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>

1 files changed, 3 insertions, 3 deletions

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index efcada7becd5..65ec2eabb392 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -384,7 +384,7 @@ got:
 /*
  * 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]);