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* [PATCH] f2fs: optimize code of f2fs_update_extent_tree_range
@ 2015-09-09  2:26 Fan Li
  2015-09-09  9:17 ` Chao Yu
  0 siblings, 1 reply; 2+ messages in thread
From: Fan Li @ 2015-09-09  2:26 UTC (permalink / raw)
  To: jaegeuk; +Cc: linux-f2fs-devel


Fix two potential problems:
1. when largest extent needs to be invalidated, it will be reset in  
   __drop_largest_extent, which makes __is_extent_same after always
   return false, and largest extent unchanged. Now we update it properly.

2. When extent is split and the latter part remains in tree, next_en 
   should be the latter part instead of next extent of original extent.
   It will cause merge failure if there is in-place update, although
   there is not, I think this fix will still makes codes less ambiguous.

This patch also simpfies codes of invalidating extents, and optimizes the
procedues that split extent into two.


Signed-off-by: Fan li <fanofcode.li@samsung.com>
---
 fs/f2fs/extent_cache.c |  150
+++++++++++++++++++-----------------------------
 1 file changed, 58 insertions(+), 92 deletions(-)

diff --git a/fs/f2fs/extent_cache.c b/fs/f2fs/extent_cache.c
index 997ac86..b95cfb3 100644
--- a/fs/f2fs/extent_cache.c
+++ b/fs/f2fs/extent_cache.c
@@ -399,7 +399,7 @@ unsigned int f2fs_update_extent_tree_range(struct inode
*inode,
 {
 	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 *en = NULL, *en1 = 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;
@@ -419,9 +419,6 @@ unsigned int f2fs_update_extent_tree_range(struct inode
*inode,
 	prev = et->largest;
 	dei.len = 0;
 
-	/* we do not guarantee that the largest extent is cached all the
time */
-	__drop_largest_extent(inode, fofs);
-
 	/* 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);
@@ -441,114 +438,83 @@ unsigned int f2fs_update_extent_tree_range(struct
inode *inode,
 
 	/* 2. invlidate all extent nodes in range [fofs, fofs + len - 1] */
 	while (en) {
-		struct rb_node *node;
+		struct rb_node *node = NULL;
+		int parts = 0;	/* # of parts current extent split into */
+		unsigned int org_end;
 
 		if (pos >= end)
 			break;
 
 		dei = en->ei;
-		en1 = en2 = NULL;
+		next_en = en1 = NULL;
 
-		node = rb_next(&en->rb_node);
+		f2fs_bug_on(sbi, pos < dei.fofs || pos >= dei.fofs +
dei.len);
 
-		/*
-		 * 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) {
+		__drop_largest_extent(inode, pos);
+
+		if (pos > dei.fofs && pos - dei.fofs >= F2FS_MIN_EXTENT_LEN)
{
 			en->ei.len = pos - dei.fofs;
+			parts = 1;
+		}
 
-			if (en->ei.len < F2FS_MIN_EXTENT_LEN) {
-				__detach_extent_node(sbi, et, en);
-				insert_p = NULL;
-				insert_parent = NULL;
-				goto update;
+		org_end = dei.fofs + dei.len;
+		if (end < org_end &&
+			org_end - end >= F2FS_MIN_EXTENT_LEN) {
+			if (parts) {
+				set_extent_info(&ei, end,
+						end - dei.fofs + dei.blk,
+						org_end - end);
+				en1 = __insert_extent_tree(sbi, et, &ei,
+							NULL, NULL);
+				next_en = en1;
+			} else {
+				en->ei.fofs = end;
+				en->ei.blk += end - dei.fofs;
+				en->ei.len -= end - dei.fofs;
+				next_en = en;
 			}
-
-			if (__is_extent_same(&dei, &et->largest))
-				et->largest = en->ei;
-			goto next;
+			parts++;
 		}
 
-		/* 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 (!next_en) {
+			node = rb_next(&en->rb_node);
+			next_en = node ?
+				rb_entry(node, struct extent_node, rb_node)
+				: NULL;
+		}
 
-			if (__is_extent_same(&dei, &et->largest))
+		if (parts) {
+			if (en->ei.len > et->largest.len)
 				et->largest = en->ei;
-			goto next;
+		} else {
+			__detach_extent_node(sbi, et, en);
 		}
 
-		__detach_extent_node(sbi, et, en);
-
 		/*
-		 * if we remove node in rb-tree, our parent node pointer may
-		 * point the wrong place, discard them.
+		 * if original extent is split into zero or two parts,
extent
+		 * tree has been altered by deletion or insertion, therefore
+		 * invalidate pointers regard to tree.
 		 */
-		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;
+		if (parts != 1) {
+			insert_p = NULL;
+			insert_parent = NULL;
 		}
 
-		/*
-		 * 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 */
+		/* update in global extent list */
 		spin_lock(&sbi->extent_lock);
-		if (en && !list_empty(&en->list))
+		if (!parts && !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)
+		/* release extent node */
+		if (!parts)
 			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;
+
+		en = next_en;
+		if (next_en)
+			pos = next_en->ei.fofs;
 	}
 
 update_extent:
@@ -557,10 +523,10 @@ update_extent:
 		struct extent_node *den = NULL;
 
 		set_extent_info(&ei, fofs, blkaddr, len);
-		en3 = __try_merge_extent_node(sbi, et, &ei, &den,
+		en1 = __try_merge_extent_node(sbi, et, &ei, &den,
 							prev_en, next_en);
-		if (!en3)
-			en3 = __insert_extent_tree(sbi, et, &ei,
+		if (!en1)
+			en1 = __insert_extent_tree(sbi, et, &ei,
 						insert_p, insert_parent);
 
 		/* give up extent_cache, if split and small updates happen
*/
@@ -572,11 +538,11 @@ update_extent:
 		}
 
 		spin_lock(&sbi->extent_lock);
-		if (en3) {
-			if (list_empty(&en3->list))
-				list_add_tail(&en3->list,
&sbi->extent_list);
+		if (en1) {
+			if (list_empty(&en1->list))
+				list_add_tail(&en1->list,
&sbi->extent_list);
 			else
-				list_move_tail(&en3->list,
&sbi->extent_list);
+				list_move_tail(&en1->list,
&sbi->extent_list);
 		}
 		if (den && !list_empty(&den->list))
 			list_del(&den->list);
-- 
1.7.9.5



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2015-09-09  2:26 [PATCH] f2fs: optimize code of f2fs_update_extent_tree_range Fan Li
2015-09-09  9:17 ` Chao Yu

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