From: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> This iterator allows the user to efficiently walk a range of the array, executing the loop body once for each entry in that range that matches the filter. This commit also includes xa_find() and xa_find_above() which are helper functions for xa_for_each() but may also be useful in their own right. In the xas family of functions, we also have xas_for_each(), xas_find(), xas_next_entry(), xas_for_each_tag(), xas_find_tag(), xas_next_tag() and xas_pause(). Signed-off-by: Matthew Wilcox <mawilcox@xxxxxxxxxxxxx> --- include/linux/xarray.h | 171 +++++++++++++++++++++ lib/xarray.c | 272 +++++++++++++++++++++++++++++++++ tools/testing/radix-tree/test.c | 13 ++ tools/testing/radix-tree/test.h | 1 + tools/testing/radix-tree/xarray-test.c | 122 +++++++++++++++ 5 files changed, 579 insertions(+) diff --git a/include/linux/xarray.h b/include/linux/xarray.h index fc9ab3b13e60..fcd7ef68933a 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -215,6 +215,10 @@ void *xa_cmpxchg(struct xarray *, unsigned long index, 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); +void *xa_find(struct xarray *xa, unsigned long *index, + unsigned long max, xa_tag_t) __attribute__((nonnull(2))); +void *xa_find_after(struct xarray *xa, unsigned long *index, + unsigned long max, xa_tag_t) __attribute__((nonnull(2))); /** * xa_init() - Initialise an empty XArray. @@ -266,6 +270,33 @@ static inline bool xa_tagged(const struct xarray *xa, xa_tag_t tag) return xa->xa_flags & XA_FLAGS_TAG(tag); } +/** + * xa_for_each() - Iterate over a portion of an XArray. + * @xa: XArray. + * @entry: Entry retrieved from array. + * @index: Index of @entry. + * @max: Maximum index to retrieve from array. + * @filter: Selection criterion. + * + * Initialise @index to the minimum index you want to retrieve from + * the array. During the iteration, @entry will have the value of the + * entry stored in @xa at @index. The iteration will skip all entries in + * the array which do not match @filter. You may modify @index during the + * iteration if you want to skip or reprocess indices. It is safe to modify + * the array during the iteration. At the end of the iteration, @entry will + * be set to NULL and @index will have a value less than or equal to max. + * + * xa_for_each() is O(n.log(n)) while xas_for_each() is O(n). You have + * to handle your own locking with xas_for_each(), and if you have to unlock + * after each iteration, it will also end up being O(n.log(n)). xa_for_each() + * will spin if it hits a retry entry; if you intend to see retry entries, + * you should use the xas_for_each() iterator instead. The xas_for_each() + * iterator will expand into more inline code than xa_for_each(). + */ +#define xa_for_each(xa, entry, index, max, filter) \ + for (entry = xa_find(xa, &index, max, filter); entry; \ + entry = xa_find_after(xa, &index, max, filter)) + /** * xa_insert() - Store this entry in the XArray unless another entry is * already present. @@ -620,6 +651,12 @@ static inline bool xas_valid(const struct xa_state *xas) return !xas_invalid(xas); } +/* True if the pointer is something other than a node */ +static inline bool xas_not_node(struct xa_node *node) +{ + return ((unsigned long)node & 3) || !node; +} + /* True if the node represents head-of-tree, RESTART or BOUNDS */ static inline bool xas_top(struct xa_node *node) { @@ -648,13 +685,16 @@ static inline bool xas_retry(struct xa_state *xas, const void *entry) void *xas_load(struct xa_state *); void *xas_store(struct xa_state *, void *entry); void *xas_create(struct xa_state *); +void *xas_find(struct xa_state *, unsigned