From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
This first function in the XArray API brings with it a lot of support
infrastructure. The advanced API is based around the xa_state which is
a more capable version of the radix_tree_iter.
As the test-suite demonstrates, it is possible to use the xarray and
radix tree APIs on the same data structure.
Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx>
---
include/linux/xarray.h | 235 ++++++++++++++++++++++++++++
lib/radix-tree.c | 43 -----
lib/xarray.c | 160 +++++++++++++++++++
tools/testing/radix-tree/.gitignore | 1 +
tools/testing/radix-tree/Makefile | 7 +-
tools/testing/radix-tree/linux/radix-tree.h | 1 -
tools/testing/radix-tree/linux/rcupdate.h | 1 +
tools/testing/radix-tree/linux/xarray.h | 1 +
tools/testing/radix-tree/xarray-test.c | 56 +++++++
9 files changed, 459 insertions(+), 46 deletions(-)
create mode 100644 tools/testing/radix-tree/xarray-test.c
diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 1aff0069458b..af52ba75e6a3 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -21,6 +21,8 @@
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/kconfig.h>
+#include <linux/kernel.h>
+#include <linux/rcupdate.h>
#include <linux/spinlock.h>
#include <linux/types.h>
@@ -67,6 +69,8 @@ static inline void xa_init(struct xarray *xa)
__xa_init(xa, 0);
}
+void *xa_load(struct xarray *, unsigned long index);
+
#define BITS_PER_XA_VALUE (BITS_PER_LONG - 1)
/**
@@ -158,6 +162,46 @@ struct xa_node {
unsigned long tags[XA_MAX_TAGS][XA_TAG_LONGS];
};
+#ifdef XA_DEBUG
+void xa_dump(const struct xarray *);
+void xa_dump_node(const struct xa_node *);
+#define XA_BUG_ON(node, x) do { \
+ if ((x) && (node)) \
+ xa_dump_node(node); \
+ BUG_ON(x); \
+ } while (0)
+#else
+#define XA_BUG_ON(node, x) do { } while (0)
+#endif
+
+/* Private */
+static inline void *xa_head(struct xarray *xa)
+{
+ return rcu_dereference_check(xa->xa_head, xa_lock_held(xa));
+}
+
+/* Private */
+static inline void *xa_head_locked(struct xarray *xa)
+{
+ return rcu_dereference_protected(xa->xa_head, xa_lock_held(xa));
+}
+
+/* Private */
+static inline void *xa_entry(struct xarray *xa,
+ const struct xa_node *node, unsigned int offset)
+{
+ XA_BUG_ON(node, offset >= XA_CHUNK_SIZE);
+ return rcu_dereference_check(node->slots[offset], xa_lock_held(xa));
+}
+
+/* Private */
+static inline void *xa_entry_locked(struct xarray *xa,
+ const struct xa_node *node, unsigned int offset)
+{
+ XA_BUG_ON(node, offset >= XA_CHUNK_SIZE);
+ return rcu_dereference_protected(node->slots[offset], xa_lock_held(xa));
+}
+
/*
* Internal entries have the bottom two bits set to the value 10b. Most
* internal entries are pointers to the next node in the tree. Since the
@@ -189,6 +233,12 @@ static inline bool xa_is_internal(void *entry)
return ((unsigned long)entry & 3) == 2;
}
+/* Private */
+static inline struct xa_node *xa_to_node(void *entry)
+{
+ return (struct xa_node *)((unsigned long)entry & ~3UL);
+}
+
/* Private */
static inline bool xa_is_node(void *entry)
{
@@ -222,4 +272,189 @@ static inline bool xa_is_sibling(void *entry)
#define XA_RETRY_ENTRY xa_mk_internal(256)
+/**
+ * xa_is_retry() - Is the entry a retry entry?
+ * @entry: Entry retrieved from the XArray
+ *
+ * Return: %true if the entry is a retry entry.
