https://www.kernel.org/doc/html/v5.0/core-api/xarray.html
https://elixir.bootlin.com/linux/latest/source/include/linux/xarray.h
Table of Contents
總覽
XArray是一種抽象的數據類型，其行爲類似於一個非常大的指針數組。它滿足了與散列或常規可調整大小的數組相同的許多需求。與散列不同，它允許您以高效緩存的方式明智地轉到下一個或上一個條目。與可調整大小的陣列相比，無需爲了擴展陣列而複製數據或更改MMU映射。與雙向鏈接列表相比，它具有更高的內存效率，可並行性和緩存友好性。它利用RCU來執行查找而無需鎖定。
當使用的索引密集聚集時，XArray實現非常有效。對對象進行哈希處理並將哈希值用作索引將不能很好地執行。XArray針對小索引進行了優化，但是對於大索引仍然具有良好的性能。如果索引可以大於， ULONG_MAX則XArray不是您的數據類型。XArray最重要的用戶是頁面緩存。
NULL數組中的每個非條目都有與其關聯的三個位，稱爲標記。每個標記可以獨立設置或清除。您可以遍歷已標記的條目。
普通指針可以直接存儲在XArray中。它們必須對齊4個字節，這對於從kmalloc()和 返回的任何指針都是正確的alloc_page()。對於任意用戶空間指針或函數指針而言，它不是正確的。您可以存儲指向靜態分配的對象的指針，只要這些對象的對齊至少爲4。
您還可以LONG_MAX在XArray中存儲0到之間的整數。您必須先使用將其轉換爲條目xa_mk_value()。從XArray檢索條目時，可以通過調用檢查它是否爲值條目xa_is_value()，然後通過調用將其轉換回整數xa_to_value()。
一些用戶希望存儲帶標籤的指針，而不是使用上述標記。他們可以調用xa_tag_pointer()以創建帶有標籤的條目，xa_untag_pointer()將帶標籤的條目變回無標籤的指針，並xa_pointer_tag()檢索條目的標籤。標記指針使用相同的位來區分值條目和普通指針，因此每個用戶必須決定是否要在任何特定XArray中存儲值條目或標記指針。
XArray不支持存儲IS_ERR()指針，因爲它與值條目或內部條目有些衝突。
XArray的一個不尋常的功能是能夠創建佔用一系列索引的條目。一旦存儲到其中，查找範圍內的任何索引將返回與查找範圍內的任何其他索引相同的條目。在一個索引上設置標記將在所有索引上設置它。存儲到任何索引將存儲到所有索引。可以將多索引條目顯式拆分爲較小的條目，或者將其存儲NULL到任何條目中都會使XArray忘記範圍。
普通API
從初始化XArray開始，DEFINE_XARRAY() 對於靜態分配的XArray或xa_init()動態分配的XArray都要初始化。剛初始化的XArray NULL 在每個索引處都包含一個指針。
然後，您可以使用設置條目，xa_store()並使用獲取條目xa_load()。xa_store將用新條目覆蓋任何條目，並返回存儲在該索引處的先前條目。您可以使用xa_erase()而不是xa_store()使用 NULL條目來調用。從未存儲到的條目，已刪除的條目和最近NULL存儲到的條目之間沒有區別。
您可以使用來有條件地替換索引中的條目 xa_cmpxchg()。像一樣cmpxchg()，只有在該索引的條目具有“舊”值時，它纔會成功。它還返回該索引處的條目。如果它返回與“舊”相同的條目，則xa_cmpxchg()成功。
如果您只想在索引的當前條目爲的情況下僅將新條目存儲到索引，則NULL可以使用如果條目不爲空xa_insert()返回-EEXIST的值。
您可以使用來查詢條目上是否設置了標記 xa_get_mark()。如果不是該條目，則NULL可以通過使用在其上設置標記，xa_set_mark()並通過調用從條目中刪除該標記xa_clear_mark()。您可以通過調用詢問XArray中的任何條目是否設置了特定標記xa_marked()。
您可以通過調用將條目從XArray複製到純數組中 xa_extract()。或者，您可以通過調用遍歷XArray中的當前條目xa_for_each()。您可能更喜歡使用 xa_find()或xa_find_after()移至XArray中的下一個當前條目。
調用xa_store_range()將同一條目存儲在一系列索引中。如果執行此操作，則其他一些操作的行爲會有些奇怪。例如，在一個索引上標記條目可能會導致在其他但不是所有其他索引上標記條目。存儲到一個索引中可能會導致某些（但不是所有）其他索引檢索到的條目發生變化。
有時您需要確保後續調用xa_store() 不需要分配內存。該xa_reserve()函數將在指示的索引處存儲保留的條目。普通API的用戶將看到此條目包含NULL。如果不需要使用保留的條目，則可以調用xa_release() 以刪除未使用的條目。如果與此同時有另一個用戶存儲到該條目，xa_release()則不執行任何操作；相反，如果您希望該條目成爲NULL，則應使用xa_erase()。使用xa_insert()上的保留條目將失敗。
如果數組中的所有條目都是NULL，xa_empty()函數將返回true。
最後，您可以通過調用從XArray刪除所有條目 xa_destroy()。如果XArray條目是指針，則您可能希望先釋放這些條目。您可以通過使用xa_for_each()迭代器遍歷XArray中的所有當前條目來實現此目的。
分配XArray
如果您用於DEFINE_XARRAY_ALLOC()定義XArray或通過將其傳遞XA_FLAGS_ALLOC給XArray進行初始化xa_init_flags()，則XArray會更改以跟蹤條目是否在使用中。
您可以調用xa_alloc()將條目存儲在XArray中任何未使用的索引處。如果需要從中斷上下文中修改數組，則可以在分配ID時使用xa_alloc_bh()或xa_alloc_irq()禁用中斷。
使用xa_store()，xa_cmpxchg()或xa_insert() 將迎來條目被分配。與普通的XArray不同，存儲 NULL會將該條目標記爲正在使用中，例如xa_reserve()。要釋放條目，請使用xa_erase()（或者xa_release()如果您只想釋放條目，則使用NULL）。
您不能XA_MARK_0與分配XArray一起使用，因爲此標記用於跟蹤條目是否空閒。其他標記可供您使用。
內存分配
的xa_store()，xa_cmpxchg()，xa_alloc()， xa_reserve()和xa_insert()功能採取以防XArray需要分配存儲器來存儲這個條目的gfp_t參數。如果要刪除該條目，則無需執行任何內存分配，並且指定的GFP標誌將被忽略。
不可能分配任何內存，特別是如果您傳遞一組限制性的GFP標誌時。在這種情況下，函數將返回一個特殊值，可以使用將其轉換爲errno xa_err()。如果您不需要確切地知道發生了哪個錯誤，使用起來 xa_is_err()會更有效率。
鎖定
使用Normal API時，您不必擔心鎖定。XArray使用RCU和內部自旋鎖來同步訪問：
無需鎖定：
採取RCU讀取鎖定：
內部採用xa_lock：
xa_store()xa_store_bh()xa_store_irq()xa_insert()xa_insert_bh()xa_insert_irq()xa_erase()xa_erase_bh()xa_erase_irq()xa_cmpxchg()xa_cmpxchg_bh()xa_cmpxchg_irq()xa_store_range()xa_alloc()xa_alloc_bh()xa_alloc_irq()xa_reserve()xa_reserve_bh()xa_reserve_irq()xa_destroy()xa_set_mark()xa_clear_mark()
假設xa_lock保留在條目上：
__xa_store()__xa_insert()__xa_erase()__xa_cmpxchg()__xa_alloc()__xa_reserve()__xa_set_mark()__xa_clear_mark()
如果您想利用鎖來保護要存儲在XArray中的數據結構，可以在調用xa_lock() 之前調用xa_load()，然後在調用之前對找到的對象進行引用計數xa_unlock()。這將防止商店在查找對象和增加引用計數之間從數組中刪除對象。您也可以使用RCU避免取消引用釋放的內存，但是對此的解釋超出了本文的範圍。
XArray在修改陣列時不會禁用中斷或softirq。從RCU鎖定提供足夠的保護，從中斷或softirq上下文中讀取XArray是安全的。
例如，如果要在進程上下文中將條目存儲在XArray中，然後在softirq上下文中刪除它們，則可以通過以下方式進行操作：
void foo_init(struct foo *foo)
{
xa_init_flags(&foo->array, XA_FLAGS_LOCK_BH);
}
int foo_store(struct foo *foo, unsigned long index, void *entry)
{
int err;
xa_lock_bh(&foo->array);
err = xa_err(__xa_store(&foo->array, index, entry, GFP_KERNEL));
if (!err)
foo->count++;
xa_unlock_bh(&foo->array);
return err;
}
/* foo_erase() is only called from softirq context */
