Add a new flag to dumpfs(8), -f, which causes dumpfs to list all free

fragments in the file system by fragment (block) number.  This new
mode does the necessary arithmetic to generate absolute fragment
numbers rather than than the cg-relative numbers printed in the default
mode.

If -f is passed once, contiguous fragment ranges are collapsed into
an X-Y format as free block lists are currently printed in regular
dumpfs output, but if specified twice, all block numbers are printed
individually, allowing both compact and more script-friendly
representation.

This proves quite handy when attempting to recover deleted data, as it
allows exclusion of non-deleted data from blocks searched.
MFC after:	1 week
Discussed with:	jeff, Richard Clayton <richard dot clayton at cl.cam.ac.uk>
Sponsored by:	Google, Inc.

2 files changed, 82 insertions, 7 deletions

diff --git a/sbin/dumpfs/dumpfs.8 b/sbin/dumpfs/dumpfs.8
index 8879f78..53e7f62 100644
--- a/sbin/dumpfs/dumpfs.8
+++ b/sbin/dumpfs/dumpfs.8
@@ -36,15 +36,18 @@
 .Nd dump file system information
 .Sh SYNOPSIS
 .Nm
+.Op Fl f
 .Op Fl m
 .Ar filesys | device
 .Sh DESCRIPTION
 The
 .Nm
 utility prints out the super block and cylinder group information
-for the file system or special device specified, unless
+for the file system or special device specified, unless the
+.Fl f
+or
 .Fl m
-is specified.
+flag is specified.
 The listing is very long and detailed.
 This
 command is useful mostly for finding out certain file system
@@ -52,6 +55,15 @@ information such as the file system block size and minimum
 free space percentage.
 .Pp
 If
+.Fl f
+is specified, a sorted list of all free fragments and free fragment ranges,
+as represented in cylinder group block free lists, is printed.
+If the flag is specified twice, contiguous free fragments are not collapsed
+into ranges and instead printed in a simple list.
+Fragment numbers may be converted to raw byte offsets by multiplying by the
+fragment size, which may be useful when recovering deleted data.
+.Pp
+If
 .Fl m
 is specified, a
 .Xr newfs 8
diff --git a/sbin/dumpfs/dumpfs.c b/sbin/dumpfs/dumpfs.c
index e0b809e..14f6ea2 100644
--- a/sbin/dumpfs/dumpfs.c
+++ b/sbin/dumpfs/dumpfs.c
@@ -1,4 +1,10 @@
 /*
+ * Copyright (c) 2009 Robert N. M. Watson
+ * All rights reserved.
+ *
+ * This software was developed at the University of Cambridge Computer
+ * Laboratory with support from a grant from Google, Inc.
+ *
  * Copyright (c) 2002 Networks Associates Technology, Inc.
  * All rights reserved.
  *
@@ -74,8 +80,11 @@ struct uufsd disk;
 
 int	dumpfs(const char *);
 int	dumpcg(void);
+int	dumpfreespace(const char *, int);
+void	dumpfreespacecg(int);
 int	marshal(const char *);
 void	pbits(void *, int);
+void	pblklist(void *, int, off_t, int);
 void	ufserr(const char *);
 void	usage(void) __dead2;
 
@@ -83,12 +92,15 @@ int
 main(int argc, char *argv[])
 {
 	const char *name;
-	int ch, domarshal, eval;
+	int ch, dofreespace, domarshal, eval;
 
-	domarshal = eval = 0;
+	dofreespace = domarshal = eval = 0;
 
-	while ((ch = getopt(argc, argv, "m")) != -1) {
+	while ((ch = getopt(argc, argv, "fm")) != -1) {
 		switch (ch) {
+		case 'f':
+			dofreespace++;
+			break;
 		case 'm':
 			domarshal = 1;
 			break;
@@ -102,6 +114,10 @@ main(int argc, char *argv[])
 
 	if (argc < 1)
 		usage();
+	if (dofreespace && domarshal)
+		usage();
+	if (dofreespace > 2)
+		usage();
 
 	while ((name = *argv++) != NULL) {
 		if (ufs_disk_fillout(&disk, name) == -1) {
@@ -109,7 +125,9 @@ main(int argc, char *argv[])
 			eval |= 1;
 			continue;
 		}
-		if (domarshal)
+		if (dofreespace)
+			eval |= dumpfreespace(name, dofreespace);
+		else if (domarshal)
 			eval |= marshal(name);
 		else
 			eval |= dumpfs(name);
@@ -333,6 +351,30 @@ dumpcg(void)
 }
 
 int
+dumpfreespace(const char *name, int fflag)
+{
+	int i;
+
+	while ((i = cgread(&disk)) != 0) {
+		if (i == -1)
+			goto err;
+		dumpfreespacecg(fflag);
+	}
+	return (0);
+err:
+	ufserr(name);
+	return (1);
+}
+
+void
+dumpfreespacecg(int fflag)
+{
+
+	pblklist(cg_blksfree(&acg), afs.fs_fpg, disk.d_lcg * afs.fs_fpg,
+	    fflag);
+}
+
+int
 marshal(const char *name)
 {
 	struct fs *fs;
@@ -401,6 +443,27 @@ pbits(void *vp, int max)
 }
 
 void
+pblklist(void *vp, int max, off_t offset, int fflag)
+{
+	int i, j;
+	char *p;
+
+	for (i = 0, p = vp; i < max; i++) {
+		if (isset(p, i)) {
+			printf("%jd", (intmax_t)(i + offset));
+			if (fflag < 2) {
+				j = i;
+				while ((i+1)<max && isset(p, i+1))
+					i++;
+				if (i != j)
+					printf("-%lld", i + offset);
+			}
+			printf("\n");
+		}
+	}
+}
+
+void
 ufserr(const char *name)
 {
 	if (disk.d_error != NULL)
@@ -412,6 +475,6 @@ ufserr(const char *name)
 void
 usage(void)
 {
-	(void)fprintf(stderr, "usage: dumpfs [-m] filesys | device\n");
+	(void)fprintf(stderr, "usage: dumpfs [-fm] filesys | device\n");
 	exit(1);
 }