[PATCH 21/62] xarray: Add xa_get_tag, xa_set_tag and xa_clear_tag

Matthew Wilcox
2017-11-22T21:22:24Z

XArray tags are slightly more strongly typed than the radix tree tags,
but occupy the same bits. This commit also adds the xas_ family of tag
operations, for cases where the caller is already holding the lock, and
xa_tagged() to ask whether any array member has a particular tag set.

Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
---
include/linux/xarray.h | 38 +++++++-
lib/radix-tree.c | 52 +++++-----
lib/xarray.c | 250 +++++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 313 insertions(+), 27 deletions(-)

diff --git a/include/linux/xarray.h b/include/linux/xarray.h
index 0e736d2db049..ab6b1f5e685a 100644
--- a/include/linux/xarray.h
+++ b/include/linux/xarray.h
@@ -48,6 +48,7 @@

#include <linux/bug.h>
#include <linux/compiler.h>
+#include <linux/gfp.h>
#include <linux/kernel.h>
#include <linux/rcupdate.h>
#include <linux/spinlock.h>
@@ -82,6 +83,33 @@ struct xarray {

void *xa_load(struct xarray *, unsigned long index);

+typedef unsigned __bitwise xa_tag_t;
+#define XA_TAG_0 ((__force xa_tag_t)0U)
+#define XA_TAG_1 ((__force xa_tag_t)1U)
+#define XA_TAG_2 ((__force xa_tag_t)2U)
+#define XA_NO_TAG ((__force xa_tag_t)4U)
+
+#define XA_TAG_MAX XA_TAG_2
+#define XA_FREE_TAG XA_TAG_0
+#define XA_FLAGS_TAG(tag) ((__force gfp_t)((2U << __GFP_BITS_SHIFT) << \
+ (__force unsigned)(tag)))
+
+/**
+ * xa_tagged() - Inquire whether any entry in this array has a tag set
+ * @xa: Array
+ * @tag: Tag value
+ *
+ * Return: True if any entry has this tag set, false if no entry does.
+ */
+static inline bool xa_tagged(const struct xarray *xa, xa_tag_t tag)
+{
+ return xa->xa_flags & XA_FLAGS_TAG(tag);
+}
+
+bool xa_get_tag(struct xarray *, unsigned long index, xa_tag_t);
+void *xa_set_tag(struct xarray *, unsigned long index, xa_tag_t);
+void *xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t);
+
#define BITS_PER_XA_VALUE (BITS_PER_LONG - 1)

/**
@@ -133,6 +161,10 @@ static inline bool xa_is_value(void *entry)
spin_unlock_irqrestore(&(xa)->xa_lock, flags)
#define xa_lock_held(xa) lockdep_is_held(&(xa)->xa_lock)

+/* Versions of the normal API which require the caller to hold the xa_lock */
+void *__xa_set_tag(struct xarray *, unsigned long index, xa_tag_t);
+void *__xa_clear_tag(struct xarray *, unsigned long index, xa_tag_t);
+
#ifdef XA_DEBUG
void xa_dump(const struct xarray *);
void xa_dump_node(const struct xa_node *);
@@ -175,7 +207,7 @@ struct xa_node {
unsigned char offset; /* Slot offset in parent */
unsigned char count; /* Total entry count */
unsigned char exceptional; /* Exceptional entry count */
- struct xa_node *parent; /* Used when ascending tree */
+ struct xa_node __rcu *parent; /* Used when ascending tree */
struct xarray * root; /* The tree we belong to */
union {
struct list_head private_list; /* For tree user */
@@ -355,6 +387,10 @@ static inline bool xas_retry(struct xa_state *xas, void *entry)

void *xas_load(struct xarray *, struct xa_state *);

+bool xas_get_tag(const struct xarray *, const struct xa_state *, xa_tag_t);
+void xas_set_tag(struct xarray *, const struct xa_state *, xa_tag_t);
+void xas_clear_tag(struct xarray *, const struct xa_state *, xa_tag_t);
+
/**
* xas_reload() - Refetch an entry from the xarray.
* @xa: XArray.
diff --git a/lib/radix-tree.c b/lib/radix-tree.c
index 930eb7d298d7..711a6d9b79fc 100644
--- a/lib/radix-tree.c
+++ b/lib/radix-tree.c
@@ -126,19 +126,19 @@ static inline gfp_t root_gfp_mask(const struct radix_tree_root *root)
return root->xa_flags & __GFP_BITS_MASK;
}