+ */
+static inline bool xa_is_retry(void *entry)
+{
+ return unlikely(entry == XA_RETRY_ENTRY);
+}
+
+/**
+ * typedef xa_update_node_t - A callback function from the XArray.
+ * @node: The node which is being processed
+ *
+ * This function is called every time the XArray updates the count of
+ * present and value entries in a node. It allows advanced users to
+ * maintain the private_list in the node.
+ */
+typedef void (*xa_update_node_t)(struct xa_node *node);
+
+/*
+ * The xa_state is opaque to its users. It contains various different pieces
+ * of state involved in the current operation on the XArray. It should be
+ * declared on the stack and passed between the various internal routines.
+ * The various elements in it should not be accessed directly, but only
+ * through the provided accessor functions. The below documentation is for
+ * the benefit of those working on the code, not for users of the XArray.
+ *
+ * @xa_node usually points to the xa_node containing the slot we're operating
+ * on (and @xa_offset is the offset in the slots array). If there is a
+ * single entry in the array at index 0, there are no allocated xa_nodes to
+ * point to, and so we store %NULL in @xa_node. @xa_node is set to
+ * the value %XAS_RESTART if the xa_state is not walked to the correct
+ * position in the tree of nodes for this operation. If an error occurs
+ * during an operation, it is set to an %XAS_ERROR value. If we run off the
+ * end of the allocated nodes, it is set to %XAS_BOUNDS.
+ */
+struct xa_state {
+ struct xarray *xa;
+ unsigned long xa_index;
+ unsigned char xa_shift;
+ unsigned char xa_sibs;
+ unsigned char xa_offset;
+ unsigned char xa_pad; /* Helps gcc generate better code */
+ struct xa_node *xa_node;
+ struct xa_node *xa_alloc;
+ xa_update_node_t xa_update;
+};
+
+/*
+ * We encode errnos in the xas->xa_node. If an error has happened, we need to
+ * drop the lock to fix it, and once we've done so the xa_state is invalid.
+ */
+#define XAS_ERROR(errno) ((struct xa_node *)(((unsigned long)errno << 1) | 1))
+#define XAS_RESTART XAS_ERROR(0)
+#define XAS_BOUNDS ((struct xa_node *)2UL)
+
+#define __XA_STATE(array, index) { \
+ .xa = array, \
+ .xa_index = index, \
+ .xa_shift = 0, \
+ .xa_sibs = 0, \
+ .xa_offset = 0, \
+ .xa_pad = 0, \
+ .xa_node = XAS_RESTART, \
+ .xa_alloc = NULL, \
+ .xa_update = NULL \
+}
+
+/**
+ * XA_STATE() - Declare an XArray operation state.
+ * @name: Name of this operation state (usually xas).
+ * @index: Initial index of interest.
+ *
+ * Declare and initialise an xa_state on the stack.
+ */
+#define XA_STATE(name, array, index) \
+ struct xa_state name = __XA_STATE(array, index)
+
+#define xas_tagged(xas, tag) xa_tagged((xas)->xa, (tag))
+#define xas_trylock(xas) xa_trylock((xas)->xa)
+#define xas_lock(xas) xa_lock((xas)->xa)
+#define xas_unlock(xas) xa_unlock((xas)->xa)
+#define xas_lock_bh(xas) xa_lock_bh((xas)->xa)
+#define xas_unlock_bh(xas) xa_unlock_bh((xas)->xa)
+#define xas_lock_irq(xas) xa_lock_irq((xas)->xa)
+#define xas_unlock_irq(xas) xa_unlock_irq((xas)->xa)
+#define xas_lock_irqsave(xas, flags) \
+ xa_lock_irqsave((xas)->xa, flags)
+#define xas_unlock_irqrestore(xas, flags) \
+ xa_unlock_irqrestore((xas)->xa, flags)
+
+/**
+ * xas_error() - Return an errno stored in the xa_state.
+ * @xas: XArray operation state.
+ *
+ * Return: 0 if no error has been noted. A negative errno if one has.
