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UBIFS: fully sort GCed nodes
The 'joinup()' function cannot deal with situations when nodes go in reverse order - it just leaves them in this order. This patch implement full nodes sorting using n*log(n) algorithm. It sorts data nodes for bulk-read, and direntry nodes for readdir(). Signed-off-by: Artem Bityutskiy <Artem.Bityutskiy@nokia.com>
This commit is contained in:
Artem Bityutskiy
parent
7d4e9ccb43
commit
f10770f5e5
432
fs/ubifs/gc.c
432
fs/ubifs/gc.c
@ -47,7 +47,7 @@
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* have to waste large pieces of free space at the end of LEB B, because nodes
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* from LEB A would not fit. And the worst situation is when all nodes are of
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* maximum size. So dark watermark is the amount of free + dirty space in LEB
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* which are guaranteed to be reclaimable. If LEB has less space, the GC migh
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* which are guaranteed to be reclaimable. If LEB has less space, the GC might
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* be unable to reclaim it. So, LEBs with free + dirty greater than dark
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* watermark are "good" LEBs from GC's point of few. The other LEBs are not so
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* good, and GC takes extra care when moving them.
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@ -56,14 +56,6 @@
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#include <linux/pagemap.h>
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#include "ubifs.h"
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/*
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* GC tries to optimize the way it fit nodes to available space, and it sorts
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* nodes a little. The below constants are watermarks which define "large",
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* "medium", and "small" nodes.
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*/
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#define MEDIUM_NODE_WM (UBIFS_BLOCK_SIZE / 4)
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#define SMALL_NODE_WM UBIFS_MAX_DENT_NODE_SZ
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/*
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* GC may need to move more than one LEB to make progress. The below constants
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* define "soft" and "hard" limits on the number of LEBs the garbage collector
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@ -116,83 +108,222 @@ static int switch_gc_head(struct ubifs_info *c)
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}
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/**
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* joinup - bring data nodes for an inode together.
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* @c: UBIFS file-system description object
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* @sleb: describes scanned LEB
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* @inum: inode number
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* @blk: block number
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* @data: list to which to add data nodes
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* list_sort - sort a list.
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* @priv: private data, passed to @cmp
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* @head: the list to sort
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* @cmp: the elements comparison function
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*
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* This function looks at the first few nodes in the scanned LEB @sleb and adds
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* them to @data if they are data nodes from @inum and have a larger block
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* number than @blk. This function returns %0 on success and a negative error
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* code on failure.
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* This function has been implemented by Mark J Roberts <mjr@znex.org>. It
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* implements "merge sort" which has O(nlog(n)) complexity. The list is sorted
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* in ascending order.
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*
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* The comparison function @cmp is supposed to return a negative value if @a is
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* than @b, and a positive value if @a is greater than @b. If @a and @b are
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* equivalent, then it does not matter what this function returns.
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*/
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static int joinup(struct ubifs_info *c, struct ubifs_scan_leb *sleb, ino_t inum,
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unsigned int blk, struct list_head *data)
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static void list_sort(void *priv, struct list_head *head,
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int (*cmp)(void *priv, struct list_head *a,
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struct list_head *b))
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{
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int err, cnt = 6, lnum = sleb->lnum, offs;
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struct ubifs_scan_node *snod, *tmp;
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union ubifs_key *key;
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struct list_head *p, *q, *e, *list, *tail, *oldhead;
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int insize, nmerges, psize, qsize, i;
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list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
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key = &snod->key;
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if (key_inum(c, key) == inum &&
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key_type(c, key) == UBIFS_DATA_KEY &&
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key_block(c, key) > blk) {
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offs = snod->offs;
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err = ubifs_tnc_has_node(c, key, 0, lnum, offs, 0);
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if (err < 0)
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return err;
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list_del(&snod->list);
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if (err) {
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list_add_tail(&snod->list, data);
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blk = key_block(c, key);
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} else
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kfree(snod);
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cnt = 6;
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} else if (--cnt == 0)
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if (list_empty(head))
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return;
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list = head->next;
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list_del(head);
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insize = 1;
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for (;;) {
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p = oldhead = list;
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list = tail = NULL;
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nmerges = 0;
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while (p) {
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nmerges++;
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q = p;
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psize = 0;
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for (i = 0; i < insize; i++) {
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psize++;
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q = q->next == oldhead ? NULL : q->next;
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if (!q)
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break;
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}
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qsize = insize;
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while (psize > 0 || (qsize > 0 && q)) {
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if (!psize) {
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e = q;
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q = q->next;
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qsize--;
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if (q == oldhead)
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q = NULL;
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} else if (!qsize || !q) {
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e = p;
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p = p->next;
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psize--;
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if (p == oldhead)
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p = NULL;
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} else if (cmp(priv, p, q) <= 0) {
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e = p;
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p = p->next;
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psize--;
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if (p == oldhead)
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p = NULL;
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} else {
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e = q;
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q = q->next;
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qsize--;
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if (q == oldhead)
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q = NULL;
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}
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if (tail)
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tail->next = e;
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else
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list = e;
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e->prev = tail;
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tail = e;
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}
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p = q;
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}
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tail->next = list;
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list->prev = tail;
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if (nmerges <= 1)
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break;
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insize *= 2;
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}
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return 0;
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head->next = list;
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head->prev = list->prev;
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list->prev->next = head;
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list->prev = head;
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}
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/**
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* move_nodes - move nodes.
