f2fs: extent cache: support unaligned extent

Compressed inode may suffer read performance issue due to it can not
use extent cache, so I propose to add this unaligned extent support
to improve it.

Currently, it only works in readonly format f2fs image.

Unaligned extent: in one compressed cluster, physical block number
will be less than logical block number, so we add an extra physical
block length in extent info in order to indicate such extent status.

The idea is if one whole cluster blocks are contiguous physically,
once its mapping info was readed at first time, we will cache an
unaligned (or aligned) extent info entry in extent cache, it expects
that the mapping info will be hitted when rereading cluster.

Merge policy:
- Aligned extents can be merged.
- Aligned extent and unaligned extent can not be merged.

Signed-off-by: Chao Yu <chao@kernel.org>

fs/f2fs/compress.c

@@ -1666,6 +1666,30 @@ void f2fs_put_page_dic(struct page *page)
 	f2fs_put_dic(dic);
 }
 
+/*
+ * check whether cluster blocks are contiguous, and add extent cache entry
+ * only if cluster blocks are logically and physically contiguous.
+ */
+int f2fs_cluster_blocks_are_contiguous(struct dnode_of_data *dn)
+{
+	bool compressed = f2fs_data_blkaddr(dn) == COMPRESS_ADDR;
+	int i = compressed ? 1 : 0;
+	block_t first_blkaddr = data_blkaddr(dn->inode, dn->node_page,
+						dn->ofs_in_node + i);
+
+	for (i += 1; i < F2FS_I(dn->inode)->i_cluster_size; i++) {
+		block_t blkaddr = data_blkaddr(dn->inode, dn->node_page,
+						dn->ofs_in_node + i);
+
+		if (!__is_valid_data_blkaddr(blkaddr))
+			break;
+		if (first_blkaddr + i - 1 != blkaddr)
+			return 0;
+	}
+
+	return compressed ? i - 1 : i;
+}
+
 const struct address_space_operations f2fs_compress_aops = {
 	.releasepage = f2fs_release_page,
 	.invalidatepage = f2fs_invalidate_page,

fs/f2fs/data.c

@@ -2126,6 +2126,8 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 	sector_t last_block_in_file;
 	const unsigned blocksize = blks_to_bytes(inode, 1);
 	struct decompress_io_ctx *dic = NULL;
+	struct extent_info_unaligned eiu;
+	bool from_dnode = true;
 	int i;
 	int ret = 0;
 
@@ -2156,18 +2158,26 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 	if (f2fs_cluster_is_empty(cc))
 		goto out;
 
+	if (f2fs_lookup_extent_cache_unaligned(inode, start_idx, &eiu))
+		from_dnode = false;
+
+	if (from_dnode)
+		goto skip_reading_dnode;
+
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
 	ret = f2fs_get_dnode_of_data(&dn, start_idx, LOOKUP_NODE);
 	if (ret)
 		goto out;
 
 	f2fs_bug_on(sbi, dn.data_blkaddr != COMPRESS_ADDR);
 
+skip_reading_dnode:
 	for (i = 1; i < cc->cluster_size; i++) {
 		block_t blkaddr;
 
-		blkaddr = data_blkaddr(dn.inode, dn.node_page,
-						dn.ofs_in_node + i);
+		blkaddr = from_dnode ? data_blkaddr(dn.inode, dn.node_page,
+					dn.ofs_in_node + i) :
+					eiu.ei.blk + i;
 
 		if (!__is_valid_data_blkaddr(blkaddr))
 			break;
@@ -2177,6 +2187,9 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 			goto out_put_dnode;
 		}
 		cc->nr_cpages++;
+
+		if (!from_dnode && i >= eiu.plen)
+			break;
 	}
 
 	/* nothing to decompress */
@@ -2196,8 +2209,9 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 		block_t blkaddr;
 		struct bio_post_read_ctx *ctx;
 
-		blkaddr = data_blkaddr(dn.inode, dn.node_page,
-						dn.ofs_in_node + i + 1);
+		blkaddr = from_dnode ? data_blkaddr(dn.inode, dn.node_page,
+					dn.ofs_in_node + i + 1) :
+					eiu.ei.blk + i + 1;
 
 		f2fs_wait_on_block_writeback(inode, blkaddr);
 
@@ -2242,13 +2256,15 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 		*last_block_in_bio = blkaddr;
 	}
 
-	f2fs_put_dnode(&dn);
+	if (from_dnode)
+		f2fs_put_dnode(&dn);
 