long max); bool xas_get_tag(const struct xa_state *, xa_tag_t); void xas_set_tag(const struct xa_state *, xa_tag_t); void xas_clear_tag(const struct xa_state *, xa_tag_t); +void *xas_find_tag(struct xa_state *, unsigned long max, xa_tag_t); void xas_init_tags(const struct xa_state *); bool xas_nomem(struct xa_state *, gfp_t); +void xas_pause(struct xa_state *); /** * xas_reload() - Refetch an entry from the xarray. @@ -727,6 +767,137 @@ static inline void xas_set_update(struct xa_state *xas, xa_update_node_t update) xas->xa_update = update; } +/* Skip over any of these entries when iterating */ +static inline bool xa_iter_skip(const void *entry) +{ + return unlikely(!entry || + (xa_is_internal(entry) && entry < XA_RETRY_ENTRY)); +} + +/** + * xas_next_entry() - Advance iterator to next present entry. + * @xas: XArray operation state. + * @max: Highest index to return. + * + * xas_next_entry() is an inline function to optimise xarray traversal for + * speed. It is equivalent to calling xas_find(), and will call xas_find() + * for all the hard cases. + * + * Return: The next present entry after the one currently referred to by @xas. + */ +static inline void *xas_next_entry(struct xa_state *xas, unsigned long max) +{ + struct xa_node *node = xas->xa_node; + void *entry; + + if (unlikely(xas_not_node(node) || node->shift)) + return xas_find(xas, max); + + do { + if (unlikely(xas->xa_index >= max)) + return xas_find(xas, max); + if (unlikely(xas->xa_offset == XA_CHUNK_MASK)) + return xas_find(xas, max); + xas->xa_index++; + xas->xa_offset++; + entry = xa_entry(xas->xa, node, xas->xa_offset); + } while (xa_iter_skip(entry)); + + return entry; +} + +/* Private */ +static inline unsigned int xas_find_chunk(struct xa_state *xas, bool advance, + xa_tag_t tag) +{ + unsigned long *addr = xas->xa_node->tags[(__force unsigned)tag]; + unsigned int offset = xas->xa_offset; + + if (advance) + offset++; + if (XA_CHUNK_SIZE == BITS_PER_LONG) { + unsigned long data = *addr & (~0UL << offset); + if (data) + return __ffs(data); + return XA_CHUNK_SIZE; + } + + return find_next_bit(addr, XA_CHUNK_SIZE, offset); +} + +/** + * xas_next_tag() - Advance iterator to next tagged entry. + * @xas: XArray operation state. + * @max: Highest index to return. + * @tag: Tag to search for. + * + * xas_next_tag() is an inline function to optimise xarray traversal for + * speed. It is equivalent to calling xas_find_tag(), and will call + * xas_find_tag() for all the hard cases. + * + * Return: The next tagged entry after the one currently referred to by @xas. + */ +static inline void *xas_next_tag(struct xa_state *xas, unsigned long max, + xa_tag_t tag) +{ + struct xa_node *node = xas->xa_node; + unsigned int offset; + + if (unlikely(xas_not_node(node) || node->shift)) + return xas_find_tag(xas, max, tag); + offset = xas_find_chunk(xas, true, tag); + xas->xa_offset = offset; + xas->xa_index = (xas->xa_index & ~XA_CHUNK_MASK) + offset; + if (xas->xa_index > max) + return NULL; + if (offset == XA_CHUNK_SIZE) + return xas_find_tag(xas, max, tag); + return xa_entry(xas->xa, node, offset); +} + +/* + * If iterating while holding a lock, drop the lock and reschedule + * every %XA_CHECK_SCHED loops. + */ +enum { + XA_CHECK_SCHED = 4096, +}; + +/** + * xas_for_each() - Iterate over a range of an XArray + * @xas: XArray operation state. + * @entry: Entry retrieved from array. + * @max: Maximum index to retrieve from array. + * + * The loop body will be executed for each entry present in the xarray + * between the current xas position and @max. @entry will be set to + * the entry retrieved from the xarray. It is safe to delete entries + * from