[PATCH 01/11 RESEND] libe2p: Add new function get_fragment_score()

[Kazuya Mio <k-mio@sx.jp.nec.com>]

This patch adds get_fragment_score() to libe2p. get_fragment_score() returns
the fragmentation score. It shows the percentage of extents whose size is
smaller than the input argument "threshold".

However, there are some cases that cannot be merged into a next extent.
The following extents are excepted from the calculation of fragmentation score:
- The extent whose initialize status is different from the next extent
- There is a hole between the extent and its next extent
- The extent is a tail

Signed-off-by: Kazuya Mio <k-mio@sx.jp.nec.com>
---
 lib/e2p/Makefile.in      |    6 +
 lib/e2p/e2p.h            |    2 
 lib/e2p/fragment_score.c |  142 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 148 insertions(+), 2 deletions(-)
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..52a8e51 100644
--- a/lib/e2p/e2p.h
+++ b/lib/e2p/e2p.h
@@ -72,3 +72,5 @@ char *e2p_os2string(int os_type);
 int e2p_string2os(char *str);
 
 unsigned int e2p_percent(int percent, unsigned int base);
+
+int get_fragment_score(int fd, size_t threshold);
diff --git a/lib/e2p/fragment_score.c b/lib/e2p/fragment_score.c
new file mode 100644
index 0000000..3ad21b9
--- /dev/null
+++ b/lib/e2p/fragment_score.c
@@ -0,0 +1,142 @@
+/*
+ * fragment_score.c --- Get file fragmentation score on ext4 filesystem.
+ *
+ * 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%
+ */
+
+#define _LARGEFILE64_SOURCE
+
+#if HAVE_ERRNO_H
+#include <errno.h>
+#endif
+#include <unistd.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/vfs.h>
+
+#include <ext2fs/ext2_types.h>
+#include <ext2fs/fiemap.h>
+
+#include "e2p.h"
+
+#define	EXT3_IOC_GETFLAGS		_IOR('f', 1, long)
+
+#ifdef HAVE_FSTAT64
+#define FSTAT		fstat64
+#define STRUCT_STAT	struct stat64
+#else
+#define FSTAT		fstat
+#define STRUCT_STAT	struct stat
+#endif
+
+static int is_target_extent(struct fiemap_extent *cur_fm_ext,
+			     struct fiemap_extent *next_fm_ext)
+{
+	/* Check a hole between the extent */
+	if ((cur_fm_ext->fe_logical + cur_fm_ext->fe_length)
+		< next_fm_ext->fe_logical)
+		return 0;
+	/* Check a defference of unwritten flag */
+	if ((cur_fm_ext->fe_flags & FIEMAP_EXTENT_UNWRITTEN)
+		!= (next_fm_ext->fe_flags & FIEMAP_EXTENT_UNWRITTEN))
+		return 0;
+
+	/* target extent */
+	return 1;
+}
+
+int get_fragment_score(int fd, size_t threshold)
+{
+	unsigned int	flags = 0;
+	STRUCT_STAT	fileinfo;
+	struct statfs	fsinfo;
+	char buf[4096] = "";
+	struct fiemap *fiemap = (struct fiemap *)buf;
+	struct fiemap_extent *fm_ext = &fiemap->fm_extents[0];
+	struct fiemap_extent prev_fm_ext;
+	int count = (sizeof(buf) - sizeof(*fiemap)) /
+			sizeof(struct fiemap_extent);
+	int tot_extents = 0;
+	int frag_extents = 0;
+	unsigned int i;
+	int first = 1, last = 0;
+
+	if (FSTAT(fd, &fileinfo) < 0 ||
+	    fstatfs(fd, &fsinfo) < 0)
+		return -1;
+	if (ioctl(fd, EXT3_IOC_GETFLAGS, &flags) < 0)
+		flags = 0;
+
+	/*
+	 * Return an error if the target file is not the following cases.
+	 * - regular file
+	 * - extent format file on ext4 filesystem
+	 */
+	if (!S_ISREG(fileinfo.st_mode) ||
+	    fsinfo.f_type != EXT2_SUPER_MAGIC ||
+	    !(flags & EXT4_EXTENTS_FL)) {
+		errno = EOPNOTSUPP;
+		return -1;
+	}
+
+	memset(fiemap, 0, sizeof(struct fiemap));
+	fiemap->fm_start = 0;
+	fiemap->fm_length = ~0ULL;
+	fiemap->fm_extent_count = count;
+
+	do {
+		fiemap->fm_flags = 0;
+		if (ioctl(fd, FS_IOC_FIEMAP, (unsigned long) fiemap) < 0)
+			return -1;
+
+		/* If 0 extents are returned, then more ioctls are not needed */
+		if (fiemap->fm_mapped_extents == 0)
+			break;
+
+		if (first != 0)
+			first = 0;
+		else {
+			/* Check the last extent gotten by previous FIEMAP */
+			if (is_target_extent(&prev_fm_ext, &fm_ext[0])) {
+				tot_extents++;
+				if (prev_fm_ext.fe_length < threshold)
+					frag_extents++;
+			}
+		}
+
+		for (i = 0; i < fiemap->fm_mapped_extents; i++) {
+			if (fm_ext[i].fe_flags & FIEMAP_EXTENT_LAST) {
+				last = 1;
+				continue;
+			}
+
+			if (fiemap->fm_mapped_extents - 1 == i) {
+				memcpy(&prev_fm_ext, &fm_ext[i],
+					sizeof(struct fiemap_extent));
+				continue;
+			}
+
+			/* Check target extent */
+			if (!is_target_extent(&fm_ext[i], &fm_ext[i+1]))
+				continue;
+
+			tot_extents++;
+
+			if (fm_ext[i].fe_length < threshold)
+				frag_extents++;
+		}
+
+		fiemap->fm_start = (fm_ext[i-1].fe_logical +
+				    fm_ext[i-1].fe_length);
+	} while (last == 0);
+
+	return tot_extents == 0 ? 0 : (100 * frag_extents) / tot_extents;
+}