diff options
Diffstat (limited to 'lib/xarray.c')
| -rw-r--r-- | lib/xarray.c | 292 |
1 files changed, 292 insertions, 0 deletions
diff --git a/lib/xarray.c b/lib/xarray.c index 2ba5a98ec618..24494f42daa6 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -128,6 +128,11 @@ 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) { @@ -136,6 +141,12 @@ 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; @@ -830,6 +841,202 @@ void xas_init_marks(const struct xa_state *xas) EXPORT_SYMBOL_GPL(xas_init_marks); /** + * 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_store(). + * + * 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; + } else if (!xas->xa_node->shift && + xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)) { + xas->xa_offset = ((xas->xa_index - 1) & XA_CHUNK_MASK) + 1; + } + + 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 (entry && !xa_is_sibling(entry)) + return entry; + + xas_advance(xas); + } + + if (!xas->xa_node) + xas->xa_node = XAS_BOUNDS; + return NULL; +} +EXPORT_SYMBOL_GPL(xas_find); + +/** + * xas_find_marked() - Find the next marked entry in the XArray. + * @xas: XArray operation state. + * @max: Highest index to return. + * @mark: Mark number to search for. + * + * If the @xas has not yet been walked to an entry, return the marked 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 return the + * first marked entry with an index > xas.xa_index. + * + * If no marked 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_store(). + * + * If no entry is found before @max is reached, @xas is set to the restart + * state. + * + * Return: The entry, if found, otherwise %NULL. + */ +void *xas_find_marked(struct xa_state *xas, unsigned long max, xa_mark_t mark) +{ + 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); + xas->xa_node = NULL; + if (xas->xa_index > max_index(entry)) + goto bounds; + if (!xa_is_node(entry)) { + if (xa_marked(xas->xa, mark)) + 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, mark); + if (offset > xas->xa_offset) { + advance = false; + xas_move_index(xas, offset); + /* Mind the wrap */ + if ((xas->xa_index - 1) >= max) + goto max; + xas->xa_offset = offset; + if (offset == XA_CHUNK_SIZE) + continue; + } + + 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 (!max) + goto max; +bounds: + xas->xa_node = XAS_BOUNDS; + return NULL; +max: + xas->xa_node = XAS_RESTART; + return NULL; +} +EXPORT_SYMBOL_GPL(xas_find_marked); + +/** * xa_init_flags() - Initialise an empty XArray with flags. * @xa: XArray. * @flags: XA_FLAG values. @@ -1152,6 +1359,91 @@ void xa_clear_mark(struct xarray *xa, unsigned long index, xa_mark_t mark) } EXPORT_SYMBOL(xa_clear_mark); +/** + * 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(). + * + * Context: Any context. Takes and releases the RCU lock. + * Return: The entry, if found, otherwise %NULL. + */ +void *xa_find(struct xarray *xa, unsigned long *indexp, + unsigned long max, xa_mark_t filter) +{ + XA_STATE(xas, xa, *indexp); + void *entry; + + rcu_read_lock(); + do { + if ((__force unsigned int)filter < XA_MAX_MARKS) + entry = xas_find_marked(&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(). + * + * Context: Any context. Takes and releases the RCU lock. + * Return: The pointer, if found, otherwise %NULL. + */ +void *xa_find_after(struct xarray *xa, unsigned long *indexp, + unsigned long max, xa_mark_t filter) +{ + XA_STATE(xas, xa, *indexp + 1); + void *entry; + + rcu_read_lock(); + for (;;) { + if ((__force unsigned int)filter < XA_MAX_MARKS) + entry = xas_find_marked(&xas, max, filter); + else + entry = xas_find(&xas, max); + if (xas.xa_shift) { + if (xas.xa_index & ((1UL << xas.xa_shift) - 1)) + continue; + } else { + if (xas.xa_offset < (xas.xa_index & XA_CHUNK_MASK)) + continue; + } + if (!xas_retry(&xas, entry)) + break; + } + 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) { |