-static inline void tag_set(struct radix_tree_node *node, unsigned int tag,
+static inline void rtag_set(struct radix_tree_node *node, unsigned int tag,
int offset)
{
__set_bit(offset, node->tags[tag]);
}

-static inline void tag_clear(struct radix_tree_node *node, unsigned int tag,
+static inline void rtag_clear(struct radix_tree_node *node, unsigned int tag,
int offset)
{
__clear_bit(offset, node->tags[tag]);
}

-static inline int tag_get(const struct radix_tree_node *node, unsigned int tag,
+static inline int rtag_get(const struct radix_tree_node *node, unsigned int tag,
int offset)
{
return test_bit(offset, node->tags[tag]);
@@ -617,14 +617,14 @@ static int radix_tree_extend(struct radix_tree_root *root, gfp_t gfp,
if (is_idr(root)) {
all_tag_set(node, IDR_FREE);
if (!root_tag_get(root, IDR_FREE)) {
- tag_clear(node, IDR_FREE, 0);
+ rtag_clear(node, IDR_FREE, 0);
root_tag_set(root, IDR_FREE);
}
} else {
/* Propagate the aggregated tag info to the new child */
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++) {
if (root_tag_get(root, tag))
- tag_set(node, tag, 0);
+ rtag_set(node, tag, 0);
}
}

@@ -689,7 +689,7 @@ static inline bool radix_tree_shrink(struct radix_tree_root *root,
* one (root->xa_head) as far as dependent read barriers go.
*/
root->xa_head = (void __rcu *)child;
- if (is_idr(root) && !tag_get(node, IDR_FREE, 0))
+ if (is_idr(root) && !rtag_get(node, IDR_FREE, 0))
root_tag_clear(root, IDR_FREE);

/*
@@ -896,7 +896,7 @@ static inline int insert_entries(struct radix_tree_node *node,
if (replace) {
node->count--;
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
- if (tag_get(node, tag, offset + i))
+ if (rtag_get(node, tag, offset + i))
tags |= 1 << tag;
} else
return -EEXIST;
@@ -909,12 +909,12 @@ static inline int insert_entries(struct radix_tree_node *node,
rcu_assign_pointer(slot[i], sibling);
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
if (tags & (1 << tag))
- tag_clear(node, tag, offset + i);
+ rtag_clear(node, tag, offset + i);
} else {
rcu_assign_pointer(slot[i], item);
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
if (tags & (1 << tag))
- tag_set(node, tag, offset);
+ rtag_set(node, tag, offset);
}
if (xa_is_node(old))
radix_tree_free_nodes(old);
@@ -972,9 +972,9 @@ int __radix_tree_insert(struct radix_tree_root *root, unsigned long index,

if (node) {
unsigned offset = get_slot_offset(node, slot);
- BUG_ON(tag_get(node, 0, offset));
- BUG_ON(tag_get(node, 1, offset));
- BUG_ON(tag_get(node, 2, offset));
+ BUG_ON(rtag_get(node, 0, offset));
+ BUG_ON(rtag_get(node, 1, offset));
+ BUG_ON(rtag_get(node, 2, offset));
} else {
BUG_ON(root_tags_get(root));
}
@@ -1110,7 +1110,7 @@ static bool node_tag_get(const struct radix_tree_root *root,
unsigned int tag, unsigned int offset)
{
if (node)
- return tag_get(node, tag, offset);
+ return rtag_get(node, tag, offset);
return root_tag_get(root, tag);
}

