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>
diff --git a/fs/ubifs/gc.c b/fs/ubifs/gc.c
index a711d33..f0f5f15 100644
--- a/fs/ubifs/gc.c
+++ b/fs/ubifs/gc.c
@@ -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.
@@ -57,14 +57,6 @@
#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
* may move.
@@ -116,83 +108,222 @@
}
/**
- * 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 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.
+ * 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.
+ *
+ * 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;
- 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)
+ 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;
+ }
+
+ 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.
- * @c: UBIFS file-system description object
- * @sleb: describes nodes to move
+ * data_nodes_cmp - compare 2 data nodes.
+ * @priv: UBIFS file-system description object
+ * @a: first data node
+ * @a: second data node
*
- * This function moves valid nodes from data LEB described by @sleb to the GC
- * journal head. The obsolete nodes are dropped.
- *
- * 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.
- *
- * 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 compares data nodes @a and @b. Returns %1 if @a has greater
+ * inode or block number, and %-1 otherwise.
*/
-static int move_nodes(struct ubifs_info *c, struct ubifs_scan_leb *sleb)
+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 sort and contains the result on exit
+ * @nondata: contains non-data nodes on exit
+ * @min: minimum node size is returned here
+ *
+ * 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;
+ *
+ * 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 and a negative error code in
+ * case of failure.
+ */
+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 @@
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;
- }
- inum = key_inum(c, &snod->key);
- blk = key_block(c, &snod->key);
- }
- 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);
+ if (snod->len < *min)
+ *min = snod->len;
- /* And find the smallest node */
- if (snod->len < min)
- min = snod->len;
+ if (key_type(c, &snod->key) != UBIFS_DATA_KEY)
+ list_move_tail(&snod->list, nondata);
}
- /*
- * Join the tree lists so that we'd have one roughly sorted list
- * ('large' will be the head of the joined list).
- */
- list_splice(&data, &large);
- list_splice(&medium, large.prev);
- list_splice(&small, large.prev);
+ /* Sort data and non-data nodes */
+ list_sort(c, &sleb->nodes, &data_nodes_cmp);
+ list_sort(c, nondata, &nondata_nodes_cmp);
+ return 0;
+}
+
+/**
+ * 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;
+}
+
+/**
+ * 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.
+ */
+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 @@
*/
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) {
- avail = c->leb_size - wbuf->offs - wbuf->used;
- list_for_each_entry_safe(snod, tmp, &large, list) {
- int new_lnum, new_offs;
+ 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;
+ 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 @@
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;
}