v1.20 Release

Finish the release notes for the 1.20 release.

Signed-off-by: Zach Brown <zab@versity.com>

ReleaseNotes.md

@@ -1,6 +1,29 @@
 Versity ScoutFS Release Notes
 =============================
 
+---
+v1.20
+\
+*Apr 22, 2024*
+
+Minor changes to packaging to better support "weak" module linking of
+the kernel module, and to including git hashes in the built package.  No
+changes in runtime behaviour.
+
+---
+v1.19
+\
+*Jan 30, 2024*
+
+Added the log\_merge\_wait\_timeout\_ms mount option to set the timeout
+for creating log merge operations.  The previous timeout, now the
+default, was too short for some systems and was resulting in consistent
+timeouts which created an excessive number of log trees waiting to be
+merged.
+
+Improved performance of many in-mount server operations when there are a
+large number of log trees waiting to be merged.
+
 ---
 v1.18
 \

kmod/Makefile

@@ -12,17 +12,22 @@ else
 SP = @:
 endif
 
-SCOUTFS_GIT_DESCRIBE := \
+SCOUTFS_GIT_DESCRIBE ?= \
 	$(shell git describe --all --abbrev=6 --long 2>/dev/null || \
 		echo no-git)
 
+ESCAPED_GIT_DESCRIBE := \
+	$(shell echo $(SCOUTFS_GIT_DESCRIBE) |sed -e 's/\//\\\//g')
+
+RPM_GITHASH ?= $(shell git rev-parse --short HEAD)
+
 SCOUTFS_ARGS := SCOUTFS_GIT_DESCRIBE=$(SCOUTFS_GIT_DESCRIBE) \
+		RPM_GITHASH=$(RPM_GITHASH) \
 		CONFIG_SCOUTFS_FS=m -C $(SK_KSRC) M=$(CURDIR)/src \
 		EXTRA_CFLAGS="-Werror"
 
 # - We use the git describe from tags to set up the RPM versioning
 RPM_VERSION := $(shell git describe --long --tags | awk -F '-' '{gsub(/^v/,""); print $$1}')
-RPM_GITHASH := $(shell git rev-parse --short HEAD)
 TARFILE = scoutfs-kmod-$(RPM_VERSION).tar
 
 
@@ -41,7 +46,8 @@ modules_install:
 
 %.spec: %.spec.in .FORCE
 	sed -e 's/@@VERSION@@/$(RPM_VERSION)/g' \
-	    -e 's/@@GITHASH@@/$(RPM_GITHASH)/g' < $< > $@+
+	    -e 's/@@GITHASH@@/$(RPM_GITHASH)/g' \
+	    -e 's/@@GITDESCRIBE@@/$(ESCAPED_GIT_DESCRIBE)/g' < $< > $@+
 	mv $@+ $@
 
 

kmod/scoutfs-kmod.spec.in

@@ -1,6 +1,7 @@
 %define kmod_name scoutfs
 %define kmod_version @@VERSION@@
 %define kmod_git_hash @@GITHASH@@
+%define kmod_git_describe @@GITDESCRIBE@@
 %define pkg_date %(date +%%Y%%m%%d)
 
 # Disable the building of the debug package(s).
@@ -75,7 +76,7 @@ echo "Building for kernel: %{kernel_version} flavors: '%{flavors_to_build}'"
 for flavor in %flavors_to_build; do
     rm -rf obj/$flavor
     cp -r source obj/$flavor
-    make SK_KSRC=%{kernel_source $flavor} -C obj/$flavor module
+    make RPM_GITHASH=%{kmod_git_hash} SCOUTFS_GIT_DESCRIBE=%{kmod_git_describe} SK_KSRC=%{kernel_source $flavor} -C obj/$flavor module
 done
 
 %install
@@ -97,10 +98,21 @@ find %{buildroot} -type f -name \*.ko -exec %{__chmod} u+x \{\} \;
 /lib/modules
 
 %post
-weak-modules --add-kernel --no-initramfs
+echo /lib/modules/%{kversion}/%{install_mod_dir}/scoutfs.ko | weak-modules --add-modules --no-initramfs
 depmod -a
 %endif
 
 %clean
 rm -rf %{buildroot}
 
+%preun
+# stash our modules for postun cleanup
+SCOUTFS_RPM_NAME=$(rpm -q %{name} | grep "%{version}-%{release}")
+rpm -ql $SCOUTFS_RPM_NAME | grep '\.ko$' > /var/run/%{name}-modules-%{version}-%{release} || true
+
+%postun
+if [ -x /sbin/weak-modules ]; then
+    cat /var/run/%{name}-modules-%{version}-%{release} | /sbin/weak-modules --remove-modules --no-initramfs
+fi
+
+rm /var/run/%{name}-modules-%{version}-%{release} || true

kmod/src/btree.c

@@ -2029,187 +2029,253 @@ int scoutfs_btree_rebalance(struct super_block *sb,
 			  key, SCOUTFS_BTREE_MAX_VAL_LEN, NULL, NULL, NULL);
 }
 
-struct merge_pos {
+struct merged_range {
+	struct scoutfs_key start;
+	struct scoutfs_key end;
+	struct rb_root root;
+	int size;
+};
+
+struct merged_item {
 	struct rb_node node;
-	struct scoutfs_btree_root *root;
-	struct scoutfs_block *bl;
-	struct scoutfs_btree_block *bt;
-	struct scoutfs_avl_node *avl;
-	struct scoutfs_key *key;
+	struct scoutfs_key key;
 	u64 seq;
 	u8 flags;
 	unsigned int val_len;
-	u8 *val;
+	u8 val[0];
 };
 
-static struct merge_pos *first_mpos(struct rb_root *root)
+static inline struct merged_item *mitem_container(struct rb_node *node)
 {
-	struct rb_node *node = rb_first(root);
-	if (node)
-		 return container_of(node, struct merge_pos, node);
+	return node ? container_of(node, struct merged_item, node) : NULL;
+}
+
+static inline struct merged_item *first_mitem(struct rb_root *root)
+{
+	return mitem_container(rb_first(root));
+}
+
+static inline struct merged_item *last_mitem(struct rb_root *root)
+{
+	return mitem_container(rb_last(root));
+}
+
+static inline struct merged_item *next_mitem(struct merged_item *mitem)
+{
+	return mitem_container(mitem ? rb_next(&mitem->node) : NULL);
+}
+
+static inline struct merged_item *prev_mitem(struct merged_item *mitem)
+{
+	return mitem_container(mitem ? rb_prev(&mitem->node) : NULL);
+}
+
+static struct merged_item *find_mitem(struct rb_root *root, struct scoutfs_key *key,
+				      struct rb_node **parent_ret, struct rb_node ***link_ret)
+{
+	struct rb_node **node = &root->rb_node;
+	struct rb_node *parent = NULL;
+	struct merged_item *mitem;
+	int cmp;
+
+	while (*node) {
+		parent = *node;
+		mitem = container_of(*node, struct merged_item, node);
+
+		cmp = scoutfs_key_compare(key, &mitem->key);
+
+		if (cmp < 0) {
+			node = &(*node)->rb_left;
+		} else if (cmp > 0) {
+			node = &(*node)->rb_right;
+		} else {
+			*parent_ret = NULL;
+			*link_ret = NULL;
+			return mitem;
+		}
+	}
+
+	*parent_ret = parent;
+	*link_ret = node;
 	return NULL;
 }
 
-static struct merge_pos *next_mpos(struct merge_pos *mpos)
+static void insert_mitem(struct merged_range *rng, struct merged_item *mitem,
+			 struct rb_node *parent, struct rb_node **link)
 {
-	struct rb_node *node;
-
-	if (mpos && (node = rb_next(&mpos->node)))
-		return container_of(node, struct merge_pos, node);
-	else
-		return NULL;
+	rb_link_node(&mitem->node, parent, link);
+	rb_insert_color(&mitem->node, &rng->root);
+	rng->size += item_len_bytes(mitem->val_len);
 }
 
-static void free_mpos(struct super_block *sb, struct merge_pos *mpos)
+static void replace_mitem(struct merged_range *rng, struct merged_item *victim,
+				struct merged_item *new)
 {
-	scoutfs_block_put(sb, mpos->bl);
-	kfree(mpos);
+	rb_replace_node(&victim->node, &new->node, &rng->root);
+	RB_CLEAR_NODE(&victim->node);
+	rng->size -= item_len_bytes(victim->val_len);
+	rng->size += item_len_bytes(new->val_len);
 }
 
-static void insert_mpos(struct rb_root *pos_root, struct merge_pos *ins)
+static void free_mitem(struct merged_range *rng, struct merged_item *mitem)
 {
-	struct rb_node **node = &pos_root->rb_node;
-	struct rb_node *parent = NULL;
-	struct merge_pos *mpos;
-	int cmp;
+	if (IS_ERR_OR_NULL(mitem))
+		return;
 
-	parent = NULL;
-	while (*node) {
-		parent = *node;
-		mpos = container_of(*node, struct merge_pos, node);
-
-		/* sort merge items by key then newest to oldest */
-		cmp = scoutfs_key_compare(ins->key, mpos->key) ?:
-		      -scoutfs_cmp(ins->seq, mpos->seq);
-
-		if (cmp < 0)
-			node = &(*node)->rb_left;
-		else
-			node = &(*node)->rb_right;
+	if (!RB_EMPTY_NODE(&mitem->node)) {
+		rng->size -= item_len_bytes(mitem->val_len);
+		rb_erase(&mitem->node, &rng->root);
 	}
 
-	rb_link_node(&ins->node, parent, node);
-	rb_insert_color(&ins->node, pos_root);
+	kfree(mitem);
+}
+
+static void trim_range_size(struct merged_range *rng, int merge_window)
+{
+	struct merged_item *mitem;
+	struct merged_item *tmp;
+
+	mitem = last_mitem(&rng->root);
+	while (mitem && rng->size > merge_window) {
+
+		rng->end = mitem->key;
+		scoutfs_key_dec(&rng->end);
+
+		tmp = mitem;
+		mitem = prev_mitem(mitem);
+		free_mitem(rng, tmp);
+	}
+}
+
+static void trim_range_end(struct merged_range *rng)
+{
+	struct merged_item *mitem;
+	struct merged_item *tmp;
+
+	mitem = last_mitem(&rng->root);
+	while (mitem && scoutfs_key_compare(&mitem->key, &rng->end) > 0) {
+		tmp = mitem;
+		mitem = prev_mitem(mitem);
+		free_mitem(rng, tmp);
+	}
 }
 
 /*
- * Find the next item in the merge_pos root in the caller's range and
- * insert it into the rbtree sorted by key and version so that merging
- * can find the next newest item at the front of the rbtree.  We free
- * the mpos on error or if there are no more items in the range.
+ * Record and combine logged items from log roots for merging with the
+ * writable destination root.  The caller is responsible for trimming
+ * the range if it gets too large or if the key range shrinks.
  */
-static int reset_mpos(struct super_block *sb, struct rb_root *pos_root, struct merge_pos *mpos,
-		      struct scoutfs_key *start, struct scoutfs_key *end)
+static int merge_read_item(struct super_block *sb, struct scoutfs_key *key, u64 seq, u8 flags,
+			   void *val, int val_len, void *arg)
 {
-	struct scoutfs_btree_item *item;
-	struct scoutfs_avl_node *next;
-	struct btree_walk_key_range kr;
-	struct scoutfs_key walk_key;
-	int ret = 0;
+	struct merged_range *rng = arg;
+	struct merged_item *mitem;
+	struct merged_item *found;
+	struct rb_node *parent;
+	struct rb_node **link;
+	int ret;
 
