[PATCH 03/13] xfs_db: add crc manipulation commands

Eric Sandeen
2015-03-17T20:33:21Z

This adds a new "crc" command to xfs_db for CRC-enabled filesystems.

If a structure has a CRC field, we can validate it, invalidate/corrupt
it, or revalidate/rewrite it:

xfs_db> sb 0
xfs_db> crc -v
crc = 0x796c814f (correct)
xfs_db> crc -i
Metadata CRC error detected at block 0x0/0x200
crc = 0x796c8150 (bad)
xfs_db> crc -r
crc = 0x796c814f (correct)

(-i and -r require "expert" write-capable mode)

This requires temporarily replacing the write verifier with
a dummy which won't recalculate the CRC on the way to disk.

It also required me to write a new flist function, which is
totally foreign to me, so hopefully done right - but it seems
to work here.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---
db/Makefile | 2 +-
db/command.c | 2 +
db/crc.c | 188 +++++++++++++++++++++++++++++++++++++++++++++++++++++
db/crc.h | 22 ++++++
db/flist.c | 34 ++++++++++
db/flist.h | 1 +
db/io.c | 24 ++++++-
db/write.h | 2 +-
man/man8/xfs_db.8 | 27 ++++++--
9 files changed, 293 insertions(+), 9 deletions(-)
create mode 100644 db/crc.c
create mode 100644 db/crc.h

diff --git a/db/Makefile b/db/Makefile
index fb01bdd..500f94b 100644
--- a/db/Makefile
+++ b/db/Makefile
@@ -8,7 +8,7 @@ include $(TOPDIR)/include/builddefs
LTCOMMAND = xfs_db

HFILES = addr.h agf.h agfl.h agi.h attr.h attrshort.h bit.h block.h bmap.h \
- btblock.h bmroot.h check.h command.h convert.h debug.h \
+ btblock.h bmroot.h check.h command.h convert.h crc.h debug.h \
dir2.h dir2sf.h dquot.h echo.h faddr.h field.h \
flist.h fprint.h frag.h freesp.h hash.h help.h init.h inode.h input.h \
io.h malloc.h metadump.h output.h print.h quit.h sb.h sig.h strvec.h \
diff --git a/db/command.c b/db/command.c
index b7e3165..d44e0a5 100644
--- a/db/command.c
+++ b/db/command.c
@@ -48,6 +48,7 @@
#include "write.h"
#include "malloc.h"
#include "dquot.h"
+#include "crc.h"

