[PATCH 7/17] [LogFS] gc.c

Joern Engel
2009-11-20T20:26:47Z

---
fs/logfs/gc.c | 730 ++++++++++++

diff --git a/fs/logfs/gc.c b/fs/logfs/gc.c
new file mode 100644
index 0000000..b3656c4
--- /dev/null
+++ b/fs/logfs/gc.c
@@ -0,0 +1,730 @@
+/*
+ * fs/logfs/gc.c - garbage collection code
+ *
+ * As should be obvious for Linux kernel code, license is GPLv2
+ *
+ * Copyright (c) 2005-2008 Joern Engel <joern@logfs.org>
+ */
+#include "logfs.h"
+#include <linux/sched.h>
+
+/*
+ * Wear leveling needs to kick in when the difference between low erase
+ * counts and high erase counts gets too big. A good value for "too big"
+ * may be somewhat below 10% of maximum erase count for the device.
+ * Why not 397, to pick a nice round number with no specific meaning? :)
+ *
+ * WL_RATELIMIT is the minimum time between two wear level events. A huge
+ * number of segments may fulfil the requirements for wear leveling at the
+ * same time. If that happens we don't want to cause a latency from hell,
+ * but just gently pick one segment every so often and minimize overhead.
+ */
+#define WL_DELTA 397
+#define WL_RATELIMIT 100
+#define MAX_OBJ_ALIASES 2600
+#define SCAN_RATIO 512 /* number of scanned segments per gc'd segment */
+#define LIST_SIZE 64 /* base size of candidate lists */
+#define SCAN_ROUNDS 128 /* maximum number of complete medium scans */
+#define SCAN_ROUNDS_HIGH 4 /* maximum number of higher-level scans */
+
+static int no_free_segments(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+
+ return super->s_free_list.count;
+}
+
+/* journal has distance -1, top-most ifile layer distance 0 */
+static u8 root_distance(struct super_block *sb, gc_level_t __gc_level)
+{
+ struct logfs_super *super = logfs_super(sb);
+ u8 gc_level = (__force u8)__gc_level;
+
+ switch (gc_level) {
+ case 0: /* fall through */
+ case 1: /* fall through */
+ case 2: /* fall through */
+ case 3:
+ /* file data or indirect blocks */
+ return super->s_ifile_levels + super->s_iblock_levels - gc_level;
+ case 6: /* fall through */
+ case 7: /* fall through */
+ case 8: /* fall through */
+ case 9:
+ /* inode file data or indirect blocks */
+ return super->s_ifile_levels - (gc_level - 6);
+ default:
+ printk(KERN_ERR"LOGFS: segment of unknown level %x found\n",
+ gc_level);
+ WARN_ON(1);
+ return super->s_ifile_levels + super->s_iblock_levels;
+ }
+}
+
+static int segment_is_reserved(struct super_block *sb, u32 segno)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct logfs_area *area;
+ void *reserved;
+ int i;
+
+ /* Some segments are reserved. Just pretend they were all valid */
+ reserved = btree_lookup32(&super->s_reserved_segments, segno);
+ if (reserved)
+ return 1;
+
+ /* Currently open segments */
+ for_each_area(i) {
+ area = super->s_area[i];
+ if (area->a_is_open && area->a_segno == segno)
+ return 1;
+ }
+
+ return 0;
+}
+
+static void logfs_mark_segment_bad(struct super_block *sb, u32 segno)
+{
+ BUG();
+}
+
+/*
+ * Returns the bytes consumed by valid objects in this segment. Object headers
+ * are counted, the segment header is not.