@@ -1280,7 +1280,7 @@ int radix_tree_split(struct radix_tree_root *root, unsigned long index,
offset = get_slot_offset(parent, slot);

for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
- if (tag_get(parent, tag, offset))
+ if (rtag_get(parent, tag, offset))
tags |= 1 << tag;

for (end = offset + 1; end < RADIX_TREE_MAP_SIZE; end++) {
@@ -1288,7 +1288,7 @@ int radix_tree_split(struct radix_tree_root *root, unsigned long index,
break;
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
if (tags & (1 << tag))
- tag_set(parent, tag, end);
+ rtag_set(parent, tag, end);
/* rcu_assign_pointer ensures tags are set before RETRY */
rcu_assign_pointer(parent->slots[end], RADIX_TREE_RETRY);
}
@@ -1319,7 +1319,7 @@ int radix_tree_split(struct radix_tree_root *root, unsigned long index,
node_to_entry(child));
for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
if (tags & (1 << tag))
- tag_set(node, tag, offset);
+ rtag_set(node, tag, offset);
}

node = child;
@@ -1333,7 +1333,7 @@ int radix_tree_split(struct radix_tree_root *root, unsigned long index,

for (tag = 0; tag < RADIX_TREE_MAX_TAGS; tag++)
if (tags & (1 << tag))
- tag_set(node, tag, offset);
+ rtag_set(node, tag, offset);
offset += n;

while (offset == RADIX_TREE_MAP_SIZE) {
@@ -1363,9 +1363,9 @@ static void node_tag_set(struct radix_tree_root *root,
unsigned int tag, unsigned int offset)
{
while (node) {
- if (tag_get(node, tag, offset))
+ if (rtag_get(node, tag, offset))
return;
- tag_set(node, tag, offset);
+ rtag_set(node, tag, offset);
offset = node->offset;
node = node->parent;
}
@@ -1403,8 +1403,8 @@ void *radix_tree_tag_set(struct radix_tree_root *root,
offset = radix_tree_descend(parent, &node, index);
BUG_ON(!node);

- if (!tag_get(parent, tag, offset))
- tag_set(parent, tag, offset);
+ if (!rtag_get(parent, tag, offset))
+ rtag_set(parent, tag, offset);
}

/* set the root's tag bit */
@@ -1432,9 +1432,9 @@ static void node_tag_clear(struct radix_tree_root *root,
unsigned int tag, unsigned int offset)
{
while (node) {
- if (!tag_get(node, tag, offset))
+ if (!rtag_get(node, tag, offset))
return;
- tag_clear(node, tag, offset);
+ rtag_clear(node, tag, offset);
if (any_tag_set(node, tag))
return;

@@ -1532,7 +1532,7 @@ int radix_tree_tag_get(const struct radix_tree_root *root,
parent = entry_to_node(node);
offset = radix_tree_descend(parent, &node, index);

- if (!tag_get(parent, tag, offset))
+ if (!rtag_get(parent, tag, offset))
return 0;
if (node == RADIX_TREE_RETRY)
break;
@@ -1721,7 +1721,7 @@ void __rcu **radix_tree_next_chunk(const struct radix_tree_root *root,
offset = radix_tree_descend(node, &child, index);

if ((flags & RADIX_TREE_ITER_TAGGED) ?
- !tag_get(node, tag, offset) : !child) {
+ !rtag_get(node, tag, offset) : !child) {
/* Hole detected */
if (flags & RADIX_TREE_ITER_CONTIG)
return NULL;
@@ -2143,7 +2143,7 @@ void __rcu **idr_get_free(struct radix_tree_root *root,

node = entry_to_node(child);
offset = radix_tree_descend(node, &child, start);
- if (!tag_get(node, IDR_FREE, offset)) {
+ if (!rtag_get(node, IDR_FREE, offset)) {
offset = radix_tree_find_next_bit(node, IDR_FREE,
offset + 1);
start = next_index(start, node, offset);
diff --git a/lib/xarray.c b/lib/xarray.c
index 1f7d30a8b61f..fbc7de5a224f 100644
--- a/lib/xarray.c
+++ b/lib/xarray.c
@@ -33,6 +33,53 @@
* @entry refers to something stored in a slot in the xarray
*/

