[v2,01/12] libe2p: Add new function e2p_get_fragscore()

diff --git a/lib/e2p/Makefile.in b/lib/e2p/Makefile.in
index 9775a98..c62a81d 100644
--- a/lib/e2p/Makefile.in
+++ b/lib/e2p/Makefile.in
@@ -19,7 +19,7 @@  all::	e2p.pc
 OBJS=		feature.o fgetflags.o fsetflags.o fgetversion.o fsetversion.o \
 		getflags.o getversion.o hashstr.o iod.o ls.o mntopts.o \
 		parse_num.o pe.o pf.o ps.o setflags.o setversion.o uuid.o \
-		ostype.o percent.o
+		ostype.o percent.o fragment_score.o
 
 SRCS=		$(srcdir)/feature.c $(srcdir)/fgetflags.c \
 		$(srcdir)/fsetflags.c $(srcdir)/fgetversion.c \
@@ -28,7 +28,7 @@  SRCS=		$(srcdir)/feature.c $(srcdir)/fgetflags.c \
 		$(srcdir)/ls.c $(srcdir)/mntopts.c $(srcdir)/parse_num.c \
 		$(srcdir)/pe.c $(srcdir)/pf.c $(srcdir)/ps.c \
 		$(srcdir)/setflags.c $(srcdir)/setversion.c $(srcdir)/uuid.c \
-		$(srcdir)/ostype.c $(srcdir)/percent.c
+		$(srcdir)/ostype.c $(srcdir)/percent.c $(srcdir)/fragment_score.c
 HFILES= e2p.h
 
 LIBRARY= libe2p
@@ -162,3 +162,5 @@  ostype.o: $(srcdir)/ostype.c $(srcdir)/e2p.h \
  $(top_srcdir)/lib/ext2fs/ext2_fs.h $(top_builddir)/lib/ext2fs/ext2_types.h
 percent.o: $(srcdir)/percent.c $(srcdir)/e2p.h \
  $(top_srcdir)/lib/ext2fs/ext2_fs.h $(top_builddir)/lib/ext2fs/ext2_types.h
+fragment_score.o: $(srcdir)/fragment_score.c $(srcdir)/e2p.h \
+ $(top_srcdir)/lib/ext2fs/ext2_fs.h $(top_builddir)/lib/ext2fs/ext2_types.h
diff --git a/lib/e2p/e2p.h b/lib/e2p/e2p.h
index 4a68dd9..5881256 100644
--- a/lib/e2p/e2p.h
+++ b/lib/e2p/e2p.h
@@ -72,3 +72,6 @@  char *e2p_os2string(int os_type);
 int e2p_string2os(char *str);
 
