From a3b803747b363b0ececd329583e0412672e7f30b Mon Sep 17 00:00:00 2001 From: Zhihao Cheng Date: Fri, 2 Feb 2024 10:22:53 +0800 Subject: mtd-utils: Extract list implementation to common lib and add list_sort support Current list implementation code is put under jffs utils, extract it into common lib, and add more list operations(eg. list_move, list_splice, etc.). Besides, add list sorting support in new source file lib/list_sort.c. This is a preparation for replacing implementation of UBIFS utils with linux kernel libs. Signed-off-by: Zhihao Cheng Signed-off-by: David Oberhollenzer --- include/list.h | 263 ++++++++++++++++++++++++++++++++++++++++++++++ jffsX-utils/Makemodule.am | 3 +- jffsX-utils/compr.c | 49 --------- jffsX-utils/compr.h | 5 +- lib/Makemodule.am | 2 + lib/list_sort.c | 246 +++++++++++++++++++++++++++++++++++++++++++ 6 files changed, 514 insertions(+), 54 deletions(-) create mode 100644 include/list.h create mode 100644 lib/list_sort.c diff --git a/include/list.h b/include/list.h new file mode 100644 index 0000000..d26c9d1 --- /dev/null +++ b/include/list.h @@ -0,0 +1,263 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2006 Silicon Graphics, Inc. + * All Rights Reserved. + */ +#ifndef __LIST_H__ +#define __LIST_H__ + +#include + +/* + * This undef is here because BSD 4.4 added some LIST_ macros into system + * header file sys/queue.h. This header is included in many other system + * headers and thus causes "macro redefined" warnings. + * + * As OS X is kind of a derivate of BSD, this affects OS X too. + * + * To use our own LIST_ macros (copied from kernel code), we have to + * at first undefine the conflicting system macros. + * + */ +#undef LIST_HEAD +#undef LIST_HEAD_INIT + +/* + * Simple, generic doubly-linked list implementation. + */ + +struct list_head { + struct list_head *next; + struct list_head *prev; +}; + +#define LIST_HEAD_INIT(name) { &(name), &(name) } + +#define LIST_HEAD(name) \ + struct list_head name = LIST_HEAD_INIT(name) + +#define INIT_LIST_HEAD(list) list_head_init(list) +static inline void list_head_init(struct list_head *list) +{ + list->next = list->prev = list; +} + +static inline void list_head_destroy(struct list_head *list) +{ + list->next = list->prev = NULL; +} + +static inline void __list_add(struct list_head *add, + struct list_head *prev, struct list_head *next) +{ + next->prev = add; + add->next = next; + add->prev = prev; + prev->next = add; +} + +static inline void list_add(struct list_head *add, struct list_head *head) +{ + __list_add(add, head, head->next); +} + +static inline void list_add_tail(struct list_head *add, struct list_head *head) +{ + __list_add(add, head->prev, head); +} + +static inline void __list_del(struct list_head *prev, struct list_head *next) +{ + next->prev = prev; + prev->next = next; +} + +static inline void list_del_init(struct list_head *entry) +{ + __list_del(entry->prev, entry->next); + list_head_init(entry); +} + +static inline void list_del(struct list_head *entry) +{ + __list_del(entry->prev, entry->next); +} + +static inline void list_move(struct list_head *list, struct list_head *head) +{ + __list_del(list->prev, list->next); + list_add(list, head); +} + +static inline void list_move_tail(struct list_head *list, struct list_head *head) +{ + __list_del(list->prev, list->next); + list_add_tail(list, head); +} + +/** + * list_is_last - tests whether @list is the last entry in list @head + * @list: the entry to test + * @head: the head of the list + */ +static inline int list_is_last(const struct list_head *list, const struct list_head *head) +{ + return list->next == head; +} + +static inline int list_empty(const struct list_head *head) +{ + return head->next == head; +} + +static inline void __list_splice(struct list_head *list, + struct list_head *prev, + struct list_head *next) +{ + struct list_head *first = list->next; + struct