+ */
+static u32 logfs_valid_bytes(struct super_block *sb, u32 segno, u32 *ec,
+ gc_level_t *gc_level)
+{
+ struct logfs_segment_entry se;
+ u32 ec_level;
+
+ logfs_get_segment_entry(sb, segno, &se);
+ if (se.ec_level == cpu_to_be32(BADSEG) ||
+ se.valid == cpu_to_be32(RESERVED))
+ return RESERVED;
+
+ ec_level = be32_to_cpu(se.ec_level);
+ *ec = ec_level >> 4;
+ *gc_level = GC_LEVEL(ec_level & 0xf);
+ return be32_to_cpu(se.valid);
+}
+
+static void logfs_cleanse_block(struct super_block *sb, u64 ofs, u64 ino,
+ u64 bix, gc_level_t gc_level)
+{
+ struct inode *inode;
+ int err, cookie;
+
+ inode = logfs_safe_iget(sb, ino, &cookie);
+ err = logfs_rewrite_block(inode, bix, ofs, gc_level, 0);
+ BUG_ON(err);
+ logfs_safe_iput(inode, cookie);
+}
+
+static u32 logfs_gc_segment(struct super_block *sb, u32 segno, u8 dist)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct logfs_segment_header sh;
+ struct logfs_object_header oh;
+ u64 ofs, ino, bix;
+ u32 seg_ofs, logical_segno, cleaned = 0;
+ int err, len, valid;
+ gc_level_t gc_level;
+
+ LOGFS_BUG_ON(segment_is_reserved(sb, segno), sb);
+
+ btree_insert32(&super->s_reserved_segments, segno, (void *)1, GFP_NOFS);
+ err = wbuf_read(sb, dev_ofs(sb, segno, 0), sizeof(sh), &sh);
+ BUG_ON(err);
+ gc_level = GC_LEVEL(sh.level);
+ logical_segno = be32_to_cpu(sh.segno);
+ if (sh.crc != logfs_crc32(&sh, sizeof(sh), 4)) {
+ logfs_mark_segment_bad(sb, segno);
+ cleaned = -1;
+ goto out;
+ }
+
+ for (seg_ofs = LOGFS_SEGMENT_HEADERSIZE;
+ seg_ofs + sizeof(oh) < super->s_segsize; ) {
+ ofs = dev_ofs(sb, logical_segno, seg_ofs);
+ err = wbuf_read(sb, dev_ofs(sb, segno, seg_ofs), sizeof(oh),
+ &oh);
+ BUG_ON(err);
+
+ if (!memchr_inv(&oh, 0xff, sizeof(oh)))
+ break;
+
+ if (oh.crc != logfs_crc32(&oh, sizeof(oh) - 4, 4)) {
+ logfs_mark_segment_bad(sb, segno);
+ cleaned = super->s_segsize - 1;
+ goto out;
+ }
+
+ ino = be64_to_cpu(oh.ino);
+ bix = be64_to_cpu(oh.bix);
+ len = sizeof(oh) + be16_to_cpu(oh.len);
+ valid = logfs_is_valid_block(sb, ofs, ino, bix, gc_level);
+ if (valid == 1) {
+ logfs_cleanse_block(sb, ofs, ino, bix, gc_level);
+ cleaned += len;
+ } else if (valid == 2) {
+ /* Will be invalid upon journal commit */
+ cleaned += len;
+ }
+ seg_ofs += len;
+ }
+out:
+ btree_remove32(&super->s_reserved_segments, segno);
+ return cleaned;
+}
+
+static struct gc_candidate *add_list(struct gc_candidate *cand,
+ struct candidate_list *list)
+{
+ struct rb_node **p = &list->rb_tree.rb_node;
+ struct rb_node *parent = NULL;
+ struct gc_candidate *cur;
+ int comp;
+
+ cand->list = list;
+ while (*p) {
+ parent = *p;
+ cur = rb_entry(parent, struct gc_candidate, rb_node);
+
+ if (list->sort_by_ec)
+ comp = cand->erase_count < cur->erase_count;
+ else
+ comp = cand->valid < cur->valid;
+
+ if (comp)
+ p = &parent->rb_left;
+ else
+ p = &parent->rb_right;
+ }
+ rb_link_node(&cand->rb_node, parent, p);
+ rb_insert_color(&cand->rb_node, &list->rb_tree);
+
+ if (list->count <= list->maxcount) {
+ list->count++;
+ return NULL;
+ }
+ cand = rb_entry(rb_last(&list->rb_tree), struct gc_candidate, rb_node);
+ rb_erase(&cand->rb_node, &list->rb_tree);
+ cand->list = NULL;
+ return cand;
+}
+
+static void remove_from_list(struct gc_candidate *cand)
+{
+ struct candidate_list *list = cand->list;
+
+ rb_erase(&cand->rb_node, &list->rb_tree);
+ list->count--;
+}
+
+static void free_candidate(struct super_block *sb, struct gc_candidate *cand)
+{
+ struct logfs_super *super = logfs_super(sb);
+
+ btree_remove32(&super->s_cand_tree, cand->segno);
+ kfree(cand);
+}
+
+u32 get_best_cand(struct super_block *sb, struct candidate_list *list, u32 *ec)
+{
+ struct gc_candidate *cand;
+ u32 segno;
+
+ BUG_ON(list->count == 0);
+
+ cand = rb_entry(rb_first(&list->rb_tree), struct gc_candidate, rb_node);
+ remove_from_list(cand);
+ segno = cand->segno;
+ if (ec)
+ *ec = cand->erase_count;
+ free_candidate(sb, cand);
+ return segno;
+}
+
+/*
+ * We have several lists to manage segments with. The reserve_list is used to
+ * deal with bad blocks. We try to keep the best (lowest ec) segments on this
+ * list.
