[PATCH v2] f2fs: update extent tree in batches

[Chao Yu]

This patch introduce a new helper f2fs_update_extent_tree_range which can
do extent mapping update at a specified range.

The main idea is:
1) punch all mapping info in extent node(s) which are at a specified range;
2) try to merge new extent mapping with adjacent node, or failing that,
   insert the mapping into extent tree as a new node.

In order to see the benefit, I add a function for stating time stamping
count as below:

uint64_t rdtsc(void)
{
	uint32_t lo, hi;
	__asm__ __volatile__ ("rdtsc" : "=a" (lo), "=d" (hi));
	return (uint64_t)hi << 32 | lo;
}

My test environment is: ubuntu, intel i7-3770, 16G memory, 256g micron ssd.

truncation path:	update extent cache from truncate_data_blocks_range
non-truncataion path:	update extent cache from other paths
total:			all update paths

a) Removing 128MB file which has one extent node mapping whole range of
file:
1. dd if=/dev/zero of=/mnt/f2fs/128M bs=1M count=128
2. sync
3. rm /mnt/f2fs/128M

Before:
		total		count		average
truncation:	7651022		32768		233.49

Patched:
		total		count		average
truncation:	3321		33		100.64

b) fsstress:
fsstress -d /mnt/f2fs -l 5 -n 100 -p 20
Test times:		5 times.

Before:
		total		count		average
truncation:	5812480.6	20911.6		277.95
non-truncation:	7783845.6	13440.8		579.12
total:		13596326.2	34352.4		395.79

Patched:
		total		count		average
truncation:	1281283.0	3041.6		421.25
non-truncation:	7355844.4	13662.8		538.38
total:		8637127.4	16704.4		517.06

1) For the updates in truncation path:
 - we can see updating in batches leads total tsc and update count reducing
   explicitly;
 - besides, for a single batched updating, punching multiple extent nodes
   in a loop, result in executing more operations, so our average tsc
   increase intensively.
2) For the updates in non-truncation path:
 - there is a little improvement, that is because for the scenario that we
   just need to update in the head or tail of extent node, new interface
   optimize to update info in extent node directly, rather than removing
   original extent node for updating and then inserting that updated one
   into cache as new node.

Signed-off-by: Chao Yu <chao2.yu@xxxxxxxxxxx>
---
v2:
 - add some performance data;
 - update description in commit log.
 fs/f2fs/extent_cache.c | 217 +++++++++++++++++++++++++++++++++++--------------
 fs/f2fs/f2fs.h         |   2 +
 fs/f2fs/file.c         |  12 ++-
 3 files changed, 170 insertions(+), 61 deletions(-)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 963b563..1193fd2 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -386,23 +386,21 @@ do_insert:
 	return en;
 }
 
-/* return true, if on-disk extent should be updated */
-static bool f2fs_update_extent_tree(struct inode *inode, pgoff_t fofs,
-							block_t blkaddr)
+unsigned int f2fs_update_extent_tree_range(struct inode *inode,
+				pgoff_t fofs, block_t blkaddr, unsigned int len)
 {
 	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
 	struct extent_tree *et = F2FS_I(inode)->extent_tree;
 	struct extent_node *en = NULL, *en1 = NULL, *en2 = NULL, *en3 = NULL;
-	struct extent_node *den = NULL, *prev_ex = NULL, *next_ex = NULL;
+	struct extent_node *prev_en = NULL, *next_en = NULL;
 	struct extent_info ei, dei, prev;
 	struct rb_node **insert_p = NULL, *insert_parent = NULL;
-	unsigned int endofs;
+	unsigned int end = fofs + len;
+	unsigned int pos = (unsigned int)fofs;
 
 	if (!et)
 		return false;
 