 	*bio_ret = bio;
 	return 0;
 
 out_put_dnode:
-	f2fs_put_dnode(&dn);
+	if (from_dnode)
+		f2fs_put_dnode(&dn);
 out:
 	for (i = 0; i < cc->cluster_size; i++) {
 		if (cc->rpages[i]) {

fs/f2fs/extent_cache.c

@@ -235,7 +235,7 @@ static struct kmem_cache *extent_node_slab;
 static struct extent_node *__attach_extent_node(struct f2fs_sb_info *sbi,
 				struct extent_tree *et, struct extent_info *ei,
 				struct rb_node *parent, struct rb_node **p,
-				bool leftmost)
+				bool leftmost, bool unaligned)
 {
 	struct extent_node *en;
 
@@ -247,6 +247,9 @@ static struct extent_node *__attach_extent_node(struct f2fs_sb_info *sbi,
 	INIT_LIST_HEAD(&en->list);
 	en->et = et;
 
+	if (unaligned)
+		en->plen = ((struct extent_info_unaligned *)ei)->plen;
+
 	rb_link_node(&en->rb_node, parent, p);
 	rb_insert_color_cached(&en->rb_node, &et->root, leftmost);
 	atomic_inc(&et->node_cnt);
@@ -320,7 +323,7 @@ static struct extent_node *__init_extent_tree(struct f2fs_sb_info *sbi,
 	struct rb_node **p = &et->root.rb_root.rb_node;
 	struct extent_node *en;
 
-	en = __attach_extent_node(sbi, et, ei, NULL, p, true);
+	en = __attach_extent_node(sbi, et, ei, NULL, p, true, false);
 	if (!en)
 		return NULL;
 
@@ -439,6 +442,17 @@ static bool f2fs_lookup_extent_tree(struct inode *inode, pgoff_t pgofs,
 		stat_inc_rbtree_node_hit(sbi);
 
 	*ei = en->ei;
+
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+	if (is_inode_flag_set(inode, FI_COMPRESSED_FILE) &&
+				f2fs_sb_has_readonly(sbi)) {
+		struct extent_info_unaligned *eiu =
+				(struct extent_info_unaligned *)ei;
+
+		eiu->plen = en->plen;
+	}
+#endif
+
 	spin_lock(&sbi->extent_lock);
 	if (!list_empty(&en->list)) {
 		list_move_tail(&en->list, &sbi->extent_list);
@@ -457,17 +471,18 @@ static bool f2fs_lookup_extent_tree(struct inode *inode, pgoff_t pgofs,
 static struct extent_node *__try_merge_extent_node(struct f2fs_sb_info *sbi,
 				struct extent_tree *et, struct extent_info *ei,
 				struct extent_node *prev_ex,
-				struct extent_node *next_ex)
+				struct extent_node *next_ex,
+				bool unaligned)
 {
 	struct extent_node *en = NULL;
 
-	if (prev_ex && __is_back_mergeable(ei, &prev_ex->ei)) {
+	if (prev_ex && __is_back_mergeable(ei, &prev_ex->ei, unaligned)) {
 		prev_ex->ei.len += ei->len;
 		ei = &prev_ex->ei;
 		en = prev_ex;
 	}
 
-	if (next_ex && __is_front_mergeable(ei, &next_ex->ei)) {
+	if (next_ex && __is_front_mergeable(ei, &next_ex->ei, unaligned)) {
 		next_ex->ei.fofs = ei->fofs;
 		next_ex->ei.blk = ei->blk;
 		next_ex->ei.len += ei->len;
@@ -495,7 +510,7 @@ static struct extent_node *__insert_extent_tree(struct f2fs_sb_info *sbi,
 				struct extent_tree *et, struct extent_info *ei,
 				struct rb_node **insert_p,
 				struct rb_node *insert_parent,
-				bool leftmost)
+				bool leftmost, bool unaligned)
 {
 	struct rb_node **p;
 	struct rb_node *parent = NULL;
@@ -512,7 +527,7 @@ static struct extent_node *__insert_extent_tree(struct f2fs_sb_info *sbi,
 	p = f2fs_lookup_rb_tree_for_insert(sbi, &et->root, &parent,
 						ei->fofs, &leftmost);
 do_insert:
-	en = __attach_extent_node(sbi, et, ei, parent, p, leftmost);
+	en = __attach_extent_node(sbi, et, ei, parent, p, leftmost, unaligned);
 	if (!en)
 		return NULL;
 