+ * The free_list contains free segments for normal usage. It usually gets the
+ * second pick after the reserve_list. But when the free_list is running short
+ * it is more important to keep the free_list full than to keep a reserve.
+ *
+ * Segments that are not free are put onto a per-level low_list. If we have
+ * to run garbage collection, we pick a candidate from there. All segments on
+ * those lists should have at least some free space so GC will make progress.
+ *
+ * And last we have the ec_list, which is used to pick segments for wear
+ * leveling.
+ *
+ * If all appropriate lists are full, we simply free the candidate and forget
+ * about that segment for a while. We have better candidates for each purpose.
+ */
+static void __add_candidate(struct super_block *sb, struct gc_candidate *cand)
+{
+ struct logfs_super *super = logfs_super(sb);
+ u32 full = super->s_segsize - LOGFS_SEGMENT_RESERVE;
+
+ if (cand->valid == 0) {
+ /* 100% free segments */
+ log_gc_noisy("add reserve segment %x (ec %x) at %llx\n",
+ cand->segno, cand->erase_count,
+ dev_ofs(sb, cand->segno, 0));
+ cand = add_list(cand, &super->s_reserve_list);
+ if (cand) {
+ log_gc_noisy("add free segment %x (ec %x) at %llx\n",
+ cand->segno, cand->erase_count,
+ dev_ofs(sb, cand->segno, 0));
+ cand = add_list(cand, &super->s_free_list);
+ }
+ } else {
+ /* good candidates for Garbage Collection */
+ if (cand->valid < full)
+ cand = add_list(cand, &super->s_low_list[cand->dist]);
+ /* good candidates for wear leveling,
+ * segments that were recently written get ignored */
+ if (cand)
+ cand = add_list(cand, &super->s_ec_list);
+ }
+ if (cand)
+ free_candidate(sb, cand);
+}
+
+static int add_candidate(struct super_block *sb, u32 segno, u32 valid, u32 ec,
+ u8 dist)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct gc_candidate *cand;
+
+ cand = kmalloc(sizeof(*cand), GFP_NOFS);
+ if (!cand)
+ return -ENOMEM;
+
+ cand->segno = segno;
+ cand->valid = valid;
+ cand->erase_count = ec;
+ cand->dist = dist;
+
+ btree_insert32(&super->s_cand_tree, segno, cand, GFP_NOFS);
+ __add_candidate(sb, cand);
+ return 0;
+}
+
+static void remove_segment_from_lists(struct super_block *sb, u32 segno)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct gc_candidate *cand;
+
+ cand = btree_lookup32(&super->s_cand_tree, segno);
+ if (cand) {
+ remove_from_list(cand);
+ free_candidate(sb, cand);
+ }
+}
+
+static void scan_segment(struct super_block *sb, u32 segno)
+{
+ u32 valid, ec = 0;
+ gc_level_t gc_level = 0;
+ u8 dist;
+
+ if (segment_is_reserved(sb, segno))
+ return;
+
+ remove_segment_from_lists(sb, segno);
+ valid = logfs_valid_bytes(sb, segno, &ec, &gc_level);
+ if (valid == RESERVED)
+ return;
+
+ dist = root_distance(sb, gc_level);
+ add_candidate(sb, segno, valid, ec, dist);
+}
+
+static struct gc_candidate *first_in_list(struct candidate_list *list)
+{
+ if (list->count == 0)
+ return NULL;
+ return rb_entry(rb_first(&list->rb_tree), struct gc_candidate, rb_node);
+}
+
+/*
+ * Find the best segment for garbage collection. Main criterion is
+ * the segment requiring the least effort to clean. Secondary
+ * criterion is to GC on the lowest level available.
