UBIFS: fully sort GCed nodes (f10770f5) · Commits · 戴 / test

fs/ubifs/gc.c

+296 −132

Original line number	Diff line number	Diff line
		@@ -47,7 +47,7 @@
		* have to waste large pieces of free space at the end of LEB B, because nodes
		* from LEB A would not fit. And the worst situation is when all nodes are of
		* maximum size. So dark watermark is the amount of free + dirty space in LEB
		* which are guaranteed to be reclaimable. If LEB has less space, the GC migh
		* which are guaranteed to be reclaimable. If LEB has less space, the GC might
		* be unable to reclaim it. So, LEBs with free + dirty greater than dark
		* watermark are "good" LEBs from GC's point of few. The other LEBs are not so
		* good, and GC takes extra care when moving them.
		@@ -56,14 +56,6 @@
		#include <linux/pagemap.h>
		#include "ubifs.h"

		/*
		* GC tries to optimize the way it fit nodes to available space, and it sorts
		* nodes a little. The below constants are watermarks which define "large",
		* "medium", and "small" nodes.
		*/
		#define MEDIUM_NODE_WM (UBIFS_BLOCK_SIZE / 4)
		#define SMALL_NODE_WM UBIFS_MAX_DENT_NODE_SZ

		/*
		* GC may need to move more than one LEB to make progress. The below constants
		* define "soft" and "hard" limits on the number of LEBs the garbage collector
		@@ -116,83 +108,222 @@ static int switch_gc_head(struct ubifs_info *c)
		}

		/**
		* joinup - bring data nodes for an inode together.
		* @c: UBIFS file-system description object
		* @sleb: describes scanned LEB
		* @inum: inode number
		* @blk: block number
		* @data: list to which to add data nodes
		* list_sort - sort a list.
		* @priv: private data, passed to @cmp
		* @head: the list to sort
		* @cmp: the elements comparison function
		*
		* This function has been implemented by Mark J Roberts <mjr@znex.org>. It
		* implements "merge sort" which has O(nlog(n)) complexity. The list is sorted
		* in ascending order.
		*
		* This function looks at the first few nodes in the scanned LEB @sleb and adds
		* them to @data if they are data nodes from @inum and have a larger block
		* number than @blk. This function returns %0 on success and a negative error
		* code on failure.
		* The comparison function @cmp is supposed to return a negative value if @a is
		* than @b, and a positive value if @a is greater than @b. If @a and @b are
		* equivalent, then it does not matter what this function returns.
		*/
		static int joinup(struct ubifs_info c, struct ubifs_scan_leb sleb, ino_t inum,
		unsigned int blk, struct list_head *data)
		static void list_sort(void priv, struct list_head head,
		int (cmp)(void priv, struct list_head *a,
		struct list_head *b))
		{
		int err, cnt = 6, lnum = sleb->lnum, offs;
		struct ubifs_scan_node snod, tmp;
		union ubifs_key *key;
		struct list_head p, q, e, list, tail, oldhead;
		int insize, nmerges, psize, qsize, i;

		if (list_empty(head))
		return;

		list = head->next;
		list_del(head);
		insize = 1;
		for (;;) {
		p = oldhead = list;
		list = tail = NULL;
		nmerges = 0;

		while (p) {
		nmerges++;
		q = p;
		psize = 0;
		for (i = 0; i < insize; i++) {
		psize++;
		q = q->next == oldhead ? NULL : q->next;
		if (!q)
		break;
		}

		list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
		key = &snod->key;
		if (key_inum(c, key) == inum &&
		key_type(c, key) == UBIFS_DATA_KEY &&
		key_block(c, key) > blk) {
		offs = snod->offs;
		err = ubifs_tnc_has_node(c, key, 0, lnum, offs, 0);
		if (err < 0)
		return err;
		list_del(&snod->list);
		if (err) {
		list_add_tail(&snod->list, data);
		blk = key_block(c, key);
		} else
		kfree(snod);
		cnt = 6;
		} else if (--cnt == 0)
		qsize = insize;
		while (psize > 0 \|\| (qsize > 0 && q)) {
		if (!psize) {
		e = q;
		q = q->next;
		qsize--;
		if (q == oldhead)
		q = NULL;
		} else if (!qsize \|\| !q) {
		e = p;
		p = p->next;
		psize--;
		if (p == oldhead)
		p = NULL;
		} else if (cmp(priv, p, q) <= 0) {
		e = p;
		p = p->next;
		psize--;
		if (p == oldhead)
		p = NULL;
		} else {
		e = q;
		q = q->next;
		qsize--;
		if (q == oldhead)
		q = NULL;
		}
		if (tail)
		tail->next = e;
		else
		list = e;
		e->prev = tail;
		tail = e;
		}
		p = q;
		}

		tail->next = list;
		list->prev = tail;

		if (nmerges <= 1)
		break;

		insize *= 2;
		}
		return 0;

		head->next = list;
		head->prev = list->prev;
		list->prev->next = head;
		list->prev = head;
		}

