[PATCH 01/13 V2] xfs_db: Allow writes of corrupted data by optionally skipping write verifiers

Eric Sandeen
2015-03-23T20:00:15Z

Being able to write corrupt data is handy if we wish to test
repair against specific types of corruptions.

Add a "-c" option to the write command which allows this by removing
the write verifier.

Note that this also skips CRC updates; it's not currently possible
to write invalid data with a valid CRC; CRC recalculation is
intertwined with validation.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
---

V2: Fix whitespace, remove "if (argc)", and test for
iocur_top->bp->b_ops before attempting to deref it.

diff --git a/db/io.c b/db/io.c
index 7f1b76a..c5898f1 100644
--- a/db/io.c
+++ b/db/io.c
@@ -457,6 +457,13 @@ write_cur_bbs(void)
}

void
+xfs_dummy_verify(
+ struct xfs_buf *bp)
+{
+ return;
+}
+
+void
write_cur(void)
{
if (iocur_sp < 0) {
diff --git a/db/io.h b/db/io.h
index 71082e6..31d96b4 100644
--- a/db/io.h
+++ b/db/io.h
@@ -63,6 +63,7 @@ extern void set_cur(const struct typ *t, __int64_t d, int c, int ring_add,
bbmap_t *bbmap);
extern void ring_add(void);
extern void set_iocur_type(const struct typ *t);
+extern void xfs_dummy_verify(struct xfs_buf *bp);

/*
* returns -1 for unchecked, 0 for bad and 1 for good
diff --git a/db/write.c b/db/write.c
index a0f14f4..655b618 100644
--- a/db/write.c
+++ b/db/write.c
@@ -38,7 +38,7 @@ static int write_f(int argc, char **argv);
static void write_help(void);

static const cmdinfo_t write_cmd =
- { "write", NULL, write_f, 0, -1, 0, N_("[field or value]..."),
+ { "write", NULL, write_f, 0, -1, 0, N_("[-c] [field or value]..."),
N_("write value to disk"), write_help };

void
@@ -79,6 +79,7 @@ write_help(void)
" String mode: 'write \"This_is_a_filename\" - write null terminated string.\n"
"\n"
" In data mode type 'write' by itself for a list of specific commands.\n\n"
+" Specifying the -c option will allow writes of invalid (corrupt) data.\n\n"
));

}
@@ -90,6 +91,10 @@ write_f(
{
pfunc_t pf;
extern char *progname;
+ int c;
+ int corrupt = 0; /* Allow write of corrupt data; skip verification */
+ struct xfs_buf_ops nowrite_ops;
+ const struct xfs_buf_ops *stashed_ops = NULL;

if (x.isreadonly & LIBXFS_ISREADONLY) {
dbprintf(_("%s started in read only mode, writing disabled\n"),
@@ -109,12 +114,34 @@ write_f(
return 0;
}

- /* move past the "write" command */
- argc--;
- argv++;
+ while ((c = getopt(argc, argv, "c")) != EOF) {
+ switch (c) {
+ case 'c':
+ corrupt = 1;
+ break;
+ default:
+ dbprintf(_("bad option for write command\n"));
+ return 0;
+ }
+ }
+
+ argc -= optind;
+ argv += optind;
+
+ if (iocur_top->bp->b_ops && corrupt) {
+ /* Temporarily remove write verifier to write bad data */
+ 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;
+ dbprintf(_("Allowing write of corrupted data\n"));
+ }

(*pf)(DB_WRITE, cur_typ->fields, argc, argv);

+ if (stashed_ops)
+ iocur_top->bp->b_ops = stashed_ops;
+
return 0;
}

diff --git a/man/man8/xfs_db.8 b/man/man8/xfs_db.8
index 4d8d4ff..d527230 100644
--- a/man/man8/xfs_db.8
+++ b/man/man8/xfs_db.8
@@ -711,7 +711,7 @@ and
bits respectively, and their string equivalent reported
(but no modifications are made).
.TP
-.BI "write [" "field value" "] ..."
+.BI "write [\-c] [" "field value" "] ..."
Write a value to disk.
Specific fields can be set in structures (struct mode),
or a block can be set to data values (data mode),
@@ -729,6 +729,12 @@ contents of the block can be shifted or rotated left or right, or filled
with a sequence, a constant value, or a random value. In this mode
.B write
with no arguments gives more information on the allowed commands.
+.RS 1.0i
+.TP 0.4i
+.B \-c
+Skip write verifiers and CRC recalculation; allows invalid data to be written
+to disk.
+.RE
.SH TYPES
This section gives the fields in each structure type and their meanings.
Note that some types of block cover multiple actual structures,