+static inline struct xa_node *xa_parent(struct xarray *xa,
+ const struct xa_node *node)
+{
+ return rcu_dereference_check(node->parent, xa_lock_held(xa));
+}
+
+static inline struct xa_node *xa_parent_locked(struct xarray *xa,
+ const struct xa_node *node)
+{
+ return rcu_dereference_protected(node->parent, xa_lock_held(xa));
+}
+
+static inline void xa_tag_set(struct xarray *xa, xa_tag_t tag)
+{
+ if (!(xa->xa_flags & XA_FLAGS_TAG(tag)))
+ xa->xa_flags |= XA_FLAGS_TAG(tag);
+}
+
+static inline void xa_tag_clear(struct xarray *xa, xa_tag_t tag)
+{
+ if (xa->xa_flags & XA_FLAGS_TAG(tag))
+ xa->xa_flags &= ~(XA_FLAGS_TAG(tag));
+}
+
+static inline bool tag_get(const struct xa_node *node, unsigned int offset,
+ xa_tag_t tag)
+{
+ return test_bit(offset, node->tags[(__force unsigned)tag]);
+}
+
+static inline void tag_set(struct xa_node *node, unsigned int offset,
+ xa_tag_t tag)
+{
+ __set_bit(offset, node->tags[(__force unsigned)tag]);
+}
+
+static inline void tag_clear(struct xa_node *node, unsigned int offset,
+ xa_tag_t tag)
+{
+ __clear_bit(offset, node->tags[(__force unsigned)tag]);
+}
+
+static inline bool tag_any_set(struct xa_node *node, xa_tag_t tag)
+{
+ return !bitmap_empty(node->tags[(__force unsigned)tag], XA_CHUNK_SIZE);
+}
+
/* extracts the offset within this node from the index */
static unsigned int get_offset(unsigned long index, struct xa_node *node)
{
@@ -114,6 +161,89 @@ void *xas_load(struct xarray *xa, struct xa_state *xas)
}
EXPORT_SYMBOL_GPL(xas_load);

