nilfs2: add helper to find existent block on metadata file
Add a new metadata file function, nilfs_mdt_find_block(), which finds
an existent block on a metadata file in a given range of blocks. This
function skips continuous hole blocks efficiently by using
nilfs_bmap_seek_key().
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/nilfs2/mdt.c b/fs/nilfs2/mdt.c
index 892cf5f..dee34d9 100644
--- a/fs/nilfs2/mdt.c
+++ b/fs/nilfs2/mdt.c
@@ -261,6 +261,60 @@
}
/**
+ * nilfs_mdt_find_block - find and get a buffer on meta data file.
+ * @inode: inode of the meta data file
+ * @start: start block offset (inclusive)
+ * @end: end block offset (inclusive)
+ * @blkoff: block offset
+ * @out_bh: place to store a pointer to buffer_head struct
+ *
+ * nilfs_mdt_find_block() looks up an existing block in range of
+ * [@start, @end] and stores pointer to a buffer head of the block to
+ * @out_bh, and block offset to @blkoff, respectively. @out_bh and
+ * @blkoff are substituted only when zero is returned.
+ *
+ * Return Value: On success, it returns 0. On error, the following negative
+ * error code is returned.
+ *
+ * %-ENOMEM - Insufficient memory available.
+ *
+ * %-EIO - I/O error
+ *
+ * %-ENOENT - no block was found in the range
+ */
+int nilfs_mdt_find_block(struct inode *inode, unsigned long start,
+ unsigned long end, unsigned long *blkoff,
+ struct buffer_head **out_bh)
+{
+ __u64 next;
+ int ret;
+
+ if (unlikely(start > end))
+ return -ENOENT;
+
+ ret = nilfs_mdt_read_block(inode, start, true, out_bh);
+ if (!ret) {
+ *blkoff = start;
+ goto out;
+ }
+ if (unlikely(ret != -ENOENT || start == ULONG_MAX))
+ goto out;
+
+ ret = nilfs_bmap_seek_key(NILFS_I(inode)->i_bmap, start + 1, &next);
+ if (!ret) {
+ if (next <= end) {
+ ret = nilfs_mdt_read_block(inode, next, true, out_bh);
+ if (!ret)
+ *blkoff = next;
+ } else {
+ ret = -ENOENT;
+ }
+ }
+out:
+ return ret;
+}
+
+/**
* nilfs_mdt_delete_block - make a hole on the meta data file.
* @inode: inode of the meta data file
* @block: block offset