ > +struct interval_tree_span_iter { > + /* private: not for use by the caller */ > + struct interval_tree_node *nodes[2]; > + unsigned long first_index; > + unsigned long last_index; > + > + /* public: */ > + union { > + unsigned long start_hole; > + unsigned long start_used; > + }; > + union { > + unsigned long last_hole; > + unsigned long last_used; > + }; > + int is_hole; > +}; > + > +void interval_tree_span_iter_first(struct interval_tree_span_iter *state, > + struct rb_root_cached *itree, > + unsigned long first_index, > + unsigned long last_index); > +void interval_tree_span_iter_advance(struct interval_tree_span_iter *iter, > + struct rb_root_cached *itree, > + unsigned long new_index); > +void interval_tree_span_iter_next(struct interval_tree_span_iter *state); > + > +static inline bool > +interval_tree_span_iter_done(struct interval_tree_span_iter *state) > +{ > + return state->is_hole == -1; > +} > + > +#define interval_tree_for_each_span(span, itree, first_index, last_index) \ > + for (interval_tree_span_iter_first(span, itree, \ > + first_index, last_index); \ > + !interval_tree_span_iter_done(span); \ > + interval_tree_span_iter_next(span)) > + > #endif /* _LINUX_INTERVAL_TREE_H */ > diff --git a/lib/Kconfig b/lib/Kconfig > index 9bbf8a4b2108e6..c6c323fd251721 100644 > --- a/lib/Kconfig > +++ b/lib/Kconfig > @@ -479,6 +479,10 @@ config INTERVAL_TREE > > for more information. > > +config INTERVAL_TREE_SPAN_ITER > + bool > + depends on INTERVAL_TREE > + > config XARRAY_MULTI > bool > help > diff --git a/lib/interval_tree.c b/lib/interval_tree.c > index 593ce56ece5050..d2882db8fa2a07 100644 > --- a/lib/interval_tree.c > +++ b/lib/interval_tree.c > @@ -15,3 +15,135 @@ EXPORT_SYMBOL_GPL(interval_tree_insert); > EXPORT_SYMBOL_GPL(interval_tree_remove); > EXPORT_SYMBOL_GPL(interval_tree_iter_first); > EXPORT_SYMBOL_GPL(interval_tree_iter_next); > + > +#ifdef CONFIG_INTERVAL_TREE_SPAN_ITER Maybe add in a kernel doc that a prerequisite is state.nodes[1] must be populated > +static void > +interval_tree_span_iter_next_gap(struct interval_tree_span_iter *state) > +{ > + struct interval_tree_node *cur = state->nodes[1]; > + > + /* > + * Roll nodes[1] into nodes[0] by advancing nodes[1] to the end of a > + * contiguous span of nodes. This makes nodes[0]->last the end of that > + * contiguous span of valid indexes that started at the original I would suggest s/contiguous span/contiguous used span and remove "of valid indexes" > + * nodes[1]->start. nodes[1] is now the next node and a hole is between nodes[1] is now the first node starting the next used span. A hole span is between nodes[0]->last and nodes[1]->start > + * nodes[0] and [1]. > + */ > + state->nodes[0] = cur; > + do { > + if (cur->last > state->nodes[0]->last) > + state->nodes[0] = cur; > + cur = interval_tree_iter_next(cur, state->first_index, > + state->last_index); > + } while (cur && (state->nodes[0]->last >= cur->start || > + state->nodes[0]->last + 1 == cur->start)); > + state->nodes[1] = cur; > +} > + > +void interval_tree_span_iter_first(struct interval_tree_span_iter *iter, > + struct rb_root_cached *itree, > + unsigned long first_index, > + unsigned long last_index) > +{ > + iter->first_index = first_index; > + iter->last_index = last_index; > + iter->nodes[0] = NULL; > + iter->nodes[1] = > + interval_tree_iter_first(itree, first_index, last_index); > + if (!iter->nodes[1]) { > + /* No nodes intersect the span, whole span is hole */ > + iter->start_hole = first_index; > + iter->last_hole = last_index; > + iter->is_hole = 1; > + return; > + } > + if (iter->nodes[1]->start > first_index) { > + /* Leading hole on first iteration */ > + iter->start_hole = first_index; > + iter->last_hole = iter->nodes[1]->start - 1; > + iter->is_hole = 1; > + interval_tree_span_iter_next_gap(iter); > + return; > + } > + > + /* Starting inside a used */ > + iter->start_used = first_index; > + iter->is_hole = 0; > + interval_tree_span_iter_next_gap(iter); > + iter->last_used = iter->nodes[0]->last; > + if (iter->last_used >= last_index) { > + iter->last_used = last_index; > + iter->nodes[0] = NULL; > + iter->nodes[1] = NULL; > + } > +} > +EXPORT_SYMBOL_GPL(interval_tree_span_iter_first); > + > +void interval_tree_span_iter_next(struct interval_tree_span_iter *iter) > +{ > + if (!iter->nodes[0] && !iter->nodes[1]) { > + iter->is_hole = -1; > + return; > + } > + > + if (iter->is_hole) { > + iter->start_used = iter->last_hole + 1; > + iter->last_used = iter->nodes[0]->last; > + if (iter->last_used >= iter->last_index) { > + iter->last_used = iter->last_index; > + iter->nodes[0] = NULL; > + iter->nodes[1] = NULL; > + } > + iter->is_hole = 0; > + return; > + } > + > + if (!iter->nodes[1]) { > + /* Trailing hole */ > + iter->start_hole = iter->nodes[0]->last + 1; > + iter->last_hole = iter->last_index; > + iter->nodes[0] = NULL; > + iter->is_hole = 1; > + return; > + } > + > + /* must have both nodes[0] and [1], interior hole */ > + iter->start_hole = iter->nodes[0]->last + 1; > + iter->last_hole = iter->nodes[1]->start - 1; > + iter->is_hole = 1; > + interval_tree_span_iter_next_gap(iter); > +} > +EXPORT_SYMBOL_GPL(interval_tree_span_iter_next); > + > +/* > + * Advance the iterator index to a specific position. The returned used/hole is > + * updated to start at new_index. This is faster than calling > + * interval_tree_span_iter_first() as it can avoid full searches in several > + * cases where the iterator is already set. > + */ > +void interval_tree_span_iter_advance(struct interval_tree_span_iter *iter, > + struct rb_root_cached *itree, > + unsigned long new_index) > +{ > + if (iter->is_hole == -1) > + return; > + > + iter->first_index = new_index; check new_index > iter->first_index? > + if (new_index > iter->last_index) { > + iter->is_hole = -1; > + return; > + } > + > + /* Rely on the union aliasing hole/used */ > + if (iter->start_hole <= new_index && new_index <= iter->last_hole) { > + iter->start_hole = new_index; > + return; > + } > + if (new_index == iter->last_hole + 1) > + interval_tree_span_iter_next(iter); > + else > + interval_tree_span_iter_first(iter, itree, new_index, > + iter->last_index); > +} > +EXPORT_SYMBOL_GPL(interval_tree_span_iter_advance); > +#endif Besides, looks good to me Reviewed-by: Eric Auger <eric.auger@redhat.com> Eric
On Tue, Nov 15, 2022 at 03:14:00PM +0100, Eric Auger wrote: > > diff --git a/lib/interval_tree.c b/lib/interval_tree.c > > index 593ce56ece5050..d2882db8fa2a07 100644 > > --- a/lib/interval_tree.c > > +++ b/lib/interval_tree.c > > @@ -15,3 +15,135 @@ EXPORT_SYMBOL_GPL(interval_tree_insert); > > EXPORT_SYMBOL_GPL(interval_tree_remove); > > EXPORT_SYMBOL_GPL(interval_tree_iter_first); > > EXPORT_SYMBOL_GPL(interval_tree_iter_next); > > + > > +#ifdef CONFIG_INTERVAL_TREE_SPAN_ITER > Maybe add in a kernel doc that a prerequisite is state.nodes[1] must be > populated Sure, lets just move the below comment up a bit: /* * Roll nodes[1] into nodes[0] by advancing nodes[1] to the end of a contiguous * span of nodes. This makes nodes[0]->last the end of that contiguous used span * indexes that started at the original nodes[1]->start. nodes[1] is now the * first node starting the next used span. A hole span is between nodes[0]->last * and nodes[1]->start. nodes[1] must be !NULL. */ > > +/* > > + * Advance the iterator index to a specific position. The returned used/hole is > > + * updated to start at new_index. This is faster than calling > > + * interval_tree_span_iter_first() as it can avoid full searches in several > > + * cases where the iterator is already set. > > + */ > > +void interval_tree_span_iter_advance(struct interval_tree_span_iter *iter, > > + struct rb_root_cached *itree, > > + unsigned long new_index) > > +{ > > + if (iter->is_hole == -1) > > + return; > > + > > + iter->first_index = new_index; > check new_index > iter->first_index? It is odd but it actually works out OK if that is violated. I guess a WARN_ON would be appropriate but I've avoided adding assertions to this code.. > > + if (new_index > iter->last_index) { > > + iter->is_hole = -1; > > + return; > > + } > > + > > + /* Rely on the union aliasing hole/used */ > > + if (iter->start_hole <= new_index && new_index <= iter->last_hole) { > > + iter->start_hole = new_index; > > + return; > > + } > > + if (new_index == iter->last_hole + 1) > > + interval_tree_span_iter_next(iter); > > + else > > + interval_tree_span_iter_first(iter, itree, new_index, > > + iter->last_index); This call will reset iter->first_index to new_index and even if it is outside the original bounds everything will work. Of course if the caller does some 'backwards' advance then they are going to probably be very sad and likely hit an infinite loop, but that applies to all kinds of backwards advances, not just going before the original bounds. Thanks, Jason
diff --git a/.clang-format b/.clang-format index 1247d54f9e49fa..96d07786dcfb46 100644 --- a/.clang-format +++ b/.clang-format @@ -440,6 +440,7 @@ ForEachMacros: - 'inet_lhash2_for_each_icsk' - 'inet_lhash2_for_each_icsk_continue' - 'inet_lhash2_for_each_icsk_rcu' + - 'interval_tree_for_each_span' - 'intlist__for_each_entry' - 'intlist__for_each_entry_safe' - 'kcore_copy__for_each_phdr' diff --git a/include/linux/interval_tree.h b/include/linux/interval_tree.h index 288c26f50732d7..2b8026a3990645 100644 --- a/include/linux/interval_tree.h +++ b/include/linux/interval_tree.h @@ -27,4 +27,62 @@ extern struct interval_tree_node * interval_tree_iter_next(struct interval_tree_node *node, unsigned long start, unsigned long last); +/** + * struct interval_tree_span_iter - Find used and unused spans. + * @start_hole: Start of an interval for a hole when is_hole == 1 + * @last_hole: Inclusive end of an interval for a hole when is_hole == 1 + * @start_used: Start of a used interval when is_hole == 0 + * @last_used: Inclusive end of a used interval when is_hole == 0 + * @is_hole: 0 == used, 1 == is_hole, -1 == done iteration + * + * This iterator travels over spans in an interval tree. It does not return + * nodes but classifies each span as either a hole, where no nodes intersect, or + * a used, which is fully covered by nodes. Each iteration step toggles between + * hole and used until the entire range is covered. The returned spans always + * fully cover the requested range. + * + * The iterator is greedy, it always returns the largest hole or used possible, + * consolidating all consecutive nodes. + * + * Use interval_tree_span_iter_done() to detect end of iteration. + */ +struct interval_tree_span_iter { + /* private: not for use by the caller */ + struct interval_tree_node *nodes[2]; + unsigned long first_index; + unsigned long last_index; + + /* public: */ + union { + unsigned long start_hole; + unsigned long start_used; + }; + union { + unsigned long last_hole; + unsigned long last_used; + }; + int is_hole; +}; + +void interval_tree_span_iter_first(struct interval_tree_span_iter *state, + struct rb_root_cached *itree, + unsigned long first_index, + unsigned long last_index); +void interval_tree_span_iter_advance(struct interval_tree_span_iter *iter, + struct rb_root_cached *itree, + unsigned long new_index); +void interval_tree_span_iter_next(struct interval_tree_span_iter *state); + +static inline bool +interval_tree_span_iter_done(struct interval_tree_span_iter *state) +{ + return state->is_hole == -1; +} + +#define interval_tree_for_each_span(span, itree, first_index, last_index) \ + for (interval_tree_span_iter_first(span, itree, \ + first_index, last_index); \ + !interval_tree_span_iter_done(span); \ + interval_tree_span_iter_next(span)) + #endif /* _LINUX_INTERVAL_TREE_H */ diff --git a/lib/Kconfig b/lib/Kconfig index 9bbf8a4b2108e6..c6c323fd251721 100644 --- a/lib/Kconfig +++ b/lib/Kconfig @@ -479,6 +479,10 @@ config INTERVAL_TREE for more information. +config INTERVAL_TREE_SPAN_ITER + bool + depends on INTERVAL_TREE + config XARRAY_MULTI bool help diff --git a/lib/interval_tree.c b/lib/interval_tree.c index 593ce56ece5050..d2882db8fa2a07 