+ *
+ * So we search the least effort segment on the lowest level first,
+ * then move up and pick another segment iff is requires significantly
+ * less effort. Hence the LOGFS_MAX_OBJECTSIZE in the comparison.
+ */
+static struct gc_candidate *get_candidate(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+ int i, max_dist;
+ struct gc_candidate *cand = NULL, *this;
+
+ max_dist = min(no_free_segments(sb), LOGFS_NO_AREAS);
+
+ for (i = max_dist; i >= 0; i--) {
+ this = first_in_list(&super->s_low_list[i]);
+ if (!this)
+ continue;
+ if (!cand)
+ cand = this;
+ if (this->valid + LOGFS_MAX_OBJECTSIZE <= cand->valid)
+ cand = this;
+ }
+ return cand;
+}
+
+static int __logfs_gc_once(struct super_block *sb, struct gc_candidate *cand)
+{
+ struct logfs_super *super = logfs_super(sb);
+ gc_level_t gc_level;
+ u32 cleaned, valid, segno, ec;
+ u8 dist;
+
+ if (!cand) {
+ log_gc("GC attempted, but no candidate found\n");
+ return 0;
+ }
+
+ segno = cand->segno;
+ dist = cand->dist;
+ valid = logfs_valid_bytes(sb, segno, &ec, &gc_level);
+ free_candidate(sb, cand);
+ log_gc("GC segment #%02x at %llx, %x required, %x free, %x valid, %llx free\n",
+ segno, (u64)segno << super->s_segshift,
+ dist, no_free_segments(sb), valid,
+ super->s_free_bytes);
+ cleaned = logfs_gc_segment(sb, segno, dist);
+ log_gc("GC segment #%02x complete - now %x valid\n", segno,
+ valid - cleaned);
+ BUG_ON(cleaned != valid);
+ return 1;
+}
+
+static int logfs_gc_once(struct super_block *sb)
+{
+ struct gc_candidate *cand;
+
+ cand = get_candidate(sb);
+ if (cand)
+ remove_from_list(cand);
+ return __logfs_gc_once(sb, cand);
+}
+
+/* returns 1 if a wrap occurs, 0 otherwise */
+static int logfs_scan_some(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+ u32 segno;
+ int i, ret = 0;
+
+ segno = super->s_sweeper;
+ for (i = SCAN_RATIO; i > 0; i--) {
+ segno++;
+ if (segno >= super->s_no_segs) {
+ segno = 0;
+ ret = 1;
+ /* Break out of the loop. We want to read a single
+ * block from the segment size on next invocation if
+ * SCAN_RATIO is set to match block size
+ */
+ break;
+ }
+
+ scan_segment(sb, segno);
+ }
+ super->s_sweeper = segno;
+ return ret;
+}
+
+/*
+ * In principle, this function should loop forever, looking for GC candidates
+ * and moving data. LogFS is designed in such a way that this loop is
+ * guaranteed to terminate.
+ *
+ * Limiting the loop to some iterations serves purely to catch cases when
+ * these guarantees have failed. An actual endless loop is an obvious bug
+ * and should be reported as such.
+ */
+static void __logfs_gc_pass(struct super_block *sb, int target)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct logfs_block *block;
+ int round, progress, last_progress = 0;
+
+ if (no_free_segments(sb) >= target &&
+ super->s_no_object_aliases < MAX_OBJ_ALIASES)
+ return;
+
+ log_gc("__logfs_gc_pass(%x)\n", target);
+ for (round = 0; round < SCAN_ROUNDS; ) {
+ if (no_free_segments(sb) >= target)
+ goto write_alias;
+
+ /* Sync in-memory state with on-medium state in case they
+ * diverged */
+ logfs_write_anchor(super->s_master_inode);
+ round += logfs_scan_some(sb);
+ if (no_free_segments(sb) >= target)
+ goto write_alias;
+ progress = logfs_gc_once(sb);
+ if (progress)
+ last_progress = round;
+ else if (round - last_progress > 2)
+ break;
+ continue;
+
+ /*
+ * The goto logic is nasty, I just don't know a better way to
+ * code it. GC is supposed to ensure two things:
+ * 1. Enough free segments are available.
+ * 2. The number of aliases is bounded.