the array in the loop body. You should hold either the RCU lock + * or the xa_lock while iterating. If you need to drop the lock, call + * xas_pause() first. + */ +#define xas_for_each(xas, entry, max) \ + for (entry = xas_find(xas, max); entry; \ + entry = xas_next_entry(xas, max)) + +/** + * xas_for_each_tag() - Iterate over a range of an XArray + * @xas: XArray operation state. + * @entry: Entry retrieved from array. + * @max: Maximum index to retrieve from array. + * @tag: Tag to search for. + * + * The loop body will be executed for each tagged entry in the xarray + * between the current xas position and @max. @entry will be set to + * the entry retrieved from the xarray. It is safe to delete entries + * from the array in the loop body. You should hold either the RCU lock + * or the xa_lock while iterating. If you need to drop the lock, call + * xas_pause() first. + */ +#define xas_for_each_tag(xas, entry, max, tag) \ + for (entry = xas_find_tag(xas, max, tag); entry; \ + entry = xas_next_tag(xas, max, tag)) + /* Internal functions, mostly shared between radix-tree.c, xarray.c and idr.c */ void xas_destroy(struct xa_state *); diff --git a/lib/xarray.c b/lib/xarray.c index d925a98fb9b8..3e6be0a07525 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -91,6 +91,11 @@ static unsigned int get_offset(unsigned long index, struct xa_node *node) return (index >> node->shift) & XA_CHUNK_MASK; } +static void xas_set_offset(struct xa_state *xas) +{ + xas->xa_offset = get_offset(xas->xa_index, xas->xa_node); +} + /* move the index either forwards (find) or backwards (sibling slot) */ static void xas_move_index(struct xa_state *xas, unsigned long offset) { @@ -99,6 +104,12 @@ static void xas_move_index(struct xa_state *xas, unsigned long offset) xas->xa_index += offset << shift; } +static void xas_advance(struct xa_state *xas) +{ + xas->xa_offset++; + xas_move_index(xas, xas->xa_offset); +} + static void *set_bounds(struct xa_state *xas) { xas->xa_node = XAS_BOUNDS; @@ -791,6 +802,191 @@ void xas_init_tags(const struct xa_state *xas) } EXPORT_SYMBOL_GPL(xas_init_tags); +/** + * xas_pause() - Pause a walk to drop a lock. + * @xas: XArray operation state. + * + * Some users need to pause a walk and drop the lock they're holding in + * order to yield to a higher priority thread or carry out an operation + * on an entry. Those users should call this function before they drop + * the lock. It resets the @xas to be suitable for the next iteration + * of the loop after the user has reacquired the lock. If most entries + * found during a walk require you to call xas_pause(), the xa_for_each() + * iterator may be more appropriate. + * + * Note that xas_pause() only works for forward iteration. If a user needs + * to pause a reverse iteration, we will need a xas_pause_rev(). + */ +void xas_pause(struct xa_state *xas) +{ + struct xa_node *node = xas->xa_node; + + if (xas_invalid(xas)) + return; + + if (node) { + unsigned int offset = xas->xa_offset; + while (++offset < XA_CHUNK_SIZE) { + if (!xa_is_sibling(xa_entry(xas->xa, node, offset))) + break; + } + xas->xa_index += (offset - xas->xa_offset) << node->shift; + } else { + xas->xa_index++; + } + xas->xa_node = XAS_RESTART; +} +EXPORT_SYMBOL_GPL(xas_pause); + +/** + * xas_find() - Find the next present entry in the XArray. + * @xas: XArray operation state. + * @max: Highest index to return. + * + * If the xas has not yet been walked to an entry, return the entry + * which has an index >= xas.xa_index. If it has been walked, the entry + * currently being pointed at has been processed, and so we move to the + * next entry. + * + * If no entry is found and the