void foo_erase(struct foo *foo, unsigned long index)
{
xa_lock(&foo->array);
__xa_erase(&foo->array, index);
foo->count--;
xa_unlock(&foo->array);
}
如果要從中斷或softirq上下文修改XArray，則需要使用xa_init_flags()， XA_FLAGS_LOCK_IRQ或初始化數組XA_FLAGS_LOCK_BH。
上面的示例還顯示了一種常見的模式，該模式希望擴展商店側xa_lock的覆蓋範圍，以保護與該數組關聯的某些統計信息。
與中斷上下文共享XArray也是可能的，或者使用xa_lock_irqsave()兩個中斷處理程序和進程上下文，或xa_lock_irq()在進程上下文和xa_lock() 在中斷處理程序。一些較常見的模式有幫助的功能，例如xa_store_bh()，xa_store_irq()， xa_erase_bh()，xa_erase_irq()，xa_cmpxchg_bh() 和xa_cmpxchg_irq()。
有時您需要使用互斥鎖來保護對XArray的訪問，因爲該鎖位於鎖定層次結構中的另一個互斥鎖之上。這並不意味着您有權使用諸如__xa_erase()不帶xa_lock之類的功能；xa_lock用於lockdep驗證，將來將用於其他目的。
該__xa_set_mark()和__xa_clear_mark()功能也可用於在那裏你仰望的條目並想原子設置或清除標記的情況。在這種情況下，使用高級API可能會更有效率，因爲它將使您免於兩次行走。
進階API
先進的API以接口爲代價提供了更高的靈活性和更好的性能，而接口卻可能更難使用且保護措施更少。高級API不會爲您完成鎖定，並且要求您在修改數組時使用xa_lock。您可以選擇在陣列上執行只讀操作時使用xa_lock還是RCU鎖。您可以在同一陣列上混合使用高級操作和普通操作。實際上，普通API是根據高級API實現的。高級API僅適用於具有GPL兼容許可證的模塊。
高級API基於xa_state。這是一個不透明的數據結構，您可以使用XA_STATE() 宏在堆棧上聲明。該宏初始化了準備開始在XArray周圍移動的xa_state。它用作遊標以維護XArray中的位置，並讓您一起進行各種操作，而不必每次都從頂部重新啓動。
xa_state也用於存儲錯誤。您可以致電 xas_error()以檢索錯誤。所有操作都將在繼續操作之前檢查xa_state是否處於錯誤狀態，因此您無需在每次調用後檢查錯誤；您可以連續撥打多個電話，並且只能在方便的時候進行檢查。XArray代碼本身當前生成的唯一錯誤是ENOMEM和 EINVAL，但是它支持任意錯誤，以備您自稱 xas_set_err()。
如果xa_state ENOMEM出錯，則調用xas_nomem() 將嘗試使用指定的gfp標誌分配更多的內存，並將其緩存在xa_state中，以備下次嘗試。這個想法是您採用xa_lock，嘗試操作並放棄鎖。該操作嘗試在持有鎖定的同時分配內存，但是更有可能失敗。放開鎖後，xas_nomem() 可以嘗試分配更多的內存。true如果值得重試該操作（即存在內存錯誤並且 分配了更多的內存），它將返回。如果它先前已經分配了內存，並且沒有使用該內存，並且沒有錯誤（或某些不是not的錯誤 ENOMEM），那麼它將釋放先前分配的內存。
內部條目
XArray爲自己的目的保留了一些條目。這些通常不會通過常規API公開，但是在使用高級API時，可能會看到它們。通常，處理它們的最佳方法是將它們傳遞給xas_retry()，如果返回則重試該操作true。
| 名稱 | 測試 | 用法 |
| 節點 | xa_is_node() |
XArray節點。使用多索引xa_state時可能可見。 |
| 兄弟 | xa_is_sibling() |
多索引條目的非規範條目。該值指示此節點中的哪個插槽具有規範條目。 |
| 重試 | xa_is_retry() |
該條目當前正在由具有xa_lock的線程修改。包含該條目的節點可以在該RCU週期結束時釋放。您應該從數組的開頭重新開始查找。 |
| 零 | xa_is_zero() |
零條目的顯示NULL方式與普通API相同，但在XArray中佔據了一個條目，可用於保留索引以備將來使用。這是通過爲分配的條目分配XArray來使用的NULL。 |
將來可能會添加其他內部條目。儘可能由處理xas_retry()。
附加功能
該xas_create_range()函數分配所有必需的內存以存儲範圍內的每個條目。如果無法分配內存，它將在xa_state中設置ENOMEM。
您可以使用xas_init_marks()將條目上的標記重置爲其默認狀態。通常，所有標記都是清除的，除非XArray被標記爲XA_FLAGS_TRACK_FREE，在這種情況下，標記0被設置，所有其他標記都被清除。將一個條目替換爲另一個條目 xas_store()不會重置該條目上的標記；如果要重設標記，則應明確地進行。
該xas_load()會走xa_state儘可能靠近入口，因爲它可以。如果您知道xa_state已經移至該條目並且需要檢查該條目沒有更改，則可以使用 xas_reload()保存函數調用。
如果您需要移至XArray中的其他索引，請調用 xas_set()。這會將光標重置到樹的頂部，這通常會使下一個操作將光標移到樹中的所需位置。如果要移至下一個或上一個索引，請調用xas_next()或xas_prev()。設置索引不會使遊標在數組中移動，因此在移至下一個或上一個索引時不需要保持鎖定。
您可以使用搜索下一個當前條目xas_find()。這等同於xa_find()和xa_find_after(); 如果光標已移至某個條目，則它將在當前引用的條目之後找到下一個條目。如果不是，它將在xa_state的索引處返回條目。在大多數情況下，使用xas_next_entry()而不是移動到下一個當前條目xas_find()將節省函數調用，但以發出更多內聯代碼爲代價。
該xas_find_marked()功能是相似的。如果尚未遍歷xa_state，它將被標記xa_state的索引處返回條目。否則，它將返回xa_state引用的條目之後的第一個標記條目。該xas_next_marked() 功能等效於xas_next_entry()。
當使用xas_for_each() 或迭代XArray的範圍時xas_for_each_marked()，可能需要暫時停止迭代。該xas_pause()函數存在用於此目的。完成必要的工作並希望恢復後，xa_state處於適當的狀態，可以在上次處理條目之後繼續迭代。如果您在迭代時禁用了中斷，那麼暫停迭代並重新啓用每個XA_CHECK_SCHED條目的中斷是一種很好的方式。
的xas_get_mark()，xas_set_mark()和 xas_clear_mark()功能需要xa_state光標已移動到xarray適當的位置; 如果您已致電xas_pause()或xas_set() 之前致電，他們將無能爲力。
您可以xas_set_update()在每次XArray更新節點時調用來調用一個回調函數。頁面緩存工作集代碼使用它來維護其僅包含影子條目的節點列表。
多索引條目
XArray能夠將多個索引綁定在一起，因此對一個索引的操作會影響所有索引。例如，存儲到任何索引中都會更改從任何索引中檢索到的條目的值。在任何索引上設置或清除標記將在每個捆綁在一起的索引上設置或清除標記。當前的實現方式僅允許將兩個均方冪對齊的範圍綁定在一起。例如，索引64-127可以捆綁在一起，但2-6可以不捆綁在一起。這樣可以節省大量內存。例如，將512個條目捆綁在一起將節省超過4kB。
您可以通過使用XA_STATE_ORDER() 或xas_set_order()調用來創建多索引條目xas_store()。xas_load()使用多索引xa_state進行調用會將xa_state移到樹中的正確位置，但是返回值沒有意義，可能是內部條目，NULL甚至當範圍內存儲了條目時也是如此。調用xas_find_conflict() 將返回該範圍內的第一個條目，或者該範圍內NULL沒有條目。該xas_for_each_conflict()迭代器將每一個重疊指定範圍項遍歷。
如果xas_load()遇到多索引條目，則不會更改xa_state中的xa_index。在XArray上進行迭代或調用時xas_find()，如果初始索引位於多索引條目的中間，則它不會被更改。隨後的調用或迭代會將索引移至該範圍內的第一個索引。每個條目僅返回一次，無論它佔用多少索引。
使用xas_next()或xas_prev()用多指標xa_state不支持。在多索引條目上使用這兩個功能之一將顯示同級條目。這些應由調用者跳過。
存儲NULL到多索引條目的任何索引中將把每個索引處的條目設置爲NULL並消除聯繫。尚不支持將多索引條目拆分爲較小範圍的條目。
功能和結構
略。
xarray.h
/* SPDX-License-Identifier: GPL-2.0+ */
#ifndef _LINUX_XARRAY_H
#define _LINUX_XARRAY_H
/*
* eXtensible Arrays
* Copyright (c) 2017 Microsoft Corporation
* Author: Matthew Wilcox <[email protected]>
*
* See Documentation/core-api/xarray.rst for how to use the XArray.