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* @c: UBIFS file-system description object
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* @sleb: describes nodes to move
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* data_nodes_cmp - compare 2 data nodes.
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* @priv: UBIFS file-system description object
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* @a: first data node
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* @a: second data node
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*
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* This function moves valid nodes from data LEB described by @sleb to the GC
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* journal head. The obsolete nodes are dropped.
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*
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* When moving nodes we have to deal with classical bin-packing problem: the
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* space in the current GC journal head LEB and in @c->gc_lnum are the "bins",
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* where the nodes in the @sleb->nodes list are the elements which should be
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* fit optimally to the bins. This function uses the "first fit decreasing"
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* strategy, although it does not really sort the nodes but just split them on
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* 3 classes - large, medium, and small, so they are roughly sorted.
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*
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* This function returns zero in case of success, %-EAGAIN if commit is
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* required, and other negative error codes in case of other failures.
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* This function compares data nodes @a and @b. Returns %1 if @a has greater
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* inode or block number, and %-1 otherwise.
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*/
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static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
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int data_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
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{
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ino_t inuma, inumb;
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struct ubifs_info *c = priv;
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struct ubifs_scan_node *sa, *sb;
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cond_resched();
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sa = list_entry(a, struct ubifs_scan_node, list);
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sb = list_entry(b, struct ubifs_scan_node, list);
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ubifs_assert(key_type(c, &sa->key) == UBIFS_DATA_KEY);
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ubifs_assert(key_type(c, &sb->key) == UBIFS_DATA_KEY);
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inuma = key_inum(c, &sa->key);
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inumb = key_inum(c, &sb->key);
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if (inuma == inumb) {
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unsigned int blka = key_block(c, &sa->key);
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unsigned int blkb = key_block(c, &sb->key);
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if (blka <= blkb)
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return -1;
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} else if (inuma <= inumb)
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return -1;
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return 1;
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}
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/*
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* nondata_nodes_cmp - compare 2 non-data nodes.
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* @priv: UBIFS file-system description object
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* @a: first node
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* @a: second node
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*
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* This function compares nodes @a and @b. It makes sure that inode nodes go
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* first and sorted by length in descending order. Directory entry nodes go
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* after inode nodes and are sorted in ascending hash valuer order.
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*/
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int nondata_nodes_cmp(void *priv, struct list_head *a, struct list_head *b)
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{
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int typea, typeb;
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ino_t inuma, inumb;
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struct ubifs_info *c = priv;
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struct ubifs_scan_node *sa, *sb;
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cond_resched();
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sa = list_entry(a, struct ubifs_scan_node, list);
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sb = list_entry(b, struct ubifs_scan_node, list);
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typea = key_type(c, &sa->key);
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typeb = key_type(c, &sb->key);
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ubifs_assert(typea != UBIFS_DATA_KEY && typeb != UBIFS_DATA_KEY);
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/* Inodes go before directory entries */
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if (typea == UBIFS_INO_KEY) {
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if (typeb == UBIFS_INO_KEY)
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return sb->len - sa->len;
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return -1;
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}
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if (typeb == UBIFS_INO_KEY)
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return 1;
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ubifs_assert(typea == UBIFS_DENT_KEY && typeb == UBIFS_DENT_KEY);
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inuma = key_inum(c, &sa->key);
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inumb = key_inum(c, &sb->key);
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if (inuma == inumb) {
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uint32_t hasha = key_hash(c, &sa->key);
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uint32_t hashb = key_hash(c, &sb->key);
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if (hasha <= hashb)
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return -1;
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} else if (inuma <= inumb)
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return -1;
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return 1;
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}
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/**
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* sort_nodes - sort nodes for GC.