-	trace_f2fs_update_extent_tree(inode, fofs, blkaddr);
-
 	write_lock(&et->lock);
 
 	if (is_inode_flag_set(F2FS_I(inode), FI_NO_EXTENT)) {
@@ -416,39 +414,143 @@ static bool f2fs_update_extent_tree(struct inode *inode, pgoff_t fofs,
 	/* we do not guarantee that the largest extent is cached all the time */
 	f2fs_drop_largest_extent(inode, fofs);
 
-	/* 1. lookup and remove existing extent info in cache */
-	en = __lookup_extent_tree_ret(et, fofs, &prev_ex, &next_ex,
+	/* 1. lookup first extent node in range [fofs, fofs + len - 1] */
+	en = __lookup_extent_tree_ret(et, fofs, &prev_en, &next_en,
 					&insert_p, &insert_parent);
-	if (!en)
-		goto update_extent;
-
-	dei = en->ei;
-	__detach_extent_node(sbi, et, en);
-
-	/* 2. if extent can be split, try to split it */
-	if (dei.len > F2FS_MIN_EXTENT_LEN) {
-		/*  insert left part of split extent into cache */
-		if (fofs - dei.fofs >= F2FS_MIN_EXTENT_LEN) {
-			set_extent_info(&ei, dei.fofs, dei.blk,
-						fofs - dei.fofs);
-			en1 = __insert_extent_tree(sbi, et, &ei, NULL, NULL);
+	if (!en) {
+		if (next_en) {
+			en = next_en;
+			f2fs_bug_on(sbi, en->ei.fofs <= pos);
+			pos = en->ei.fofs;
+		} else {
+			/*
+			 * skip searching in the tree since there is no
+			 * larger extent node in the cache.
+			 */
+			goto update_extent;
+		}
+	}
+
+	/* 2. invlidate all extent nodes in range [fofs, fofs + len - 1] */
+	while (en) {
+		struct rb_node *node;
+
+		if (pos >= end)
+			break;
+
+		dei = en->ei;
+		en1 = en2 = NULL;
+
+		node = rb_next(&en->rb_node);
+
+		/*
+		 * 2.1 there are four cases when we invalidate blkaddr in extent
+		 * node, |V: valid address, X: will be invalidated|
+		 */
+		/* case#1, invalidate right part of extent node |VVVVVXXXXX| */
+		if (pos > dei.fofs && end >= dei.fofs + dei.len) {
+			en->ei.len = pos - dei.fofs;
+
+			if (en->ei.len < F2FS_MIN_EXTENT_LEN) {
+				__detach_extent_node(sbi, et, en);
+				insert_p = NULL;
+				insert_parent = NULL;
+				goto update;
+			}
+
+			if (__is_extent_same(&dei, &et->largest))
+				et->largest = en->ei;
+			goto next;
+		}
+
+		/* case#2, invalidate left part of extent node |XXXXXVVVVV| */
+		if (pos <= dei.fofs && end < dei.fofs + dei.len) {
+			en->ei.fofs = end;
+			en->ei.blk += end - dei.fofs;
+			en->ei.len -= end - dei.fofs;
+
+			if (en->ei.len < F2FS_MIN_EXTENT_LEN) {
+				__detach_extent_node(sbi, et, en);
+				insert_p = NULL;
+				insert_parent = NULL;
+				goto update;
+			}
+
+			if (__is_extent_same(&dei, &et->largest))
+				et->largest = en->ei;
+			goto next;
 		}
 