*/
#include <linux/bug.h>
#include <linux/compiler.h>
#include <linux/gfp.h>
#include <linux/kconfig.h>
#include <linux/kernel.h>
#include <linux/rcupdate.h>
#include <linux/spinlock.h>
#include <linux/types.h>
/*
* The bottom two bits of the entry determine how the XArray interprets
* the contents:
*
* 00: Pointer entry
* 10: Internal entry
* x1: Value entry or tagged pointer
*
* Attempting to store internal entries in the XArray is a bug.
*
* Most internal entries are pointers to the next node in the tree.
* The following internal entries have a special meaning:
*
* 0-62: Sibling entries
* 256: Zero entry
* 257: Retry entry
*
* Errors are also represented as internal entries, but use the negative
* space (-4094 to -2). They're never stored in the slots array; only
* returned by the normal API.
*/
#define BITS_PER_XA_VALUE (BITS_PER_LONG - 1)
/**
* xa_mk_value() - Create an XArray entry from an integer.
* @v: Value to store in XArray.
*
* Context: Any context.
* Return: An entry suitable for storing in the XArray.
*/
static inline void *xa_mk_value(unsigned long v)
{
WARN_ON((long)v < 0);
return (void *)((v << 1) | 1);
}
/**
* xa_to_value() - Get value stored in an XArray entry.
* @entry: XArray entry.
*
* Context: Any context.
* Return: The value stored in the XArray entry.
*/
static inline unsigned long xa_to_value(const void *entry)
{
return (unsigned long)entry >> 1;
}
/**
* xa_is_value() - Determine if an entry is a value.
* @entry: XArray entry.
*
* Context: Any context.
* Return: True if the entry is a value, false if it is a pointer.
*/
static inline bool xa_is_value(const void *entry)
{
return (unsigned long)entry & 1;
}
/**
* xa_tag_pointer() - Create an XArray entry for a tagged pointer.
* @p: Plain pointer.
* @tag: Tag value (0, 1 or 3).
*
* If the user of the XArray prefers, they can tag their pointers instead
* of storing value entries. Three tags are available (0, 1 and 3).
* These are distinct from the xa_mark_t as they are not replicated up
* through the array and cannot be searched for.
*
* Context: Any context.
* Return: An XArray entry.
*/
static inline void *xa_tag_pointer(void *p, unsigned long tag)
{
return (void *)((unsigned long)p | tag);
}
/**
* xa_untag_pointer() - Turn an XArray entry into a plain pointer.
* @entry: XArray entry.
*
* If you have stored a tagged pointer in the XArray, call this function
* to get the untagged version of the pointer.
*
* Context: Any context.
* Return: A pointer.
*/
static inline void *xa_untag_pointer(void *entry)
{
return (void *)((unsigned long)entry & ~3UL);
}
/**
* xa_pointer_tag() - Get the tag stored in an XArray entry.
* @entry: XArray entry.
*
* If you have stored a tagged pointer in the XArray, call this function
* to get the tag of that pointer.
*
* Context: Any context.
* Return: A tag.
*/
static inline unsigned int xa_pointer_tag(void *entry)
{
return (unsigned long)entry & 3UL;
}
/*
* xa_mk_internal() - Create an internal entry.
* @v: Value to turn into an internal entry.
*
* Internal entries are used for a number of purposes. Entries 0-255 are
* used for sibling entries (only 0-62 are used by the current code). 256
* is used for the retry entry. 257 is used for the reserved / zero entry.
* Negative internal entries are used to represent errnos. Node pointers
* are also tagged as internal entries in some situations.
*
* Context: Any context.
* Return: An XArray internal entry corresponding to this value.
*/
static inline void *xa_mk_internal(unsigned long v)
{
return (void *)((v << 2) | 2);
}
/*
* xa_to_internal() - Extract the value from an internal entry.
* @entry: XArray entry.
*
* Context: Any context.
* Return: The value which was stored in the internal entry.
*/
static inline unsigned long xa_to_internal(const void *entry)
{
return (unsigned long)entry >> 2;
}
/*
* xa_is_internal() - Is the entry an internal entry?
* @entry: XArray entry.
*
* Context: Any context.
* Return: %true if the entry is an internal entry.
*/
static inline bool xa_is_internal(const void *entry)
{
return ((unsigned long)entry & 3) == 2;
}
#define XA_ZERO_ENTRY xa_mk_internal(257)
/**
* xa_is_zero() - Is the entry a zero entry?
* @entry: Entry retrieved from the XArray
*
* The normal API will return NULL as the contents of a slot containing
* a zero entry. You can only see zero entries by using the advanced API.
*
* Return: %true if the entry is a zero entry.
*/
static inline bool xa_is_zero(const void *entry)
{
return unlikely(entry == XA_ZERO_ENTRY);
}
/**
* xa_is_err() - Report whether an XArray operation returned an error
* @entry: Result from calling an XArray function
*
* If an XArray operation cannot complete an operation, it will return
* a special value indicating an error. This function tells you
* whether an error occurred; xa_err() tells you which error occurred.
*
* Context: Any context.
* Return: %true if the entry indicates an error.
*/
static inline bool xa_is_err(const void *entry)
{
return unlikely(xa_is_internal(entry) &&
entry >= xa_mk_internal(-MAX_ERRNO));
}
/**
* xa_err() - Turn an XArray result into an errno.
* @entry: Result from calling an XArray function.
*
* If an XArray operation cannot complete an operation, it will return
* a special pointer value which encodes an errno. This function extracts
* the errno from the pointer value, or returns 0 if the pointer does not
* represent an errno.
*
* Context: Any context.
* Return: A negative errno or 0.