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* @c: UBIFS file-system description object
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* @sleb: describes nodes to sort and contains the result on exit
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* @nondata: contains non-data nodes on exit
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* @min: minimum node size is returned here
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*
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* This function sorts the list of inodes to garbage collect. First of all, it
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* kills obsolete nodes and separates data and non-data nodes to the
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* @sleb->nodes and @nondata lists correspondingly.
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*
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* Data nodes are then sorted in block number order - this is important for
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* bulk-read; data nodes with lower inode number go before data nodes with
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* higher inode number, and data nodes with lower block number go before data
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* nodes with higher block number;
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*
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* Non-data nodes are sorted as follows.
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* o First go inode nodes - they are sorted in descending length order.
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* o Then go directory entry nodes - they are sorted in hash order, which
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* should supposedly optimize 'readdir()'. Direntry nodes with lower parent
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* inode number go before direntry nodes with higher parent inode number,
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* and direntry nodes with lower name hash values go before direntry nodes
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* with higher name hash values.
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*
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* This function returns zero in case of success and a negative error code in
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* case of failure.
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*/
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static int sort_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
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struct list_head *nondata, int *min)
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{
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struct ubifs_scan_node *snod, *tmp;
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struct list_head data, large, medium, small;
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struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
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int avail, err, min = INT_MAX;
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unsigned int blk = 0;
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ino_t inum = 0;
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INIT_LIST_HEAD(&data);
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INIT_LIST_HEAD(&large);
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INIT_LIST_HEAD(&medium);
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INIT_LIST_HEAD(&small);
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*min = INT_MAX;
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while (!list_empty(&sleb->nodes)) {
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struct list_head *lst = sleb->nodes.next;
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snod = list_entry(lst, struct ubifs_scan_node, list);
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/* Separate data nodes and non-data nodes */
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list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
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int err;
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ubifs_assert(snod->type != UBIFS_IDX_NODE);
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ubifs_assert(snod->type != UBIFS_REF_NODE);
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@ -201,53 +332,72 @@ static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
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err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
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snod->offs, 0);
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if (err < 0)
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goto out;
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return err;
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list_del(lst);
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if (!err) {
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/* The node is obsolete, remove it from the list */
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list_del(&snod->list);
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kfree(snod);
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continue;
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}
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/*
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* Sort the list of nodes so that data nodes go first, large
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* nodes go second, and small nodes go last.
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*/
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if (key_type(c, &snod->key) == UBIFS_DATA_KEY) {
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if (inum != key_inum(c, &snod->key)) {
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if (inum) {
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/*
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* Try to move data nodes from the same
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* inode together.
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*/
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err = joinup(c, sleb, inum, blk, &data);
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if (err)
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goto out;
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}
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inum = key_inum(c, &snod->key);
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blk = key_block(c, &snod->key);
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}
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list_add_tail(lst, &data);
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} else if (snod->len > MEDIUM_NODE_WM)
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list_add_tail(lst, &large);
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else if (snod->len > SMALL_NODE_WM)
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list_add_tail(lst, &medium);
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else
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list_add_tail(lst, &small);
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if (snod->len < *min)
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*min = snod->len;
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/* And find the smallest node */
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if (snod->len < min)
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min = snod->len;
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if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
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list_move_tail(&snod->list, nondata);
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}
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/*
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* Join the tree lists so that we'd have one roughly sorted list
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* ('large' will be the head of the joined list).
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*/
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list_splice(&data, &large);
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list_splice(&medium, large.prev);
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list_splice(&small, large.prev);
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/* Sort data and non-data nodes */
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list_sort(c, &sleb->nodes, &data_nodes_cmp);
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list_sort(c, nondata, &nondata_nodes_cmp);
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return 0;
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}
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/**
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* move_node - move a node.
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* @c: UBIFS file-system description object
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* @sleb: describes the LEB to move nodes from
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* @snod: the mode to move
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* @wbuf: write-buffer to move node to
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*
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* This function moves node @snod to @wbuf, changes TNC correspondingly, and
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* destroys @snod. Returns zero in case of success and a negative error code in
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* case of failure.
