f2fs: readahead multi pages of directory for performance

We have no so such readahead mechanism in ->iterate() path as the one in
->read() path, it cause low performance when we read large directory.
This patch add readahead in f2fs_readdir() for better performance.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk.kim@samsung.com>

2 files changed, 8 insertions, 0 deletions

diff --git a/fs/f2fs/dir.c b/fs/f2fs/dir.c
index 972fd0ef230f..3581c2bde21b 100644
--- a/fs/f2fs/dir.c
+++ b/fs/f2fs/dir.c
@@ -637,11 +637,17 @@ static int f2fs_readdir(struct file *file, struct dir_context *ctx)
         struct f2fs_dentry_block *dentry_blk = NULL;
         struct f2fs_dir_entry *de = NULL;
         struct page *dentry_page = NULL;
+        struct file_ra_state *ra = &file->f_ra;
         unsigned int n = ((unsigned long)ctx->pos / NR_DENTRY_IN_BLOCK);
         unsigned char d_type = DT_UNKNOWN;
 
         bit_pos = ((unsigned long)ctx->pos % NR_DENTRY_IN_BLOCK);
 
+        /* readahead for multi pages of dir */
+        if (npages - n > 1 && !ra_has_index(ra, n))
+                page_cache_sync_readahead(inode->i_mapping, ra, file, n,
+                                min(npages - n, (pgoff_t)MAX_DIR_RA_PAGES));
+
         for (; n < npages; n++) {
                 dentry_page = get_lock_data_page(inode, n);
                 if (IS_ERR(dentry_page))
diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e77be7cb1e60..2b67679f88b6 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -182,6 +182,8 @@ enum {
 
 #define F2FS_LINK_MAX           32000   /* maximum link count per file */
 
+#define MAX_DIR_RA_PAGES        4       /* maximum ra pages of dir */
+
 /* for in-memory extent cache entry */
 #define F2FS_MIN_EXTENT_LEN     16      /* minimum extent length */