*/
static inline int xa_err(void *entry)
{
/* xa_to_internal() would not do sign extension. */
if (xa_is_err(entry))
return (long)entry >> 2;
return 0;
}
/**
* struct xa_limit - Represents a range of IDs.
* @min: The lowest ID to allocate (inclusive).
* @max: The maximum ID to allocate (inclusive).
*
* This structure is used either directly or via the XA_LIMIT() macro
* to communicate the range of IDs that are valid for allocation.
* Two common ranges are predefined for you:
* * xa_limit_32b - [0 - UINT_MAX]
* * xa_limit_31b - [0 - INT_MAX]
*/
struct xa_limit {
u32 max;
u32 min;
};
#define XA_LIMIT(_min, _max) (struct xa_limit) { .min = _min, .max = _max }
#define xa_limit_32b XA_LIMIT(0, UINT_MAX)
#define xa_limit_31b XA_LIMIT(0, INT_MAX)
typedef unsigned __bitwise xa_mark_t;
#define XA_MARK_0 ((__force xa_mark_t)0U)
#define XA_MARK_1 ((__force xa_mark_t)1U)
#define XA_MARK_2 ((__force xa_mark_t)2U)
#define XA_PRESENT ((__force xa_mark_t)8U)
#define XA_MARK_MAX XA_MARK_2
#define XA_FREE_MARK XA_MARK_0
enum xa_lock_type {
XA_LOCK_IRQ = 1,
XA_LOCK_BH = 2,
};
/*
* Values for xa_flags. The radix tree stores its GFP flags in the xa_flags,
* and we remain compatible with that.
*/
#define XA_FLAGS_LOCK_IRQ ((__force gfp_t)XA_LOCK_IRQ)
#define XA_FLAGS_LOCK_BH ((__force gfp_t)XA_LOCK_BH)
#define XA_FLAGS_TRACK_FREE ((__force gfp_t)4U)
#define XA_FLAGS_ZERO_BUSY ((__force gfp_t)8U)
#define XA_FLAGS_ALLOC_WRAPPED ((__force gfp_t)16U)
#define XA_FLAGS_ACCOUNT ((__force gfp_t)32U)
#define XA_FLAGS_MARK(mark) ((__force gfp_t)((1U << __GFP_BITS_SHIFT) << \
(__force unsigned)(mark)))
/* ALLOC is for a normal 0-based alloc. ALLOC1 is for an 1-based alloc */
#define XA_FLAGS_ALLOC (XA_FLAGS_TRACK_FREE | XA_FLAGS_MARK(XA_FREE_MARK))
#define XA_FLAGS_ALLOC1 (XA_FLAGS_TRACK_FREE | XA_FLAGS_ZERO_BUSY)
/**
* struct xarray - The anchor of the XArray.
* @xa_lock: Lock that protects the contents of the XArray.
*
* To use the xarray, define it statically or embed it in your data structure.
* It is a very small data structure, so it does not usually make sense to
* allocate it separately and keep a pointer to it in your data structure.
*
* You may use the xa_lock to protect your own data structures as well.
*/
/*
* If all of the entries in the array are NULL, @xa_head is a NULL pointer.
* If the only non-NULL entry in the array is at index 0, @xa_head is that
* entry. If any other entry in the array is non-NULL, @xa_head points
* to an @xa_node.
*/
struct xarray {
spinlock_t xa_lock;
/* private: The rest of the data structure is not to be used directly. */
gfp_t xa_flags;
void __rcu * xa_head;
};
#define XARRAY_INIT(name, flags) { \
.xa_lock = __SPIN_LOCK_UNLOCKED(name.xa_lock), \
.xa_flags = flags, \
.xa_head = NULL, \
}
/**
* DEFINE_XARRAY_FLAGS() - Define an XArray with custom flags.
* @name: A string that names your XArray.
* @flags: XA_FLAG values.
*
* This is intended for file scope definitions of XArrays. It declares
* and initialises an empty XArray with the chosen name and flags. It is
* equivalent to calling xa_init_flags() on the array, but it does the
* initialisation at compiletime instead of runtime.
*/
#define DEFINE_XARRAY_FLAGS(name, flags) \
struct xarray name = XARRAY_INIT(name, flags)
/**
* DEFINE_XARRAY() - Define an XArray.
* @name: A string that names your XArray.
*
* This is intended for file scope definitions of XArrays. It declares
* and initialises an empty XArray with the chosen name. It is equivalent
* to calling xa_init() on the array, but it does the initialisation at
* compiletime instead of runtime.
*/
#define DEFINE_XARRAY(name) DEFINE_XARRAY_FLAGS(name, 0)
/**
* DEFINE_XARRAY_ALLOC() - Define an XArray which allocates IDs starting at 0.
* @name: A string that names your XArray.
*
* This is intended for file scope definitions of allocating XArrays.
* See also DEFINE_XARRAY().
*/
#define DEFINE_XARRAY_ALLOC(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC)
/**
* DEFINE_XARRAY_ALLOC1() - Define an XArray which allocates IDs starting at 1.
* @name: A string that names your XArray.
*
* This is intended for file scope definitions of allocating XArrays.
* See also DEFINE_XARRAY().
*/
#define DEFINE_XARRAY_ALLOC1(name) DEFINE_XARRAY_FLAGS(name, XA_FLAGS_ALLOC1)
void *xa_load(struct xarray *, unsigned long index);
void *xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
void *xa_erase(struct xarray *, unsigned long index);
void *xa_store_range(struct xarray *, unsigned long first, unsigned long last,
void *entry, gfp_t);
bool xa_get_mark(struct xarray *, unsigned long index, xa_mark_t);
void xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
void xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
void *xa_find(struct xarray *xa, unsigned long *index,
unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
void *xa_find_after(struct xarray *xa, unsigned long *index,
unsigned long max, xa_mark_t) __attribute__((nonnull(2)));
unsigned int xa_extract(struct xarray *, void **dst, unsigned long start,
unsigned long max, unsigned int n, xa_mark_t);
void xa_destroy(struct xarray *);
/**
* xa_init_flags() - Initialise an empty XArray with flags.
* @xa: XArray.
* @flags: XA_FLAG values.
*
* If you need to initialise an XArray with special flags (eg you need
* to take the lock from interrupt context), use this function instead
* of xa_init().
*
* Context: Any context.
*/
static inline void xa_init_flags(struct xarray *xa, gfp_t flags)
{
spin_lock_init(&xa->xa_lock);
xa->xa_flags = flags;
xa->xa_head = NULL;
}
/**
* xa_init() - Initialise an empty XArray.
* @xa: XArray.
*
* An empty XArray is full of NULL entries.
*
* Context: Any context.
*/
static inline void xa_init(struct xarray *xa)
{
xa_init_flags(xa, 0);
}
/**
* xa_empty() - Determine if an array has any present entries.
* @xa: XArray.
*
* Context: Any context.
* Return: %true if the array contains only NULL pointers.
*/
static inline bool xa_empty(const struct xarray *xa)
{
return xa->xa_head == NULL;
}
/**
* xa_marked() - Inquire whether any entry in this array has a mark set
* @xa: Array
* @mark: Mark value
*
* Context: Any context.
* Return: %true if any entry has this mark set.
*/
static inline bool xa_marked(const struct xarray *xa, xa_mark_t mark)
{
return xa->xa_flags & XA_FLAGS_MARK(mark);
}
/**
* xa_for_each_range() - Iterate over a portion of an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
* @start: First index to retrieve from array.
* @last: Last index to retrieve from array.
*
* During the iteration, @entry will have the value of the entry stored
* in @xa at @index. 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_range() 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_range() 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_range().
*
* Context: Any context. Takes and releases the RCU lock.
*/
#define xa_for_each_range(xa, index, entry, start, last) \
for (index = start, \
entry = xa_find(xa, &index, last, XA_PRESENT); \
entry; \
entry = xa_find_after(xa, &index, last, XA_PRESENT))
/**
* xa_for_each_start() - Iterate over a portion of an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
* @start: First index to retrieve from array.