+ */
+static inline int xas_error(const struct xa_state *xas)
+{
+ unsigned long v = (unsigned long)xas->xa_node;
+ return (v & 1) ? -(v >> 1) : 0;
+}
+
+/**
+ * xas_set_err() - Note an error in the xa_state.
+ * @xas: XArray operation state.
+ * @err: Negative error number.
+ *
+ * You can call this function with @err set to 0 to take the xa_state
+ * out of the error state. The next operation will walk it to the correct
+ * location.
+ */
+static inline void xas_set_err(struct xa_state *xas, long err)
+{
+ xas->xa_node = XAS_ERROR(-err);
+}
+
+/**
+ * xas_invalid() - Is the xas in a retry or error state?
+ * @xas: XArray operation state.
+ *
+ * Return: %true if the xas cannot be used for operations.
+ */
+static inline bool xas_invalid(const struct xa_state *xas)
+{
+ return (unsigned long)xas->xa_node & 3;
+}
+
+/**
+ * xas_valid() - Is the xas a valid cursor into the array?
+ * @xas: XArray operation state.
+ *
+ * Return: %true if the xas can be used for operations.
+ */
+static inline bool xas_valid(const struct xa_state *xas)
+{
+ return !xas_invalid(xas);
+}
+
+/**
+ * xas_retry() - Handle a retry entry.
+ * @xas: XArray operation state.
+ * @entry: Entry from xarray.
+ *
+ * An RCU-protected read may see a retry entry as a side-effect of a
+ * simultaneous modification. This function sets up the @xas to retry
+ * the walk from the head of the array.
+ *
+ * Return: true if the operation needs to be retried.
+ */
+static inline bool xas_retry(struct xa_state *xas, void *entry)
+{
+ if (!xa_is_retry(entry))
+ return false;
+ xas->xa_node = XAS_RESTART;
+ return true;
+}
+
+void *xas_load(struct xa_state *);
+
+/**
+ * xas_reload() - Refetch an entry from the xarray.
+ * @xas: XArray operation state.
+ *
+ * Use this function to check that a previously loaded entry still has
+ * the same value. This is useful for the lockless pagecache lookup where
+ * we walk the array with only the RCU lock to protect us, lock the page,
+ * then check that the page hasn't moved since we looked it up.
+ *
+ * The caller guarantees that @xas is still valid. If it may be in an
+ * error or restart state, call xas_load() instead.
+ *
+ * Return: The entry at this location in the xarray.
+ */
+static inline void *xas_reload(struct xa_state *xas)
+{
+ struct xa_node *node = xas->xa_node;
+
+ if (node)
+ return xa_entry(xas->xa, node, xas->xa_offset);
+ return xa_head(xas->xa);
+}
+
#endif /* _LINUX_XARRAY_H */
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 930eb7d298d7..a919c60b10a4 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -255,49 +255,6 @@ static unsigned long next_index(unsigned long index,
}
#ifndef __KERNEL__
-static void dump_node(struct radix_tree_node *node, unsigned long index)
-{
- unsigned long i;
-
- pr_debug("radix node: %p offset %d indices %lu-%lu parent %p tags %lx %lx %lx shift %d count %d exceptional %d\n",
- node, node->offset, index, index | node_maxindex(node),
- node->parent,
- node->tags[0][0], node->tags[1][0], node->tags[2][0],
- node->shift, node->count, node->exceptional);
-
- for (i = 0; i < RADIX_TREE_MAP_SIZE; i++) {
- unsigned long first = index | (i << node->shift);
- unsigned long last = first | ((1UL << node->shift) - 1);
- void *entry = node->slots[i];
- if (!entry)
- continue;
- if (entry == RADIX_TREE_RETRY) {
- pr_debug("radix retry offset %ld indices %lu-%lu parent %p\n",
- i, first, last, node);
- } else if (!radix_tree_is_internal_node(entry)) {