-	/* always erase before freeing or inserting */
-	if (!RB_EMPTY_NODE(&mpos->node)) {
-		rb_erase(&mpos->node, pos_root);
-		RB_CLEAR_NODE(&mpos->node);
-	}
-
-	/*
-	 * advance to next item via the avl tree.   The caller's pos is
-	 * only ever incremented past the last key so we can use next to
-	 * iterate rather than using search to skip past multiple items.
-	 */
-	if (mpos->avl)
-		mpos->avl = scoutfs_avl_next(&mpos->bt->item_root, mpos->avl);
-
-	/* find the next leaf with the key if we run out of items */
-	walk_key = *start;
-	while (!mpos->avl && !scoutfs_key_is_zeros(&walk_key)) {
-		scoutfs_block_put(sb, mpos->bl);
-		mpos->bl = NULL;
-		ret = btree_walk(sb, NULL, NULL, mpos->root, BTW_NEXT, &walk_key,
-				 0, &mpos->bl, &kr, NULL);
-		if (ret < 0) {
-			if (ret == -ENOENT)
-				ret = 0;
-			free_mpos(sb, mpos);
+	found = find_mitem(&rng->root, key, &parent, &link);
+	if (found) {
+		ret = scoutfs_forest_combine_deltas(key, found->val, found->val_len, val, val_len);
+		if (ret < 0)
+			goto out;
+		if (ret > 0) {
+			if (ret == SCOUTFS_DELTA_COMBINED) {
+				scoutfs_inc_counter(sb, btree_merge_delta_combined);
+			} else if (ret == SCOUTFS_DELTA_COMBINED_NULL) {
+				scoutfs_inc_counter(sb, btree_merge_delta_null);
+				free_mitem(rng, found);
+			}
+			ret = 0;
 			goto out;
 		}
-		mpos->bt = mpos->bl->data;
 
-		mpos->avl = scoutfs_avl_search(&mpos->bt->item_root, cmp_key_item,
-					       start, NULL, NULL, &next, NULL) ?: next;
-		if (mpos->avl == NULL)
-			walk_key = kr.iter_next;
+		if (found->seq >= seq) {
+			ret = 0;
+			goto out;
+		}
 	}
 
-	/* see if we're out of items within the range */
-	item = node_item(mpos->avl);
-	if (!item || scoutfs_key_compare(item_key(item), end) > 0) {
-		free_mpos(sb, mpos);
-		ret = 0;
+	mitem = kmalloc(offsetof(struct merged_item, val[val_len]), GFP_NOFS);
+	if (!mitem) {
+		ret = -ENOMEM;
 		goto out;
 	}
 
-	/* insert the next item within range at its version */
-	mpos->key = item_key(item);
-	mpos->seq = le64_to_cpu(item->seq);
-	mpos->flags = item->flags;
-	mpos->val_len = item_val_len(item);
-	mpos->val = item_val(mpos->bt, item);
+	mitem->key = *key;
+	mitem->seq = seq;
+	mitem->flags = flags;
+	mitem->val_len = val_len;
+	if (val_len)
+		memcpy(mitem->val, val, val_len);
+
+	if (found) {
+		replace_mitem(rng, found, mitem);
+		free_mitem(rng, found);
+	} else {
+		insert_mitem(rng, mitem, parent, link);
+	}
 
-	insert_mpos(pos_root, mpos);
 	ret = 0;
 out:
 	return ret;
 }
 
 /*
- * The caller has reset all the merge positions for all the input log
- * btree roots and wants the next logged item it should try and merge
- * with the items in the fs_root.
+ * Read a range of merged items.  The caller has set the key bounds of
+ * the range.  We read a merge window's worth of items from blocks in
+ * each input btree.
  *
- * We look ahead in the logged item stream to see if we should merge any
- * older logged delta items into one result for the caller.  We also
- * take this opportunity to skip and reset the mpos for any older
- * versions of the first item.
+ * The caller can only use the smallest range that overlaps with all the
+ * blocks that we read.  We start reading from the range's start key so
+ * it will always be present and we don't need to adjust it.  The final
+ * block we read from each input might not cover the range's end so it
+ * needs to be adjusted.
+ *
+ * The end range can also shrink if we have to drop items because the
+ * items exceeded the merge window size.
  */
-static int next_resolved_mpos(struct super_block *sb, struct rb_root *pos_root,
-			      struct scoutfs_key *end, struct merge_pos **mpos_ret)
+static int read_merged_range(struct super_block *sb, struct merged_range *rng,
+			     struct list_head *inputs, int merge_window)
 {
-	struct merge_pos *mpos;
-	struct merge_pos *next;
+	struct scoutfs_btree_root_head *rhead;
+	struct scoutfs_key start;
+	struct scoutfs_key end;
 	struct scoutfs_key key;
 	int ret = 0;
+	int i;
 
-	while ((mpos = first_mpos(pos_root)) && (next = next_mpos(mpos)) &&
-	       !scoutfs_key_compare(mpos->key, next->key)) {
+	list_for_each_entry(rhead, inputs, head) {
+		key = rng->start;
 
-		ret = scoutfs_forest_combine_deltas(mpos->key, mpos->val, mpos->val_len,
-						    next->val, next->val_len);
-		if (ret < 0)
-			break;
-
-		/* reset advances to the next item */
-		key = *mpos->key;
-		scoutfs_key_inc(&key);
-
-		/* always skip next combined or older version */
-		ret = reset_mpos(sb, pos_root, next, &key, end);
-		if (ret < 0)
-			break;
-
-		if (ret == SCOUTFS_DELTA_COMBINED) {
-			scoutfs_inc_counter(sb, btree_merge_delta_combined);
-		} else if (ret == SCOUTFS_DELTA_COMBINED_NULL) {
-			scoutfs_inc_counter(sb, btree_merge_delta_null);
-			/* if merging resulted in no info, skip current */
-			ret = reset_mpos(sb, pos_root, mpos, &key, end);
+		for (i = 0; i < merge_window; i += SCOUTFS_BLOCK_LG_SIZE) {
+			start = key;
+			end = rng->end;
+			ret = scoutfs_btree_read_items(sb, &rhead->root, &key, &start, &end,
+						       merge_read_item, rng);
 			if (ret < 0)
+				goto out;
+
+			if (scoutfs_key_compare(&end, &rng->end) >= 0)
 				break;
+
+			key = end;
+			scoutfs_key_inc(&key);
 		}
+
+		if (scoutfs_key_compare(&end, &rng->end) < 0) {
+			rng->end = end;
+			trim_range_end(rng);
+		}
+
+		if (rng->size > merge_window)
+			trim_range_size(rng, merge_window);
 	}
 
-	*mpos_ret = mpos;
+	trace_scoutfs_btree_merge_read_range(sb, &rng->start, &rng->end, rng->size);
+	ret = 0;
+out:
 	return ret;
 }
 
@@ -2226,6 +2292,13 @@ static int next_resolved_mpos(struct super_block *sb, struct rb_root *pos_root,
  * to allocators running low or needing to join/split the parent.
  * *next_ret is set to the next key which hasn't been merged so that the
  * caller can retry with a new allocator and subtree.
+ *
+ * The number of input roots can be immense.  The merge_window specifies
+ * the size of the set of merged items that we'll maintain as we iterate
+ * over all the input roots.  Once we've merged items into the window
+ * from all the input roots the merged input items are then merged to
+ * the writable destination root.  It may take multiple passes of
+ * windows of merged items to cover the input key range.
  */
 int scoutfs_btree_merge(struct super_block *sb,
 			struct scoutfs_alloc *alloc,
@@ -2235,18 +2308,16 @@ int scoutfs_btree_merge(struct super_block *sb,
 			struct scoutfs_key *next_ret,
 			struct scoutfs_btree_root *root,
 			struct list_head *inputs,
-			bool subtree, int dirty_limit, int alloc_low)
+			bool subtree, int dirty_limit, int alloc_low, int merge_window)
 {
-	struct scoutfs_btree_root_head *rhead;
-	struct rb_root pos_root = RB_ROOT;
 	struct scoutfs_btree_item *item;
 	struct scoutfs_btree_block *bt;
 	struct scoutfs_block *bl = NULL;
 	struct btree_walk_key_range kr;
 	struct scoutfs_avl_node *par;
-	struct scoutfs_key next;
-	struct merge_pos *mpos;
-	struct merge_pos *tmp;
+	struct merged_item *mitem;
+	struct merged_item *tmp;
+	struct merged_range rng;
 	int walk_val_len;
 	int walk_flags;
 	bool is_del;
@@ -2257,49 +2328,59 @@ int scoutfs_btree_merge(struct super_block *sb,
 	trace_scoutfs_btree_merge(sb, root, start, end);
 	scoutfs_inc_counter(sb, btree_merge);
 
-	list_for_each_entry(rhead, inputs, head) {
-		mpos = kzalloc(sizeof(*mpos), GFP_NOFS);
-		if (!mpos) {
-			ret = -ENOMEM;
-			goto out;
-		}
-
-		RB_CLEAR_NODE(&mpos->node);
-		mpos->root = &rhead->root;
-
-		ret = reset_mpos(sb, &pos_root, mpos, start, end);
-		if (ret < 0)
-			goto out;
-	}
-
 	walk_flags = BTW_DIRTY;
 	if (subtree)
 		walk_flags |= BTW_SUBTREE;
 	walk_val_len = 0;
 
-	while ((ret = next_resolved_mpos(sb, &pos_root, end, &mpos)) == 0 && mpos) {
+	rng.start = *start;
+	rng.end = *end;
+	rng.root = RB_ROOT;
+	rng.size = 0;
+
+	ret = read_merged_range(sb, &rng, inputs, merge_window);
+	if (ret < 0)
+		goto out;
+
+	for (;;) {
+		/* read next window as it empties (and it is possible to read an empty range) */
+		mitem = first_mitem(&rng.root);
+		if (!mitem) {
+			/* done if the read range hit the end */
+			if (scoutfs_key_compare(&rng.end, end) >= 0)
+				break;
+
+			/* read next batch of merged items */
+			rng.start = rng.end;
+			scoutfs_key_inc(&rng.start);
+			rng.end = *end;
+			ret = read_merged_range(sb, &rng, inputs, merge_window);
+			if (ret < 0)
+				break;
+			continue;
+		}
 
 		if (scoutfs_block_writer_dirty_bytes(sb, wri) >= dirty_limit) {
 			scoutfs_inc_counter(sb, btree_merge_dirty_limit);
 			ret = -ERANGE;
-			*next_ret = *mpos->key;
+			*next_ret = mitem->key;
 			goto out;
 		}
 
 		if (scoutfs_alloc_meta_low(sb, alloc, alloc_low)) {
 			scoutfs_inc_counter(sb, btree_merge_alloc_low);
 			ret = -ERANGE;
-			*next_ret = *mpos->key;
+			*next_ret = mitem->key;
 			goto out;
 		}
 
 		scoutfs_block_put(sb, bl);
 		bl = NULL;
 		ret = btree_walk(sb, alloc, wri, root, walk_flags,
-			         mpos->key, walk_val_len, &bl, &kr, NULL);
+			         &mitem->key, walk_val_len, &bl, &kr, NULL);
 		if (ret < 0) {
 			if (ret == -ERANGE)
-				*next_ret = *mpos->key;
+				*next_ret = mitem->key;
 			goto out;
 		}
 		bt = bl->data;
@@ -2311,22 +2392,21 @@ int scoutfs_btree_merge(struct super_block *sb,
 			continue;
 		}
 
-		while ((ret = next_resolved_mpos(sb, &pos_root, end, &mpos)) == 0 && mpos) {
-
+		while (mitem) {
 			/* walk to new leaf if we exceed parent ref key */
-			if (scoutfs_key_compare(mpos->key, &kr.end) > 0)
+			if (scoutfs_key_compare(&mitem->key, &kr.end) > 0)
 				break;
 
 			/* see if there's an existing item */
-			item = leaf_item_hash_search(sb, bt, mpos->key);
-			is_del = !!(mpos->flags & SCOUTFS_ITEM_FLAG_DELETION);
+			item = leaf_item_hash_search(sb, bt, &mitem->key);
+			is_del = !!(mitem->flags & SCOUTFS_ITEM_FLAG_DELETION);
 
 			/* see if we're merging delta items */
 			if (item && !is_del)
-				delta = scoutfs_forest_combine_deltas(mpos->key,
+				delta = scoutfs_forest_combine_deltas(&mitem->key,
 								      item_val(bt, item),
 								      item_val_len(item),
-								      mpos->val, mpos->val_len);
+								      mitem->val, mitem->val_len);
 			else
 				delta = 0;
 			if (delta < 0) {
@@ -2338,40 +2418,38 @@ int scoutfs_btree_merge(struct super_block *sb,
 				scoutfs_inc_counter(sb, btree_merge_delta_null);
 			}
 