array is smaller than @max, the iterator + * is set to the smallest index not yet in the array. This allows @xas + * to be immediately passed to xas_create(). + * + * Return: The entry, if found, otherwise NULL. + */ +void *xas_find(struct xa_state *xas, unsigned long max) +{ + void *entry; + + if (xas_error(xas)) + return NULL; + + if (!xas->xa_node) { + xas->xa_index = 1; + return set_bounds(xas); + } else if (xas_top(xas->xa_node)) { + entry = xas_load(xas); + if (entry || xas_not_node(xas->xa_node)) + return entry; + } + + xas_advance(xas); + + while (xas->xa_node && (xas->xa_index <= max)) { + if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) { + xas->xa_offset = xas->xa_node->offset + 1; + xas->xa_node = xa_parent(xas->xa, xas->xa_node); + continue; + } + + entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset); + if (xa_is_node(entry)) { + xas->xa_node = xa_to_node(entry); + xas->xa_offset = 0; + continue; + } + if (!xa_iter_skip(entry)) + return entry; + + xas_advance(xas); + } + + if (!xas->xa_node) + xas->xa_node = XAS_BOUNDS; + return NULL; +} +EXPORT_SYMBOL_GPL(xas_find); + +/** + * xas_find_tag() - Find the next tagged entry in the XArray. + * @xas: XArray operation state. + * @max: Highest index to return. + * @tag: Tag number to search for. + * + * If the xas has not yet been walked to an entry, return the tagged entry + * which has an index >= xas.xa_index. If it has been walked, the entry + * currently being pointed at has been processed, and so we move to the + * next tagged entry. + * + * If no tagged entry is found and the array is smaller than @max, @xas is + * set to the bounds state and xas->xa_index is set to the smallest index + * not yet in the array. This allows @xas to be immediately passed to + * xas_create(). + * + * Return: The entry, if found, otherwise %NULL. + */ +void *xas_find_tag(struct xa_state *xas, unsigned long max, xa_tag_t tag) +{ + bool advance = true; + unsigned int offset; + void *entry; + + if (xas_error(xas)) + return NULL; + + if (!xas->xa_node) { + xas->xa_index = 1; + goto out; + } else if (xas_top(xas->xa_node)) { + advance = false; + entry = xa_head(xas->xa); + if (xas->xa_index > max_index(entry)) + goto out; + if (!xa_is_node(entry)) { + if (xa_tagged(xas->xa, tag)) { + xas->xa_node = NULL; + return entry; + } + xas->xa_index = 1; + goto out; + } + xas->xa_node = xa_to_node(entry); + xas->xa_offset = xas->xa_index >> xas->xa_node->shift; + } + + while (xas->xa_index <= max) { + if (unlikely(xas->xa_offset == XA_CHUNK_SIZE)) { + xas->xa_offset = xas->xa_node->offset + 1; + xas->xa_node = xa_parent(xas->xa, xas->xa_node); + if (!xas->xa_node) + break; + advance = false; + continue; + } + + if (!advance) { + entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset); + if (xa_is_sibling(entry)) { + xas->xa_offset = xa_to_sibling(entry); + xas_move_index(xas, xas->xa_offset); + } + } + + offset = xas_find_chunk(xas, advance, tag); + if (offset > xas->xa_offset) { + advance = false; + xas_move_index(xas, offset); + xas->xa_offset = offset; + if (offset == XA_CHUNK_SIZE) + continue; + if (xas->xa_index > max) + break; + } + + entry = xa_entry(xas->xa, xas->xa_node, xas->xa_offset); + if (!xa_is_node(entry)) + return entry; + xas->xa_node = xa_to_node(entry); + xas_set_offset(xas); + } + + out: + if (!xas->xa_node) + xas->xa_node = XAS_BOUNDS; + return NULL; +} +EXPORT_SYMBOL_GPL(xas_find_tag); + /** * xa_init_flags() - Initialise an empty XArray with flags. * @xa: XArray. @@ -1096,6 +1292,82 @@ void xa_clear_tag(struct xarray *xa, unsigned long index, xa_tag_t tag) } EXPORT_SYMBOL(xa_clear_tag); +/** + * xa_find() - Search the XArray