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*/
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static int move_node(struct ubifs_info *c, struct ubifs_scan_leb *sleb,
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struct ubifs_scan_node *snod, struct ubifs_wbuf *wbuf)
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{
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int err, new_lnum = wbuf->lnum, new_offs = wbuf->offs + wbuf->used;
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cond_resched();
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err = ubifs_wbuf_write_nolock(wbuf, snod->node, snod->len);
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if (err)
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return err;
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err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
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snod->offs, new_lnum, new_offs,
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snod->len);
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list_del(&snod->list);
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kfree(snod);
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return err;
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}
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/**
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* move_nodes - move nodes.
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* @c: UBIFS file-system description object
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* @sleb: describes the LEB to move nodes from
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*
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* This function moves valid nodes from data LEB described by @sleb to the GC
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* journal head. This function returns zero in case of success, %-EAGAIN if
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* commit is required, and other negative error codes in case of other
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* failures.
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*/
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static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
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{
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int err, min;
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LIST_HEAD(nondata);
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struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
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if (wbuf->lnum == -1) {
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/*
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@ -256,42 +406,59 @@ static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
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*/
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err = switch_gc_head(c);
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if (err)
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goto out;
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return err;
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}
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err = sort_nodes(c, sleb, &nondata, &min);
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if (err)
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goto out;
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/* Write nodes to their new location. Use the first-fit strategy */
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while (1) {
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avail = c->leb_size - wbuf->offs - wbuf->used;
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list_for_each_entry_safe(snod, tmp, &large, list) {
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int new_lnum, new_offs;
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int avail;
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struct ubifs_scan_node *snod, *tmp;
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/* Move data nodes */
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list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
|
||||
avail = c->leb_size - wbuf->offs - wbuf->used;
|
||||
if (snod->len > avail)
|
||||
/*
|
||||
* Do not skip data nodes in order to optimize
|
||||
* bulk-read.
|
||||
*/
|
||||
break;
|
||||
|
||||
err = move_node(c, sleb, snod, wbuf);
|
||||
if (err)
|
||||
goto out;
|
||||
}
|
||||
|
||||
/* Move non-data nodes */
|
||||
list_for_each_entry_safe(snod, tmp, &nondata, list) {
|
||||
avail = c->leb_size - wbuf->offs - wbuf->used;
|
||||
if (avail < min)
|
||||
break;
|
||||
|
||||
if (snod->len > avail)
|
||||
/* This node does not fit */
|
||||
if (snod->len > avail) {
|
||||
/*
|
||||
* Keep going only if this is an inode with
|
||||
* some data. Otherwise stop and switch the GC
|
||||
* head. IOW, we assume that data-less inode
|
||||
* nodes and direntry nodes are roughly of the
|
||||
* same size.
|
||||
*/
|
||||
if (key_type(c, &snod->key) == UBIFS_DENT_KEY ||
|
||||
snod->len == UBIFS_INO_NODE_SZ)
|
||||
break;
|
||||
continue;
|
||||
}
|
||||
|
||||
cond_resched();
|
||||
|
||||
new_lnum = wbuf->lnum;
|
||||
new_offs = wbuf->offs + wbuf->used;
|
||||
err = ubifs_wbuf_write_nolock(wbuf, snod->node,
|
||||
snod->len);
|
||||
err = move_node(c, sleb, snod, wbuf);
|
||||
if (err)
|
||||
goto out;
|
||||
err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
|
||||
snod->offs, new_lnum, new_offs,
|
||||
snod->len);
|
||||
if (err)
|
||||
goto out;
|
||||
|
||||
avail = c->leb_size - wbuf->offs - wbuf->used;
|
||||
list_del(&snod->list);
|
||||
kfree(snod);
|
||||
}
|
||||
|
||||
if (list_empty(&large))
|
||||
if (list_empty(&sleb->nodes) && list_empty(&nondata))
|
||||
break;
|
||||
|
||||
/*
|
||||
@ -306,10 +473,7 @@ static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
|
||||
return 0;
|
||||
|
||||
out:
|
||||
list_for_each_entry_safe(snod, tmp, &large, list) {
|
||||
list_del(&snod->list);
|
||||
kfree(snod);
|
||||
}
|
||||
list_splice_tail(&nondata, &sleb->nodes);
|
||||
return err;
|
||||
}
|
||||
|
||||
|
||||
Loading…
Reference in New Issue
Block a user