+ * When 1. is achieved, we take a look at 2. and write back
+ * some alias-containing blocks, if necessary. However, after
+ * each such write we need to go back to 1., as writes can
+ * consume free segments.
+ */
+write_alias:
+ if (super->s_no_object_aliases < MAX_OBJ_ALIASES)
+ return;
+ if (list_empty(&super->s_object_alias)) {
+ /* All aliases are still in btree */
+ return;
+ }
+ log_gc("Write back one alias\n");
+ block = list_entry(super->s_object_alias.next,
+ struct logfs_block, alias_list);
+ block->ops->write_block(block);
+ /*
+ * To round off the nasty goto logic, we reset round here. It
+ * is a safety-net for GC not making any progress and limited
+ * to something reasonably small. If incremented it for every
+ * single alias, the loop could terminate rather quickly.
+ */
+ round = 0;
+ }
+ LOGFS_BUG(sb);
+}
+
+static int wl_ratelimit(struct super_block *sb, u64 *next_event)
+{
+ struct logfs_super *super = logfs_super(sb);
+
+ if (*next_event < super->s_gec) {
+ *next_event = super->s_gec + WL_RATELIMIT;
+ return 0;
+ }
+ return 1;
+}
+
+static void logfs_wl_pass(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct gc_candidate *wl_cand, *free_cand;
+
+ if (wl_ratelimit(sb, &super->s_wl_gec_ostore))
+ return;
+
+ wl_cand = first_in_list(&super->s_ec_list);
+ if (!wl_cand)
+ return;
+ free_cand = first_in_list(&super->s_free_list);
+ if (!free_cand)
+ return;
+
+ if (wl_cand->erase_count < free_cand->erase_count + WL_DELTA) {
+ remove_from_list(wl_cand);
+ __logfs_gc_once(sb, wl_cand);
+ }
+}
+
+/*
+ * The journal needs wear leveling as well. But moving the journal is an
+ * expensive operation so we try to avoid it as much as possible. And if we
+ * have to do it, we move the whole journal, not individual segments.
+ *
+ * Ratelimiting is not strictly necessary here, it mainly serves to avoid the
+ * calculations. First we check whether moving the journal would be a
+ * significant improvement. That means that a) the current journal segments
+ * have more wear than the future journal segments and b) the current journal
+ * segments have more wear than normal ostore segments.
+ * Rationale for b) is that we don't have to move the journal if it is aging
+ * less than the ostore, even if the reserve segments age even less (they are
+ * excluded from wear leveling, after all).
+ * Next we check that the superblocks have less wear than the journal. Since
+ * moving the journal requires writing the superblocks, we have to protect the
+ * superblocks even more than the journal.
+ *
+ * Also we double the acceptable wear difference, compared to ostore wear
+ * leveling. Journal data is read and rewritten rapidly, comparatively. So
+ * soft errors have much less time to accumulate and we allow the journal to
+ * be a bit worse than the ostore.
+ */
+static void logfs_journal_wl_pass(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct gc_candidate *cand;
+ u32 min_journal_ec = -1, max_reserve_ec = 0;
+ int i;
+
+ if (wl_ratelimit(sb, &super->s_wl_gec_journal))
+ return;
+
+ if (super->s_reserve_list.count < super->s_no_journal_segs) {
+ /* Reserve is not full enough to move complete journal */
+ return;
+ }
+
+ journal_for_each(i)
+ if (super->s_journal_seg[i])
+ min_journal_ec = min(min_journal_ec,
+ super->s_journal_ec[i]);
+ cand = rb_entry(rb_first(&super->s_free_list.rb_tree),
+ struct gc_candidate, rb_node);
+ max_reserve_ec = cand->erase_count;
+ for (i = 0; i < 2; i++) {
+ struct logfs_segment_entry se;
+ u32 segno = seg_no(sb, super->s_sb_ofs[i]);
+ u32 ec;
+
+ logfs_get_segment_entry(sb, segno, &se);
+ ec = be32_to_cpu(se.ec_level) >> 4;
+ max_reserve_ec = max(max_reserve_ec, ec);
+ }
+
+ if (min_journal_ec > max_reserve_ec + 2 * WL_DELTA) {
+ do_logfs_journal_wl_pass(sb);
+ }
+}
+
+void logfs_gc_pass(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+
+ //BUG_ON(mutex_trylock(&logfs_super(sb)->s_w_mutex));
+ /* Write journal before free space is getting saturated with dirty
+ * objects.
