Ocfs2: Add a new code 'OCFS2_INFO_FREEFRAG' for o2info ioctl.

This new code is a bit more complicated than former ones, the goal is to
show user all statistics required to take a deep insight into filesystem
on how the disk is being fragmentaed.

The goal is achieved by scaning global bitmap from (cluster)group to group
to figure out following factors in the filesystem:

        - How many free chunks in a fixed size as user requested.
        - How many real free chunks in all size.
        - Min/Max/Avg size(in) clusters of free chunks.
        - How do free chunks distribute(in size) in terms of a histogram,
          just like following:
          ---------------------------------------------------------
          Extent Size Range :  Free extents  Free Clusters  Percent
             32K...   64K-  :             1             1    0.00%
              1M...    2M-  :             9           288    0.03%
              8M...   16M-  :             2           831    0.09%
             32M...   64M-  :             1          2047    0.23%
            128M...  256M-  :             1          8191    0.92%
            256M...  512M-  :             2         21706    2.43%
            512M... 1024M-  :            27        858623   96.29%
          ---------------------------------------------------------

Userspace ioctl() call eventually gets the above info returned by passing
a 'struct ocfs2_info_freefrag' with the chunk_size being specified first.

Signed-off-by: Tristan Ye <tristan.ye@oracle.com>

1 files changed, 23 insertions, 0 deletions

diff --git a/fs/ocfs2/ocfs2_ioctl.h b/fs/ocfs2/ocfs2_ioctl.h
index 6b4b39a83662..18b6770dc468 100644
--- a/fs/ocfs2/ocfs2_ioctl.h
+++ b/fs/ocfs2/ocfs2_ioctl.h
@@ -152,6 +152,28 @@ struct ocfs2_info_freeinode {
 	__u32 ifi_pad;
 };
 
+#define OCFS2_INFO_MAX_HIST     (32)
+
+struct ocfs2_info_freefrag {
+	struct ocfs2_info_request iff_req;
+	struct ocfs2_info_freefrag_stats { /* (out) */
+		struct ocfs2_info_free_chunk_list {
+			__u32 fc_chunks[OCFS2_INFO_MAX_HIST];
+			__u32 fc_clusters[OCFS2_INFO_MAX_HIST];
+		} ffs_fc_hist;
+		__u32 ffs_clusters;
+		__u32 ffs_free_clusters;
+		__u32 ffs_free_chunks;
+		__u32 ffs_free_chunks_real;
+		__u32 ffs_min; /* Minimum free chunksize in clusters */
+		__u32 ffs_max;
+		__u32 ffs_avg;
+		__u32 ffs_pad;
+	} iff_ffs;
+	__u32 iff_chunksize; /* chunksize in clusters(in) */
+	__u32 iff_pad;
+};
+
 /* Codes for ocfs2_info_request */
 enum ocfs2_info_type {
 	OCFS2_INFO_CLUSTERSIZE = 1,
@@ -162,6 +184,7 @@ enum ocfs2_info_type {
 	OCFS2_INFO_FS_FEATURES,
 	OCFS2_INFO_JOURNAL_SIZE,
 	OCFS2_INFO_FREEINODE,
+	OCFS2_INFO_FREEFRAG,
 	OCFS2_INFO_NUM_TYPES
 };