cmdinfo_t *cmdtab;
int ncmds;
@@ -123,6 +124,7 @@ init_commands(void)
bmap_init();
check_init();
convert_init();
+ crc_init();
debug_init();
echo_init();
frag_init();
diff --git a/db/crc.c b/db/crc.c
new file mode 100644
index 0000000..b58a594
--- /dev/null
+++ b/db/crc.c
@@ -0,0 +1,188 @@
+/*
+ * Copyright (c) 2014 Red Hat, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include <xfs/libxfs.h>
+#include "addr.h"
+#include "command.h"
+#include "type.h"
+#include "faddr.h"
+#include "fprint.h"
+#include "field.h"
+#include "flist.h"
+#include "io.h"
+#include "init.h"
+#include "output.h"
+#include "bit.h"
+#include "print.h"
+
+static int crc_f(int argc, char **argv);
+static void crc_help(void);
+
+static const cmdinfo_t crc_cmd =
+ { "crc", NULL, crc_f, 0, 1, 0, "[-i|-r|-v]",
+ N_("manipulate crc values for V5 filesystem structures"), crc_help };
+
+void
+crc_init(void)
+{
+ if (xfs_sb_version_hascrc(&mp->m_sb))
+ add_command(&crc_cmd);
+}
+
+static void
+crc_help(void)
+{
+ dbprintf(_(
+"\n"
+" 'crc' validates, invalidates, or recalculates the crc value for\n"
+" the current on-disk metadata structures in Version 5 filesystems.\n"
+"\n"
+" Usage: \"crc [-i|-r|-v]\"\n"
+"\n"
+));
+
+}
+
+static int
+crc_f(
+ int argc,
+ char **argv)
+{
+ struct xfs_buf_ops nowrite_ops;
+ const struct xfs_buf_ops *stashed_ops = NULL;
+ extern char *progname;
+ const field_t *fields;
+ const ftattr_t *fa;
+ flist_t *fl;
+ int invalidate = 0;
+ int recalculate = 0;
+ int validate = 0;
+ int c;
+
+ if (cur_typ == NULL) {
+ dbprintf(_("no current type\n"));
+ return 0;
+ }
+
+ if (cur_typ->fields == NULL) {
+ dbprintf(_("current type (%s) is not a structure\n"),
+ cur_typ->name);
+ return 0;
+ }
+
+ if (argc) while ((c = getopt(argc, argv, "irv")) != EOF) {
+ switch (c) {
+ case 'i':
+ invalidate = 1;
+ break;
+ case 'r':
+ recalculate = 1;
+ break;
+ case 'v':
+ validate = 1;
+ break;
+ default:
+ dbprintf(_("bad option for crc command\n"));
+ return 0;
+ }
+ } else
+ validate = 1;
+
+ if (invalidate + recalculate + validate > 1) {
+ dbprintf(_("crc command accepts only one option\n"));
+ return 0;
+ }
+
+ if ((invalidate || recalculate) &&
+ ((x.isreadonly & LIBXFS_ISREADONLY) || !expert_mode)) {
+ dbprintf(_("%s not in expert mode, writing disabled\n"),
+ progname);
+ return 0;
+ }
+
+ fields = cur_typ->fields;
+
+ /* if we're a root field type, go down 1 layer to get field list */
+ if (fields->name[0] == '\0') {
+ fa = &ftattrtab[fields->ftyp];
+ ASSERT(fa->ftyp == fields->ftyp);
+ fields = fa->subfld;
+ }
+
+ /* Search for a CRC field */
+ fl = flist_find_ftyp(fields, FLDT_CRC);
+ if (!fl) {
+ dbprintf(_("No CRC field found for type %s\n"), cur_typ->name);
+ return 0;
+ }
+
+ /* run down the field list and set offsets into the data */
+ if (!flist_parse(fields, fl, iocur_top->data, 0)) {
+ flist_free(fl);
+ dbprintf(_("parsing error\n"));
+ return 0;
+ }
+
+ if (invalidate) {
+ flist_t *sfl;
+ int bit_length;
+ int parentoffset;
+ int crc;
+
+ sfl = fl;
+ parentoffset = 0;
+ while (sfl->child) {
+ parentoffset = sfl->offset;
+ sfl = sfl->child;
+ }
+ ASSERT(sfl->fld->ftyp == FLDT_CRC);
+
+ bit_length = fsize(sfl->fld, iocur_top->data, parentoffset, 0);
+ bit_length *= fcount(sfl->fld, iocur_top->data, parentoffset);
+ crc = getbitval(iocur_top->data, sfl->offset, bit_length, BVUNSIGNED);
+ /* Off by one.. */
+ crc = cpu_to_be32(crc + 1);
+ setbitval(iocur_top->data, sfl->offset, bit_length, &crc);
+
+ /* Temporarily remove write verifier to write a bad CRC */
+ stashed_ops = iocur_top->bp->b_ops;
+ nowrite_ops.verify_read = stashed_ops->verify_read;
+ nowrite_ops.verify_write = xfs_dummy_verify;
+ iocur_top->bp->b_ops = &nowrite_ops;
+ }
+
+ if (invalidate || recalculate) {
+ if (invalidate)
+ dbprintf(_("Invalidating CRC:\n"));
+ else
+ dbprintf(_("Recalculating CRC:\n"));
+
+ write_cur();
+ if (stashed_ops)
+ iocur_top->bp->b_ops = stashed_ops;
+ /* re-verify to get proper b_error state */
+ iocur_top->bp->b_ops->verify_read(iocur_top->bp);
+ } else
+ dbprintf(_("Verifying CRC:\n"));
+
+ /* And show us what we've got! */
+ flist_print(fl);
+ print_flist(fl);
+ flist_free(fl);
+ return 0;
+}
diff --git a/db/crc.h b/db/crc.h
new file mode 100644
index 0000000..9f44615
--- /dev/null
+++ b/db/crc.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) 2014 Red Hat, Inc.
+ * All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+struct field;
+
+extern void crc_init(void);
+extern void crc_struct(const field_t *fields, int argc, char **argv);
diff --git a/db/flist.c b/db/flist.c
index 33f7da7..fa19f70 100644
--- a/db/flist.c
+++ b/db/flist.c
@@ -411,6 +411,40 @@ flist_split(
return v;
}