list_head *last = list->prev; + + first->prev = prev; + prev->next = first; + + last->next = next; + next->prev = last; +} + +static inline void list_splice(struct list_head *list, struct list_head *head) +{ + if (!list_empty(list)) + __list_splice(list, head, head->next); +} + +static inline void list_splice_tail(struct list_head *list, + struct list_head *head) +{ + if (!list_empty(list)) + __list_splice(list, head->prev, head); +} + +static inline void list_splice_init(struct list_head *list, + struct list_head *head) +{ + if (!list_empty(list)) { + __list_splice(list, head, head->next); + list_head_init(list); + } +} + +#define list_entry(ptr, type, member) ({ \ + const typeof( ((type *)0)->member ) *__mptr = (ptr); \ + (type *)( (char *)__mptr - offsetof(type,member) );}) + +#define list_for_each(pos, head) \ + for (pos = (head)->next; pos != (head); pos = pos->next) + +#define list_for_each_safe(pos, n, head) \ + for (pos = (head)->next, n = pos->next; pos != (head); \ + pos = n, n = pos->next) + +#define list_for_each_entry(pos, head, member) \ + for (pos = list_entry((head)->next, typeof(*pos), member); \ + &pos->member != (head); \ + pos = list_entry(pos->member.next, typeof(*pos), member)) + +#define list_for_each_entry_safe(pos, n, head, member) \ + for (pos = list_entry((head)->next, typeof(*pos), member), \ + n = list_entry(pos->member.next, typeof(*pos), member); \ + &pos->member != (head); \ + pos = n, n = list_entry(n->member.next, typeof(*n), member)) + +#define list_first_entry(ptr, type, member) \ + list_entry((ptr)->next, type, member) + +#define container_of(ptr, type, member) ({ \ + const typeof( ((type *)0)->member ) *__mptr = (ptr); \ + (type *)( (char *)__mptr - offsetof(type,member) );}) + +/** + * list_entry_is_head - test if the entry points to the head of the list + * @pos: the type * to cursor + * @head: the head for your list. + * @member: the name of the list_head within the struct. + */ +#define list_entry_is_head(pos, head, member) \ + (&pos->member == (head)) + +typedef int __attribute__((nonnull(2,3))) (*list_cmp_func_t)(void *, + const struct list_head *, const struct list_head *); +__attribute__((nonnull(2,3))) +void list_sort(void *priv, struct list_head *head, list_cmp_func_t cmp); + +/** + * list_splice_tail_init - join two lists and reinitialise the emptied list + * @list: the new list to add. + * @head: the place to add it in the first list. + * + * Each of the lists is a queue. + * The list at @list is reinitialised + */ +static inline void list_splice_tail_init(struct list_head *list, + struct list_head *head) +{ + if (!list_empty(list)) { + __list_splice(list, head->prev, head); + INIT_LIST_HEAD(list); + } +} + +/** + * list_replace - replace old entry by new one + * @old : the element to be replaced + * @new : the new element to insert + * + * If @old was empty, it will be overwritten. + */ +static inline void list_replace(struct list_head *old, + struct list_head *new) +{ + new->next = old->next; + new->next->prev = new; + new->prev = old->prev; + new->prev->next = new; +} + +/** + * list_last_entry - get the last element from a list + * @ptr: the list head to take the element from. + * @type: the type of the struct this is embedded in. + * @member: the name of the list_head within the struct. + * + * Note, that list is expected to be not empty. + */ +#define list_last_entry(ptr, type, member) \ + list_entry((ptr)->prev, type, member) + +/** + * list_prev_entry - get the prev element in list + * @pos: the type * to cursor + * @member: the name of the list_head within the struct. + */ +#define list_prev_entry(pos, member) \ + list_entry((pos)->member.prev, typeof(*(pos)), member) + +/** + * list_next_entry - get the next element in list + * @pos: the type * to cursor + * @member: the name of the list_head within the struct. + */ +#define list_next_entry(pos, member) \ + list_entry((pos)->member.next, typeof(*(pos)), member) + +/** + * list_for_each_entry_reverse - iterate backwards over list of given type. + * @pos: the type * to use as a loop cursor. + * @head: the head for your list. + * @member: the name of the list_head within the struct. + */ +#define list_for_each_entry_reverse(pos, head, member) \ + for (pos = list_last_entry(head, typeof(*pos), member); \ + &pos->member != (head); \ + pos = list_prev_entry(pos, member)) + +#endif /* __LIST_H__ */ diff --git a/jffsX-utils/Makemodule.am b/jffsX-utils/Makemodule.am index 266c12e..2374b85 100644 --- a/jffsX-utils/Makemodule.am +++ b/jffsX-utils/Makemodule.am @@ -9,7 +9,8 @@ mkfs_jffs2_SOURCES = \ jffsX-utils/rbtree.h \ jffsX-utils/summary.h \ include/linux/jffs2.h \ - include/mtd/jffs2-user.h + include/mtd/jffs2-user.h \ + include/list.h mkfs_jffs2_LDADD = libmtd.a $(ZLIB_LIBS) $(LZO_LIBS) mkfs_jffs2_CPPFLAGS = $(AM_CPPFLAGS) $(ZLIB_CFLAGS) $(LZO_CFLAGS) diff --git a/jffsX-utils/compr.c b/jffsX-utils/compr.c index 01176eb..d408ef8 100644 --- a/jffsX-utils/compr.c +++ b/jffsX-utils/compr.c @@ -17,55 +17,6 @@ extern int page_size; -/* LIST IMPLEMENTATION (from linux/list.h) */ - -#define LIST_HEAD_INIT(name) { &(name), &(name) } - -#define LIST_HEAD(name) \ - struct list_head name = LIST_HEAD_INIT(name) - -static inline void __list_add(struct list_head *new, - struct list_head *prev, - struct list_head *next) -{ - next->prev = new; - new->next = next; - new->prev = prev; - prev->next = new; -} - -static inline void list_add(struct list_head *new, struct list_head *head) -{ - __list_add(new, head, head->next); -} - -static inline void list_add_tail(struct list_head *new, struct list_head *head) -{ - __list_add(new, head->prev, head); -} - -static inline void __list_del(struct list_head *prev, struct list_head *next) -{ - next->prev = prev; - prev->next = next; -} - -static inline void list_del(struct list_head *entry) -{ - __list_del(entry->prev, entry->next); - entry->next = (void *) 0; - entry->prev = (void *) 0; -} - -#define list_entry(ptr, type, member) \ - ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member))) - -#define list_for_each_entry(pos, head, member) \ - for (pos = list_entry((head)->next, typeof(*pos), member); \ - &pos->member != (head); \ - pos = list_entry(pos->member.next, typeof(*pos), member)) - - /* Available compressors are on this list */ static LIST_HEAD(jffs2_compressor_list); diff --git a/jffsX-utils/compr.h b/jffsX-utils/compr.h index f1f5975..6969952 100644 --- a/jffsX-utils/compr.h +++ b/jffsX-utils/compr.h @@ -15,6 +15,7 @@ #include #include #include "linux/jffs2.h" +#include "list.h" #define CONFIG_JFFS2_RTIME @@ -49,10 +50,6 @@ #define KERN_INFO #define KERN_DEBUG -struct list_head { - struct list_head *next, *prev; -}; - void jffs2_set_compression_mode(int mode); int jffs2_get_compression_mode(void); int jffs2_set_compression_mode_name(const char *mode_name); diff --git a/lib/Makemodule.am b/lib/Makemodule.am index 570896b..7f890da 100644 --- a/lib/Makemodule.am +++ b/lib/Makemodule.am @@ -5,6 +5,8 @@ libmtd_a_SOURCES = \ include/libfec.h \ lib/common.c \ include/common.h \ + lib/list_sort.c \ + include/list.h \ lib/libcrc32.c \ include/crc32.h \ lib/libmtd_legacy.c \ diff --git a/lib/list_sort.c b/lib/list_sort.c new file mode 100644 index 0000000..d873438 --- /dev/null +++ b/lib/list_sort.c @@ -0,0 +1,246 @@ +// SPDX-License-Identifier: GPL-2.0 +#include "list.h" + +/* + * Returns a list organized in an intermediate format suited + * to chaining of merge() calls: null-terminated, no reserved or + * sentinel head node, "prev" links not maintained. + */ +__attribute__((nonnull(2,3,4))) +static struct list_head *merge(void *priv, list_cmp_func_t cmp, + struct list_head *a, struct list_head *b) +{ + struct list_head *head, **tail = &head; + + for (;;) { + /* if equal, take 