		/**
		* move_nodes - move nodes.
		* data_nodes_cmp - compare 2 data nodes.
		* @priv: UBIFS file-system description object
		* @a: first data node
		* @a: second data node
		*
		* This function compares data nodes @a and @b. Returns %1 if @a has greater
		* inode or block number, and %-1 otherwise.
		*/
		int data_nodes_cmp(void priv, struct list_head a, struct list_head *b)
		{
		ino_t inuma, inumb;
		struct ubifs_info *c = priv;
		struct ubifs_scan_node sa, sb;

		cond_resched();
		sa = list_entry(a, struct ubifs_scan_node, list);
		sb = list_entry(b, struct ubifs_scan_node, list);
		ubifs_assert(key_type(c, &sa->key) == UBIFS_DATA_KEY);
		ubifs_assert(key_type(c, &sb->key) == UBIFS_DATA_KEY);

		inuma = key_inum(c, &sa->key);
		inumb = key_inum(c, &sb->key);

		if (inuma == inumb) {
		unsigned int blka = key_block(c, &sa->key);
		unsigned int blkb = key_block(c, &sb->key);

		if (blka <= blkb)
		return -1;
		} else if (inuma <= inumb)
		return -1;

		return 1;
		}

		/*
		* nondata_nodes_cmp - compare 2 non-data nodes.
		* @priv: UBIFS file-system description object
		* @a: first node
		* @a: second node
		*
		* This function compares nodes @a and @b. It makes sure that inode nodes go
		* first and sorted by length in descending order. Directory entry nodes go
		* after inode nodes and are sorted in ascending hash valuer order.
		*/
		int nondata_nodes_cmp(void priv, struct list_head a, struct list_head *b)
		{
		int typea, typeb;
		ino_t inuma, inumb;
		struct ubifs_info *c = priv;
		struct ubifs_scan_node sa, sb;

		cond_resched();
		sa = list_entry(a, struct ubifs_scan_node, list);
		sb = list_entry(b, struct ubifs_scan_node, list);
		typea = key_type(c, &sa->key);
		typeb = key_type(c, &sb->key);
		ubifs_assert(typea != UBIFS_DATA_KEY && typeb != UBIFS_DATA_KEY);

		/* Inodes go before directory entries */
		if (typea == UBIFS_INO_KEY) {
		if (typeb == UBIFS_INO_KEY)
		return sb->len - sa->len;
		return -1;
		}
		if (typeb == UBIFS_INO_KEY)
		return 1;

		ubifs_assert(typea == UBIFS_DENT_KEY && typeb == UBIFS_DENT_KEY);
		inuma = key_inum(c, &sa->key);
		inumb = key_inum(c, &sb->key);

		if (inuma == inumb) {
		uint32_t hasha = key_hash(c, &sa->key);
		uint32_t hashb = key_hash(c, &sb->key);

		if (hasha <= hashb)
		return -1;
		} else if (inuma <= inumb)
		return -1;

		return 1;
		}

		/**
		* sort_nodes - sort nodes for GC.
		* @c: UBIFS file-system description object
		* @sleb: describes nodes to move
		* @sleb: describes nodes to sort and contains the result on exit
		* @nondata: contains non-data nodes on exit
		* @min: minimum node size is returned here
		*
		* This function moves valid nodes from data LEB described by @sleb to the GC
		* journal head. The obsolete nodes are dropped.
		* This function sorts the list of inodes to garbage collect. First of all, it
		* kills obsolete nodes and separates data and non-data nodes to the
		* @sleb->nodes and @nondata lists correspondingly.
		*
		* Data nodes are then sorted in block number order - this is important for
		* bulk-read; data nodes with lower inode number go before data nodes with
		* higher inode number, and data nodes with lower block number go before data
		* nodes with higher block number;
		*
		* When moving nodes we have to deal with classical bin-packing problem: the
		* space in the current GC journal head LEB and in @c->gc_lnum are the "bins",
		* where the nodes in the @sleb->nodes list are the elements which should be
		* fit optimally to the bins. This function uses the "first fit decreasing"
		* strategy, although it does not really sort the nodes but just split them on
		* 3 classes - large, medium, and small, so they are roughly sorted.
		* Non-data nodes are sorted as follows.
		* o First go inode nodes - they are sorted in descending length order.
		* o Then go directory entry nodes - they are sorted in hash order, which
		* should supposedly optimize 'readdir()'. Direntry nodes with lower parent
		* inode number go before direntry nodes with higher parent inode number,
		* and direntry nodes with lower name hash values go before direntry nodes
		* with higher name hash values.
		*
		* This function returns zero in case of success, %-EAGAIN if commit is
		* required, and other negative error codes in case of other failures.
		* This function returns zero in case of success and a negative error code in
		* case of failure.
		*/
		static int move_nodes(struct ubifs_info c, struct ubifs_scan_leb sleb)
		static int sort_nodes(struct ubifs_info c, struct ubifs_scan_leb sleb,
		struct list_head nondata, int min)
		{
		struct ubifs_scan_node snod, tmp;
		struct list_head data, large, medium, small;
		struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;
		int avail, err, min = INT_MAX;
		unsigned int blk = 0;
		ino_t inum = 0;