100644 --- a/lib/interval_tree.c +++ b/lib/interval_tree.c @@ -15,3 +15,135 @@ EXPORT_SYMBOL_GPL(interval_tree_insert); EXPORT_SYMBOL_GPL(interval_tree_remove); EXPORT_SYMBOL_GPL(interval_tree_iter_first); EXPORT_SYMBOL_GPL(interval_tree_iter_next); + +#ifdef CONFIG_INTERVAL_TREE_SPAN_ITER +static void +interval_tree_span_iter_next_gap(struct interval_tree_span_iter *state) +{ + struct interval_tree_node *cur = state->nodes[1]; + + /* + * Roll nodes[1] into nodes[0] by advancing nodes[1] to the end of a + * contiguous span of nodes. This makes nodes[0]->last the end of that + * contiguous span of valid indexes that started at the original + * nodes[1]->start. nodes[1] is now the next node and a hole is between + * nodes[0] and [1]. + */ + state->nodes[0] = cur; + do { + if (cur->last > state->nodes[0]->last) + state->nodes[0] = cur; + cur = interval_tree_iter_next(cur, state->first_index, + state->last_index); + } while (cur && (state->nodes[0]->last >= cur->start || + state->nodes[0]->last + 1 == cur->start)); + state->nodes[1] = cur; +} + +void interval_tree_span_iter_first(struct interval_tree_span_iter *iter, + struct rb_root_cached *itree, + unsigned long first_index, + unsigned long last_index) +{ + iter->first_index = first_index; + iter->last_index = last_index; + iter->nodes[0] = NULL; + iter->nodes[1] = + interval_tree_iter_first(itree, first_index, last_index); + if (!iter->nodes[1]) { + /* No nodes intersect the span, whole span is hole */ + iter->start_hole = first_index; + iter->last_hole = last_index; + iter->is_hole = 1; + return; + } + if (iter->nodes[1]->start > first_index) { + /* Leading hole on first iteration */ + iter->start_hole = first_index; + iter->last_hole = iter->nodes[1]->start - 1; + iter->is_hole = 1; + interval_tree_span_iter_next_gap(iter); + return; + } + + /* Starting inside a used */ + iter->start_used = first_index; + iter->is_hole = 0; + interval_tree_span_iter_next_gap(iter); + iter->last_used = iter->nodes[0]->last; + if (iter->last_used >= last_index) { + iter->last_used = last_index; + iter->nodes[0] = NULL; + iter->nodes[1] = NULL; + } +} +EXPORT_SYMBOL_GPL(interval_tree_span_iter_first); + +void interval_tree_span_iter_next(struct interval_tree_span_iter *iter) +{ + if (!iter->nodes[0] && !iter->nodes[1]) { + iter->is_hole = -1; + return; + } + + if (iter->is_hole) { + iter->start_used = iter->last_hole + 1; + iter->last_used = iter->nodes[0]->last; + if (iter->last_used >= iter->last_index) { + iter->last_used = iter->last_index; + iter->nodes[0] = NULL; + iter->nodes[1] = NULL; + } + iter->is_hole = 0; + return; + } + + if (!iter->nodes[1]) { + /* Trailing hole */ + iter->start_hole = iter->nodes[0]->last + 1; + iter->last_hole = iter->last_index; + iter->nodes[0] = NULL; + iter->is_hole = 1; + return; + } + + /* must have both nodes[0] and [1], interior hole */ + iter->start_hole = iter->nodes[0]->last + 1; + iter->last_hole = iter->nodes[1]->start - 1; + iter->is_hole = 1; + interval_tree_span_iter_next_gap(iter); +} +EXPORT_SYMBOL_GPL(interval_tree_span_iter_next); + +/* + * Advance the iterator index to a specific position. The returned used/hole is + * updated to start at new_index. This is faster than calling + * interval_tree_span_iter_first() as it can avoid full searches in several + * cases where the iterator is already set. + */ +void interval_tree_span_iter_advance(struct interval_tree_span_iter *iter, + struct rb_root_cached *itree, + unsigned long new_index) +{ + if (iter->is_hole == -1) + return; + + iter->first_index = new_index; + if (new_index > iter->last_index) { + iter->is_hole = -1; + return; + } + + /* Rely on the union aliasing hole/used */ + if (iter->start_hole <= new_index && new_index <= iter->last_hole) { + iter->start_hole = new_index; + return; + } + if (new_index == iter->last_hole + 1) + interval_tree_span_iter_next(iter); + else + interval_tree_span_iter_first(iter, itree, new_index, + iter->last_index); +} +EXPORT_SYMBOL_GPL(interval_tree_span_iter_advance); +#endif