'a' -- important for sort stability */ + if (cmp(priv, a, b) <= 0) { + *tail = a; + tail = &a->next; + a = a->next; + if (!a) { + *tail = b; + break; + } + } else { + *tail = b; + tail = &b->next; + b = b->next; + if (!b) { + *tail = a; + break; + } + } + } + return head; +} + +/* + * Combine final list merge with restoration of standard doubly-linked + * list structure. This approach duplicates code from merge(), but + * runs faster than the tidier alternatives of either a separate final + * prev-link restoration pass, or maintaining the prev links + * throughout. + */ +__attribute__((nonnull(2,3,4,5))) +static void merge_final(void *priv, list_cmp_func_t cmp, struct list_head *head, + struct list_head *a, struct list_head *b) +{ + struct list_head *tail = head; + unsigned int count = 0; + + for (;;) { + /* if equal, take 'a' -- important for sort stability */ + if (cmp(priv, a, b) <= 0) { + tail->next = a; + a->prev = tail; + tail = a; + a = a->next; + if (!a) + break; + } else { + tail->next = b; + b->prev = tail; + tail = b; + b = b->next; + if (!b) { + b = a; + break; + } + } + } + + /* Finish linking remainder of list b on to tail */ + tail->next = b; + do { + /* + * If the merge is highly unbalanced (e.g. the input is + * already sorted), this loop may run many iterations. + * Continue callbacks to the client even though no + * element comparison is needed, so the client's cmp() + * routine can invoke cond_resched() periodically. + */ + if (!++count) + cmp(priv, b, b); + b->prev = tail; + tail = b; + b = b->next; + } while (b); + + /* And the final links to make a circular doubly-linked list */ + tail->next = head; + head->prev = tail; +} + +/** + * list_sort - sort a list + * @priv: private data, opaque to list_sort(), passed to @cmp + * @head: the list to sort + * @cmp: the elements comparison function + * + * The comparison function @cmp must return > 0 if @a should sort after + * @b ("@a > @b" if you want an ascending sort), and <= 0 if @a should + * sort before @b *or* their original order should be preserved. It is + * always called with the element that came first in the input in @a, + * and list_sort is a stable sort, so it is not necessary to distinguish + * the @a < @b and @a == @b cases. + * + * This is compatible with two styles of @cmp function: + * - The traditional style which returns <0 / =0 / >0, or + * - Returning a boolean 0/1. + * The latter offers a chance to save a few cycles in the comparison + * (which is used by e.g. plug_ctx_cmp() in block/blk-mq.c). + * + * A good way to write a multi-word comparison is:: + * + * if (a->high != b->high) + * return a->high > b->high; + * if (a->middle != b->middle) + * return a->middle > b->middle; + * return a->low > b->low; + * + * + * This mergesort is as eager as possible while always performing at least + * 2:1 balanced merges. Given two pending sublists of size 2^k, they are + * merged to a size-2^(k+1) list as soon as we have 2^k following elements. + * + * Thus, it will avoid cache thrashing as long as 3*2^k elements can + * fit into the cache. Not quite as good as a fully-eager bottom-up + * mergesort, but it does use 0.2*n fewer comparisons, so is faster in + * the common case that everything fits into L1. + * + * + * The merging is controlled by "count", the number of elements in the + * pending lists. This is beautifully simple code, but rather subtle. + * + * Each time we increment "count", we set one bit (bit k) and clear + * bits k-1 .. 