@@ -594,7 +609,7 @@ static void f2fs_update_extent_tree_range(struct inode *inode,
 						end - dei.fofs + dei.blk,
 						org_end - end);
 				en1 = __insert_extent_tree(sbi, et, &ei,
-							NULL, NULL, true);
+						NULL, NULL, true, false);
 				next_en = en1;
 			} else {
 				en->ei.fofs = end;
@@ -633,9 +648,10 @@ static void f2fs_update_extent_tree_range(struct inode *inode,
 	if (blkaddr) {
 
 		set_extent_info(&ei, fofs, blkaddr, len);
-		if (!__try_merge_extent_node(sbi, et, &ei, prev_en, next_en))
+		if (!__try_merge_extent_node(sbi, et, &ei,
+					prev_en, next_en, false))
 			__insert_extent_tree(sbi, et, &ei,
-					insert_p, insert_parent, leftmost);
+				insert_p, insert_parent, leftmost, false);
 
 		/* give up extent_cache, if split and small updates happen */
 		if (dei.len >= 1 &&
@@ -661,6 +677,47 @@ static void f2fs_update_extent_tree_range(struct inode *inode,
 		f2fs_mark_inode_dirty_sync(inode, true);
 }
 
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+void f2fs_update_extent_tree_range_unaligned(struct inode *inode,
+				pgoff_t fofs, block_t blkaddr, unsigned int llen,
+				unsigned int plen)
+{
+	struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
+	struct extent_tree *et = F2FS_I(inode)->extent_tree;
+	struct extent_node *en = NULL;
+	struct extent_node *prev_en = NULL, *next_en = NULL;
+	struct extent_info_unaligned eiu;
+	struct rb_node **insert_p = NULL, *insert_parent = NULL;
+	bool leftmost = false;
+
+	trace_f2fs_update_extent_tree_range(inode, fofs, blkaddr, llen);
+
+	/* it is safe here to check FI_NO_EXTENT w/o et->lock in ro image */
+	if (is_inode_flag_set(inode, FI_NO_EXTENT))
+		return;
+
+	write_lock(&et->lock);
+
+	en = (struct extent_node *)f2fs_lookup_rb_tree_ret(&et->root,
+				(struct rb_entry *)et->cached_en, fofs,
+				(struct rb_entry **)&prev_en,
+				(struct rb_entry **)&next_en,
+				&insert_p, &insert_parent, false,
+				&leftmost);
+	f2fs_bug_on(sbi, en);
+
+	set_extent_info(&eiu.ei, fofs, blkaddr, llen);
+	eiu.plen = plen;
+
+	if (!__try_merge_extent_node(sbi, et, (struct extent_info *)&eiu,
+				prev_en, next_en, true))
+		__insert_extent_tree(sbi, et, (struct extent_info *)&eiu,
+				insert_p, insert_parent, leftmost, true);
+
+	write_unlock(&et->lock);
+}
+#endif
+
 unsigned int f2fs_shrink_extent_tree(struct f2fs_sb_info *sbi, int nr_shrink)
 {
 	struct extent_tree *et, *next;
@@ -818,6 +875,17 @@ bool f2fs_lookup_extent_cache(struct inode *inode, pgoff_t pgofs,
 	return f2fs_lookup_extent_tree(inode, pgofs, ei);
 }
 
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+bool f2fs_lookup_extent_cache_unaligned(struct inode *inode, pgoff_t pgofs,
+					struct extent_info_unaligned *eiu)
+{
+	if (!f2fs_may_extent_tree(inode))
+		return false;
+
+	return f2fs_lookup_extent_tree(inode, pgofs, (struct extent_info *)eiu);
+}
+#endif
+
 void f2fs_update_extent_cache(struct dnode_of_data *dn)
 {
 	pgoff_t fofs;

fs/f2fs/f2fs.h

@@ -582,11 +582,21 @@ struct extent_info {
 	u32 blk;			/* start block address of the extent */
 };
 
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+struct extent_info_unaligned {
+	struct extent_info ei;		/* extent info */
+	unsigned int plen;		/* physical extent length of compressed blocks */
+};
+#endif
+
 struct extent_node {
 	struct rb_node rb_node;		/* rb node located in rb-tree */
 	struct extent_info ei;		/* extent info */
 	struct list_head list;		/* node in global extent list of sbi */
 	struct extent_tree *et;		/* extent tree pointer */
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+	unsigned int plen;		/* physical extent length of compressed blocks */
+#endif
 };
 
 struct extent_tree {
@@ -821,22 +831,32 @@ static inline bool __is_discard_front_mergeable(struct discard_info *cur,
 }
 
