nilfs2: add bmap function to seek a valid key

Add a new bmap function, nilfs_bmap_seek_key(), which seeks a valid
entry and returns its key starting from a given key.  This function
can be used to skip hole blocks efficiently.

Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/fs/nilfs2/direct.c b/fs/nilfs2/direct.c
index 82f4865e86dd..ebf89fd8ac1a 100644
--- a/fs/nilfs2/direct.c
+++ b/fs/nilfs2/direct.c
@@ -173,6 +173,21 @@ static int nilfs_direct_delete(struct nilfs_bmap *bmap, __u64 key)
         return ret;
 }
 
+static int nilfs_direct_seek_key(const struct nilfs_bmap *direct, __u64 start,
+                                 __u64 *keyp)
+{
+        __u64 key;
+
+        for (key = start; key <= NILFS_DIRECT_KEY_MAX; key++) {
+                if (nilfs_direct_get_ptr(direct, key) !=
+                    NILFS_BMAP_INVALID_PTR) {
+                        *keyp = key;
+                        return 0;
+                }
+        }
+        return -ENOENT;
+}
+
 static int nilfs_direct_last_key(const struct nilfs_bmap *direct, __u64 *keyp)
 {
         __u64 key, lastkey;
@@ -355,7 +370,9 @@ static const struct nilfs_bmap_operations nilfs_direct_ops = {
         .bop_assign             =       nilfs_direct_assign,
         .bop_mark               =       NULL,
 
+        .bop_seek_key           =       nilfs_direct_seek_key,
         .bop_last_key           =       nilfs_direct_last_key,
+
         .bop_check_insert       =       nilfs_direct_check_insert,
         .bop_check_delete       =       NULL,
         .bop_gather_data        =       nilfs_direct_gather_data,