Implement set of pointers. Pointers can be added, deleted and
iterated. It's currently implemented as a thin rbtree wrapper making
addition and removal O(log N). A drawback is that iteration isn't RCU
safe, which is okay for now. This will be used to remove
inode->i_devices.
v2: In ptrset_add(), ptrset_find_slot() moved before new elem
allocation to avoid unnecessary alloc/free and -ENOMEM reporting
on -EEXIST cases. Suggested by Azat Khuzhin.
Signed-off-by: Tejun Heo <tj@xxxxxxxxxx>
Cc: Azat Khuzhin <a3at.mail@xxxxxxxxx>
---
include/linux/ptrset.h | 74 ++++++++++++++++++++++++++++
lib/Makefile | 2
lib/ptrset.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 204 insertions(+), 1 deletion(-)
--- /dev/null
+++ b/include/linux/ptrset.h
@@ -0,0 +1,74 @@
+/*
+ * include/linux/ptrset.h - set of pointers
+ *
+ * Copyright (C) 2014 Tejun Heo, Red Hat Inc.
+ *
+ * A ptrset contains an unordered set of pointers. Pointers can be added,
+ * deleted and iterated. Addition and removal complexities are O(log N)
+ * where N is the total number of elements in the ptrset.
+ */
+
+#ifndef __PTRSET_H
+#define __PTRSET_H
+
+#include <linux/preempt.h>
+#include <linux/rbtree.h>
+
+struct ptrset {
+ struct rb_root root;
+};
+
+struct ptrset_elem {
+ void *ptr;
+ struct rb_node node;
+};
+
+struct ptrset_iter {
+ struct ptrset_elem *pos;
+ struct ptrset_elem *next;
+};
+
+#define PTRSET_INITIALIZER { .root = RB_ROOT, }
+#define DEFINE_PTRSET(set) struct ptrset set = PTRSET_INITIALIZER
+
+static inline void ptrset_init(struct ptrset *set)
+{
+ *set = (struct ptrset)PTRSET_INITIALIZER;
+}
+
+void ptrset_preload(gfp_t gfp);
+int __must_check ptrset_add(void *ptr, struct ptrset *set, gfp_t gfp);
+int ptrset_del(void *ptr, struct ptrset *set);
+
+/**
+ * ptrset_preload_end - end preload section started with ptrset_preload()
+ *
+ * Each ptrset_preload() should be matched with an invocation of this
+ * function. See ptrset_preload() for details.
+ */
+static inline void ptrset_preload_end(void)
+{
+ preempt_enable();
+}
+
+/**
+ * ptrset_for_each - iterate pointers in a ptrset
+ * @ptr_cur: the cursor pointer variable (can be a pointer to any type)
+ * @set: the target ptrset
+ * @iter: pointer to struct ptrset_iter used to store iteration state
+ *
+ * Iterate @ptr_cur over all pointers in @set using @iter as the temp
+ * storage. The order of iteration is undefined and the iterated pointers
+ * may be deleted during iteration.
+ *
+ * The caller is responsible for synchronization. This is not RCU safe.
+ */
+#define ptrset_for_each(ptr_cur, set, iter) \
+ rbtree_postorder_for_each_entry_safe((iter)->pos, (iter)->next, \
+ &(set)->root, node) \
+ if (({ (ptr_cur) = (iter)->pos->ptr; \
+ false; })) \
+ ; \
+ else
+
+#endif /* __PTRSET_H */
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -8,7 +8,7 @@ KBUILD_CFLAGS = $(subst -pg,,$(ORIG_CFLA
endif
lib-y := ctype.o string.o vsprintf.o cmdline.o \
- rbtree.o radix-tree.o dump_stack.o timerqueue.o\
+ rbtree.o radix-tree.o dump_stack.o timerqueue.o ptrset.o \
idr.o int_sqrt.o extable.o \
sha1.o md5.o irq_regs.o argv_split.o \
proportions.o flex_proportions.o ratelimit.o show_mem.o \
--- /dev/null
+++ b/lib/ptrset.c
@@ -0,0 +1,129 @@
+/*
+ * lib/ptrset.c - set of pointers
+ *
+ * Copyright (C) 2014 Tejun Heo, Red Hat Inc.
