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Date: Sat, 20 Dec 2014 13:19:09 -0800
From: "Darrick J. Wong" <darrick.wong@...cle.com>
To: tytso@....edu, darrick.wong@...cle.com
Cc: linux-ext4@...r.kernel.org
Subject: [PATCH 21/31] debugfs: optionally create undo file
Provide the user with an option to create an undo file so that they
can roll back a failed debugfs expedition.
Signed-off-by: Darrick J. Wong <darrick.wong@...cle.com>
---
debugfs/debugfs.8.in | 16 +++++++
debugfs/debugfs.c | 108 +++++++++++++++++++++++++++++++++++++++++++++++---
2 files changed, 116 insertions(+), 8 deletions(-)
diff --git a/debugfs/debugfs.8.in b/debugfs/debugfs.8.in
index 04c280d..81899a3 100644
--- a/debugfs/debugfs.8.in
+++ b/debugfs/debugfs.8.in
@@ -31,6 +31,10 @@ request
data_source_device
]
[
+.B \-z
+.I undo_file
+]
+[
device
]
.SH DESCRIPTION
@@ -130,6 +134,16 @@ and then exit.
print the version number of
.B debugfs
and exit.
+.TP
+.BI \-z " undo_file"
+Before overwriting a file system block, write the old contents of the block to
+an undo file. This undo file can be used with e2undo(8) to restore the old
+contents of the file system should something go wrong. If the empty string is
+passed as the undo_file argument, the undo file will be written to a file named
+resize2fs-\fIdevice\fR.e2undo in the directory specified via the
+\fIE2FSPROGS_UNDO_DIR\fR environment variable.
+
+WARNING: The undo file cannot be used to recover from a power or system crash.
.SH SPECIFYING FILES
Many
.B debugfs
@@ -532,7 +546,7 @@ to those inodes. The
flag will enable checking the file type information in the directory
entry to make sure it matches the inode's type.
.TP
-.BI open " [-weficD] [-b blocksize] [-s superblock] device"
+.BI open " [-weficD] [-b blocksize] [-s superblock] [-z undo_file] device"
Open a filesystem for editing. The
.I -f
flag forces the filesystem to be opened even if there are some unknown
diff --git a/debugfs/debugfs.c b/debugfs/debugfs.c
index fe57366..7576a1a 100644
--- a/debugfs/debugfs.c
+++ b/debugfs/debugfs.c
@@ -48,12 +48,92 @@ ext2_filsys current_fs;
quota_ctx_t current_qctx;
ext2_ino_t root, cwd;
+static int debugfs_setup_tdb(const char *device_name, char *undo_file,
+ io_manager *io_ptr)
+{
+ errcode_t retval = ENOMEM;
+ char *tdb_dir = NULL, *tdb_file = NULL;
+ char *dev_name, *tmp_name;
+ int free_tdb_dir = 0;
+
+ if (undo_file && undo_file[0] != 0) {
+ if ((unlink(undo_file) < 0) && (errno != ENOENT)) {
+ retval = errno;
+ goto err;
+ }
+
+ set_undo_io_backing_manager(*io_ptr);
+ *io_ptr = undo_io_manager;
+ retval = set_undo_io_backup_file(undo_file);
+ if (retval)
+ goto err;
+ printf("Overwriting existing filesystem; this can be undone "
+ "using the command:\n"
+ " e2undo %s %s\n\n",
+ undo_file, device_name);
+ return 0;
+ }
+
+ /*
+ * Configuration via a conf file would be
+ * nice
+ */
+ tdb_dir = getenv("E2FSPROGS_UNDO_DIR");
+
+ if (tdb_dir == NULL || !strcmp(tdb_dir, "none") || (tdb_dir[0] == 0) ||
+ access(tdb_dir, W_OK)) {
+ if (free_tdb_dir)
+ free(tdb_dir);
+ return 0;
+ }
+
+ tmp_name = strdup(device_name);
+ if (!tmp_name)
+ goto errout;
+ dev_name = basename(tmp_name);
+ tdb_file = malloc(strlen(tdb_dir) + 8 + strlen(dev_name) + 7 + 1);
+ if (!tdb_file) {
+ free(tmp_name);
+ goto errout;
+ }
+ sprintf(tdb_file, "%s/debugfs-%s.e2undo", tdb_dir, dev_name);