-			trace_scoutfs_btree_merge_items(sb, mpos->root,
-					mpos->key, mpos->val_len,
+			trace_scoutfs_btree_merge_items(sb, &mitem->key, mitem->val_len,
 					item ? root : NULL,
 					item ? item_key(item) : NULL,
 					item ? item_val_len(item) : 0, is_del);
 
 			/* rewalk and split if ins/update needs room */
-			if (!is_del && !delta && !mid_free_item_room(bt, mpos->val_len)) {
+			if (!is_del && !delta && !mid_free_item_room(bt, mitem->val_len)) {
 				walk_flags |= BTW_INSERT;
-				walk_val_len = mpos->val_len;
+				walk_val_len = mitem->val_len;
 				break;
 			}
 
 			/* insert missing non-deletion merge items */
 			if (!item && !is_del) {
-				scoutfs_avl_search(&bt->item_root,
-						   cmp_key_item, mpos->key,
+				scoutfs_avl_search(&bt->item_root, cmp_key_item, &mitem->key,
 						   &cmp, &par, NULL, NULL);
-				create_item(bt, mpos->key, mpos->seq, mpos->flags,
-					    mpos->val, mpos->val_len, par, cmp);
+				create_item(bt, &mitem->key, mitem->seq, mitem->flags,
+					    mitem->val, mitem->val_len, par, cmp);
 				scoutfs_inc_counter(sb, btree_merge_insert);
 			}
 
 			/* update existing items */
 			if (item && !is_del && !delta) {
-				item->seq = cpu_to_le64(mpos->seq);
-				item->flags = mpos->flags;
-				update_item_value(bt, item, mpos->val, mpos->val_len);
+				item->seq = cpu_to_le64(mitem->seq);
+				item->flags = mitem->flags;
+				update_item_value(bt, item, mitem->val, mitem->val_len);
 				scoutfs_inc_counter(sb, btree_merge_update);
 			}
 
 			/* update combined delta item seq */
 			if (delta == SCOUTFS_DELTA_COMBINED) {
-				item->seq = cpu_to_le64(mpos->seq);
+				item->seq = cpu_to_le64(mitem->seq);
 			}
 
 			/*
@@ -2403,21 +2481,18 @@ int scoutfs_btree_merge(struct super_block *sb,
 			walk_flags &= ~(BTW_INSERT | BTW_DELETE);
 			walk_val_len = 0;
 
-			/* finished with this key, skip any older items */
-			next = *mpos->key;
-			scoutfs_key_inc(&next);
-			ret = reset_mpos(sb, &pos_root, mpos, &next, end);
-			if (ret < 0)
-				goto out;
+			/* finished with this merged item */
+			tmp = mitem;
+			mitem = next_mitem(mitem);
+			free_mitem(&rng, tmp);
 		}
 	}
 
 	ret = 0;
 out:
 	scoutfs_block_put(sb, bl);
-	rbtree_postorder_for_each_entry_safe(mpos, tmp, &pos_root, node) {
-		free_mpos(sb, mpos);
-	}
+	rbtree_postorder_for_each_entry_safe(mitem, tmp, &rng.root, node)
+		free_mitem(&rng, mitem);
 
 	return ret;
 }

kmod/src/btree.h

@@ -119,7 +119,7 @@ int scoutfs_btree_merge(struct super_block *sb,
 			struct scoutfs_key *next_ret,
 			struct scoutfs_btree_root *root,
 			struct list_head *input_list,
-			bool subtree, int dirty_limit, int alloc_low);
+			bool subtree, int dirty_limit, int alloc_low, int merge_window);
 
 int scoutfs_btree_free_blocks(struct super_block *sb,
 			      struct scoutfs_alloc *alloc,

kmod/src/counters.h

@@ -145,6 +145,7 @@
 	EXPAND_COUNTER(lock_shrink_work)			\
 	EXPAND_COUNTER(lock_unlock)				\
 	EXPAND_COUNTER(lock_wait)				\
+	EXPAND_COUNTER(log_merge_wait_timeout)			\
 	EXPAND_COUNTER(net_dropped_response)			\
 	EXPAND_COUNTER(net_send_bytes)				\
 	EXPAND_COUNTER(net_send_error)				\

kmod/src/forest.c

@@ -721,7 +721,8 @@ static void scoutfs_forest_log_merge_worker(struct work_struct *work)
 	ret = scoutfs_btree_merge(sb, &alloc, &wri, &req.start, &req.end,
 				  &next, &comp.root, &inputs,
 				  !!(req.flags & cpu_to_le64(SCOUTFS_LOG_MERGE_REQUEST_SUBTREE)),
-				  SCOUTFS_LOG_MERGE_DIRTY_BYTE_LIMIT, 10);
+				  SCOUTFS_LOG_MERGE_DIRTY_BYTE_LIMIT, 10,
+				  (2 * 1024 * 1024));
 	if (ret == -ERANGE) {
 		comp.remain = next;
 		le64_add_cpu(&comp.flags, SCOUTFS_LOG_MERGE_COMP_REMAIN);

kmod/src/options.c

@@ -33,6 +33,7 @@ enum {
 	Opt_acl,
 	Opt_data_prealloc_blocks,
 	Opt_data_prealloc_contig_only,
+	Opt_log_merge_wait_timeout_ms,
 	Opt_metadev_path,
 	Opt_noacl,
 	Opt_orphan_scan_delay_ms,
@@ -45,6 +46,7 @@ static const match_table_t tokens = {
 	{Opt_acl, "acl"},
 	{Opt_data_prealloc_blocks, "data_prealloc_blocks=%s"},
 	{Opt_data_prealloc_contig_only, "data_prealloc_contig_only=%s"},
+	{Opt_log_merge_wait_timeout_ms, "log_merge_wait_timeout_ms=%s"},
 	{Opt_metadev_path, "metadev_path=%s"},
 	{Opt_noacl, "noacl"},
 	{Opt_orphan_scan_delay_ms, "orphan_scan_delay_ms=%s"},
@@ -113,6 +115,10 @@ static void free_options(struct scoutfs_mount_options *opts)
 	kfree(opts->metadev_path);
 }
 
+#define MIN_LOG_MERGE_WAIT_TIMEOUT_MS		100UL
+#define DEFAULT_LOG_MERGE_WAIT_TIMEOUT_MS	500
+#define MAX_LOG_MERGE_WAIT_TIMEOUT_MS		(60 * MSEC_PER_SEC)
+
 #define MIN_ORPHAN_SCAN_DELAY_MS	100UL
 #define DEFAULT_ORPHAN_SCAN_DELAY_MS	(10 * MSEC_PER_SEC)
 #define MAX_ORPHAN_SCAN_DELAY_MS	(60 * MSEC_PER_SEC)
@@ -126,11 +132,27 @@ static void init_default_options(struct scoutfs_mount_options *opts)
 
 	opts->data_prealloc_blocks = SCOUTFS_DATA_PREALLOC_DEFAULT_BLOCKS;
 	opts->data_prealloc_contig_only = 1;
+	opts->log_merge_wait_timeout_ms = DEFAULT_LOG_MERGE_WAIT_TIMEOUT_MS;
 	opts->orphan_scan_delay_ms = -1;
 	opts->quorum_heartbeat_timeout_ms = SCOUTFS_QUORUM_DEF_HB_TIMEO_MS;
 	opts->quorum_slot_nr = -1;
 }
 
+static int verify_log_merge_wait_timeout_ms(struct super_block *sb, int ret, int val)
+{
+	if (ret < 0) {
+		scoutfs_err(sb, "failed to parse log_merge_wait_timeout_ms value");
+		return -EINVAL;
+	}
+	if (val < MIN_LOG_MERGE_WAIT_TIMEOUT_MS || val > MAX_LOG_MERGE_WAIT_TIMEOUT_MS) {
+		scoutfs_err(sb, "invalid log_merge_wait_timeout_ms value %d, must be between %lu and %lu",
+			    val, MIN_LOG_MERGE_WAIT_TIMEOUT_MS, MAX_LOG_MERGE_WAIT_TIMEOUT_MS);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int verify_quorum_heartbeat_timeout_ms(struct super_block *sb, int ret, u64 val)
 {
 	if (ret < 0) {
@@ -196,6 +218,14 @@ static int parse_options(struct super_block *sb, char *options, struct scoutfs_m
 			opts->data_prealloc_contig_only = nr;
 			break;
 
+		case Opt_log_merge_wait_timeout_ms:
+			ret = match_int(args, &nr);
+			ret = verify_log_merge_wait_timeout_ms(sb, ret, nr);
+			if (ret < 0)
+				return ret;
+			opts->log_merge_wait_timeout_ms = nr;
+			break;
+
 		case Opt_metadev_path:
 			ret = parse_bdev_path(sb, &args[0], &opts->metadev_path);
 			if (ret < 0)
@@ -422,6 +452,43 @@ static ssize_t data_prealloc_contig_only_store(struct kobject *kobj, struct kobj
 }
 SCOUTFS_ATTR_RW(data_prealloc_contig_only);
 
+static ssize_t log_merge_wait_timeout_ms_show(struct kobject *kobj, struct kobj_attribute *attr,
+						char *buf)
+{
+	struct super_block *sb = SCOUTFS_SYSFS_ATTRS_SB(kobj);
+	struct scoutfs_mount_options opts;
+
+	scoutfs_options_read(sb, &opts);
+
+	return snprintf(buf, PAGE_SIZE, "%u", opts.log_merge_wait_timeout_ms);
+}
+static ssize_t log_merge_wait_timeout_ms_store(struct kobject *kobj, struct kobj_attribute *attr,
+						 const char *buf, size_t count)
+{
+	struct super_block *sb = SCOUTFS_SYSFS_ATTRS_SB(kobj);
+	DECLARE_OPTIONS_INFO(sb, optinf);
+	char nullterm[30]; /* more than enough for octal -U64_MAX */
+	int val;
+	int len;
+	int ret;
+
+	len = min(count, sizeof(nullterm) - 1);
+	memcpy(nullterm, buf, len);
+	nullterm[len] = '\0';
+
+	ret = kstrtoint(nullterm, 0, &val);
+	ret = verify_log_merge_wait_timeout_ms(sb, ret, val);
+	if (ret == 0) {
+		write_seqlock(&optinf->seqlock);
+		optinf->opts.log_merge_wait_timeout_ms = val;
+		write_sequnlock(&optinf->seqlock);
+		ret = count;
+	}
+
+	return ret;
+}
+SCOUTFS_ATTR_RW(log_merge_wait_timeout_ms);
+
 static ssize_t metadev_path_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
 {
 	struct super_block *sb = SCOUTFS_SYSFS_ATTRS_SB(kobj);
@@ -525,6 +592,7 @@ SCOUTFS_ATTR_RO(quorum_slot_nr);
 static struct attribute *options_attrs[] = {
 	SCOUTFS_ATTR_PTR(data_prealloc_blocks),
 	SCOUTFS_ATTR_PTR(data_prealloc_contig_only),
+	SCOUTFS_ATTR_PTR(log_merge_wait_timeout_ms),
 	SCOUTFS_ATTR_PTR(metadev_path),
 	SCOUTFS_ATTR_PTR(orphan_scan_delay_ms),
 	SCOUTFS_ATTR_PTR(quorum_heartbeat_timeout_ms),

kmod/src/options.h

@@ -8,6 +8,7 @@
 struct scoutfs_mount_options {
 	u64 data_prealloc_blocks;
 	bool data_prealloc_contig_only;
+	unsigned int log_merge_wait_timeout_ms;
 	char *metadev_path;
 	unsigned int orphan_scan_delay_ms;
 	int quorum_slot_nr;

kmod/src/scoutfs_trace.h

@@ -439,6 +439,7 @@ DECLARE_EVENT_CLASS(scoutfs_trans_hold_release_class,
 		SCSB_TRACE_ASSIGN(sb);
 		__entry->journal_info = (unsigned long)journal_info;
 		__entry->holders = holders;
+		__entry->ret = ret;
 	),
 
 	TP_printk(SCSBF" journal_info 0x%0lx holders %d ret %d",
@@ -1746,21 +1747,41 @@ TRACE_EVENT(scoutfs_btree_merge,
 		  sk_trace_args(end))
 );
 