for an entry. + * @xa: XArray. + * @indexp: Pointer to an index. + * @max: Maximum index to search to. + * @filter: Selection criterion. + * + * Finds the entry in @xa which matches the @filter, and has the lowest + * index that is at least @indexp and no more than @max. + * If an entry is found, @indexp is updated to be the index of the entry. + * This function is protected by the RCU read lock, so it may not find + * entries which are being simultaneously added. It will not return an + * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find(). + * + * Return: The entry, if found, otherwise NULL. + */ +void *xa_find(struct xarray *xa, unsigned long *indexp, + unsigned long max, xa_tag_t filter) +{ + XA_STATE(xas, xa, *indexp); + void *entry; + + rcu_read_lock(); + do { + if ((__force unsigned int)filter < XA_MAX_TAGS) + entry = xas_find_tag(&xas, max, filter); + else + entry = xas_find(&xas, max); + } while (xas_retry(&xas, entry)); + rcu_read_unlock(); + + if (entry) + *indexp = xas.xa_index; + return entry; +} +EXPORT_SYMBOL(xa_find); + +/** + * xa_find_after() - Search the XArray for a present entry. + * @xa: XArray. + * @indexp: Pointer to an index. + * @max: Maximum index to search to. + * @filter: Selection criterion. + * + * Finds the entry in @xa which matches the @filter and has the lowest + * index that is above @indexp and no more than @max. + * If an entry is found, @indexp is updated to be the index of the entry. + * This function is protected by the RCU read lock, so it may miss entries + * which are being simultaneously added. It will not return an + * %XA_RETRY_ENTRY; if you need to see retry entries, use xas_find(). + * + * Return: The pointer, if found, otherwise NULL. + */ +void *xa_find_after(struct xarray *xa, unsigned long *indexp, + unsigned long max, xa_tag_t filter) +{ + XA_STATE(xas, xa, *indexp + 1); + void *entry; + + rcu_read_lock(); + do { + if ((__force unsigned int)filter < XA_MAX_TAGS) + entry = xas_find_tag(&xas, max, filter); + else + entry = xas_find(&xas, max); + if (*indexp >= xas.xa_index) + entry = xas_next_entry(&xas, max); + } while (xas_retry(&xas, entry)); + rcu_read_unlock(); + + if (entry) + *indexp = xas.xa_index; + return entry; +} +EXPORT_SYMBOL(xa_find_after); + #ifdef XA_DEBUG void xa_dump_node(const struct xa_node *node) { diff --git a/tools/testing/radix-tree/test.c b/tools/testing/radix-tree/test.c index f151588d04a0..e9b4a4ed9bf5 100644 --- a/tools/testing/radix-tree/test.c +++ b/tools/testing/radix-tree/test.c @@ -244,6 +244,19 @@ unsigned long find_item(struct radix_tree_root *root, void *item) return found; } +static LIST_HEAD(item_nodes); + +void item_update_node(struct xa_node *node) +{ + if (node->count) { + if (list_empty(&node->private_list)) + list_add(&node->private_list, &item_nodes); + } else { + if (!list_empty(&node->private_list)) + list_del_init(&node->private_list); + } +} + static int verify_node(struct radix_tree_node *slot, unsigned int tag, int tagged) { diff --git a/tools/testing/radix-tree/test.h b/tools/testing/radix-tree/test.h index ffd162645c11..f97cacd1422d 100644 --- a/tools/testing/radix-tree/test.h +++ b/tools/testing/radix-tree/test.h @@ -30,6 +30,7 @@ void item_gang_check_present(struct radix_tree_root *root, void item_full_scan(struct radix_tree_root *root, unsigned long start, unsigned long nr, int chunk); void item_kill_tree(struct radix_tree_root *root); +void item_update_node(struct xa_node *node); int tag_tagged_items(struct radix_tree_root *, pthread_mutex_t *, unsigned long start, unsigned long end, unsigned batch, diff --git a/tools/testing/radix-tree/xarray-test.c b/tools/testing/radix-tree/xarray-test.c