- pr_debug("radix entry %p offset %ld indices %lu-%lu parent %p\n",
- entry, i, first, last, node);
- } else if (xa_is_sibling(entry)) {
- pr_debug("radix sblng %p offset %ld indices %lu-%lu parent %p val %p\n",
- entry, i, first, last, node,
- node->slots[xa_to_sibling(entry)]);
- } else {
- dump_node(entry_to_node(entry), first);
- }
- }
-}
-
-/* For debug */
-static void radix_tree_dump(struct radix_tree_root *root)
-{
- pr_debug("radix root: %p xa_head %p tags %x\n",
- root, root->xa_head,
- root->xa_flags >> ROOT_TAG_SHIFT);
- if (!radix_tree_is_internal_node(root->xa_head))
- return;
- dump_node(entry_to_node(root->xa_head), 0);
-}
-
static void dump_ida_node(void *entry, unsigned long index)
{
unsigned long i;
diff --git a/lib/xarray.c b/lib/xarray.c
index 67ddcb3e630c..2f77e4c5d0b8 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -31,6 +31,94 @@
* @entry refers to something stored in a slot in the xarray
*/
+/* extracts the offset within this node from the index */
+static unsigned int get_offset(unsigned long index, struct xa_node *node)
+{
+ return (index >> node->shift) & XA_CHUNK_MASK;
+}
+
+static void *set_bounds(struct xa_state *xas)
+{
+ xas->xa_node = XAS_BOUNDS;
+ return NULL;
+}
+
+/*
+ * Starts a walk. If the @xas is already valid, we assume that it's on
+ * the right path and just return where we've got to. If we're in an
+ * error state, return NULL. If the index is outside the current scope
+ * of the xarray, return NULL without changing @xas->xa_node. Otherwise
+ * set @xas->xa_node to NULL and return the current head of the array.
+ */
+static void *xas_start(struct xa_state *xas)
+{
+ void *entry;
+
+ if (xas_valid(xas))
+ return xas_reload(xas);
+ if (xas_error(xas))
+ return NULL;
+
+ entry = xa_head(xas->xa);
+ if (!xa_is_node(entry)) {
+ if (xas->xa_index)
+ return set_bounds(xas);
+ } else {
+ if ((xas->xa_index >> xa_to_node(entry)->shift) > XA_CHUNK_MASK)
+ return set_bounds(xas);
+ }
+
+ xas->xa_node = NULL;
+ return entry;
+}
+
+static void *xas_descend(struct xa_state *xas, struct xa_node *node)
+{
+ unsigned int offset = get_offset(xas->xa_index, node);
+ void *entry = xa_entry(xas->xa, node, offset);
+
+ if (xa_is_sibling(entry)) {
+ offset = xa_to_sibling(entry);
+ entry = xa_entry(xas->xa, node, offset);
+ /* Move xa_index to the first index of this entry */
+ xas->xa_index = (((xas->xa_index >> node->shift) &
+ ~XA_CHUNK_MASK) | offset) << node->shift;
+ }
+
+ xas->xa_node = node;
+ xas->xa_offset = offset;
+ return entry;
+}
+
+/**
+ * xas_load() - Load an entry from the XArray (advanced).
+ * @xas: XArray operation state.
+ *
+ * Usually walks the @xas to the appropriate state to load the entry stored
+ * at xa_index. However, it will do nothing and return NULL if @xas is
+ * holding an error. If the xa_shift indicates we're operating on a
+ * multislot entry, it will terminate early and potentially return an
+ * internal entry. xas_load() will never expand the tree (see xas_create()).
+ *
+ * The caller should hold the xa_lock or the RCU lock.
+ *
+ * Return: Usually an entry in the XArray, but see description for exceptions.
+ */
+void *xas_load(struct xa_state *xas)
+{
+ void *entry = xas_start(xas);
+
+ while (xa_is_node(entry)) {
+ struct xa_node *node = xa_to_node(entry);
+
+ if (xas->xa_shift > node->shift)
+ break;
+ entry = xas_descend(xas, node);
+ }
+ return entry;
+}
+EXPORT_SYMBOL_GPL(xas_load);
+
/**
* __xa_init() - Initialise an empty XArray.
