f2fs: introduce readahead mode of node pages

Previously, f2fs reads several node pages ahead when get_dnode_of_data is called
with RDONLY_NODE flag.
And, this flag is set by the following functions.
- get_data_block_ro
- get_lock_data_page
- do_write_data_page
- truncate_blocks
- truncate_hole

However, this readahead mechanism is initially introduced for the use of
get_data_block_ro to enhance the sequential read performance.

So, let's clarify all the cases with the additional modes as follows.

enum {
	ALLOC_NODE,	/* allocate a new node page if needed */
	LOOKUP_NODE,	/* look up a node without readahead */
	LOOKUP_NODE_RA,	/*
			 * look up a node with readahead called
			 * by get_datablock_ro.
			 */
}
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>
Reviewed-by: Namjae Jeon <namjae.jeon@samsung.com>

fs/f2fs/data.c

@@ -183,7 +183,7 @@ struct page *find_data_page(struct inode *inode, pgoff_t index)
 	f2fs_put_page(page, 0);
 
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = get_dnode_of_data(&dn, index, RDONLY_NODE);
+	err = get_dnode_of_data(&dn, index, LOOKUP_NODE);
 	if (err)
 		return ERR_PTR(err);
 	f2fs_put_dnode(&dn);
@@ -222,7 +222,7 @@ struct page *get_lock_data_page(struct inode *inode, pgoff_t index)
 	int err;
 
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = get_dnode_of_data(&dn, index, RDONLY_NODE);
+	err = get_dnode_of_data(&dn, index, LOOKUP_NODE);
 	if (err)
 		return ERR_PTR(err);
 	f2fs_put_dnode(&dn);
@@ -262,7 +262,7 @@ struct page *get_new_data_page(struct inode *inode, pgoff_t index,
 	int err;
 
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = get_dnode_of_data(&dn, index, 0);
+	err = get_dnode_of_data(&dn, index, ALLOC_NODE);
 	if (err)
 		return ERR_PTR(err);
 
@@ -392,7 +392,7 @@ static int get_data_block_ro(struct inode *inode, sector_t iblock,
 
 	/* When reading holes, we need its node page */
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = get_dnode_of_data(&dn, pgofs, RDONLY_NODE);
+	err = get_dnode_of_data(&dn, pgofs, LOOKUP_NODE_RA);
 	if (err)
 		return (err == -ENOENT) ? 0 : err;
 
@@ -443,7 +443,7 @@ int do_write_data_page(struct page *page)
 	int err = 0;
 
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = get_dnode_of_data(&dn, page->index, RDONLY_NODE);
+	err = get_dnode_of_data(&dn, page->index, LOOKUP_NODE);
 	if (err)
 		return err;
 
@@ -607,7 +607,7 @@ static int f2fs_write_begin(struct file *file, struct address_space *mapping,
 	mutex_lock_op(sbi, DATA_NEW);
 
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = get_dnode_of_data(&dn, index, 0);
+	err = get_dnode_of_data(&dn, index, ALLOC_NODE);
 	if (err) {
 		mutex_unlock_op(sbi, DATA_NEW);
 		f2fs_put_page(page, 1);

fs/f2fs/f2fs.h

@@ -125,11 +125,15 @@ static inline int update_sits_in_cursum(struct f2fs_summary_block *rs, int i)
 					 * file keeping -1 as its node offset to
 					 * distinguish from index node blocks.
 					 */
-#define RDONLY_NODE		1	/*
-					 * specify a read-only mode when getting
-					 * a node block. 0 is read-write mode.
-					 * used by get_dnode_of_data().
+enum {
+	ALLOC_NODE,			/* allocate a new node page if needed */
+	LOOKUP_NODE,			/* look up a node without readahead */
+	LOOKUP_NODE_RA,			/*
+					 * look up a node with readahead called
+					 * by get_datablock_ro.
 					 */
+};
+
 #define F2FS_LINK_MAX		32000	/* maximum link count per file */
 