*
* During the iteration, @entry will have the value of the entry stored
* in @xa at @index. 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_start() 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_start() 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_start().
*
* Context: Any context. Takes and releases the RCU lock.
*/
#define xa_for_each_start(xa, index, entry, start) \
xa_for_each_range(xa, index, entry, start, ULONG_MAX)
/**
* xa_for_each() - Iterate over present entries in an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
*
* During the iteration, @entry will have the value of the entry stored
* in @xa at @index. 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().
*
* Context: Any context. Takes and releases the RCU lock.
*/
#define xa_for_each(xa, index, entry) \
xa_for_each_start(xa, index, entry, 0)
/**
* xa_for_each_marked() - Iterate over marked entries in an XArray.
* @xa: XArray.
* @index: Index of @entry.
* @entry: Entry retrieved from array.
* @filter: Selection criterion.
*
* 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_marked() is O(n.log(n)) while xas_for_each_marked() 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_marked() will spin if it hits a retry entry; if you intend to
* see retry entries, you should use the xas_for_each_marked() iterator
* instead. The xas_for_each_marked() iterator will expand into more inline
* code than xa_for_each_marked().
*
* Context: Any context. Takes and releases the RCU lock.
*/
#define xa_for_each_marked(xa, index, entry, filter) \
for (index = 0, entry = xa_find(xa, &index, ULONG_MAX, filter); \
entry; entry = xa_find_after(xa, &index, ULONG_MAX, filter))
#define xa_trylock(xa) spin_trylock(&(xa)->xa_lock)
#define xa_lock(xa) spin_lock(&(xa)->xa_lock)
#define xa_unlock(xa) spin_unlock(&(xa)->xa_lock)
#define xa_lock_bh(xa) spin_lock_bh(&(xa)->xa_lock)
#define xa_unlock_bh(xa) spin_unlock_bh(&(xa)->xa_lock)
#define xa_lock_irq(xa) spin_lock_irq(&(xa)->xa_lock)
#define xa_unlock_irq(xa) spin_unlock_irq(&(xa)->xa_lock)
#define xa_lock_irqsave(xa, flags) \
spin_lock_irqsave(&(xa)->xa_lock, flags)
#define xa_unlock_irqrestore(xa, flags) \
spin_unlock_irqrestore(&(xa)->xa_lock, flags)
#define xa_lock_nested(xa, subclass) \
spin_lock_nested(&(xa)->xa_lock, subclass)
#define xa_lock_bh_nested(xa, subclass) \
spin_lock_bh_nested(&(xa)->xa_lock, subclass)
#define xa_lock_irq_nested(xa, subclass) \
spin_lock_irq_nested(&(xa)->xa_lock, subclass)
#define xa_lock_irqsave_nested(xa, flags, subclass) \
spin_lock_irqsave_nested(&(xa)->xa_lock, flags, subclass)
/*
* Versions of the normal API which require the caller to hold the
* xa_lock. If the GFP flags allow it, they will drop the lock to
* allocate memory, then reacquire it afterwards. These functions
* may also re-enable interrupts if the XArray flags indicate the
* locking should be interrupt safe.
*/
void *__xa_erase(struct xarray *, unsigned long index);
void *__xa_store(struct xarray *, unsigned long index, void *entry, gfp_t);
void *__xa_cmpxchg(struct xarray *, unsigned long index, void *old,
void *entry, gfp_t);
int __must_check __xa_insert(struct xarray *, unsigned long index,
void *entry, gfp_t);
int __must_check __xa_alloc(struct xarray *, u32 *id, void *entry,
struct xa_limit, gfp_t);
int __must_check __xa_alloc_cyclic(struct xarray *, u32 *id, void *entry,
struct xa_limit, u32 *next, gfp_t);
void __xa_set_mark(struct xarray *, unsigned long index, xa_mark_t);
void __xa_clear_mark(struct xarray *, unsigned long index, xa_mark_t);
/**
* xa_store_bh() - Store this entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* This function is like calling xa_store() except it disables softirqs
* while holding the array lock.
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs.
* Return: The entry which used to be at this index.
*/
static inline void *xa_store_bh(struct xarray *xa, unsigned long index,
void *entry, gfp_t gfp)
{
void *curr;
xa_lock_bh(xa);
curr = __xa_store(xa, index, entry, gfp);
xa_unlock_bh(xa);
return curr;
}
/**
* xa_store_irq() - Store this entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* This function is like calling xa_store() except it disables interrupts
* while holding the array lock.
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts.
* Return: The entry which used to be at this index.
*/
static inline void *xa_store_irq(struct xarray *xa, unsigned long index,
void *entry, gfp_t gfp)
{
void *curr;
xa_lock_irq(xa);
curr = __xa_store(xa, index, entry, gfp);
xa_unlock_irq(xa);
return curr;
}
/**
* xa_erase_bh() - Erase this entry from the XArray.
* @xa: XArray.
* @index: Index of entry.
*
* After this function returns, loading from @index will return %NULL.
* If the index is part of a multi-index entry, all indices will be erased
* and none of the entries will be part of a multi-index entry.
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs.
* Return: The entry which used to be at this index.
*/
static inline void *xa_erase_bh(struct xarray *xa, unsigned long index)
{
void *entry;
xa_lock_bh(xa);
entry = __xa_erase(xa, index);
xa_unlock_bh(xa);
return entry;
}
/**
* xa_erase_irq() - Erase this entry from the XArray.
* @xa: XArray.
* @index: Index of entry.
*
* After this function returns, loading from @index will return %NULL.
* If the index is part of a multi-index entry, all indices will be erased
* and none of the entries will be part of a multi-index entry.
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts.
* Return: The entry which used to be at this index.
*/
static inline void *xa_erase_irq(struct xarray *xa, unsigned long index)
{
void *entry;
xa_lock_irq(xa);
entry = __xa_erase(xa, index);
xa_unlock_irq(xa);
return entry;
}
/**
* xa_cmpxchg() - Conditionally replace an entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @old: Old value to test against.
* @entry: New value to place in array.
* @gfp: Memory allocation flags.
*
* If the entry at @index is the same as @old, replace it with @entry.
* If the return value is equal to @old, then the exchange was successful.
*
* Context: Any context. Takes and releases the xa_lock. May sleep
* if the @gfp flags permit.
* Return: The old value at this index or xa_err() if an error happened.
*/
static inline void *xa_cmpxchg(struct xarray *xa, unsigned long index,
void *old, void *entry, gfp_t gfp)
{
void *curr;
xa_lock(xa);
curr = __xa_cmpxchg(xa, index, old, entry, gfp);
xa_unlock(xa);
return curr;
}
/**
* xa_cmpxchg_bh() - Conditionally replace an entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @old: Old value to test against.
* @entry: New value to place in array.
* @gfp: Memory allocation flags.
*
* This function is like calling xa_cmpxchg() except it disables softirqs
* while holding the array lock.
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs. May sleep if the @gfp flags permit.
* Return: The old value at this index or xa_err() if an error happened.
*/
static inline void *xa_cmpxchg_bh(struct xarray *xa, unsigned long index,
void *old, void *entry, gfp_t gfp)
{
void *curr;
xa_lock_bh(xa);
curr = __xa_cmpxchg(xa, index, old, entry, gfp);
xa_unlock_bh(xa);
return curr;
}
/**
* xa_cmpxchg_irq() - Conditionally replace an entry in the XArray.
* @xa: XArray.
* @index: Index into array.
* @old: Old value to test against.
* @entry: New value to place in array.
* @gfp: Memory allocation flags.
*
* This function is like calling xa_cmpxchg() except it disables interrupts
* while holding the array lock.
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts. May sleep if the @gfp flags permit.