+ */
+
+#include <linux/ptrset.h>
+#include <linux/slab.h>
+#include <linux/percpu.h>
+
+static DEFINE_PER_CPU(struct ptrset_elem *, ptrset_preload_elem);
+
+/**
+ * ptrset_preload - preload for ptrset_add()
+ * @gfp: allocation mask to use for preloading
+ *
+ * Preload per-cpu ptrset_elem buffer for ptrset_add(). Can only be used
+ * from process context and each ptrset_preload() invocation should be
+ * matched with ptrset_preload_end(). Note that preemption is disabled
+ * while preloaded.
+ *
+ * The first ptrset_add() in the preloaded section can be treated as if it
+ * were invoked with @gfp used for preloading. This allows using more
+ * permissive allocation masks for ptrsets protected by spinlocks.
+ */
+void ptrset_preload(gfp_t gfp)
+{
+ /*
+ * Consuming preload buffer from non-process context breaks preload
+ * allocation guarantee. Disallow usage from those contexts.
+ */
+ WARN_ON_ONCE(in_interrupt());
+ might_sleep_if(gfp & __GFP_WAIT);
+
+ preempt_disable();
+
+ if (!__this_cpu_read(ptrset_preload_elem)) {
+ struct ptrset_elem *new;
+
+ preempt_enable();
+ new = kmalloc(sizeof(*new), gfp);
+ preempt_disable();
+
+ new = __this_cpu_xchg(ptrset_preload_elem, new);
+ kfree(new);
+ }
+}
+
+static __always_inline bool ptrset_find_slot(void *ptr, struct ptrset *set,
+ struct rb_node ***slotp,
+ struct rb_node **parentp)
+{
+ struct rb_node **slot = &set->root.rb_node, *parent = NULL;
+
+ while (*slot) {
+ struct ptrset_elem *elem =
+ container_of(*slot, struct ptrset_elem, node);
+
+ parent = *slot;
+ if (ptr < elem->ptr) {
+ slot = &(*slot)->rb_left;
+ } else if (ptr > elem->ptr) {
+ slot = &(*slot)->rb_right;
+ } else {
+ *slotp = slot;
+ return true;
+ }
+ }
+
+ *slotp = slot;
+ if (parentp)
+ *parentp = parent;
+ return false;
+}
+
+/**
+ * ptrset_add - add a pointer to a ptrset
+ * @ptr: the pointer to add
+ * @set: the target ptrset
+ * @gfp: the allocation mask to use
+ *
+ * Allocate a ptrset_elem using @gfp, init with @ptr and add to @set.
+ * Returns 0 on success, -ENOMEM if allocation failed and -EEXIST if @ptr
+ * already exists in @set.
+ *
+ * The caller is responsible for synchronization.
+ */
+int ptrset_add(void *ptr, struct ptrset *set, gfp_t gfp)
+{
+ struct ptrset_elem *elem;
+ struct rb_node *parent, **slot;
+
+ if (ptrset_find_slot(ptr, set, &slot, &parent))
+ return -EEXIST;
+
+ elem = kmalloc(sizeof(*elem), gfp);
+ if (!elem && !in_interrupt()) /* see ptrset_preload() */
+ elem = this_cpu_xchg(ptrset_preload_elem, NULL);
+ if (!elem)
+ return -ENOMEM;
+ elem->ptr = ptr;
+
+ rb_link_node(&elem->node, parent, slot);
+ rb_insert_color(&elem->node, &set->root);
+ return 0;
+}
+
+/**
+ * ptrset_del - delete a pointer from a ptrset
+ * @ptr: the pointer to delete
+ * @set: the target ptrset
+ *
+ * Delete @ptr from @set. Returns 0 on success, -ENOENT if @ptr is not in
+ * @set.
+ *
+ * The caller is responsible for synchronization.
+ */
+int ptrset_del(void *ptr, struct ptrset *set)
+{
+ struct rb_node **slot, *node;
+
+ if (!ptrset_find_slot(ptr, set, &slot, NULL))
+ return -ENOENT;
+
+ node = *slot;
+ rb_erase(node, &set->root);
+ kfree(container_of(node, struct ptrset_elem, node));
+ return 0;
+}
--
To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