+TRACE_EVENT(scoutfs_btree_merge_read_range,
+	TP_PROTO(struct super_block *sb, struct scoutfs_key *start, struct scoutfs_key *end,
+		 int size),
+
+	TP_ARGS(sb, start, end, size),
+
+	TP_STRUCT__entry(
+		SCSB_TRACE_FIELDS
+		sk_trace_define(start)
+		sk_trace_define(end)
+		__field(int, size)
+	),
+
+	TP_fast_assign(
+		SCSB_TRACE_ASSIGN(sb);
+		sk_trace_assign(start, start);
+		sk_trace_assign(end, end);
+		__entry->size = size;
+	),
+
+	TP_printk(SCSBF" start "SK_FMT" end "SK_FMT" size %d",
+		  SCSB_TRACE_ARGS, sk_trace_args(start), sk_trace_args(end), __entry->size)
+);
+
 TRACE_EVENT(scoutfs_btree_merge_items,
 	TP_PROTO(struct super_block *sb,
-		 struct scoutfs_btree_root *m_root,
 		 struct scoutfs_key *m_key, int m_val_len,
 		 struct scoutfs_btree_root *f_root,
 		 struct scoutfs_key *f_key, int f_val_len,
 		 int is_del),
 
-	TP_ARGS(sb, m_root, m_key, m_val_len, f_root, f_key, f_val_len, is_del),
+	TP_ARGS(sb, m_key, m_val_len, f_root, f_key, f_val_len, is_del),
 
 	TP_STRUCT__entry(
 		SCSB_TRACE_FIELDS
-		__field(__u64, m_root_blkno)
-		__field(__u64, m_root_seq)
-		__field(__u8, m_root_height)
 		sk_trace_define(m_key)
 		__field(int, m_val_len)
 		__field(__u64, f_root_blkno)
@@ -1773,10 +1794,6 @@ TRACE_EVENT(scoutfs_btree_merge_items,
 
 	TP_fast_assign(
 		SCSB_TRACE_ASSIGN(sb);
-		__entry->m_root_blkno = m_root ?
-					le64_to_cpu(m_root->ref.blkno) : 0;
-		__entry->m_root_seq = m_root ? le64_to_cpu(m_root->ref.seq) : 0;
-		__entry->m_root_height = m_root ? m_root->height : 0;
 		sk_trace_assign(m_key, m_key);
 		__entry->m_val_len = m_val_len;
 		__entry->f_root_blkno = f_root ?
@@ -1788,11 +1805,9 @@ TRACE_EVENT(scoutfs_btree_merge_items,
 		__entry->is_del = !!is_del;
 	),
 
-	TP_printk(SCSBF" merge item root blkno %llu seq %llu height %u key "SK_FMT" val_len %d, fs item root blkno %llu seq %llu height %u key "SK_FMT" val_len %d, is_del %d",
-		  SCSB_TRACE_ARGS, __entry->m_root_blkno, __entry->m_root_seq,
-		  __entry->m_root_height, sk_trace_args(m_key),
-		  __entry->m_val_len, __entry->f_root_blkno,
-		  __entry->f_root_seq, __entry->f_root_height,
+	TP_printk(SCSBF" merge item key "SK_FMT" val_len %d, fs item root blkno %llu seq %llu height %u key "SK_FMT" val_len %d, is_del %d",
+		  SCSB_TRACE_ARGS, sk_trace_args(m_key), __entry->m_val_len,
+		  __entry->f_root_blkno, __entry->f_root_seq, __entry->f_root_height,
 		  sk_trace_args(f_key), __entry->f_val_len, __entry->is_del)
 );
 
@@ -2075,6 +2090,71 @@ TRACE_EVENT(scoutfs_trans_seq_last,
 		  SCSB_TRACE_ARGS, __entry->s_rid, __entry->trans_seq)
 );
 
+TRACE_EVENT(scoutfs_server_finalize_items,
+	TP_PROTO(struct super_block *sb, u64 rid, u64 item_rid, u64 item_nr, u64 item_flags,
+		 u64 item_get_trans_seq),
+
+	TP_ARGS(sb, rid, item_rid, item_nr, item_flags, item_get_trans_seq),
+
+	TP_STRUCT__entry(
+		SCSB_TRACE_FIELDS
+		__field(__u64, c_rid)
+		__field(__u64, item_rid)
+		__field(__u64, item_nr)
+		__field(__u64, item_flags)
+		__field(__u64, item_get_trans_seq)
+	),
+
+	TP_fast_assign(
+		SCSB_TRACE_ASSIGN(sb);
+		__entry->c_rid = rid;
+		__entry->item_rid = item_rid;
+		__entry->item_nr = item_nr;
+		__entry->item_flags = item_flags;
+		__entry->item_get_trans_seq = item_get_trans_seq;
+	),
+
+	TP_printk(SCSBF" rid %016llx item_rid %016llx item_nr %llu item_flags 0x%llx item_get_trans_seq %llu",
+		  SCSB_TRACE_ARGS, __entry->c_rid, __entry->item_rid, __entry->item_nr,
+		  __entry->item_flags, __entry->item_get_trans_seq)
+);
+
+TRACE_EVENT(scoutfs_server_finalize_decision,
+	TP_PROTO(struct super_block *sb, u64 rid, bool saw_finalized, bool others_active,
+		 bool ours_visible, bool finalize_ours, unsigned int delay_ms,
+		 u64 finalize_sent_seq),
+
+	TP_ARGS(sb, rid, saw_finalized, others_active, ours_visible, finalize_ours, delay_ms,
+		finalize_sent_seq),
+
+	TP_STRUCT__entry(
+		SCSB_TRACE_FIELDS
+		__field(__u64, c_rid)
+		__field(bool, saw_finalized)
+		__field(bool, others_active)
+		__field(bool, ours_visible)
+		__field(bool, finalize_ours)
+		__field(unsigned int, delay_ms)
+		__field(__u64, finalize_sent_seq)
+	),
+
+	TP_fast_assign(
+		SCSB_TRACE_ASSIGN(sb);
+		__entry->c_rid = rid;
+		__entry->saw_finalized = saw_finalized;
+		__entry->others_active = others_active;
+		__entry->ours_visible = ours_visible;
+		__entry->finalize_ours = finalize_ours;
+		__entry->delay_ms = delay_ms;
+		__entry->finalize_sent_seq = finalize_sent_seq;
+	),
+
+	TP_printk(SCSBF" rid %016llx saw_finalized %u others_active %u ours_visible %u finalize_ours %u delay_ms %u finalize_sent_seq %llu",
+		  SCSB_TRACE_ARGS, __entry->c_rid, __entry->saw_finalized, __entry->others_active,
+		  __entry->ours_visible, __entry->finalize_ours, __entry->delay_ms,
+		  __entry->finalize_sent_seq)
+);
+
 TRACE_EVENT(scoutfs_get_log_merge_status,
 	TP_PROTO(struct super_block *sb, u64 rid, struct scoutfs_key *next_range_key,
 		 u64 nr_requests, u64 nr_complete, u64 seq),
@@ -2799,6 +2879,81 @@ TRACE_EVENT(scoutfs_omap_should_delete,
 		  SCSB_TRACE_ARGS, __entry->ino, __entry->nlink, __entry->ret)
 );
 
+#define SSCF_FMT "[bo %llu bs %llu es %llu]"
+#define SSCF_FIELDS(pref)					\
+	__field(__u64, pref##_blkno)				\
+	__field(__u64, pref##_blocks)				\
+	__field(__u64, pref##_entries)
+#define SSCF_ASSIGN(pref, sfl)					\
+	__entry->pref##_blkno = le64_to_cpu((sfl)->ref.blkno);	\
+	__entry->pref##_blocks = le64_to_cpu((sfl)->blocks);	\
+	__entry->pref##_entries = le64_to_cpu((sfl)->entries);
+#define SSCF_ENTRY_ARGS(pref)					\
+	__entry->pref##_blkno,					\
+	__entry->pref##_blocks,					\
+	__entry->pref##_entries
+
+DECLARE_EVENT_CLASS(scoutfs_srch_compact_class,
+	TP_PROTO(struct super_block *sb, struct scoutfs_srch_compact *sc),
+
+	TP_ARGS(sb, sc),
+
+	TP_STRUCT__entry(
+		SCSB_TRACE_FIELDS
+		__field(__u64, id)
+		__field(__u8, nr)
+		__field(__u8, flags)
+		SSCF_FIELDS(out)
+		__field(__u64, in0_blk)
+		__field(__u64, in0_pos)
+		SSCF_FIELDS(in0)
+		__field(__u64, in1_blk)
+		__field(__u64, in1_pos)
+		SSCF_FIELDS(in1)
+		__field(__u64, in2_blk)
+		__field(__u64, in2_pos)
+		SSCF_FIELDS(in2)
+		__field(__u64, in3_blk)
+		__field(__u64, in3_pos)
+		SSCF_FIELDS(in3)
+	),
+
+	TP_fast_assign(
+		SCSB_TRACE_ASSIGN(sb);
+		__entry->id = le64_to_cpu(sc->id);
+		__entry->nr = sc->nr;
+		__entry->flags = sc->flags;
+		SSCF_ASSIGN(out, &sc->out)
+		__entry->in0_blk = le64_to_cpu(sc->in[0].blk);
+		__entry->in0_pos = le64_to_cpu(sc->in[0].pos);
+		SSCF_ASSIGN(in0, &sc->in[0].sfl)
+		__entry->in1_blk = le64_to_cpu(sc->in[0].blk);
+		__entry->in1_pos = le64_to_cpu(sc->in[0].pos);
+		SSCF_ASSIGN(in1, &sc->in[1].sfl)
+		__entry->in2_blk = le64_to_cpu(sc->in[0].blk);
+		__entry->in2_pos = le64_to_cpu(sc->in[0].pos);
+		SSCF_ASSIGN(in2, &sc->in[2].sfl)
+		__entry->in3_blk = le64_to_cpu(sc->in[0].blk);
+		__entry->in3_pos = le64_to_cpu(sc->in[0].pos);
+		SSCF_ASSIGN(in3, &sc->in[3].sfl)
+	),
+
+	TP_printk(SCSBF" id %llu nr %u flags 0x%x out "SSCF_FMT" in0 b %llu p %llu "SSCF_FMT" in1 b %llu p %llu "SSCF_FMT" in2 b %llu p %llu "SSCF_FMT" in3 b %llu p %llu "SSCF_FMT,
+		  SCSB_TRACE_ARGS, __entry->id, __entry->nr, __entry->flags, SSCF_ENTRY_ARGS(out),
+		  __entry->in0_blk, __entry->in0_pos, SSCF_ENTRY_ARGS(in0),
+		  __entry->in1_blk, __entry->in1_pos, SSCF_ENTRY_ARGS(in1),
+		  __entry->in2_blk, __entry->in2_pos, SSCF_ENTRY_ARGS(in2),
+		  __entry->in3_blk, __entry->in3_pos, SSCF_ENTRY_ARGS(in3))
+);
+DEFINE_EVENT(scoutfs_srch_compact_class, scoutfs_srch_compact_client_send,
+	TP_PROTO(struct super_block *sb, struct scoutfs_srch_compact *sc),
+	TP_ARGS(sb, sc)
+);
+DEFINE_EVENT(scoutfs_srch_compact_class, scoutfs_srch_compact_client_recv,
+	TP_PROTO(struct super_block *sb, struct scoutfs_srch_compact *sc),
+	TP_ARGS(sb, sc)
+);
+
 #endif /* _TRACE_SCOUTFS_H */
 
 /* This part must be outside protection */

kmod/src/server.c

@@ -148,6 +148,8 @@ struct server_info {
 	struct scoutfs_quorum_config qconf;
 	/* a running server maintains a private dirty super */
 	struct scoutfs_super_block dirty_super;
+
+	u64 finalize_sent_seq;
 };
 
 #define DECLARE_SERVER_INFO(sb, name) \
@@ -413,6 +415,27 @@ static void server_hold_commit(struct super_block *sb, struct commit_hold *hold)
 	wait_event(cusers->waitq, hold_commit(sb, server, cusers, hold));
 }
 