 /* for in-memory extent cache entry */

fs/f2fs/file.c

@@ -43,7 +43,7 @@ static int f2fs_vm_page_mkwrite(struct vm_area_struct *vma,
 
 	/* block allocation */
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = get_dnode_of_data(&dn, page->index, 0);
+	err = get_dnode_of_data(&dn, page->index, ALLOC_NODE);
 	if (err) {
 		mutex_unlock_op(sbi, DATA_NEW);
 		goto out;
@@ -258,7 +258,7 @@ static int truncate_blocks(struct inode *inode, u64 from)
 	mutex_lock_op(sbi, DATA_TRUNC);
 
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	err = get_dnode_of_data(&dn, free_from, RDONLY_NODE);
+	err = get_dnode_of_data(&dn, free_from, LOOKUP_NODE);
 	if (err) {
 		if (err == -ENOENT)
 			goto free_next;
@@ -420,7 +420,7 @@ int truncate_hole(struct inode *inode, pgoff_t pg_start, pgoff_t pg_end)
 
 		mutex_lock_op(sbi, DATA_TRUNC);
 		set_new_dnode(&dn, inode, NULL, NULL, 0);
-		err = get_dnode_of_data(&dn, index, RDONLY_NODE);
+		err = get_dnode_of_data(&dn, index, LOOKUP_NODE);
 		if (err) {
 			mutex_unlock_op(sbi, DATA_TRUNC);
 			if (err == -ENOENT)
@@ -504,7 +504,7 @@ static int expand_inode_data(struct inode *inode, loff_t offset,
 		mutex_lock_op(sbi, DATA_NEW);
 
 		set_new_dnode(&dn, inode, NULL, NULL, 0);
-		ret = get_dnode_of_data(&dn, index, 0);
+		ret = get_dnode_of_data(&dn, index, ALLOC_NODE);
 		if (ret) {
 			mutex_unlock_op(sbi, DATA_NEW);
 			break;

fs/f2fs/node.c

@@ -384,7 +384,7 @@ static int get_node_path(long block, int offset[4], unsigned int noffset[4])
 /*
  * Caller should call f2fs_put_dnode(dn).
  */
-int get_dnode_of_data(struct dnode_of_data *dn, pgoff_t index, int ro)
+int get_dnode_of_data(struct dnode_of_data *dn, pgoff_t index, int mode)
 {
 	struct f2fs_sb_info *sbi = F2FS_SB(dn->inode->i_sb);
 	struct page *npage[4];
@@ -411,7 +411,7 @@ int get_dnode_of_data(struct dnode_of_data *dn, pgoff_t index, int ro)
 	for (i = 1; i <= level; i++) {
 		bool done = false;
 
-		if (!nids[i] && !ro) {
+		if (!nids[i] && mode == ALLOC_NODE) {
 			mutex_lock_op(sbi, NODE_NEW);
 
 			/* alloc new node */
@@ -434,7 +434,7 @@ int get_dnode_of_data(struct dnode_of_data *dn, pgoff_t index, int ro)
 			alloc_nid_done(sbi, nids[i]);
 			mutex_unlock_op(sbi, NODE_NEW);
 			done = true;
-		} else if (ro && i == level && level > 1) {
+		} else if (mode == LOOKUP_NODE_RA && i == level && level > 1) {
 			npage[i] = get_node_page_ra(parent, offset[i - 1]);
 			if (IS_ERR(npage[i])) {
 				err = PTR_ERR(npage[i]);

fs/f2fs/recovery.c

@@ -247,7 +247,7 @@ static void do_recover_data(struct f2fs_sb_info *sbi, struct inode *inode,
 		end = start + ADDRS_PER_BLOCK;
 
 	set_new_dnode(&dn, inode, NULL, NULL, 0);
-	if (get_dnode_of_data(&dn, start, 0))
+	if (get_dnode_of_data(&dn, start, ALLOC_NODE))
 		return;
 
 	wait_on_page_writeback(dn.node_page);