+ */
+ if (super->s_dirty_used_bytes + super->s_dirty_free_bytes
+ + LOGFS_MAX_OBJECTSIZE >= super->s_free_bytes)
+ logfs_write_anchor(super->s_master_inode);
+ __logfs_gc_pass(sb, logfs_super(sb)->s_total_levels);
+ logfs_wl_pass(sb);
+ logfs_journal_wl_pass(sb);
+}
+
+static int check_area(struct super_block *sb, int i)
+{
+ struct logfs_super *super = logfs_super(sb);
+ struct logfs_area *area = super->s_area[i];
+ struct logfs_object_header oh;
+ u32 segno = area->a_segno;
+ u32 ofs = area->a_used_bytes;
+ __be32 crc;
+ int err;
+
+ if (!area->a_is_open)
+ return 0;
+
+ for (ofs = area->a_used_bytes;
+ ofs <= super->s_segsize - sizeof(oh);
+ ofs += (u32)be16_to_cpu(oh.len) + sizeof(oh)) {
+ err = wbuf_read(sb, dev_ofs(sb, segno, ofs), sizeof(oh), &oh);
+ if (err)
+ return err;
+
+ if (!memchr_inv(&oh, 0xff, sizeof(oh)))
+ break;
+
+ crc = logfs_crc32(&oh, sizeof(oh) - 4, 4);
+ if (crc != oh.crc) {
+ printk(KERN_INFO "interrupted header at %llx\n",
+ dev_ofs(sb, segno, ofs));
+ return 0;
+ }
+ }
+ if (ofs != area->a_used_bytes) {
+ printk(KERN_INFO "%x bytes unaccounted data found at %llx\n",
+ ofs - area->a_used_bytes,
+ dev_ofs(sb, segno, area->a_used_bytes));
+ area->a_used_bytes = ofs;
+ }
+ return 0;
+}
+
+int logfs_check_areas(struct super_block *sb)
+{
+ int i, err;
+
+ for_each_area(i) {
+ err = check_area(sb, i);
+ if (err)
+ return err;
+ }
+ return 0;
+}
+
+static void logfs_init_candlist(struct candidate_list *list, int maxcount,
+ int sort_by_ec)
+{
+ list->count = 0;
+ list->maxcount = maxcount;
+ list->sort_by_ec = sort_by_ec;
+ list->rb_tree = RB_ROOT;
+}
+
+int logfs_init_gc(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+ int i;
+
+ btree_init_mempool32(&super->s_cand_tree, super->s_btree_pool);
+ logfs_init_candlist(&super->s_free_list, LIST_SIZE + SCAN_RATIO, 1);
+ logfs_init_candlist(&super->s_reserve_list,
+ super->s_bad_seg_reserve, 1);
+ for_each_area(i)
+ logfs_init_candlist(&super->s_low_list[i], LIST_SIZE, 0);
+ logfs_init_candlist(&super->s_ec_list, LIST_SIZE, 1);
+ return 0;
+}
+
+static void logfs_cleanup_list(struct super_block *sb,
+ struct candidate_list *list)
+{
+ struct gc_candidate *cand;
+
+ while (list->count) {
+ cand = rb_entry(list->rb_tree.rb_node, struct gc_candidate,
+ rb_node);
+ remove_from_list(cand);
+ free_candidate(sb, cand);
+ }
+ BUG_ON(list->rb_tree.rb_node);
+}
+
+void logfs_cleanup_gc(struct super_block *sb)
+{
+ struct logfs_super *super = logfs_super(sb);
+ int i;
+
+ if (!super->s_free_list.count)
+ return;
+
+ /*
+ * FIXME: The btree may still contain a single empty node. So we
+ * call the grim visitor to clean up that mess. Btree code should
+ * do it for us, really.
+ */
+ btree_grim_visitor32(&super->s_cand_tree, 0, NULL);
+ logfs_cleanup_list(sb, &super->s_free_list);
+ logfs_cleanup_list(sb, &super->s_reserve_list);
+ for_each_area(i)
+ logfs_cleanup_list(sb, &super->s_low_list[i]);
+ logfs_cleanup_list(sb, &super->s_ec_list);
+}