+/*
+ * Return the higher of the avail or freed used by the active commit
+ * since this holder joined the commit.  This is *not* the amount used
+ * by the holder, we don't track per-holder alloc use.
+ */
+static u32 server_hold_alloc_used_since(struct super_block *sb, struct commit_hold *hold)
+{
+	DECLARE_SERVER_INFO(sb, server);
+	u32 avail_used;
+	u32 freed_used;
+	u32 avail_now;
+	u32 freed_now;
+
+	scoutfs_alloc_meta_remaining(&server->alloc, &avail_now, &freed_now);
+
+	avail_used = hold->avail - avail_now;
+	freed_used = hold->freed - freed_now;
+
+	return max(avail_used, freed_used);
+}
+
 /*
  * This is called while holding the commit and returns once the commit
  * is successfully written.  Many holders can all wait for all holders
@@ -938,22 +961,24 @@ static int find_log_trees_item(struct super_block *sb,
 }
 
 /*
- * Find the next log_trees item from the key.  Fills the caller's log_trees and sets
- * the key past the returned log_trees for iteration.  Returns 0 when done, > 0 for each
- * item, and -errno on fatal errors.
+ * Find the log_trees item with the greatest nr for each rid.  Fills the
+ * caller's log_trees and sets the key before the returned log_trees for
+ * the next iteration.  Returns 0 when done, > 0 for each item, and
+ * -errno on fatal errors.
  */
-static int for_each_lt(struct super_block *sb, struct scoutfs_btree_root *root,
-		       struct scoutfs_key *key, struct scoutfs_log_trees *lt)
+static int for_each_rid_last_lt(struct super_block *sb, struct scoutfs_btree_root *root,
+				struct scoutfs_key *key, struct scoutfs_log_trees *lt)
 {
 	SCOUTFS_BTREE_ITEM_REF(iref);
 	int ret;
 
-	ret = scoutfs_btree_next(sb, root, key, &iref);
+	ret = scoutfs_btree_prev(sb, root, key, &iref);
 	if (ret == 0) {
 		if (iref.val_len == sizeof(struct scoutfs_log_trees)) {
 			memcpy(lt, iref.val, iref.val_len);
 			*key = *iref.key;
-			scoutfs_key_inc(key);
+			key->sklt_nr = 0;
+			scoutfs_key_dec(key);
 			ret = 1;
 		} else {
 			ret = -EIO;
@@ -1048,21 +1073,13 @@ static int next_log_merge_item(struct super_block *sb,
  * abandoned log btree finalized.  If it takes too long each client has
  * a change to make forward progress before being asked to commit again.
  *
- * We're waiting on heavy state that is protected by mutexes and
- * transaction machinery.  It's tricky to recreate that state for
- * lightweight condition tests that don't change task state.  Instead of
- * trying to get that right, particularly as we unwind after success or
- * after timeouts, waiters use an unsatisfying poll.   Short enough to
- * not add terrible latency, given how heavy and infrequent this already
- * is, and long enough to not melt the cpu.  This could be tuned if it
- * becomes a problem.
- *
  * This can end up finalizing a new empty log btree if a new mount
  * happens to arrive at just the right time.  That's fine, merging will
  * ignore and tear down the empty input.
  */
-#define FINALIZE_POLL_MS	(11)
-#define FINALIZE_TIMEOUT_MS	(MSEC_PER_SEC / 2)
+#define FINALIZE_POLL_MIN_DELAY_MS	5U
+#define FINALIZE_POLL_MAX_DELAY_MS	100U
+#define FINALIZE_POLL_DELAY_GROWTH_PCT	150U
 static int finalize_and_start_log_merge(struct super_block *sb, struct scoutfs_log_trees *lt,
 					u64 rid, struct commit_hold *hold)
 {
@@ -1070,8 +1087,10 @@ static int finalize_and_start_log_merge(struct super_block *sb, struct scoutfs_l
 	struct scoutfs_super_block *super = DIRTY_SUPER_SB(sb);
 	struct scoutfs_log_merge_status stat;
 	struct scoutfs_log_merge_range rng;
+	struct scoutfs_mount_options opts;
 	struct scoutfs_log_trees each_lt;
 	struct scoutfs_log_trees fin;
+	unsigned int delay_ms;
 	unsigned long timeo;
 	bool saw_finalized;
 	bool others_active;
@@ -1079,10 +1098,14 @@ static int finalize_and_start_log_merge(struct super_block *sb, struct scoutfs_l
 	bool ours_visible;
 	struct scoutfs_key key;
 	char *err_str = NULL;
+	ktime_t start;
 	int ret;
 	int err;
 
-	timeo = jiffies + msecs_to_jiffies(FINALIZE_TIMEOUT_MS);
+	scoutfs_options_read(sb, &opts);
+	timeo = jiffies + msecs_to_jiffies(opts.log_merge_wait_timeout_ms);
+	delay_ms = FINALIZE_POLL_MIN_DELAY_MS;
+	start = ktime_get_raw();
 
 	for (;;) {
 		/* nothing to do if there's already a merge in flight */
@@ -1099,8 +1122,13 @@ static int finalize_and_start_log_merge(struct super_block *sb, struct scoutfs_l
 		saw_finalized = false;
 		others_active = false;
 		ours_visible = false;
-		scoutfs_key_init_log_trees(&key, 0, 0);
-		while ((ret = for_each_lt(sb, &super->logs_root, &key, &each_lt)) > 0) {
+		scoutfs_key_init_log_trees(&key, U64_MAX, U64_MAX);
+		while ((ret = for_each_rid_last_lt(sb, &super->logs_root, &key, &each_lt)) > 0) {
+
+			trace_scoutfs_server_finalize_items(sb, rid, le64_to_cpu(each_lt.rid),
+							    le64_to_cpu(each_lt.nr),
+							    le64_to_cpu(each_lt.flags),
+							    le64_to_cpu(each_lt.get_trans_seq));
 
 			if ((le64_to_cpu(each_lt.flags) & SCOUTFS_LOG_TREES_FINALIZED))
 				saw_finalized = true;
@@ -1125,6 +1153,10 @@ static int finalize_and_start_log_merge(struct super_block *sb, struct scoutfs_l
 		finalize_ours = (lt->item_root.height > 2) ||
 				(le32_to_cpu(lt->meta_avail.flags) & SCOUTFS_ALLOC_FLAG_LOW);
 
+		trace_scoutfs_server_finalize_decision(sb, rid, saw_finalized, others_active,
+						       ours_visible, finalize_ours, delay_ms,
+						       server->finalize_sent_seq);
+
 		/* done if we're not finalizing and there's no finalized */
 		if (!finalize_ours && !saw_finalized) {
 			ret = 0;
@@ -1132,12 +1164,13 @@ static int finalize_and_start_log_merge(struct super_block *sb, struct scoutfs_l
 		}
 
 		/* send sync requests soon to give time to commit */
-		scoutfs_key_init_log_trees(&key, 0, 0);
+		scoutfs_key_init_log_trees(&key, U64_MAX, U64_MAX);
 		while (others_active &&
-		       (ret = for_each_lt(sb, &super->logs_root, &key, &each_lt)) > 0) {
+		       (ret = for_each_rid_last_lt(sb, &super->logs_root, &key, &each_lt)) > 0) {
 
 			if ((le64_to_cpu(each_lt.flags) & SCOUTFS_LOG_TREES_FINALIZED) ||
-			    (le64_to_cpu(each_lt.rid) == rid))
+			    (le64_to_cpu(each_lt.rid) == rid) ||
+			    (le64_to_cpu(each_lt.get_trans_seq) <= server->finalize_sent_seq))
 				continue;
 
 			ret = scoutfs_net_submit_request_node(sb, server->conn,
@@ -1157,6 +1190,8 @@ static int finalize_and_start_log_merge(struct super_block *sb, struct scoutfs_l
 			break;
 		}
 
+		server->finalize_sent_seq = scoutfs_server_seq(sb);
+
 		/* Finalize ours if it's visible to others */
 		if (ours_visible) {
 			fin = *lt;
@@ -1194,13 +1229,16 @@ static int finalize_and_start_log_merge(struct super_block *sb, struct scoutfs_l
 			if (ret < 0)
 				err_str = "applying commit before waiting for finalized";
 
-			msleep(FINALIZE_POLL_MS);
+			msleep(delay_ms);
+			delay_ms = min(delay_ms * FINALIZE_POLL_DELAY_GROWTH_PCT / 100,
+				       FINALIZE_POLL_MAX_DELAY_MS);
 
 			server_hold_commit(sb, hold);
 			mutex_lock(&server->logs_mutex);
 
 			/* done if we timed out */
 			if (time_after(jiffies, timeo)) {
+				scoutfs_inc_counter(sb, log_merge_wait_timeout);
 				ret = 0;
 				break;
 			}
@@ -1783,43 +1821,29 @@ out:
  * Give the caller the last seq before outstanding client commits.  All
  * seqs up to and including this are stable, new client transactions can
  * only have greater seqs.
+ *
+ * For each rid, only its greatest log trees nr can be an open commit.
+ * We look at the last log_trees item for each client rid and record its
+ * trans seq if it hasn't been committed.
  */
 static int get_stable_trans_seq(struct super_block *sb, u64 *last_seq_ret)
 {
 	struct scoutfs_super_block *super = DIRTY_SUPER_SB(sb);
 	DECLARE_SERVER_INFO(sb, server);
-	SCOUTFS_BTREE_ITEM_REF(iref);
-	struct scoutfs_log_trees *lt;
+	struct scoutfs_log_trees lt;
 	struct scoutfs_key key;
 	u64 last_seq = 0;
 	int ret;
 
 	last_seq = scoutfs_server_seq(sb) - 1;
-	scoutfs_key_init_log_trees(&key, 0, 0);
 
 	mutex_lock(&server->logs_mutex);
 
-	for (;; scoutfs_key_inc(&key)) {
-		ret = scoutfs_btree_next(sb, &super->logs_root, &key, &iref);
-		if (ret == 0) {
-			if (iref.val_len == sizeof(*lt)) {
-				lt = iref.val;
-				if ((le64_to_cpu(lt->get_trans_seq) >
-				     le64_to_cpu(lt->commit_trans_seq)) &&
-				     le64_to_cpu(lt->get_trans_seq) <= last_seq) {
-					last_seq = le64_to_cpu(lt->get_trans_seq) - 1;
-				}
-				key = *iref.key;
-			} else {
-				ret = -EIO;
-			}
-			scoutfs_btree_put_iref(&iref);
-		}
-		if (ret < 0) {
-			if (ret == -ENOENT) {
-				ret = 0;
-				break;
-			}
+	scoutfs_key_init_log_trees(&key, U64_MAX, U64_MAX);
+	while ((ret = for_each_rid_last_lt(sb, &super->logs_root, &key, &lt)) > 0) {
+		if ((le64_to_cpu(lt.get_trans_seq) > le64_to_cpu(lt.commit_trans_seq)) &&
+		     le64_to_cpu(lt.get_trans_seq) <= last_seq) {
+			last_seq = le64_to_cpu(lt.get_trans_seq) - 1;
 		}
 	}
 
@@ -2471,9 +2495,11 @@ static void server_log_merge_free_work(struct work_struct *work)
 
 	while (!server_is_stopping(server)) {
 
-		server_hold_commit(sb, &hold);
-		mutex_lock(&server->logs_mutex);
-		commit = true;
+		if (!commit) {
+			server_hold_commit(sb, &hold);
+			mutex_lock(&server->logs_mutex);
+			commit = true;
+		}
 
 		ret = next_log_merge_item(sb, &super->log_merge,
 					  SCOUTFS_LOG_MERGE_FREEING_ZONE,
@@ -2520,12 +2546,14 @@ static void server_log_merge_free_work(struct work_struct *work)
 		/* freed blocks are in allocator, we *have* to update fr */
 		BUG_ON(ret < 0);
 
-		mutex_unlock(&server->logs_mutex);
-		ret = server_apply_commit(sb, &hold, ret);
-		commit = false;
-		if (ret < 0) {
-			err_str = "looping commit del/upd freeing item";
-			break;
+		if (server_hold_alloc_used_since(sb, &hold) >= COMMIT_HOLD_ALLOC_BUDGET / 2) {
+			mutex_unlock(&server->logs_mutex);
+			ret = server_apply_commit(sb, &hold, ret);
+			commit = false;
+			if (ret < 0) {
+				err_str = "looping commit del/upd freeing item";
+				break;
+			}
 		}
 	}
 