		INIT_LIST_HEAD(&data);
		INIT_LIST_HEAD(&large);
		INIT_LIST_HEAD(&medium);
		INIT_LIST_HEAD(&small);
		*min = INT_MAX;

		while (!list_empty(&sleb->nodes)) {
		struct list_head *lst = sleb->nodes.next;

		snod = list_entry(lst, struct ubifs_scan_node, list);
		/* Separate data nodes and non-data nodes */
		list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
		int err;

		ubifs_assert(snod->type != UBIFS_IDX_NODE);
		ubifs_assert(snod->type != UBIFS_REF_NODE);
		@@ -201,53 +332,72 @@ static int move_nodes(struct ubifs_info c, struct ubifs_scan_leb sleb)
		err = ubifs_tnc_has_node(c, &snod->key, 0, sleb->lnum,
		snod->offs, 0);
		if (err < 0)
		goto out;
		return err;

		list_del(lst);
		if (!err) {
		/* The node is obsolete, remove it from the list */
		list_del(&snod->list);
		kfree(snod);
		continue;
		}

		/*
		* Sort the list of nodes so that data nodes go first, large
		* nodes go second, and small nodes go last.
		*/
		if (key_type(c, &snod->key) == UBIFS_DATA_KEY) {
		if (inum != key_inum(c, &snod->key)) {
		if (inum) {
		/*
		* Try to move data nodes from the same
		* inode together.
		*/
		err = joinup(c, sleb, inum, blk, &data);
		if (err)
		goto out;
		if (snod->len < *min)
		*min = snod->len;

		if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
		list_move_tail(&snod->list, nondata);
		}
		inum = key_inum(c, &snod->key);
		blk = key_block(c, &snod->key);

		/* Sort data and non-data nodes */
		list_sort(c, &sleb->nodes, &data_nodes_cmp);
		list_sort(c, nondata, &nondata_nodes_cmp);
		return 0;
		}
		list_add_tail(lst, &data);
		} else if (snod->len > MEDIUM_NODE_WM)
		list_add_tail(lst, &large);
		else if (snod->len > SMALL_NODE_WM)
		list_add_tail(lst, &medium);
		else
		list_add_tail(lst, &small);

		/* And find the smallest node */
		if (snod->len < min)
		min = snod->len;
		/**
		* move_node - move a node.
		* @c: UBIFS file-system description object
		* @sleb: describes the LEB to move nodes from
		* @snod: the mode to move
		* @wbuf: write-buffer to move node to
		*
		* This function moves node @snod to @wbuf, changes TNC correspondingly, and
		* destroys @snod. Returns zero in case of success and a negative error code in
		* case of failure.
		*/
		static int move_node(struct ubifs_info c, struct ubifs_scan_leb sleb,
		struct ubifs_scan_node snod, struct ubifs_wbuf wbuf)
		{
		int err, new_lnum = wbuf->lnum, new_offs = wbuf->offs + wbuf->used;

		cond_resched();
		err = ubifs_wbuf_write_nolock(wbuf, snod->node, snod->len);
		if (err)
		return err;

		err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
		snod->offs, new_lnum, new_offs,
		snod->len);
		list_del(&snod->list);
		kfree(snod);
		return err;
		}

		/*
		* Join the tree lists so that we'd have one roughly sorted list
		* ('large' will be the head of the joined list).
		/**
		* move_nodes - move nodes.
		* @c: UBIFS file-system description object
		* @sleb: describes the LEB to move nodes from
		*
		* This function moves valid nodes from data LEB described by @sleb to the GC
		* journal head. This function returns zero in case of success, %-EAGAIN if
		* commit is required, and other negative error codes in case of other
		* failures.
		*/
		list_splice(&data, &large);
		list_splice(&medium, large.prev);
		list_splice(&small, large.prev);
		static int move_nodes(struct ubifs_info c, struct ubifs_scan_leb sleb)
		{
		int err, min;
		LIST_HEAD(nondata);
		struct ubifs_wbuf *wbuf = &c->jheads[GCHD].wbuf;

		if (wbuf->lnum == -1) {
		/*
		@@ -256,42 +406,59 @@ static int move_nodes(struct ubifs_info c, struct ubifs_scan_leb sleb)
		*/
		err = switch_gc_head(c);
		if (err)
		goto out;
		return err;
		}

		err = sort_nodes(c, sleb, &nondata, &min);
		if (err)
		goto out;

		/* Write nodes to their new location. Use the first-fit strategy */
		while (1) {
		int avail;
		struct ubifs_scan_node snod, tmp;

		/* Move data nodes */
		list_for_each_entry_safe(snod, tmp, &sleb->nodes, list) {
		avail = c->leb_size - wbuf->offs - wbuf->used;
		list_for_each_entry_safe(snod, tmp, &large, list) {
		int new_lnum, new_offs;
		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);
		if (err)
		goto out;
		err = ubifs_tnc_replace(c, &snod->key, sleb->lnum,
		snod->offs, new_lnum, new_offs,
		snod->len);
		err = move_node(c, sleb, snod, wbuf);
		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;
		}

Admin message