+ free(tmp_name);
+
+ if ((unlink(tdb_file) < 0) && (errno != ENOENT)) {
+ retval = errno;
+ goto errout;
+ }
+
+ set_undo_io_backing_manager(*io_ptr);
+ *io_ptr = undo_io_manager;
+ retval = set_undo_io_backup_file(tdb_file);
+ if (retval)
+ goto errout;
+ printf("Overwriting existing filesystem; this can be undone "
+ "using the command:\n"
+ " e2undo %s %s\n\n", tdb_file, device_name);
+
+ if (free_tdb_dir)
+ free(tdb_dir);
+ free(tdb_file);
+ return 0;
+
+errout:
+ if (free_tdb_dir)
+ free(tdb_dir);
+ free(tdb_file);
+err:
+ com_err("debugfs", retval, "while trying to setup undo file\n");
+ return retval;
+}
+
static void open_filesystem(char *device, int open_flags, blk64_t superblock,
blk64_t blocksize, int catastrophic,
- char *data_filename)
+ char *data_filename, char *undo_file)
{
int retval;
io_channel data_io = 0;
+ io_manager io_ptr = unix_io_manager;
if (superblock != 0 && blocksize == 0) {
com_err(device, 0, "if you specify the superblock, you must also specify the block size");
@@ -84,8 +164,14 @@ static void open_filesystem(char *device, int open_flags, blk64_t superblock,
if (catastrophic)
open_flags |= EXT2_FLAG_SKIP_MMP;
+ if (undo_file) {
+ retval = debugfs_setup_tdb(device, undo_file, &io_ptr);
+ if (retval)
+ exit(1);
+ }
+
retval = ext2fs_open(device, open_flags, superblock, blocksize,
- unix_io_manager, ¤t_fs);
+ io_ptr, ¤t_fs);
if (retval) {
com_err(device, retval, "while opening filesystem");
if (retval == EXT2_ET_BAD_MAGIC)
@@ -136,9 +222,10 @@ void do_open_filesys(int argc, char **argv)
blk64_t blocksize = 0;
int open_flags = EXT2_FLAG_SOFTSUPP_FEATURES | EXT2_FLAG_64BITS;
char *data_filename = 0;
+ char *undo_file = NULL;
reset_getopt();
- while ((c = getopt (argc, argv, "iwfecb:s:d:D")) != EOF) {
+ while ((c = getopt (argc, argv, "iwfecb:s:d:Dz:")) != EOF) {
switch (c) {
case 'i':
open_flags |= EXT2_FLAG_IMAGE_FILE;
@@ -177,6 +264,9 @@ void do_open_filesys(int argc, char **argv)
if (err)
return;
break;
+ case 'z':
+ undo_file = optarg;
+ break;
default:
goto print_usage;
}
@@ -188,7 +278,7 @@ void do_open_filesys(int argc, char **argv)
return;
open_filesystem(argv[optind], open_flags,
superblock, blocksize, catastrophic,
- data_filename);
+ data_filename, undo_file);
return;
print_usage:
@@ -2219,7 +2309,7 @@ int main(int argc, char **argv)
"Usage: %s [-b blocksize] [-s superblock] [-f cmd_file] "
"[-R request] [-V] ["
#ifndef READ_ONLY
- "[-w] "
+ "[-w] [-z undo_file] "
#endif
"[-c] device]";
int c;
@@ -2234,7 +2324,8 @@ int main(int argc, char **argv)
#ifdef READ_ONLY
const char *opt_string = "nicR:f:b:s:Vd:D";
#else
- const char *opt_string = "niwcR:f:b:s:Vd:D";
+ const char *opt_string = "niwcR:f:b:s:Vd:Dz:";
+ char *undo_file = NULL;
#endif
if (debug_prog_name == 0)
@@ -2291,6 +2382,9 @@ int main(int argc, char **argv)
fprintf(stderr, "\tUsing %s\n",
error_message(EXT2_ET_BASE));
exit(0);
+ case 'z':
+ undo_file = optarg;
+ break;
default:
com_err(argv[0], 0, usage, debug_prog_name);
return 1;
@@ -2299,7 +2393,7 @@ int main(int argc, char **argv)
if (optind < argc)
open_filesystem(argv[optind], open_flags,
superblock, blocksize, catastrophic,
- data_filename);
+ data_filename, undo_file);
sci_idx = ss_create_invocation(debug_prog_name, "0.0", (char *) NULL,
&debug_cmds, &retval);
--
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