@@ -4298,6 +4326,7 @@ static void scoutfs_server_worker(struct work_struct *work)
 	scoutfs_info(sb, "server starting at "SIN_FMT, SIN_ARG(&sin));
 
 	scoutfs_block_writer_init(sb, &server->wri);
+	server->finalize_sent_seq = 0;
 
 	/* first make sure no other servers are still running */
 	ret = scoutfs_quorum_fence_leaders(sb, &server->qconf, server->term);

kmod/src/srch.c

@@ -31,6 +31,8 @@
 #include "counters.h"
 #include "scoutfs_trace.h"
 #include "triggers.h"
+#include "sysfs.h"
+#include "msg.h"
 
 /*
  * This srch subsystem gives us a way to find inodes that have a given
@@ -69,10 +71,14 @@ struct srch_info {
 	atomic_t shutdown;
 	struct workqueue_struct *workq;
 	struct delayed_work compact_dwork;
+	struct scoutfs_sysfs_attrs ssa;
+	atomic_t compact_delay_ms;
 };
 
 #define DECLARE_SRCH_INFO(sb, name) \
 	struct srch_info *name = SCOUTFS_SB(sb)->srch_info
+#define DECLARE_SRCH_INFO_KOBJ(kobj, name) \
+	DECLARE_SRCH_INFO(SCOUTFS_SYSFS_ATTRS_SB(kobj), name)
 
 #define SRE_FMT "%016llx.%llu.%llu"
 #define SRE_ARG(sre)						\
@@ -2208,8 +2214,15 @@ static int delete_files(struct super_block *sb, struct scoutfs_alloc *alloc,
 	return ret;
 }
 
-/* wait 10s between compact attempts on error, immediate after success */
-#define SRCH_COMPACT_DELAY_MS (10 * MSEC_PER_SEC)
+static void queue_compact_work(struct srch_info *srinf, bool immediate)
+{
+	unsigned long delay;
+
+	if (!atomic_read(&srinf->shutdown)) {
+		delay = immediate ? 0 : msecs_to_jiffies(atomic_read(&srinf->compact_delay_ms));
+		queue_delayed_work(srinf->workq, &srinf->compact_dwork, delay);
+	}
+}
 
 /*
  * Get a compaction operation from the server, sort the entries from the
@@ -2237,7 +2250,6 @@ static void scoutfs_srch_compact_worker(struct work_struct *work)
 	struct super_block *sb = srinf->sb;
 	struct scoutfs_block_writer wri;
 	struct scoutfs_alloc alloc;
-	unsigned long delay;
 	int ret;
 	int err;
 
@@ -2250,6 +2262,8 @@ static void scoutfs_srch_compact_worker(struct work_struct *work)
 	scoutfs_block_writer_init(sb, &wri);
 
 	ret = scoutfs_client_srch_get_compact(sb, sc);
+	if (ret >= 0)
+		trace_scoutfs_srch_compact_client_recv(sb, sc);
 	if (ret < 0 || sc->nr == 0)
 		goto out;
 
@@ -2278,6 +2292,7 @@ commit:
 	sc->meta_freed = alloc.freed;
 	sc->flags |= ret < 0 ? SCOUTFS_SRCH_COMPACT_FLAG_ERROR : 0;
 
+	trace_scoutfs_srch_compact_client_send(sb, sc);
 	err = scoutfs_client_srch_commit_compact(sb, sc);
 	if (err < 0 && ret == 0)
 		ret = err;
@@ -2288,14 +2303,56 @@ out:
 		scoutfs_inc_counter(sb, srch_compact_error);
 
 	scoutfs_block_writer_forget_all(sb, &wri);
-	if (!atomic_read(&srinf->shutdown)) {
-		delay = (sc->nr > 0 && ret == 0) ? 0 : msecs_to_jiffies(SRCH_COMPACT_DELAY_MS);
-		queue_delayed_work(srinf->workq, &srinf->compact_dwork, delay);
-	}
+	queue_compact_work(srinf, sc->nr > 0 && ret == 0);
 
 	kfree(sc);
 }
 
+static ssize_t compact_delay_ms_show(struct kobject *kobj, struct kobj_attribute *attr, char *buf)
+{
+	DECLARE_SRCH_INFO_KOBJ(kobj, srinf);
+
+	return snprintf(buf, PAGE_SIZE, "%u", atomic_read(&srinf->compact_delay_ms));
+}
+
+#define MIN_COMPACT_DELAY_MS MSEC_PER_SEC
+#define DEF_COMPACT_DELAY_MS (10 * MSEC_PER_SEC)
+#define MAX_COMPACT_DELAY_MS (60 * MSEC_PER_SEC)
+
+static ssize_t compact_delay_ms_store(struct kobject *kobj, struct kobj_attribute *attr,
+				      const char *buf, size_t count)
+{
+	struct super_block *sb = SCOUTFS_SYSFS_ATTRS_SB(kobj);
+	DECLARE_SRCH_INFO(sb, srinf);
+	char nullterm[30]; /* more than enough for octal -U64_MAX */
+	u64 val;
+	int len;
+	int ret;
+
+	len = min(count, sizeof(nullterm) - 1);
+	memcpy(nullterm, buf, len);
+	nullterm[len] = '\0';
+
+	ret = kstrtoll(nullterm, 0, &val);
+	if (ret < 0 || val < MIN_COMPACT_DELAY_MS || val > MAX_COMPACT_DELAY_MS) {
+		scoutfs_err(sb, "invalid compact_delay_ms value, must be between %lu and %lu",
+			    MIN_COMPACT_DELAY_MS, MAX_COMPACT_DELAY_MS);
+		return -EINVAL;
+	}
+
+	atomic_set(&srinf->compact_delay_ms, val);
+	cancel_delayed_work(&srinf->compact_dwork);
+	queue_compact_work(srinf, false);
+
+	return count;
+}
+SCOUTFS_ATTR_RW(compact_delay_ms);
+
+static struct attribute *srch_attrs[] = {
+	SCOUTFS_ATTR_PTR(compact_delay_ms),
+	NULL,
+};
+
 void scoutfs_srch_destroy(struct super_block *sb)
 {
 	struct scoutfs_sb_info *sbi = SCOUTFS_SB(sb);
@@ -2312,6 +2369,8 @@ void scoutfs_srch_destroy(struct super_block *sb)
 		destroy_workqueue(srinf->workq);
 	}
 
+	scoutfs_sysfs_destroy_attrs(sb, &srinf->ssa);
+
 	kfree(srinf);
 	sbi->srch_info = NULL;
 }
@@ -2329,8 +2388,15 @@ int scoutfs_srch_setup(struct super_block *sb)
 	srinf->sb = sb;
 	atomic_set(&srinf->shutdown, 0);
 	INIT_DELAYED_WORK(&srinf->compact_dwork, scoutfs_srch_compact_worker);
+	scoutfs_sysfs_init_attrs(sb, &srinf->ssa);
+	atomic_set(&srinf->compact_delay_ms, DEF_COMPACT_DELAY_MS);
+
 	sbi->srch_info = srinf;
 
+	ret = scoutfs_sysfs_create_attrs(sb, &srinf->ssa, srch_attrs, "srch");
+	if (ret < 0)
+		goto out;
+
 	srinf->workq = alloc_workqueue("scoutfs_srch_compact",
 				       WQ_NON_REENTRANT | WQ_UNBOUND |
 				       WQ_HIGHPRI, 0);
@@ -2339,8 +2405,7 @@ int scoutfs_srch_setup(struct super_block *sb)
 		goto out;
 	}
 
-	queue_delayed_work(srinf->workq, &srinf->compact_dwork,
-			   msecs_to_jiffies(SRCH_COMPACT_DELAY_MS));
+	queue_compact_work(srinf, false);
 
 	ret = 0;
 out:

tests/README.md

@@ -25,8 +25,9 @@ All options can be seen by running with -h.
 This script is built to test multi-node systems on one host by using
 different mounts of the same devices.  The script creates a fake block
 device in front of each fs block device for each mount that will be
-tested.  Currently it will create free loop devices and will mount on
-/mnt/test.[0-9].
+tested.  It will create predictable device mapper devices and mounts
+them on /mnt/test.N.  These static device names and mount paths limit
+the script to a single execution per host.
 
 All tests will be run by default.  Particular tests can be included or
 excluded by providing test name regular expressions with the -I and -E
@@ -104,8 +105,8 @@ used during the test.
 
 | Variable         | Description          | Origin          | Example           |
 | ---------------- | -------------------  | --------------- | ----------------- |
-| T\_MB[0-9]       | per-mount meta bdev  | created per run | /dev/loop0        |
-| T\_DB[0-9]       | per-mount data bdev  | created per run | /dev/loop1        |
+| T\_MB[0-9]       | per-mount meta bdev  | created per run | /dev/mapper/\_scoutfs\_test\_meta\_[0-9]        |
+| T\_DB[0-9]       | per-mount data bdev  | created per run | /dev/mapper/\_scoutfs\_test\_data\_[0-9]        |
 | T\_D[0-9]        | per-mount test dir   | made for test   | /mnt/test.[0-9]/t |
 | T\_META\_DEVICE  | main FS meta bdev    | -M              | /dev/vda          |
 | T\_DATA\_DEVICE  | main FS data bdev    | -D              | /dev/vdb          |

tests/funcs/filter.sh

@@ -6,6 +6,61 @@ t_filter_fs()
 	    -e 's@Device: [a-fA-F0-9]*h/[0-9]*d@Device: 0h/0d@g'
 }
 
+#
+# We can hit a spurious kasan warning that was fixed upstream:
+#
+#  e504e74cc3a2 x86/unwind/orc: Disable KASAN checking in the ORC unwinder, part 2
+#
+# KASAN can get mad when the unwinder doesn't find ORC metadata and
+# wanders up without using frames and hits the KASAN stack red zones.
+# We can ignore these messages.
+#
+# They're bracketed by:
+# [ 2687.690127] ==================================================================
+# [ 2687.691366] BUG: KASAN: stack-out-of-bounds in get_reg+0x1bc/0x230
+# ...
+# [ 2687.706220] ==================================================================
+# [ 2687.707284] Disabling lock debugging due to kernel taint
+#
+# That final lock debugging message may not be included.
+#
+ignore_harmless_unwind_kasan_stack_oob()
+{
+awk '
+        BEGIN {
+                in_soob = 0
+                soob_nr = 0
+        }
+        ( !in_soob && $0 ~ /==================================================================/ ) {
+                in_soob = 1
+                soob_nr = NR
+                saved = $0
+        }
+        ( in_soob == 1 && NR == (soob_nr + 1) ) {
+                if (match($0, /KASAN: stack-out-of-bounds in get_reg/) != 0) {
+                        in_soob = 2
+                } else {
+                        in_soob = 0
+                        print saved
+                }
+		saved=""
+        }
+        ( in_soob == 2 && $0 ~ /==================================================================/ ) {
+                in_soob = 3
+                soob_nr = NR
+        }
+        ( in_soob == 3 && NR > soob_nr && $0 !~ /Disabling lock debugging/ ) {
+                in_soob = 0
+        }
+        ( !in_soob ) { print $0 }
+        END {
+                if (saved) {
+                        print saved
+                }
+        }
+'
+}
+
 #
 # Filter out expected messages.  Putting messages here implies that
 # tests aren't relying on messages to discover failures.. they're
@@ -86,10 +141,12 @@ t_filter_dmesg()
 	re="$re|scoutfs .* critical transaction commit failure.*"
 
 	# change-devices causes loop device resizing
+	re="$re|loop: module loaded"
 	re="$re|loop[0-9].* detected capacity change from.*"
 