* Return: The old value at this index or xa_err() if an error happened.
*/
static inline void *xa_cmpxchg_irq(struct xarray *xa, unsigned long index,
void *old, void *entry, gfp_t gfp)
{
void *curr;
xa_lock_irq(xa);
curr = __xa_cmpxchg(xa, index, old, entry, gfp);
xa_unlock_irq(xa);
return curr;
}
/**
* xa_insert() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present. Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Any context. Takes and releases the xa_lock. May sleep if
* the @gfp flags permit.
* Return: 0 if the store succeeded. -EBUSY if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
static inline int __must_check xa_insert(struct xarray *xa,
unsigned long index, void *entry, gfp_t gfp)
{
int err;
xa_lock(xa);
err = __xa_insert(xa, index, entry, gfp);
xa_unlock(xa);
return err;
}
/**
* xa_insert_bh() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present. Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs. May sleep if the @gfp flags permit.
* Return: 0 if the store succeeded. -EBUSY if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
static inline int __must_check xa_insert_bh(struct xarray *xa,
unsigned long index, void *entry, gfp_t gfp)
{
int err;
xa_lock_bh(xa);
err = __xa_insert(xa, index, entry, gfp);
xa_unlock_bh(xa);
return err;
}
/**
* xa_insert_irq() - Store this entry in the XArray unless another entry is
* already present.
* @xa: XArray.
* @index: Index into array.
* @entry: New entry.
* @gfp: Memory allocation flags.
*
* Inserting a NULL entry will store a reserved entry (like xa_reserve())
* if no entry is present. Inserting will fail if a reserved entry is
* present, even though loading from this index will return NULL.
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts. May sleep if the @gfp flags permit.
* Return: 0 if the store succeeded. -EBUSY if another entry was present.
* -ENOMEM if memory could not be allocated.
*/
static inline int __must_check xa_insert_irq(struct xarray *xa,
unsigned long index, void *entry, gfp_t gfp)
{
int err;
xa_lock_irq(xa);
err = __xa_insert(xa, index, entry, gfp);
xa_unlock_irq(xa);
return err;
}
/**
* xa_alloc() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
*
* Context: Any context. Takes and releases the xa_lock. May sleep if
* the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
* -EBUSY if there are no free entries in @limit.
*/
static inline __must_check int xa_alloc(struct xarray *xa, u32 *id,
void *entry, struct xa_limit limit, gfp_t gfp)
{
int err;
xa_lock(xa);
err = __xa_alloc(xa, id, entry, limit, gfp);
xa_unlock(xa);
return err;
}
/**
* xa_alloc_bh() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs. May sleep if the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
* -EBUSY if there are no free entries in @limit.
*/
static inline int __must_check xa_alloc_bh(struct xarray *xa, u32 *id,
void *entry, struct xa_limit limit, gfp_t gfp)
{
int err;
xa_lock_bh(xa);
err = __xa_alloc(xa, id, entry, limit, gfp);
xa_unlock_bh(xa);
return err;
}
/**
* xa_alloc_irq() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts. May sleep if the @gfp flags permit.
* Return: 0 on success, -ENOMEM if memory could not be allocated or
* -EBUSY if there are no free entries in @limit.
*/
static inline int __must_check xa_alloc_irq(struct xarray *xa, u32 *id,
void *entry, struct xa_limit limit, gfp_t gfp)
{
int err;
xa_lock_irq(xa);
err = __xa_alloc(xa, id, entry, limit, gfp);
xa_unlock_irq(xa);
return err;
}
/**
* xa_alloc_cyclic() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of allocated ID.
* @next: Pointer to next ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
* Context: Any context. Takes and releases the xa_lock. May sleep if
* the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
* allocation succeeded after wrapping, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry,
struct xa_limit limit, u32 *next, gfp_t gfp)
{
int err;
xa_lock(xa);
err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
xa_unlock(xa);
return err;
}
/**
* xa_alloc_cyclic_bh() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of allocated ID.
* @next: Pointer to next ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs. May sleep if the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
* allocation succeeded after wrapping, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry,
struct xa_limit limit, u32 *next, gfp_t gfp)
{
int err;
xa_lock_bh(xa);
err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
xa_unlock_bh(xa);
return err;
}
/**
* xa_alloc_cyclic_irq() - Find somewhere to store this entry in the XArray.
* @xa: XArray.
* @id: Pointer to ID.
* @entry: New entry.
* @limit: Range of allocated ID.
* @next: Pointer to next ID to allocate.
* @gfp: Memory allocation flags.
*
* Finds an empty entry in @xa between @limit.min and @limit.max,
* stores the index into the @id pointer, then stores the entry at
* that index. A concurrent lookup will not see an uninitialised @id.
* The search for an empty entry will start at @next and will wrap
* around if necessary.
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts. May sleep if the @gfp flags permit.
* Return: 0 if the allocation succeeded without wrapping. 1 if the
* allocation succeeded after wrapping, -ENOMEM if memory could not be
* allocated or -EBUSY if there are no free entries in @limit.
*/
static inline int xa_alloc_cyclic_irq(struct xarray *xa, u32 *id, void *entry,
struct xa_limit limit, u32 *next, gfp_t gfp)
{
int err;
xa_lock_irq(xa);
err = __xa_alloc_cyclic(xa, id, entry, limit, next, gfp);
xa_unlock_irq(xa);
return err;
}
/**
* xa_reserve() - Reserve this index in the XArray.
* @xa: XArray.
* @index: Index into array.
* @gfp: Memory allocation flags.
*
* Ensures there is somewhere to store an entry at @index in the array.
* If there is already something stored at @index, this function does
* nothing. If there was nothing there, the entry is marked as reserved.
* Loading from a reserved entry returns a %NULL pointer.
*
* If you do not use the entry that you have reserved, call xa_release()
* or xa_erase() to free any unnecessary memory.
*
* Context: Any context. Takes and releases the xa_lock.
* May sleep if the @gfp flags permit.
* Return: 0 if the reservation succeeded or -ENOMEM if it failed.
*/
static inline __must_check
int xa_reserve(struct xarray *xa, unsigned long index, gfp_t gfp)
{
return xa_err(xa_cmpxchg(xa, index, NULL, XA_ZERO_ENTRY, gfp));
}
/**
* xa_reserve_bh() - Reserve this index in the XArray.
* @xa: XArray.
* @index: Index into array.
* @gfp: Memory allocation flags.
*
* A softirq-disabling version of xa_reserve().
*
* Context: Any context. Takes and releases the xa_lock while
* disabling softirqs.
* Return: 0 if the reservation succeeded or -ENOMEM if it failed.
*/
static inline __must_check
int xa_reserve_bh(struct xarray *xa, unsigned long index, gfp_t gfp)
{
return xa_err(xa_cmpxchg_bh(xa, index, NULL, XA_ZERO_ENTRY, gfp));
}
/**
* xa_reserve_irq() - Reserve this index in the XArray.
* @xa: XArray.
* @index: Index into array.
* @gfp: Memory allocation flags.
*
* An interrupt-disabling version of xa_reserve().
*
* Context: Process context. Takes and releases the xa_lock while
* disabling interrupts.
* Return: 0 if the reservation succeeded or -ENOMEM if it failed.
*/
static inline __must_check
int xa_reserve_irq(struct xarray *xa, unsigned long index, gfp_t gfp)
{
return xa_err(xa_cmpxchg_irq(xa, index, NULL, XA_ZERO_ENTRY, gfp));
}
/**
* xa_release() - Release a reserved entry.
* @xa: XArray.
* @index: Index of entry.
*
* After calling xa_reserve(), you can call this function to release the
* reservation. If the entry at @index has been stored to, this function
* will do nothing.