* @xa: XArray.
@@ -45,3 +133,75 @@ void __xa_init(struct xarray *xa, gfp_t flags)
xa->xa_head = NULL;
}
EXPORT_SYMBOL(__xa_init);
+
+/**
+ * xa_load() - Load an entry from an XArray.
+ * @xa: XArray.
+ * @index: index into array.
+ *
+ * Return: The entry at @index in @xa.
+ */
+void *xa_load(struct xarray *xa, unsigned long index)
+{
+ XA_STATE(xas, xa, index);
+ void *entry;
+
+ rcu_read_lock();
+ do {
+ entry = xas_load(&xas);
+ } while (xas_retry(&xas, entry));
+ rcu_read_unlock();
+
+ return entry;
+}
+EXPORT_SYMBOL(xa_load);
+
+#ifdef XA_DEBUG
+void xa_dump_entry(void *entry, unsigned long index)
+{
+ if (!entry)
+ return;
+
+ if (xa_is_value(entry))
+ printk("%lu: value %#lx\n", index, xa_to_value(entry));
+ else if (!xa_is_internal(entry))
+ printk("%lu: %p\n", index, entry);
+ else if (xa_is_node(entry)) {
+ unsigned long i;
+ struct xa_node *node = xa_to_node(entry);
+ printk("node %p %s %d parent %p shift %d count %d "
+ "exceptional %d tags %lx %lx %lx indices %lu-%lu\n",
+ node, node->parent ? "offset" : "max", node->offset,
+ node->parent, node->shift, node->count,
+ node->exceptional,
+ node->tags[0][0], node->tags[1][0], node->tags[2][0],
+ index, index |
+ (((unsigned long)XA_CHUNK_SIZE << node->shift) - 1));
+ for (i = 0; i < XA_CHUNK_SIZE; i++)
+ xa_dump_entry(node->slots[i],
+ index + (i << node->shift));
+ } else if (xa_is_retry(entry))
+ printk("%lu: retry (%ld)\n", index, xa_to_internal(entry));
+ else if (xa_is_sibling(entry))
+ printk("%lu: sibling (%ld)\n", index, xa_to_sibling(entry));
+ else
+ printk("%lu: UNKNOWN ENTRY (%p)\n", index, entry);
+}
+
+void xa_dump_node(const struct xa_node *node)
+{
+ printk("xadn: node %p %s %d parent %p shift %d count %d "
+ "exceptional %d array %p list %p %p tags %lx %lx %lx\n",
+ node, node->parent ? "offset" : "max", node->offset,
+ node->parent, node->shift, node->count,
+ node->exceptional, node->root, node->private_list.prev,
+ node->private_list.next,
+ node->tags[0][0], node->tags[1][0], node->tags[2][0]);
+}
+
+void xa_dump(const struct xarray *xa)
+{
+ printk("xarray: %p %x %p\n", xa, xa->xa_flags, xa->xa_head);
+ xa_dump_entry(xa->xa_head, 0);
+}
+#endif
diff --git a/tools/testing/radix-tree/.gitignore b/tools/testing/radix-tree/.gitignore
index 8d4df7a72a8e..833136896b91 100644
--- a/tools/testing/radix-tree/.gitignore
+++ b/tools/testing/radix-tree/.gitignore
@@ -5,3 +5,4 @@ main
multiorder
radix-tree.c
xarray.c
+xarray-test
diff --git a/tools/testing/radix-tree/Makefile b/tools/testing/radix-tree/Makefile
index 3868bc189199..749ef734a87c 100644
--- a/tools/testing/radix-tree/Makefile
+++ b/tools/testing/radix-tree/Makefile
@@ -3,10 +3,11 @@
CFLAGS += -I. -I../../include -g -O2 -Wall -D_LGPL_SOURCE -fsanitize=address
LDFLAGS += -fsanitize=address
LDLIBS+= -lpthread -lurcu
-TARGETS = main idr-test multiorder
+TARGETS = main idr-test multiorder xarray-test
CORE_OFILES := xarray.o radix-tree.o idr.o linux.o test.o find_bit.o