 	# ignore systemd-journal rotating
 	re="$re|systemd-journald.*"
 
-	egrep -v "($re)" 
+	egrep -v "($re)" | \
+		ignore_harmless_unwind_kasan_stack_oob
 }

tests/golden/createmany-parallel-mounts

@@ -1,3 +1,4 @@
 == measure initial createmany
 == measure initial createmany
 == measure two concurrent createmany runs
+== cleanup

tests/golden/large-fragmented-free

@@ -1,3 +1,4 @@
+== setting longer hung task timeout
 == creating fragmented extents
 == unlink file with moved extents to free extents per block
 == cleanup

tests/golden/srch-safe-merge-pos

@@ -1,4 +1,4 @@
-== snapshot errors
+== initialize per-mount values
 == arm compaction triggers
 trigger srch_compact_logs_pad_safe armed: 1
 trigger srch_merge_stop_safe armed: 1
@@ -10,72 +10,28 @@ trigger srch_compact_logs_pad_safe armed: 1
 trigger srch_merge_stop_safe armed: 1
 trigger srch_compact_logs_pad_safe armed: 1
 trigger srch_merge_stop_safe armed: 1
-== force lots of small rotated log files for compaction
+== compact more often
+== create padded sorted inputs by forcing log rotation
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
+trigger srch_compact_logs_pad_safe armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
+trigger srch_compact_logs_pad_safe armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
+trigger srch_compact_logs_pad_safe armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
 trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-trigger srch_force_log_rotate armed: 1
-== wait for compaction
-== test and disarm compaction triggers
-== verify triggers and errors
+trigger srch_compact_logs_pad_safe armed: 1
+== compaction of padded should stop at safe
+== verify no compaction errors
 == cleanup

tests/run-tests.sh

@@ -326,16 +326,10 @@ unmount_all() {
 		cmd wait $p
 	done
 
-	# delete all temp meta devices
-	for dev in $(losetup --associated "$T_META_DEVICE" | cut -d : -f 1); do
-		if [ -e "$dev" ]; then
-			cmd losetup -d "$dev"
-		fi
-	done
-	# delete all temp data devices
-	for dev in $(losetup --associated "$T_DATA_DEVICE" | cut -d : -f 1); do
-		if [ -e "$dev" ]; then
-			cmd losetup -d "$dev"
+	# delete all temp devices
+	for dev in /dev/mapper/_scoutfs_test_*; do
+		if [ -b "$dev" ]; then
+			cmd dmsetup remove $dev
 		fi
 	done
 }
@@ -434,6 +428,12 @@ $T_UTILS/fenced/scoutfs-fenced > "$T_FENCED_LOG" 2>&1 &
 fenced_pid=$!
 fenced_log "started fenced pid $fenced_pid in the background"
 
+# setup dm tables
+echo "0 $(blockdev --getsz $T_META_DEVICE) linear $T_META_DEVICE 0" > \
+	$T_RESULTS/dmtable.meta
+echo "0 $(blockdev --getsz $T_DATA_DEVICE) linear $T_DATA_DEVICE 0" > \
+	$T_RESULTS/dmtable.data
+
 #
 # mount concurrently so that a quorum is present to elect the leader and
 # start a server.
@@ -442,10 +442,13 @@ msg "mounting $T_NR_MOUNTS mounts on meta $T_META_DEVICE data $T_DATA_DEVICE"
 pids=""
 for i in $(seq 0 $((T_NR_MOUNTS - 1))); do
 
-	meta_dev=$(losetup --find --show $T_META_DEVICE)
-	test -b "$meta_dev" || die "failed to create temp device $meta_dev"
-	data_dev=$(losetup --find --show $T_DATA_DEVICE)
-	test -b "$data_dev" || die "failed to create temp device $data_dev"
+	name="_scoutfs_test_meta_$i"
+	cmd dmsetup create "$name" --table "$(cat $T_RESULTS/dmtable.meta)"
+	meta_dev="/dev/mapper/$name"
+
+	name="_scoutfs_test_data_$i"
+	cmd dmsetup create "$name" --table "$(cat $T_RESULTS/dmtable.data)"
+	data_dev="/dev/mapper/$name"
 
 	dir="/mnt/test.$i"
 	test -d "$dir" || cmd mkdir -p "$dir"

tests/src/bulk_create_paths.c

@@ -1,6 +1,7 @@
 #include <unistd.h>
 #include <stdlib.h>
 #include <stdio.h>
+#include <stdarg.h>
 #include <errno.h>
 #include <string.h>
 #include <sys/stat.h>
@@ -35,10 +36,10 @@ struct opts {
 	unsigned int dry_run:1,
 		     ls_output:1,
 		     quiet:1,
-		     user_xattr:1,
-		     same_srch_xattr:1,
-		     group_srch_xattr:1,
-		     unique_srch_xattr:1;
+		     xattr_set:1,
+		     xattr_file:1,
+		     xattr_group:1;
+	char *xattr_name;
 };
 
 struct stats {
@@ -149,12 +150,31 @@ static void free_dir(struct dir *dir)
 	free(dir);
 }
 
+static size_t snprintf_off(void *buf, size_t sz, size_t off, char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	if (off >= sz)
+		return sz;
+
+	va_start(ap, fmt);
+	ret = vsnprintf(buf + off, sz - off, fmt, ap);
+	va_end(ap);
+
+	if (ret <= 0)
+		return sz;
+
+	return off + ret;
+}
+
 static void create_dir(struct dir *dir, struct opts *opts,
 		       struct stats *stats)
 {
 	struct str_list *s;
-	char name[100];
+	char name[256]; /* max len and null term */
 	char val = 'v';
+	size_t off;
 	int rc;
 	int i;
 
@@ -175,29 +195,21 @@ static void create_dir(struct dir *dir, struct opts *opts,
 		rc = mknod(s->str, S_IFREG | 0644, 0);
 		error_exit(rc, "mknod %s failed"ERRF, s->str, ERRA);
 
-		rc = 0;
-		if (rc == 0 && opts->user_xattr) {
-			strcpy(name, "user.scoutfs_bcp");
-			rc = setxattr(s->str, name, &val, 1, 0);
-		}
-		if (rc == 0 && opts->same_srch_xattr) {
-			strcpy(name, "scoutfs.srch.scoutfs_bcp");
-			rc = setxattr(s->str, name, &val, 1, 0);
-		}
-		if (rc == 0 && opts->group_srch_xattr) {
-			snprintf(name, sizeof(name),
-				 "scoutfs.srch.scoutfs_bcp.group.%lu",
-				 stats->files / 10000);
-			rc = setxattr(s->str, name, &val, 1, 0);
-		}
-		if (rc == 0 && opts->unique_srch_xattr) {
-			snprintf(name, sizeof(name),
-				 "scoutfs.srch.scoutfs_bcp.unique.%lu",
-				 stats->files);
+		if (opts->xattr_set) {
+			off = snprintf_off(name, sizeof(name), 0, "%s", opts->xattr_name);
+			if (opts->xattr_file)
+				off = snprintf_off(name, sizeof(name), off,
+						   "-f-%lu", stats->files);
+			if (opts->xattr_group)
+				off = snprintf_off(name, sizeof(name), off,
+						   "-g-%lu", stats->files / 10000);
+
+			error_exit(off >= sizeof(name), "xattr name longer than 255 bytes");
+
 			rc = setxattr(s->str, name, &val, 1, 0);
+			error_exit(rc, "setxattr %s %s failed"ERRF, s->str, name, ERRA);
 		}
 
-		error_exit(rc, "setxattr %s %s failed"ERRF, s->str, name, ERRA);
 
 		stats->files++;
 		rate_banner(opts, stats);
@@ -365,11 +377,10 @@ static void usage(void)
 	       " -d DIR | create all files in DIR top level directory\n"
 	       " -n     | dry run, only parse, don't create any files\n"
 	       " -q     | quiet, don't regularly print rates\n"
+	       " -F     | append \"-f-NR\" file nr to xattr name, requires -X\n"
+	       " -G     | append \"-g-NR\" file nr/10000 to xattr name, requires -X\n"
 	       " -L     | parse ls output; only reg, skip meta, paths at ./\n"
-	       " -X     | set the same user. xattr name in all files\n"
-	       " -S     | set the same .srch. xattr name in all files\n"
-	       " -G     | set a .srch. xattr name shared by groups of files\n"
-	       " -U     | set a unique .srch. xattr name in all files\n");
+	       " -X NAM | set named xattr in all files\n");
 }
 
 int main(int argc, char **argv)
@@ -386,7 +397,7 @@ int main(int argc, char **argv)
 
 	memset(&opts, 0, sizeof(opts));
 
-        while ((c = getopt(argc, argv, "d:nqLXSGU")) != -1) {
+        while ((c = getopt(argc, argv, "d:nqFGLX:")) != -1) {
                 switch(c) {
                 case 'd':
                         top_dir = strdup(optarg);
@@ -397,20 +408,19 @@ int main(int argc, char **argv)
                 case 'q':
                         opts.quiet = 1;
                         break;
+                case 'F':
+                        opts.xattr_file = 1;
+                        break;
+                case 'G':
+                        opts.xattr_group = 1;
+                        break;
                 case 'L':
                         opts.ls_output = 1;
                         break;
                 case 'X':
-                        opts.user_xattr = 1;
-                        break;
-                case 'S':
-                        opts.same_srch_xattr = 1;
-                        break;
-                case 'G':
-                        opts.group_srch_xattr = 1;
-                        break;
-                case 'U':
-                        opts.unique_srch_xattr = 1;
+			opts.xattr_set = 1;
+			opts.xattr_name = strdup(optarg);
+			error_exit(!opts.xattr_name, "error allocating xattr name");
                         break;
                 case '?':
                         printf("Unknown option '%c'\n", optopt);
@@ -419,6 +429,11 @@ int main(int argc, char **argv)
                 }
         }
 
+	error_exit(opts.xattr_file && !opts.xattr_set,
+		   "must specify xattr -X when appending file nr with -F");
+	error_exit(opts.xattr_group && !opts.xattr_set,
+		   "must specify xattr -X when appending file nr with -G");
+
 	if (!opts.dry_run) {
 		error_exit(!top_dir,
 			   "must specify top level directory with -d");

tests/tests/createmany-parallel-mounts.sh

@@ -7,9 +7,11 @@ t_require_mounts 2
 
 COUNT=50000
 
-# Prep dirs for test. Each mount needs to make their own parent dir for
-# the createmany run, otherwise both dirs will end up in the same inode
-# group, causing updates to bounce that lock around.
+#
+# Prep dirs for test.  We have per-directory inode number allocators so
+# by putting each createmany in a per-mount dir they get their own inode
+# number region and cluster locks.
+#
 echo "== measure initial createmany"
 mkdir -p $T_D0/dir/0
 mkdir $T_D1/dir/1
@@ -17,18 +19,20 @@ mkdir $T_D1/dir/1
 echo "== measure initial createmany"
 START=$SECONDS
 createmany -o "$T_D0/file_" $COUNT >> $T_TMP.full
+sync
 SINGLE=$((SECONDS - START))
 echo single $SINGLE >> $T_TMP.full
 
 echo "== measure two concurrent createmany runs"
 START=$SECONDS
-createmany -o $T_D0/dir/0/file $COUNT > /dev/null &
+(cd $T_D0/dir/0; createmany -o ./file_ $COUNT > /dev/null) &
 pids="$!"
-createmany -o $T_D1/dir/1/file $COUNT > /dev/null &
+(cd $T_D1/dir/1; createmany -o ./file_ $COUNT > /dev/null) &
 pids="$pids $!"
 for p in $pids; do
         wait $p
 done
+sync
 BOTH=$((SECONDS - START))
 echo both $BOTH >> $T_TMP.full
 
@@ -41,7 +45,10 @@ echo both $BOTH >> $T_TMP.full
 # synchronized operation.
 FACTOR=200
 if [ "$BOTH" -gt $(($SINGLE*$FACTOR)) ]; then
-	echo "both createmany took $BOTH sec, more than $FACTOR x single $SINGLE sec"
+	t_fail "both createmany took $BOTH sec, more than $FACTOR x single $SINGLE sec"
 fi
 
+echo "== cleanup"
+find $T_D0/dir -delete
+
 t_pass

tests/tests/large-fragmented-free.sh

@@ -10,6 +10,30 @@ EXTENTS_PER_BTREE_BLOCK=600
 EXTENTS_PER_LIST_BLOCK=8192
 FREED_EXTENTS=$((EXTENTS_PER_BTREE_BLOCK * EXTENTS_PER_LIST_BLOCK))
 