+/**
+ * xas_get_tag() - Returns the state of this tag.
+ * @xa: XArray.
+ * @xas: XArray operation state.
+ * @tag: Tag number.
+ *
+ * Return: true if the tag is set, false if the tag is clear or @xas
+ * is in an error state.
+ */
+bool xas_get_tag(const struct xarray *xa, const struct xa_state *xas,
+ xa_tag_t tag)
+{
+ if (xas_invalid(xas))
+ return false;
+ if (!xas->xa_node)
+ return xa_tagged(xa, tag);
+ return tag_get(xas->xa_node, xas->xa_offset, tag);
+}
+EXPORT_SYMBOL_GPL(xas_get_tag);
+
+/**
+ * xas_set_tag() - Sets the tag on this entry and its parents.
+ * @xa: XArray.
+ * @xas: XArray operation state.
+ * @tag: Tag number.
+ *
+ * Sets the specified tag on this entry, and walks up the tree setting it
+ * on all the ancestor entries. Does nothing if @xas has not been walked to
+ * an entry, or is in an error state.
+ */
+void xas_set_tag(struct xarray *xa, const struct xa_state *xas, xa_tag_t tag)
+{
+ struct xa_node *node = xas->xa_node;
+ unsigned int offset = xas->xa_offset;
+
+ if (xas_invalid(xas))
+ return;
+
+ while (node) {
+ if (tag_get(node, offset, tag))
+ return;
+ tag_set(node, offset, tag);
+ offset = node->offset;
+ node = xa_parent_locked(xa, node);
+ }
+
+ if (!xa_tagged(xa, tag))
+ xa_tag_set(xa, tag);
+}
+EXPORT_SYMBOL_GPL(xas_set_tag);
+
+/**
+ * xas_clear_tag() - Clears the tag on this entry and its parents.
+ * @xa: XArray.
+ * @xas: XArray operation state.
+ * @tag: Tag number.
+ *
+ * Clears the specified tag on this entry, and walks back to the head
+ * attempting to clear it on all the ancestor entries. Does nothing if
+ * @xas has not been walked to an entry, or is in an error state.
+ */
+void xas_clear_tag(struct xarray *xa, const struct xa_state *xas, xa_tag_t tag)
+{
+ struct xa_node *node = xas->xa_node;
+ unsigned int offset = xas->xa_offset;
+
+ if (xas_invalid(xas))
+ return;
+
+ while (node) {
+ tag_clear(node, offset, tag);
+ if (tag_any_set(node, tag))
+ return;
+
+ offset = node->offset;
+ node = xa_parent_locked(xa, node);
+ }
+
+ if (xa_tagged(xa, tag))
+ xa_tag_clear(xa, tag);
+}
+EXPORT_SYMBOL_GPL(xas_clear_tag);
+
/**
* xa_load() - Load an entry from an XArray.
* @xa: XArray.
@@ -135,3 +265,123 @@ void *xa_load(struct xarray *xa, unsigned long index)
return entry;
}
EXPORT_SYMBOL(xa_load);
+
+/**
+ * __xa_set_tag() - Set this tag on this entry.
+ * @xa: XArray.
+ * @index: Index of entry.
+ * @tag: Tag number.
+ *
+ * Attempting to set a tag on a NULL entry does not succeed.
+ * This function expects the xa_lock to be held on entry.
+ *
+ * Return: The entry at this index.
+ */
+void *__xa_set_tag(struct xarray *xa, unsigned long index, xa_tag_t tag)
+{
+ XA_STATE(xas, index);
+ void *entry = xas_load(xa, &xas);
+
+ if (entry)
+ xas_set_tag(xa, &xas, tag);
+
+ return entry;
+}
+EXPORT_SYMBOL_GPL(__xa_set_tag);
+
+/**
+ * __xa_clear_tag() - Clear this tag on this entry.
+ * @xa: XArray.
+ * @index: Index of entry.
+ * @tag: Tag number.
+ *
+ * This function expects the xa_lock to be held on entry.
+ *
+ * Return: The entry at this index.
+ */
+void *__xa_clear_tag(struct xarray *xa, unsigned long index, xa_tag_t tag)
+{
+ XA_STATE(xas, index);
+ void *entry = xas_load(xa, &xas);
+
+ if (entry)
+ xas_clear_tag(xa, &xas, tag);
+
+ return entry;
+}
+EXPORT_SYMBOL_GPL(__xa_clear_tag);
+
+/**
+ * xa_get_tag() - Inquire whether this tag is set on this entry.
+ * @xa: XArray.
+ * @index: Index of entry.
+ * @tag: Tag number.
+ *
+ * This function uses the RCU read lock, so the result may be out of date
+ * by the time it returns. If you need the result to be stable, use a lock.
+ *
+ * Return: True if the entry at @index has this tag set, false if it doesn't.
+ */
+bool xa_get_tag(struct xarray *xa, unsigned long index, xa_tag_t tag)
+{
+ XA_STATE(xas, index);
+ void *entry;
+
+ rcu_read_lock();
+ entry = xas_start(xa, &xas);
+ while (xas_get_tag(xa, &xas, tag)) {
+ if (!xa_is_node(entry))
+ goto found;
+ entry = xas_descend(xa, &xas, xa_to_node(entry));
+ }
+ rcu_read_unlock();
+ return false;
+ found:
+ rcu_read_unlock();
+ return true;
+}
+EXPORT_SYMBOL(xa_get_tag);
+
+/**
+ * xa_set_tag() - Set this tag on this entry.
+ * @xa: XArray.
+ * @index: Index of entry.
+ * @tag: Tag number.
+ *
+ * Attempting to set a tag on a NULL entry does not succeed.
+ *
+ * Return: The entry at this index.
+ */
+void *xa_set_tag(struct xarray *xa, unsigned long index, xa_tag_t tag)
+{
+ unsigned long flags;
+ void *entry;
+
+ xa_lock_irqsave(xa, flags);
+ entry = __xa_set_tag(xa, index, tag);
+ xa_unlock_irqrestore(xa, flags);
+
+ return entry;
+}
+EXPORT_SYMBOL(xa_set_tag);
+
+/**
+ * xa_clear_tag() - Clear this tag on this entry.
+ * @xa: XArray.
+ * @index: Index of entry.
+ * @tag: Tag number.
+ *
+ * Return: The entry at this index.
+ */
+void *xa_clear_tag(struct xarray *xa, unsigned long index, xa_tag_t tag)
+{
+ unsigned long flags;
+ void *entry;
+
+ xa_lock_irqsave(xa, flags);
+ entry = __xa_clear_tag(xa, index, tag);
+ xa_unlock_irqrestore(xa, flags);
+
+ return entry;
+}
+EXPORT_SYMBOL(xa_clear_tag);
--
2.15.0