-		/* insert right part of split extent into cache */
-		endofs = dei.fofs + dei.len - 1;
-		if (endofs - fofs >= F2FS_MIN_EXTENT_LEN) {
-			set_extent_info(&ei, fofs + 1,
-				fofs - dei.fofs + dei.blk + 1, endofs - fofs);
-			en2 = __insert_extent_tree(sbi, et, &ei, NULL, NULL);
+		__detach_extent_node(sbi, et, en);
+
+		/*
+		 * if we remove node in rb-tree, our parent node pointer may
+		 * point the wrong place, discard them.
+		 */
+		insert_p = NULL;
+		insert_parent = NULL;
+
+		/* case#3, invalidate entire extent node |XXXXXXXXXX| */
+		if (pos <= dei.fofs && end >= dei.fofs + dei.len) {
+			if (__is_extent_same(&dei, &et->largest))
+				et->largest.len = 0;
+			goto update;
+		}
+
+		/*
+		 * case#4, invalidate data in the middle of extent node
+		 * |VVVXXXXVVV|
+		 */
+		if (dei.len > F2FS_MIN_EXTENT_LEN) {
+			unsigned int endofs;
+
+			/*  insert left part of split extent into cache */
+			if (pos - dei.fofs >= F2FS_MIN_EXTENT_LEN) {
+				set_extent_info(&ei, dei.fofs, dei.blk,
+							pos - dei.fofs);
+				en1 = __insert_extent_tree(sbi, et, &ei,
+								NULL, NULL);
+			}
+
+			/* insert right part of split extent into cache */
+			endofs = dei.fofs + dei.len;
+			if (endofs - end >= F2FS_MIN_EXTENT_LEN) {
+				set_extent_info(&ei, end,
+						end - dei.fofs + dei.blk,
+						endofs - end);
+				en2 = __insert_extent_tree(sbi, et, &ei,
+								NULL, NULL);
+			}
 		}
+update:
+		/* 2.2 update in global extent list */
+		spin_lock(&sbi->extent_lock);
+		if (en && !list_empty(&en->list))
+			list_del(&en->list);
+		if (en1)
+			list_add_tail(&en1->list, &sbi->extent_list);
+		if (en2)
+			list_add_tail(&en2->list, &sbi->extent_list);
+		spin_unlock(&sbi->extent_lock);
+
+		/* 2.3 release extent node */
+		if (en)
+			kmem_cache_free(extent_node_slab, en);
+next:
+		en = node ? rb_entry(node, struct extent_node, rb_node) : NULL;
+		next_en = en;
+		if (en)
+			pos = en->ei.fofs;
 	}
 
 update_extent:
 	/* 3. update extent in extent cache */
 	if (blkaddr) {
-		set_extent_info(&ei, fofs, blkaddr, 1);
+		struct extent_node *den = NULL;
+
+		set_extent_info(&ei, fofs, blkaddr, len);
 		en3 = __try_merge_extent_node(sbi, et, &ei, &den,
-						prev_ex, next_ex);
+							prev_en, next_en);
 		if (!en3)
 			en3 = __insert_extent_tree(sbi, et, &ei,
 						insert_p, insert_parent);
@@ -460,36 +562,21 @@ update_extent:
 			et->largest.len = 0;
 			set_inode_flag(F2FS_I(inode), FI_NO_EXTENT);
 		}
-	}
 
-	/* 4. update in global extent list */
-	spin_lock(&sbi->extent_lock);
-	if (en && !list_empty(&en->list))
-		list_del(&en->list);
-	/*
-	 * en1 and en2 split from en, they will become more and more smaller
-	 * fragments after splitting several times. So if the length is smaller
-	 * than F2FS_MIN_EXTENT_LEN, we will not add them into extent tree.
-	 */
-	if (en1)
-		list_add_tail(&en1->list, &sbi->extent_list);
-	if (en2)
-		list_add_tail(&en2->list, &sbi->extent_list);
-	if (en3) {
-		if (list_empty(&en3->list))
-			list_add_tail(&en3->list, &sbi->extent_list);
-		else
-			list_move_tail(&en3->list, &sbi->extent_list);
-	}
-	if (den && !list_empty(&den->list))
-		list_del(&den->list);
-	spin_unlock(&sbi->extent_lock);
+		spin_lock(&sbi->extent_lock);
+		if (en3) {
+			if (list_empty(&en3->list))
+				list_add_tail(&en3->list, &sbi->extent_list);
+			else
+				list_move_tail(&en3->list, &sbi->extent_list);
+		}
+		if (den && !list_empty(&den->list))
+			list_del(&den->list);
+		spin_unlock(&sbi->extent_lock);
 