0. Each time this happens (except the very first time + * for each bit, when count increments to 2^k), we merge two lists of + * size 2^k into one list of size 2^(k+1). + * + * This merge happens exactly when the count reaches an odd multiple of + * 2^k, which is when we have 2^k elements pending in smaller lists, + * so it's safe to merge away two lists of size 2^k. + * + * After this happens twice, we have created two lists of size 2^(k+1), + * which will be merged into a list of size 2^(k+2) before we create + * a third list of size 2^(k+1), so there are never more than two pending. + * + * The number of pending lists of size 2^k is determined by the + * state of bit k of "count" plus two extra pieces of information: + * + * - The state of bit k-1 (when k == 0, consider bit -1 always set), and + * - Whether the higher-order bits are zero or non-zero (i.e. + * is count >= 2^(k+1)). + * + * There are six states we distinguish. "x" represents some arbitrary + * bits, and "y" represents some arbitrary non-zero bits: + * 0: 00x: 0 pending of size 2^k; x pending of sizes < 2^k + * 1: 01x: 0 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k + * 2: x10x: 0 pending of size 2^k; 2^k + x pending of sizes < 2^k + * 3: x11x: 1 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k + * 4: y00x: 1 pending of size 2^k; 2^k + x pending of sizes < 2^k + * 5: y01x: 2 pending of size 2^k; 2^(k-1) + x pending of sizes < 2^k + * (merge and loop back to state 2) + * + * We gain lists of size 2^k in the 2->3 and 4->5 transitions (because + * bit k-1 is set while the more significant bits are non-zero) and + * merge them away in the 5->2 transition. Note in particular that just + * before the 5->2 transition, all lower-order bits are 11 (state 3), + * so there is one list of each smaller size. + * + * When we reach the end of the input, we merge all the pending + * lists, from smallest to largest. If you work through cases 2 to + * 5 above, you can see that the number of elements we merge with a list + * of size 2^k varies from 2^(k-1) (cases 3 and 5 when x == 0) to + * 2^(k+1) - 1 (second merge of case 5 when x == 2^(k-1) - 1). + */ +__attribute__((nonnull(2,3))) +void list_sort(void *priv, struct list_head *head, list_cmp_func_t cmp) +{ + struct list_head *list = head->next, *pending = NULL; + size_t count = 0; /* Count of pending */ + + if (list == head->prev) /* Zero or one elements */ + return; + + /* Convert to a null-terminated singly-linked list. */ + head->prev->next = NULL; + + /* + * Data structure invariants: + * - All lists are singly linked and null-terminated; prev + * pointers are not maintained. + * - pending is a prev-linked "list of lists" of sorted + * sublists awaiting further merging. + * - Each of the sorted sublists is power-of-two in size. + * - Sublists are sorted by size and age, smallest & newest at front. + * - There are zero to two sublists of each size. + * - A pair of pending sublists are merged as soon as the number + * of following pending elements equals their size (i.e. + * each time count reaches an odd multiple of that size). + * That ensures each later final merge will be at worst 2:1. + * - Each round consists of: + * - Merging the two sublists selected by the highest bit + * which flips when count is incremented, and + * - Adding an element from the input as a size-1 sublist. + */ + do { + size_t bits; + struct list_head **tail = &pending; + + /* Find the least-significant clear bit in count */ + for (bits = count; bits & 1; bits >>= 1) + tail = &(*tail)->prev; + /* Do the indicated merge */ + if (bits) { + struct list_head *a = *tail, *b = a->prev; + + a = merge(priv, cmp, b, a); + /* Install the merged result in place of the inputs */ + a->prev = b->prev; + *tail = a; + } + + /* Move one element from input list to pending */ + list->prev = pending; + pending = list; + list = list->next; + pending->next = NULL; + count++; + } while (list); + + /* End of input; merge together all the pending lists. */ + list = pending; + pending = pending->prev; + for (;;) { + struct list_head *next = pending->prev; + + if (!next) + break; + list = merge(priv, cmp, pending, list); + pending = next; + } + /* The final merge, rebuilding prev links */ + merge_final(priv, cmp, head, pending, list); +} -- cgit v1.2.3