*/
static inline void xa_release(struct xarray *xa, unsigned long index)
{
xa_cmpxchg(xa, index, XA_ZERO_ENTRY, NULL, 0);
}
/* Everything below here is the Advanced API. Proceed with caution. */
/*
* The xarray is constructed out of a set of 'chunks' of pointers. Choosing
* the best chunk size requires some tradeoffs. A power of two recommends
* itself so that we can walk the tree based purely on shifts and masks.
* Generally, the larger the better; as the number of slots per level of the
* tree increases, the less tall the tree needs to be. But that needs to be
* balanced against the memory consumption of each node. On a 64-bit system,
* xa_node is currently 576 bytes, and we get 7 of them per 4kB page. If we
* doubled the number of slots per node, we'd get only 3 nodes per 4kB page.
*/
#ifndef XA_CHUNK_SHIFT
#define XA_CHUNK_SHIFT (CONFIG_BASE_SMALL ? 4 : 6)
#endif
#define XA_CHUNK_SIZE (1UL << XA_CHUNK_SHIFT)
#define XA_CHUNK_MASK (XA_CHUNK_SIZE - 1)
#define XA_MAX_MARKS 3
#define XA_MARK_LONGS DIV_ROUND_UP(XA_CHUNK_SIZE, BITS_PER_LONG)
/*
* @count is the count of every non-NULL element in the ->slots array
* whether that is a value entry, a retry entry, a user pointer,
* a sibling entry or a pointer to the next level of the tree.
* @nr_values is the count of every element in ->slots which is
* either a value entry or a sibling of a value entry.
*/
struct xa_node {
unsigned char shift; /* Bits remaining in each slot */
unsigned char offset; /* Slot offset in parent */
unsigned char count; /* Total entry count */
unsigned char nr_values; /* Value entry count */
struct xa_node __rcu *parent; /* NULL at top of tree */
struct xarray *array; /* The array we belong to */
union {
struct list_head private_list; /* For tree user */
struct rcu_head rcu_head; /* Used when freeing node */
};
void __rcu *slots[XA_CHUNK_SIZE];
union {
unsigned long tags[XA_MAX_MARKS][XA_MARK_LONGS];
unsigned long marks[XA_MAX_MARKS][XA_MARK_LONGS];
};
};
void xa_dump(const struct xarray *);
void xa_dump_node(const struct xa_node *);
#ifdef XA_DEBUG
#define XA_BUG_ON(xa, x) do { \
if (x) { \
xa_dump(xa); \
BUG(); \
} \
} while (0)
#define XA_NODE_BUG_ON(node, x) do { \
if (x) { \
if (node) xa_dump_node(node); \
BUG(); \
} \
} while (0)
#else
#define XA_BUG_ON(xa, x) do { } while (0)
#define XA_NODE_BUG_ON(node, x) do { } while (0)
#endif
/* Private */
static inline void *xa_head(const struct xarray *xa)
{
return rcu_dereference_check(xa->xa_head,
lockdep_is_held(&xa->xa_lock));
}
/* Private */
static inline void *xa_head_locked(const struct xarray *xa)
{
return rcu_dereference_protected(xa->xa_head,
lockdep_is_held(&xa->xa_lock));
}
/* Private */
static inline void *xa_entry(const struct xarray *xa,
const struct xa_node *node, unsigned int offset)
{
XA_NODE_BUG_ON(node, offset >= XA_CHUNK_SIZE);
return rcu_dereference_check(node->slots[offset],
lockdep_is_held(&xa->xa_lock));
}
/* Private */
static inline void *xa_entry_locked(const struct xarray *xa,
const struct xa_node *node, unsigned int offset)
{
XA_NODE_BUG_ON(node, offset >= XA_CHUNK_SIZE);
return rcu_dereference_protected(node->slots[offset],
lockdep_is_held(&xa->xa_lock));
}
/* Private */
static inline struct xa_node *xa_parent(const struct xarray *xa,
const struct xa_node *node)
{
return rcu_dereference_check(node->parent,
lockdep_is_held(&xa->xa_lock));
}
/* Private */
static inline struct xa_node *xa_parent_locked(const struct xarray *xa,
const struct xa_node *node)
{
return rcu_dereference_protected(node->parent,
lockdep_is_held(&xa->xa_lock));
}
/* Private */
static inline void *xa_mk_node(const struct xa_node *node)
{
return (void *)((unsigned long)node | 2);
}
/* Private */
static inline struct xa_node *xa_to_node(const void *entry)
{
return (struct xa_node *)((unsigned long)entry - 2);
}
/* Private */
static inline bool xa_is_node(const void *entry)
{
return xa_is_internal(entry) && (unsigned long)entry > 4096;
}
/* Private */
static inline void *xa_mk_sibling(unsigned int offset)
{
return xa_mk_internal(offset);
}
/* Private */
static inline unsigned long xa_to_sibling(const void *entry)
{
return xa_to_internal(entry);
}
/**
* xa_is_sibling() - Is the entry a sibling entry?
* @entry: Entry retrieved from the XArray
*
* Return: %true if the entry is a sibling entry.
*/
static inline bool xa_is_sibling(const void *entry)
{
return IS_ENABLED(CONFIG_XARRAY_MULTI) && xa_is_internal(entry) &&
(entry < xa_mk_sibling(XA_CHUNK_SIZE - 1));
}
#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(const void *entry)
{
return unlikely(entry == XA_RETRY_ENTRY);
}
/**
* xa_is_advanced() - Is the entry only permitted for the advanced API?
* @entry: Entry to be stored in the XArray.
*
* Return: %true if the entry cannot be stored by the normal API.
*/
static inline bool xa_is_advanced(const void *entry)
{
return xa_is_internal(entry) && (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.
*
* Context: The xa_lock is held and interrupts may be disabled.
* Implementations should not drop the xa_lock, nor re-enable
* interrupts.
*/
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 XA_ERROR(errno) ((struct xa_node *)(((unsigned long)errno << 2) | 2UL))
#define XAS_BOUNDS ((struct xa_node *)1UL)
#define XAS_RESTART ((struct xa_node *)3UL)
#define __XA_STATE(array, index, shift, sibs) { \
.xa = array, \
.xa_index = index, \
.xa_shift = shift, \
.xa_sibs = sibs, \
.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).
* @array: Array to operate on.
* @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, 0, 0)
/**
* XA_STATE_ORDER() - Declare an XArray operation state.
* @name: Name of this operation state (usually xas).
* @array: Array to operate on.
* @index: Initial index of interest.
* @order: Order of entry.
*
* Declare and initialise an xa_state on the stack. This variant of
* XA_STATE() allows you to specify the 'order' of the element you
* want to operate on.`
*/
#define XA_STATE_ORDER(name, array, index, order) \
struct xa_state name = __XA_STATE(array, \
(index >> order) << order, \
order - (order % XA_CHUNK_SHIFT), \
(1U << (order % XA_CHUNK_SHIFT)) - 1)
#define xas_marked(xas, mark) xa_marked((xas)->xa, (mark))
#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)
{
return xa_err(xas->xa_node);
}
/**
* xas_set_err() - Note an error in the xa_state.
* @xas: XArray operation state.
* @err: Negative error number.
*
* Only call this function with a negative @err; zero or positive errors
* will probably not behave the way you think they should. If you want
* to clear the error from an xa_state, use xas_reset().
*/
static inline void xas_set_err(struct xa_state *xas, long err)
{
xas->xa_node = XA_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_is_node() - Does the xas point to a node?
* @xas: XArray operation state.
*
* Return: %true if the xas currently references a node.
*/
static inline bool xas_is_node(const struct xa_state *xas)
{
return xas_valid(xas) && xas->xa_node;
}
/* 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 RESTART or an error */
static inline bool xas_frozen(struct xa_node *node)
{
return (unsigned long)node & 2;
}
/* True if the node represents head-of-tree, RESTART or BOUNDS */
static inline bool xas_top(struct xa_node *node)
{
return node <= XAS_RESTART;
}
/**
* xas_reset() - Reset an XArray operation state.