+#
+# This test specifically creates a pathologically sparse file that will
+# be as expensive as possible to free.  This is usually fine on
+# dedicated or reasonable hardware, but trying to run this in
+# virtualized debug kernels can take a very long time.  This test is
+# about making sure that the server doesn't fail, not that the platform
+# can handle the scale of work that our btree formats happen to require
+# while execution is bogged down with use-after-free memory reference
+# tracking.  So we give the test a lot more breathing room before
+# deciding that its hung.
+#
+echo "== setting longer hung task timeout"
+if [ -w /proc/sys/kernel/hung_task_timeout_secs ]; then
+	secs=$(cat /proc/sys/kernel/hung_task_timeout_secs)
+	test "$secs" -gt 0 || \
+		t_fail "confusing value '$secs' from /proc/sys/kernel/hung_task_timeout_secs"
+	restore_hung_task_timeout()
+	{
+		echo "$secs" > /proc/sys/kernel/hung_task_timeout_secs
+	}
+	trap restore_hung_task_timeout EXIT
+	echo "$((secs * 5))" > /proc/sys/kernel/hung_task_timeout_secs
+fi
+
 echo "== creating fragmented extents"
 fragmented_data_extents $FREED_EXTENTS $EXTENTS_PER_BTREE_BLOCK "$T_D0/alloc" "$T_D0/move"
 

tests/tests/srch-basic-functionality.sh

@@ -9,6 +9,7 @@ LOG=340000
 LIM=1000000
 
 SEQF="%.20g"
+SXA="scoutfs.srch.test-srch-basic-functionality"
 
 t_require_commands touch rm setfattr scoutfs find_xattrs
 
@@ -27,20 +28,20 @@ diff_srch_find()
 
 echo "== create new xattrs"
 touch "$T_D0/"{create,update}
-setfattr -n scoutfs.srch.test -v 1 "$T_D0/"{create,update} 2>&1 | t_filter_fs
-diff_srch_find scoutfs.srch.test
+setfattr -n $SXA -v 1 "$T_D0/"{create,update} 2>&1 | t_filter_fs
+diff_srch_find $SXA
 
 echo "== update existing xattr"
-setfattr -n scoutfs.srch.test -v 2 "$T_D0/update" 2>&1 | t_filter_fs
-diff_srch_find scoutfs.srch.test
+setfattr -n $SXA -v 2 "$T_D0/update" 2>&1 | t_filter_fs
+diff_srch_find $SXA
 
 echo "== remove an xattr"
-setfattr -x scoutfs.srch.test "$T_D0/create" 2>&1 | t_filter_fs
-diff_srch_find scoutfs.srch.test
+setfattr -x $SXA "$T_D0/create" 2>&1 | t_filter_fs
+diff_srch_find $SXA
 
 echo "== remove xattr with files"
 rm -f "$T_D0/"{create,update}
-diff_srch_find scoutfs.srch.test
+diff_srch_find $SXA
 
 echo "== trigger small log merges by rotating single block with unmount"
 sv=$(t_server_nr)
@@ -56,7 +57,7 @@ while [ "$i" -lt "8" ]; do
 
 		eval path="\$T_D${nr}/single-block-$i"
 		touch "$path"
-		setfattr -n scoutfs.srch.single-block-logs -v $i "$path"
+		setfattr -n $SXA -v $i "$path"
 		t_umount $nr
 		t_mount $nr
 
@@ -65,51 +66,51 @@ while [ "$i" -lt "8" ]; do
 done
 # wait for srch compaction worker delay
 sleep 10
-rm -rf "$T_D0/single-block-*"
+find "$T_D0" -type f -name 'single-block-*' -delete
 
 echo "== create entries in current log"
 DIR="$T_D0/dir"
 NR=$((LOG / 4))
 mkdir -p "$DIR"
-seq -f "f-$SEQF" 1 $NR | src/bulk_create_paths -S -d "$DIR" > /dev/null
-diff_srch_find scoutfs.srch.scoutfs_bcp
+seq -f "f-$SEQF" 1 $NR | src/bulk_create_paths -X $SXA -d "$DIR" > /dev/null
+diff_srch_find $SXA
 
 echo "== delete small fraction"
-seq -f "$DIR/f-$SEQF" 1 7 $NR | xargs setfattr -x scoutfs.srch.scoutfs_bcp
-diff_srch_find scoutfs.srch.scoutfs_bcp
+seq -f "$DIR/f-$SEQF" 1 7 $NR | xargs setfattr -x $SXA
+diff_srch_find $SXA
 
 echo "== remove files"
 rm -rf "$DIR"
-diff_srch_find scoutfs.srch.scoutfs_bcp
+diff_srch_find $SXA
 
 echo "== create entries that exceed one log"
 NR=$((LOG * 3 / 2))
 mkdir -p "$DIR"
-seq -f "f-$SEQF" 1 $NR | src/bulk_create_paths -S -d "$DIR" > /dev/null
-diff_srch_find scoutfs.srch.scoutfs_bcp
+seq -f "f-$SEQF" 1 $NR | src/bulk_create_paths -X $SXA -d "$DIR" > /dev/null
+diff_srch_find $SXA
 
 echo "== delete fractions in phases"
 for i in $(seq 1 3); do
-	seq -f "$DIR/f-$SEQF" $i 3 $NR | xargs setfattr -x scoutfs.srch.scoutfs_bcp
-	diff_srch_find scoutfs.srch.scoutfs_bcp
+	seq -f "$DIR/f-$SEQF" $i 3 $NR | xargs setfattr -x $SXA
+	diff_srch_find $SXA
 done
 
 echo "== remove files"
 rm -rf "$DIR"
-diff_srch_find scoutfs.srch.scoutfs_bcp
+diff_srch_find $SXA
 
 echo "== create entries for exceed search entry limit"
 NR=$((LIM * 3 / 2))
 mkdir -p "$DIR"
-seq -f "f-$SEQF" 1 $NR | src/bulk_create_paths -S -d "$DIR" > /dev/null
-diff_srch_find scoutfs.srch.scoutfs_bcp
+seq -f "f-$SEQF" 1 $NR | src/bulk_create_paths -X $SXA -d "$DIR" > /dev/null
+diff_srch_find $SXA
 
 echo "== delete half"
-seq -f "$DIR/f-$SEQF" 1 2 $NR | xargs setfattr -x scoutfs.srch.scoutfs_bcp
-diff_srch_find scoutfs.srch.scoutfs_bcp
+seq -f "$DIR/f-$SEQF" 1 2 $NR | xargs setfattr -x $SXA
+diff_srch_find $SXA
 
 echo "== entirely remove third batch"
 rm -rf "$DIR"
-diff_srch_find scoutfs.srch.scoutfs_bcp
+diff_srch_find $SXA
 
 t_pass

tests/tests/srch-safe-merge-pos.sh

@@ -4,10 +4,9 @@
 # block.  Resuming from that position would return an error and
 # compaction would stop making forward progress.
 #
-# We use triggers to make sure that we create the circumstance where a
-# sorted srch block ends at the _SAFE_BYTES offsset and that a merge
-# request stops with a partial block at that specific offset.  We then
-# watch error counters to make sure compaction doesn't get stuck.
+# We use triggers to pad the output of log compaction to end on the safe
+# offset and then cause compaction of those padded inputs to stop at the
+# safe offset.  Continuation will either succeed or return errors.  
 #
 
 # forcing rotation, so just a few
@@ -15,11 +14,20 @@ NR=10
 SEQF="%.20g"
 COMPACT_NR=4
 
-echo "== snapshot errors"
+echo "== initialize per-mount values"
 declare -a err
+declare -a compact_delay
 for nr in $(t_fs_nrs); do
 	err[$nr]=$(t_counter srch_compact_error $nr)
+	compact_delay[$nr]=$(cat $(t_sysfs_path $nr)/srch/compact_delay_ms)
 done
+restore_compact_delay()
+{
+	for nr in $(t_fs_nrs); do
+		echo ${compact_delay[$nr]} > $(t_sysfs_path $nr)/srch/compact_delay_ms
+	done
+}
+trap restore_compact_delay EXIT
 
 echo "== arm compaction triggers"
 for nr in $(t_fs_nrs); do
@@ -27,37 +35,50 @@ for nr in $(t_fs_nrs); do
 	t_trigger_arm srch_merge_stop_safe $nr
 done
 
-echo "== force lots of small rotated log files for compaction"
-sv=$(t_server_nr)
-iter=1
-while [ $iter -le $((COMPACT_NR * COMPACT_NR * COMPACT_NR)) ]; do
-	t_trigger_arm srch_force_log_rotate $sv
-
-	seq -f "f-$iter-$SEQF" 1 10 | src/bulk_create_paths -S -d "$T_D0" > /dev/null
-	sync
-
-	test "$(t_trigger_get srch_force_log_rotate $sv)" == "0" || \
-		t_fail "srch_force_log_rotate didn't trigger"
-
-	((iter++))
-done
-
-echo "== wait for compaction"
-sleep 15
-
-echo "== test and disarm compaction triggers"
-pad=0
-merge_stop=0
+echo "== compact more often"
 for nr in $(t_fs_nrs); do
-	test "$(t_trigger_get srch_compact_logs_pad_safe $nr)" == "0" && pad=1
-	t_trigger_set srch_compact_logs_pad_safe $nr 0
-	test "$(t_trigger_get srch_merge_stop_safe $nr)" == "0" && merge_stop=1
-	t_trigger_set srch_merge_stop_safe $nr 0
+	echo 1000 > $(t_sysfs_path $nr)/srch/compact_delay_ms
 done
 
-echo "== verify triggers and errors" 
-test $pad == 1 || t_fail "srch_compact_logs_pad_safe didn't trigger"
-test $merge_stop == 1 || t_fail "srch_merge_stop_safe didn't trigger"
+echo "== create padded sorted inputs by forcing log rotation"
+sv=$(t_server_nr)
+for i in $(seq 1 $COMPACT_NR); do
+	for j in $(seq 1 $COMPACT_NR); do
+		t_trigger_arm srch_force_log_rotate $sv
+
+		seq -f "f-$i-$j-$SEQF" 1 10 | \
+			bulk_create_paths -X "scoutfs.srch.t-srch-safe-merge-pos" -d "$T_D0" > \
+			/dev/null
+		sync
+
+		test "$(t_trigger_get srch_force_log_rotate $sv)" == "0" || \
+			t_fail "srch_force_log_rotate didn't trigger"
+	done
+
+	padded=0
+	while test $padded == 0 && sleep .5; do
+		for nr in $(t_fs_nrs); do
+			if [ "$(t_trigger_get srch_compact_logs_pad_safe $nr)" == "0" ]; then
+				t_trigger_arm srch_compact_logs_pad_safe $nr
+				padded=1
+				break
+			fi
+			test "$(t_counter srch_compact_error $nr)" == "${err[$nr]}" || \
+				t_fail "srch_compact_error counter increased on mount $nr"
+		done
+	done
+done
+
+echo "== compaction of padded should stop at safe"
+sleep 2
+for nr in $(t_fs_nrs); do
+	if [ "$(t_trigger_get srch_merge_stop_safe $nr)" == "0" ]; then
+		break
+	fi
+done
+
+echo "== verify no compaction errors"
+sleep 2
 for nr in $(t_fs_nrs); do
 	test "$(t_counter srch_compact_error $nr)" == "${err[$nr]}" || \
 		t_fail "srch_compact_error counter increased on mount $nr"

utils/man/scoutfs.5

@@ -55,6 +55,19 @@ with initial sparse regions (perhaps by multiple threads writing to
 different regions) and wasted space isn't an issue (perhaps because the
 file population contains few small files).
 .TP
+.B log_merge_wait_timeout_ms=<number>
+This option sets the amount of time, in milliseconds, that log merge
+creation can wait before timing out.  This setting is per-mount, only
+changes the behavior of that mount, and only affects the server when it
+is running in that mount.
+.sp
+This determines how long it may take for mounts to synchronize
+committing their log trees to create a log merge operation.  Setting it
+too high can create long latencies in the event that a mount takes a
+long time to commit their log.  Setting it too low can result in the
+creation of excessive numbers of log trees that are never merged.  The
+default is 500 and it can not be less than 100 nor greater than 60000.
+.TP
 .B metadev_path=<device>
 The metadev_path option specifies the path to the block device that
 contains the filesystem's metadata.