index d6a969d999d9..26b25be81656 100644 --- a/tools/testing/radix-tree/xarray-test.c +++ b/tools/testing/radix-tree/xarray-test.c @@ -49,6 +49,29 @@ void check_xa_tag(struct xarray *xa) assert(xa_get_tag(xa, 0, XA_TAG_0) == false); } +void check_xas_retry(struct xarray *xa) +{ + XA_STATE(xas, xa, 0); + + xa_store(xa, 0, xa_mk_value(0), GFP_KERNEL); + xa_store(xa, 1, xa_mk_value(1), GFP_KERNEL); + + assert(xas_find(&xas, ULONG_MAX) == xa_mk_value(0)); + xa_erase(xa, 1); + assert(xa_is_retry(xas_reload(&xas))); + assert(!xas_retry(&xas, NULL)); + assert(!xas_retry(&xas, xa_mk_value(0))); + assert(xas_retry(&xas, XA_RETRY_ENTRY)); + assert(xas.xa_node == XAS_RESTART); + assert(xas_next_entry(&xas, ULONG_MAX) == xa_mk_value(0)); + assert(xas.xa_node == NULL); + + xa_store(xa, 1, xa_mk_value(1), GFP_KERNEL); + assert(xa_is_internal(xas_reload(&xas))); + xas.xa_node = XAS_RESTART; + assert(xas_next_entry(&xas, ULONG_MAX) == xa_mk_value(0)); +} + void check_xa_load(struct xarray *xa) { unsigned long i, j; @@ -142,6 +165,98 @@ void check_multi_store(struct xarray *xa) } } +void check_multi_find(struct xarray *xa) +{ + unsigned long index; + xa_store_order(xa, 12, 2, xa_mk_value(12), GFP_KERNEL); + xa_store(xa, 16, xa_mk_value(16), GFP_KERNEL); + + index = 0; + assert(xa_find(xa, &index, ULONG_MAX, XA_PRESENT) == xa_mk_value(12)); + assert(index == 12); + index = 13; + assert(xa_find(xa, &index, ULONG_MAX, XA_PRESENT) == xa_mk_value(12)); + assert(index >= 12 && index < 16); + assert(xa_find_after(xa, &index, ULONG_MAX, XA_PRESENT) == xa_mk_value(16)); + assert(index == 16); + xa_erase(xa, 12); + xa_erase(xa, 16); + assert(xa_empty(xa)); +} + +void check_find(struct xarray *xa) +{ + unsigned long i, j, k; + + assert(xa_empty(xa)); + + for (i = 0; i < 100; i++) { + xa_store(xa, i, xa_mk_value(i), GFP_KERNEL); + xa_set_tag(xa, i, XA_TAG_0); + for (j = 0; j < i; j++) { + xa_store(xa, j, xa_mk_value(j), GFP_KERNEL); + xa_set_tag(xa, j, XA_TAG_0); + for (k = 0; k < 100; k++) { + unsigned long index = k; + void *entry = xa_find(xa, &index, ULONG_MAX, + XA_PRESENT); + if (k <= j) + assert(index == j); + else if (k <= i) + assert(index == i); + else + assert(entry == NULL); + + index = k; + entry = xa_find(xa, &index, ULONG_MAX, + XA_TAG_0); + if (k <= j) + assert(index == j); + else if (k <= i) + assert(index == i); + else + assert(entry == NULL); + } + xa_erase(xa, j); + } + xa_erase(xa, i); + } + assert(xa_empty(xa)); + check_multi_find(xa); +} + +void check_xas_delete(struct xarray *xa) +{ + XA_STATE(xas, xa, 0); + void *entry; + unsigned long i, j; + + xas_set_update(&xas, item_update_node); + for (i = 0; i < 200; i++) { + for (j = i; j < 2 * i + 17; j++) { + xas_set(&xas, j); + do { + xas_store(&xas, xa_mk_value(j)); + } while (xas_nomem(&xas, GFP_KERNEL)); + } + + xas_set(&xas, ULONG_MAX); + do { + xas_store(&xas, xa_mk_value(0)); + } while (xas_nomem(&xas, GFP_KERNEL)); + xas_store(&xas, NULL); + + xas_set(&xas, 0); + j = i; + xas_for_each(&xas, entry, ULONG_MAX) { + assert(entry == xa_mk_value(j)); + xas_store(&xas, NULL); + j++; + } + assert(xa_empty(xa)); + } +} + void xarray_checks(void) { DEFINE_XARRAY(array); @@ -152,6 +267,9 @@ void xarray_checks(void) check_xa_tag(&array); item_kill_tree(&array); + check_xas_retry(&array); + item_kill_tree(&array); + check_xa_load(&array); item_kill_tree(&array); @@ -161,6 +279,10 @@ void xarray_checks(void) check_cmpxchg(&array); check_multi_store(&array); item_kill_tree(&array); + + check_find(&array); + check_xas_delete(&array); + item_kill_tree(&array); } int __weak main(void) -- 2.15.1 -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html