 static inline bool __is_extent_mergeable(struct extent_info *back,
-						struct extent_info *front)
+				struct extent_info *front, bool unaligned)
 {
+	if (unaligned) {
+		struct extent_info_unaligned *be =
+				(struct extent_info_unaligned *)back;
+		struct extent_info_unaligned *fe =
+				(struct extent_info_unaligned *)front;
+
+		if (be->ei.len != be->plen || fe->ei.len != fe->plen)
+			return false;
+	}
+
 	return (back->fofs + back->len == front->fofs &&
 			back->blk + back->len == front->blk);
 }
 
 static inline bool __is_back_mergeable(struct extent_info *cur,
-						struct extent_info *back)
+				struct extent_info *back, bool unaligned)
 {
-	return __is_extent_mergeable(back, cur);
+	return __is_extent_mergeable(back, cur, unaligned);
 }
 
 static inline bool __is_front_mergeable(struct extent_info *cur,
-						struct extent_info *front)
+				struct extent_info *front, bool unaligned)
 {
-	return __is_extent_mergeable(cur, front);
+	return __is_extent_mergeable(cur, front, unaligned);
 }
 
 extern void f2fs_mark_inode_dirty_sync(struct inode *inode, bool sync);
@@ -3995,6 +4015,10 @@ unsigned int f2fs_destroy_extent_node(struct inode *inode);
 void f2fs_destroy_extent_tree(struct inode *inode);
 bool f2fs_lookup_extent_cache(struct inode *inode, pgoff_t pgofs,
 			struct extent_info *ei);
+#ifdef CONFIG_F2FS_FS_COMPRESSION
+bool f2fs_lookup_extent_cache_unaligned(struct inode *inode, pgoff_t pgofs,
+					struct extent_info_unaligned *eiu);
+#endif
 void f2fs_update_extent_cache(struct dnode_of_data *dn);
 void f2fs_update_extent_cache_range(struct dnode_of_data *dn,
 			pgoff_t fofs, block_t blkaddr, unsigned int len);
@@ -4074,6 +4098,7 @@ int f2fs_read_multi_pages(struct compress_ctx *cc, struct bio **bio_ret,
 struct decompress_io_ctx *f2fs_alloc_dic(struct compress_ctx *cc);
 void f2fs_decompress_end_io(struct decompress_io_ctx *dic, bool failed);
 void f2fs_put_page_dic(struct page *page);
+int f2fs_cluster_blocks_are_contiguous(struct dnode_of_data *dn);
 int f2fs_init_compress_ctx(struct compress_ctx *cc);
 void f2fs_destroy_compress_ctx(struct compress_ctx *cc, bool reuse);
 void f2fs_init_compress_info(struct f2fs_sb_info *sbi);
@@ -4102,6 +4127,9 @@ void f2fs_invalidate_compress_pages(struct f2fs_sb_info *sbi, nid_t ino);
 		sbi->compr_written_block += blocks;			\
 		sbi->compr_saved_block += diff;				\
 	} while (0)
+void f2fs_update_extent_tree_range_unaligned(struct inode *inode,
+				pgoff_t fofs, block_t blkaddr, unsigned int llen,
+				unsigned int plen);
 #else
 static inline bool f2fs_is_compressed_page(struct page *page) { return false; }
 static inline bool f2fs_is_compress_backend_ready(struct inode *inode)
@@ -4128,6 +4156,7 @@ static inline void f2fs_put_page_dic(struct page *page)
 {
 	WARN_ON_ONCE(1);
 }
+static inline int f2fs_cluster_blocks_are_contiguous(struct dnode_of_data *dn) { return 0; }
 static inline int f2fs_init_compress_inode(struct f2fs_sb_info *sbi) { return 0; }
 static inline void f2fs_destroy_compress_inode(struct f2fs_sb_info *sbi) { }
 static inline int f2fs_init_page_array_cache(struct f2fs_sb_info *sbi) { return 0; }
@@ -4143,6 +4172,9 @@ static inline bool f2fs_load_compressed_page(struct f2fs_sb_info *sbi,
 static inline void f2fs_invalidate_compress_pages(struct f2fs_sb_info *sbi,
 							nid_t ino) { }
 #define inc_compr_inode_stat(inode)		do { } while (0)
+static inline void f2fs_update_extent_tree_range_unaligned(struct inode *inode,
+				pgoff_t fofs, block_t blkaddr, unsigned int llen,
+				unsigned int plen) { }
 #endif
 
 static inline void set_compress_context(struct inode *inode)