+/*
+ * Given a set of fields, scan for a field of the given type.
+ * Return an flist leading to the first found field
+ * of that type.
+ * Return NULL if no field of the given type is found.
+ */
+flist_t *
+flist_find_ftyp(
+ const field_t *fields,
+ fldt_t type)
+{
+ flist_t *fl;
+ const field_t *f;
+ const ftattr_t *fa;
+
+ for (f = fields; f->name; f++) {
+ fl = flist_make(f->name);
+ fl->fld = f;
+ if (f->ftyp == type)
+ return fl;
+ fa = &ftattrtab[f->ftyp];
+ if (fa->subfld) {
+ flist_t *nfl;
+ nfl = flist_find_ftyp(fa->subfld, type);
+ if (nfl) {
+ fl->child = nfl;
+ return fl;
+ }
+ }
+ flist_free(fl);
+ }
+ return NULL;
+}
+
static void
ftok_free(
ftok_t *ft)
diff --git a/db/flist.h b/db/flist.h
index 5c9fba0..3f4b312 100644
--- a/db/flist.h
+++ b/db/flist.h
@@ -37,3 +37,4 @@ extern int flist_parse(const struct field *fields, flist_t *fl, void *obj,
int startoff);
extern void flist_print(flist_t *fl);
extern flist_t *flist_scan(char *name);
+extern flist_t *flist_find_ftyp(const field_t *fields, fldt_t type);
diff --git a/db/io.c b/db/io.c
index 91858e2..732b320 100644
--- a/db/io.c
+++ b/db/io.c
@@ -27,6 +27,7 @@
#include "output.h"
#include "init.h"
#include "malloc.h"
+#include "crc.h"

static int pop_f(int argc, char **argv);
static void pop_help(void);
@@ -466,22 +467,41 @@ xfs_dummy_verify(
void
write_cur(void)
{
+ int skip_crc = 0;
+
+ if (iocur_top->bp->b_ops &&
+ iocur_top->bp->b_ops->verify_write == xfs_dummy_verify)
+ skip_crc = 1;
+
if (iocur_sp < 0) {
dbprintf(_("nothing to write\n"));
return;
}

- if (iocur_top->ino_buf) {
+ if (iocur_top->ino_buf && !skip_crc) {
libxfs_dinode_calc_crc(mp, iocur_top->data);
iocur_top->ino_crc_ok = 1;
}
- if (iocur_top->dquot_buf)
+
+ if (iocur_top->dquot_buf && !skip_crc)
xfs_update_cksum(iocur_top->data, sizeof(struct xfs_dqblk),
XFS_DQUOT_CRC_OFF);
if (iocur_top->bbmap)
write_cur_bbs();
else
write_cur_buf();
+
+ /* If we didn't write the crc automatically, re-check validity */
+ if (iocur_top->ino_buf && skip_crc) {
+ xfs_dinode_t *dip;
+ xfs_ino_t ino;
+
+ dip = iocur_top->data;
+ ino = iocur_top->ino;
+ iocur_top->ino_crc_ok = xfs_verify_cksum((char *)dip,
+ mp->m_sb.sb_inodesize,
+ XFS_DINODE_CRC_OFF);
+ }
}

void
diff --git a/db/write.h b/db/write.h
index 31e2665..664ddcc 100644
--- a/db/write.h
+++ b/db/write.h
@@ -20,5 +20,5 @@ struct field;

extern void write_init(void);
extern void write_block(const field_t *fields, int argc, char **argv);
-extern void write_string(const field_t *fields, int argc, char **argv);
extern void write_struct(const field_t *fields, int argc, char **argv);
+extern void write_string(const field_t *fields, int argc, char **argv);
diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
index d527230..46a1f39 100644
--- a/man/man8/xfs_db.8
+++ b/man/man8/xfs_db.8
@@ -87,16 +87,14 @@ or
.I filename
read-only. This option is required if the filesystem is mounted.
It is only necessary to omit this flag if a command that changes data
-.RB ( write ", " blocktrash )
+.RB ( write ", " blocktrash ", " crc )
is to be used.
.TP
.B \-x
Specifies expert mode.
This enables the
-.B write
-and
-.B blocktrash
-commands.
+.RB ( write ", " blocktrash ", " crc
+invalidate/revalidate) commands.
.TP
.B \-V
Prints the version number and exits.
@@ -409,6 +407,25 @@ conversions such as
.I agb
.BR fsblock .
.TP
+.B crc [\-i|\-r|\-v]
+Invalidates, revalidates, or validates the CRC (checksum)
+field of the current structure, if it has one.
+This command is available only on CRC-enabled filesystems.
+With no argument, validation is performed.
+Each command will display the resulting CRC value and state.
+.RS 1.0i
+.TP 0.4i
+.B \-i
+Invalidate the structure's CRC value (incrementing it by one),
+and write it to disk.
+.TP
+.B \-r
+Recalculate the current structure's correct CRC value, and write it to disk.
+.TP
+.B \-v
+Validate and display the current value and state of the structure's CRC.
+.RE
+.TP
.BI "daddr [" d ]
Set current address to the daddr (512 byte block) given by
.IR d .
--
1.7.1