OFILES = main.o $(CORE_OFILES) regression1.o regression2.o regression3.o \
- tag_check.o multiorder.o idr-test.o iteration_check.o benchmark.o
+ tag_check.o multiorder.o idr-test.o iteration_check.o benchmark.o \
+ xarray-test.o
ifndef SHIFT
SHIFT=3
@@ -23,6 +24,8 @@ main: $(OFILES)
idr-test: idr-test.o $(CORE_OFILES)
+xarray-test: idr-test.o $(CORE_OFILES)
+
multiorder: multiorder.o $(CORE_OFILES)
clean:
diff --git a/tools/testing/radix-tree/linux/radix-tree.h b/tools/testing/radix-tree/linux/radix-tree.h
index 40c9671ee365..36fb716d5557 100644
--- a/tools/testing/radix-tree/linux/radix-tree.h
+++ b/tools/testing/radix-tree/linux/radix-tree.h
@@ -5,7 +5,6 @@
#include "generated/map-shift.h"
#include "linux/bug.h"
#include "../../../../include/linux/radix-tree.h"
-#include <linux/xarray.h>
extern int kmalloc_verbose;
extern int test_verbose;
diff --git a/tools/testing/radix-tree/linux/rcupdate.h b/tools/testing/radix-tree/linux/rcupdate.h
index 73ed33658203..25010bf86c1d 100644
--- a/tools/testing/radix-tree/linux/rcupdate.h
+++ b/tools/testing/radix-tree/linux/rcupdate.h
@@ -6,5 +6,6 @@
#define rcu_dereference_raw(p) rcu_dereference(p)
#define rcu_dereference_protected(p, cond) rcu_dereference(p)
+#define rcu_dereference_check(p, cond) rcu_dereference(p)
#endif
diff --git a/tools/testing/radix-tree/linux/xarray.h b/tools/testing/radix-tree/linux/xarray.h
index df3812cda376..3eaf9596c2a6 100644
--- a/tools/testing/radix-tree/linux/xarray.h
+++ b/tools/testing/radix-tree/linux/xarray.h
@@ -1,2 +1,3 @@
#include "generated/map-shift.h"
+#define XA_DEBUG
#include "../../../../include/linux/xarray.h"
diff --git a/tools/testing/radix-tree/xarray-test.c b/tools/testing/radix-tree/xarray-test.c
new file mode 100644
index 000000000000..3f8f19cb3739
--- /dev/null
+++ b/tools/testing/radix-tree/xarray-test.c
@@ -0,0 +1,56 @@
+/*
+ * xarray-test.c: Test the XArray API
+ * Copyright (c) 2017 Microsoft Corporation <mawilcox@xxxxxxxxxxxxx>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms and conditions of the GNU General Public License,
+ * version 2, as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
+ * more details.
+ */
+#include <linux/bitmap.h>
+#include <linux/xarray.h>
+#include <linux/slab.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+
+#include "test.h"
+
+void check_xa_load(struct xarray *xa)
+{
+ unsigned long i, j;
+
+ for (i = 0; i < 1024; i++) {
+ for (j = 0; j < 1024; j++) {
+ void *entry = xa_load(xa, j);
+ if (j < i)
+ assert(xa_to_value(entry) == j);
+ else
+ assert(!entry);
+ }
+ radix_tree_insert(xa, i, xa_mk_value(i));
+ }
+}
+
+void xarray_checks(void)
+{
+ RADIX_TREE(array, GFP_KERNEL);
+
+ check_xa_load(&array);
+
+ item_kill_tree(&array);
+}
+
+int __weak main(void)
+{
+ radix_tree_init();
+ xarray_checks();
+ radix_tree_cpu_dead(1);
+ rcu_barrier();
+ if (nr_allocated)
+ printf("nr_allocated = %d\n", nr_allocated);
+ return 0;
+}
--
2.15.0
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