-	/* 5. release extent node */
-	if (en)
-		kmem_cache_free(extent_node_slab, en);
-	if (den)
-		kmem_cache_free(extent_node_slab, den);
+		if (den)
+			kmem_cache_free(extent_node_slab, den);
+	}
 
 	if (is_inode_flag_set(F2FS_I(inode), FI_NO_EXTENT))
 		__free_extent_tree(sbi, et, true);
@@ -645,10 +732,22 @@ void f2fs_update_extent_cache(struct dnode_of_data *dn)
 
 	f2fs_bug_on(F2FS_I_SB(dn->inode), dn->data_blkaddr == NEW_ADDR);
 
+
 	fofs = start_bidx_of_node(ofs_of_node(dn->node_page), fi) +
 							dn->ofs_in_node;
 
-	if (f2fs_update_extent_tree(dn->inode, fofs, dn->data_blkaddr))
+	if (f2fs_update_extent_tree_range(dn->inode, fofs, dn->data_blkaddr, 1))
+		sync_inode_page(dn);
+}
+
+void f2fs_update_extent_cache_range(struct dnode_of_data *dn,
+				pgoff_t fofs, block_t blkaddr, unsigned int len)
+
+{
+	if (!f2fs_may_extent_tree(dn->inode))
+		return;
+
+	if (f2fs_update_extent_tree_range(dn->inode, fofs, blkaddr, len))
 		sync_inode_page(dn);
 }
 
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e25918d..c34eb7e 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2033,6 +2033,8 @@ unsigned int f2fs_destroy_extent_node(struct inode *);
 void f2fs_destroy_extent_tree(struct inode *);
 bool f2fs_lookup_extent_cache(struct inode *, pgoff_t, struct extent_info *);
 void f2fs_update_extent_cache(struct dnode_of_data *);
+void f2fs_update_extent_cache_range(struct dnode_of_data *dn,
+						pgoff_t, block_t, unsigned int);
 void init_extent_cache_info(struct f2fs_sb_info *);
 int __init create_extent_cache(void);
 void destroy_extent_cache(void);
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 86a5c76..8120f86 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -445,9 +445,9 @@ static int f2fs_file_open(struct inode *inode, struct file *filp)
 
 int truncate_data_blocks_range(struct dnode_of_data *dn, int count)
 {
-	int nr_free = 0, ofs = dn->ofs_in_node;
 	struct f2fs_sb_info *sbi = F2FS_I_SB(dn->inode);
 	struct f2fs_node *raw_node;
+	int nr_free = 0, ofs = dn->ofs_in_node, len = count;
 	__le32 *addr;
 
 	raw_node = F2FS_NODE(dn->node_page);
@@ -460,14 +460,22 @@ int truncate_data_blocks_range(struct dnode_of_data *dn, int count)
 
 		dn->data_blkaddr = NULL_ADDR;
 		set_data_blkaddr(dn);
-		f2fs_update_extent_cache(dn);
 		invalidate_blocks(sbi, blkaddr);
 		if (dn->ofs_in_node == 0 && IS_INODE(dn->node_page))
 			clear_inode_flag(F2FS_I(dn->inode),
 						FI_FIRST_BLOCK_WRITTEN);
 		nr_free++;
 	}
+
 	if (nr_free) {
+		pgoff_t fofs;
+		/*
+		 * once we invalidate valid blkaddr in range [ofs, ofs + count],
+		 * we will invalidate all blkaddr in the whole range.
+		 */
+		fofs = start_bidx_of_node(ofs_of_node(dn->node_page),
+						F2FS_I(dn->inode)) + ofs;
+		f2fs_update_extent_cache_range(dn, fofs, 0, len);
 		dec_valid_block_count(sbi, dn->inode, nr_free);
 		set_page_dirty(dn->node_page);
 		sync_inode_page(dn);
-- 
2.4.2


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