 unsigned int e2p_percent(int percent, unsigned int base);
+
+unsigned int e2p_get_fragscore(int fd, unsigned int threshold,
+			unsigned int max_chunk_blks, int *errp);
diff --git a/lib/e2p/fragment_score.c b/lib/e2p/fragment_score.c
new file mode 100644
index 0000000..03778c7
--- /dev/null
+++ b/lib/e2p/fragment_score.c
@@ -0,0 +1,132 @@ 
+/*
+ * fragment_score.c --- Get file fragmentation score.
+ *
+ * Copyright (C) 2011	Kazuya Mio <k-mio@sx.jp.nec.com>
+ *			NEC Software Tohoku, Ltd.
+ *
+ * %Begin-Header%
+ * This file may be redistributed under the terms of the GNU Library
+ * General Public License, version 2.
+ * %End-Header%
+ */
+
+#if HAVE_ERRNO_H
+#include <errno.h>
+#endif
+#include <string.h>
+#include <sys/ioctl.h>
+#include <ext2fs/ext2_types.h>
+#include <ext2fs/fiemap.h>
+#include "e2p.h"
+
+#define FIGETBSZ	_IO(0x00, 2)
+
+#define bad_contiguous_exts(max, cnt, len) \
+	((!max && cnt > 1) || len <= (__u64)max * (cnt - 1))
+
+static int is_extent_continued(struct fiemap_extent *prev_fm_ext,
+			     struct fiemap_extent *cur_fm_ext)
+{
+	/* Check a hole between the extent */
+	if ((prev_fm_ext->fe_logical + prev_fm_ext->fe_length)
+		< cur_fm_ext->fe_logical)
+		return 0;
+
+	/* Check a defference of unwritten flag */
+	if ((prev_fm_ext->fe_flags & FIEMAP_EXTENT_UNWRITTEN)
+		!= (cur_fm_ext->fe_flags & FIEMAP_EXTENT_UNWRITTEN))
+		return 0;
+
+	/* Two extents are continued */
+	return 1;
+}
+
+/*
+ * This function returns the fragmentation score that shows how badly fragmented
+ * the file might be. The score is extents per @threshold, so the higher score
+ * means the worse fragmentation.
+ *
+ * Fragmentation score treats extents, whose file offset continues and
+ * whose status is the same, as one chunk. If the number of extents
+ * in chunk is equal to the ideal number of extents, the chunk is not used for
+ * the fragmentation score because there is no fragment in the chunk.
+ * The ideal number of extents is calculated based on @max_chunk_blks.
+ */
+unsigned int  e2p_get_fragscore(int fd, unsigned int threshold,
+					unsigned int max_chunk_blks, int *errp)
+{
+	char buf[4096] = "";
+	struct fiemap *fiemap = (struct fiemap *)buf;
+	struct fiemap_extent *fm_ext = &fiemap->fm_extents[0];
+	struct fiemap_extent prev_fm_ext;
+	unsigned int count = (sizeof(buf) - sizeof(*fiemap)) /
+				sizeof(struct fiemap_extent);
+	unsigned int total_cnt = 0, total_len = 0;
+	unsigned int ext_cnt = 0, ext_len = 0;
+	unsigned int i;
+	int bs, last = 0;
+
+	if (!threshold) {
+		*errp = EINVAL;
+		return 0;
+	}
+
+	/* Get the block size */
+	if (ioctl(fd, FIGETBSZ, &bs) < 0) {
+		*errp = errno;
+		return 0;
+	}
+
+	memset(fiemap, 0, sizeof(struct fiemap));
+	fiemap->fm_length = ~0ULL;
+	fiemap->fm_extent_count = count;
+
+	do {
+		if (ioctl(fd, FS_IOC_FIEMAP, (unsigned long) fiemap) < 0) {
+			*errp = errno;
+			return 0;
+		}
+
+		/* If 0 extents are returned, then more ioctls are not needed */
+		if (fiemap->fm_mapped_extents == 0)
+			break;
+
+		for (i = 0; i < fiemap->fm_mapped_extents; i++) {
+			if (ext_cnt && !is_extent_continued(&prev_fm_ext,
+								&fm_ext[i])) {
+				if (bad_contiguous_exts(max_chunk_blks,
+							ext_cnt, ext_len)) {
+					total_cnt += ext_cnt;
+					total_len += ext_len;
+				}
+				ext_cnt = 0;
+				ext_len = 0;
+			}
+			ext_cnt++;
+			ext_len += fm_ext[i].fe_length / bs;
+
+			memcpy(&prev_fm_ext, &fm_ext[i],
+					sizeof(struct fiemap_extent));
+
+			if (fm_ext[i].fe_flags & FIEMAP_EXTENT_LAST)
+				last = 1;
+		}
+
+		fiemap->fm_start = (fm_ext[i-1].fe_logical +
+				    fm_ext[i-1].fe_length);
+	} while (last == 0);
+
+	/* Check the tail contiguous extent */
+	if (ext_cnt) {
+		if (bad_contiguous_exts(max_chunk_blks, ext_cnt, ext_len)) {
+			total_cnt += ext_cnt;
+			total_len += ext_len;
+		}
+	}
+
+	/* Return 0 if there is no valid contiguous extent */
+	if (!total_len)
+		return 0;
+
+	return (unsigned int)(total_cnt / ((double)total_len / threshold));
+}