* @xas: XArray operation state.
*
* Resets the error or walk state of the @xas so future walks of the
* array will start from the root. Use this if you have dropped the
* xarray lock and want to reuse the xa_state.
*
* Context: Any context.
*/
static inline void xas_reset(struct xa_state *xas)
{
xas->xa_node = XAS_RESTART;
}
/**
* xas_retry() - Retry the operation if appropriate.
* @xas: XArray operation state.
* @entry: Entry from xarray.
*
* The advanced functions may sometimes return an internal entry, such as
* a retry entry or a zero entry. This function sets up the @xas to restart
* the walk from the head of the array if needed.
*
* Context: Any context.
* Return: true if the operation needs to be retried.
*/
static inline bool xas_retry(struct xa_state *xas, const void *entry)
{
if (xa_is_zero(entry))
return true;
if (!xa_is_retry(entry))
return false;
xas_reset(xas);
return true;
}
void *xas_load(struct xa_state *);
void *xas_store(struct xa_state *, void *entry);
void *xas_find(struct xa_state *, unsigned long max);
void *xas_find_conflict(struct xa_state *);
bool xas_get_mark(const struct xa_state *, xa_mark_t);
void xas_set_mark(const struct xa_state *, xa_mark_t);
void xas_clear_mark(const struct xa_state *, xa_mark_t);
void *xas_find_marked(struct xa_state *, unsigned long max, xa_mark_t);
void xas_init_marks(const struct xa_state *);
bool xas_nomem(struct xa_state *, gfp_t);
void xas_pause(struct xa_state *);
void xas_create_range(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);
}
/**
* xas_set() - Set up XArray operation state for a different index.
* @xas: XArray operation state.
* @index: New index into the XArray.
*
* Move the operation state to refer to a different index. This will
* have the effect of starting a walk from the top; see xas_next()
* to move to an adjacent index.
*/
static inline void xas_set(struct xa_state *xas, unsigned long index)
{
xas->xa_index = index;
xas->xa_node = XAS_RESTART;
}
/**
* xas_set_order() - Set up XArray operation state for a multislot entry.
* @xas: XArray operation state.
* @index: Target of the operation.
* @order: Entry occupies 2^@order indices.
*/
static inline void xas_set_order(struct xa_state *xas, unsigned long index,
unsigned int order)
{
#ifdef CONFIG_XARRAY_MULTI
xas->xa_index = order < BITS_PER_LONG ? (index >> order) << order : 0;
xas->xa_shift = order - (order % XA_CHUNK_SHIFT);
xas->xa_sibs = (1 << (order % XA_CHUNK_SHIFT)) - 1;
xas->xa_node = XAS_RESTART;
#else
BUG_ON(order > 0);
xas_set(xas, index);
#endif
}
/**
* xas_set_update() - Set up XArray operation state for a callback.
* @xas: XArray operation state.
* @update: Function to call when updating a node.
*
* The XArray can notify a caller after it has updated an xa_node.
* This is advanced functionality and is only needed by the page cache.
*/
static inline void xas_set_update(struct xa_state *xas, xa_update_node_t update)
{
xas->xa_update = update;
}
/**
* 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 ||
xas->xa_offset != (xas->xa_index & XA_CHUNK_MASK)))
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);
entry = xa_entry(xas->xa, node, xas->xa_offset + 1);
if (unlikely(xa_is_internal(entry)))
return xas_find(xas, max);
xas->xa_offset++;
xas->xa_index++;
} while (!entry);
return entry;
}
/* Private */
static inline unsigned int xas_find_chunk(struct xa_state *xas, bool advance,
xa_mark_t mark)
{
unsigned long *addr = xas->xa_node->marks[(__force unsigned)mark];
unsigned int offset = xas->xa_offset;
if (advance)
offset++;
if (XA_CHUNK_SIZE == BITS_PER_LONG) {
if (offset < XA_CHUNK_SIZE) {
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_marked() - Advance iterator to next marked entry.
* @xas: XArray operation state.
* @max: Highest index to return.
* @mark: Mark to search for.
*
* xas_next_marked() is an inline function to optimise xarray traversal for
* speed. It is equivalent to calling xas_find_marked(), and will call
* xas_find_marked() for all the hard cases.
*
* Return: The next marked entry after the one currently referred to by @xas.
*/
static inline void *xas_next_marked(struct xa_state *xas, unsigned long max,
xa_mark_t mark)
{
struct xa_node *node = xas->xa_node;
void *entry;
unsigned int offset;
if (unlikely(xas_not_node(node) || node->shift))
return xas_find_marked(xas, max, mark);
offset = xas_find_chunk(xas, true, mark);
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_marked(xas, max, mark);
entry = xa_entry(xas->xa, node, offset);
if (!entry)
return xas_find_marked(xas, max, mark);
return entry;
}
/*
* 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 the 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_marked() - Iterate over a range of an XArray.
* @xas: XArray operation state.
* @entry: Entry retrieved from the array.
* @max: Maximum index to retrieve from array.
* @mark: Mark to search for.
*
* The loop body will be executed for each marked 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_marked(xas, entry, max, mark) \
for (entry = xas_find_marked(xas, max, mark); entry; \
entry = xas_next_marked(xas, max, mark))
/**
* xas_for_each_conflict() - Iterate over a range of an XArray.
* @xas: XArray operation state.
* @entry: Entry retrieved from the array.
*
* The loop body will be executed for each entry in the XArray that lies
* within the range specified by @xas. If the loop completes successfully,
* any entries that lie in this range will be replaced by @entry. The caller
* may break out of the loop; if they do so, the contents of the XArray will
* be unchanged. The operation may fail due to an out of memory condition.
* The caller may also call xa_set_err() to exit the loop while setting an
* error to record the reason.
*/
#define xas_for_each_conflict(xas, entry) \
while ((entry = xas_find_conflict(xas)))
void *__xas_next(struct xa_state *);
void *__xas_prev(struct xa_state *);
/**
* xas_prev() - Move iterator to previous index.
* @xas: XArray operation state.
*
* If the @xas was in an error state, it will remain in an error state
* and this function will return %NULL. If the @xas has never been walked,
* it will have the effect of calling xas_load(). Otherwise one will be
* subtracted from the index and the state will be walked to the correct
* location in the array for the next operation.
*
* If the iterator was referencing index 0, this function wraps
* around to %ULONG_MAX.
*
* Return: The entry at the new index. This may be %NULL or an internal
* entry.
*/
static inline void *xas_prev(struct xa_state *xas)
{
struct xa_node *node = xas->xa_node;
if (unlikely(xas_not_node(node) || node->shift ||
xas->xa_offset == 0))
return __xas_prev(xas);
xas->xa_index--;
xas->xa_offset--;
return xa_entry(xas->xa, node, xas->xa_offset);
}
/**
* xas_next() - Move state to next index.
* @xas: XArray operation state.
*
* If the @xas was in an error state, it will remain in an error state
* and this function will return %NULL. If the @xas has never been walked,
* it will have the effect of calling xas_load(). Otherwise one will be
* added to the index and the state will be walked to the correct
* location in the array for the next operation.
*
* If the iterator was referencing index %ULONG_MAX, this function wraps
* around to 0.
*
* Return: The entry at the new index. This may be %NULL or an internal
* entry.
*/
static inline void *xas_next(struct xa_state *xas)
{
struct xa_node *node = xas->xa_node;
if (unlikely(xas_not_node(node) || node->shift ||
xas->xa_offset == XA_CHUNK_MASK))
return __xas_next(xas);
xas->xa_index++;
xas->xa_offset++;
return xa_entry(xas->xa, node, xas->xa_offset);
}
#endif /* _LINUX_XARRAY_H */