dm flakey: add corrupt_bio_byte feature
Add corrupt_bio_byte feature to simulate corruption by overwriting a byte at a
specified position with a specified value during intervals when the device is
"down".
Signed-off-by: Mike Snitzer <snitzer@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
diff --git a/Documentation/device-mapper/dm-flakey.txt b/Documentation/device-mapper/dm-flakey.txt
index 1b66c86..6ff5c23 100644
--- a/Documentation/device-mapper/dm-flakey.txt
+++ b/Documentation/device-mapper/dm-flakey.txt
@@ -32,3 +32,22 @@
drop_writes:
All write I/O is silently ignored.
Read I/O is handled correctly.
+
+ corrupt_bio_byte <Nth_byte> <direction> <value> <flags>:
+ During <down interval>, replace <Nth_byte> of the data of
+ each matching bio with <value>.
+
+ <Nth_byte>: The offset of the byte to replace.
+ Counting starts at 1, to replace the first byte.
+ <direction>: Either 'r' to corrupt reads or 'w' to corrupt writes.
+ 'w' is incompatible with drop_writes.
+ <value>: The value (from 0-255) to write.
+ <flags>: Perform the replacement only if bio->bi_rw has all the
+ selected flags set.
+
+Examples:
+ corrupt_bio_byte 32 r 1 0
+ - replaces the 32nd byte of READ bios with the value 1
+
+ corrupt_bio_byte 224 w 0 32
+ - replaces the 224th byte of REQ_META (=32) bios with the value 0
diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index e7c4c2a..89f73ca 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -1,6 +1,6 @@
/*
* Copyright (C) 2003 Sistina Software (UK) Limited.
- * Copyright (C) 2004, 2010 Red Hat, Inc. All rights reserved.
+ * Copyright (C) 2004, 2010-2011 Red Hat, Inc. All rights reserved.
*
* This file is released under the GPL.
*/
@@ -15,6 +15,9 @@
#define DM_MSG_PREFIX "flakey"
+#define all_corrupt_bio_flags_match(bio, fc) \
+ (((bio)->bi_rw & (fc)->corrupt_bio_flags) == (fc)->corrupt_bio_flags)
+
/*
* Flakey: Used for testing only, simulates intermittent,
* catastrophic device failure.
@@ -26,6 +29,10 @@
unsigned up_interval;
unsigned down_interval;
unsigned long flags;
+ unsigned corrupt_bio_byte;
+ unsigned corrupt_bio_rw;
+ unsigned corrupt_bio_value;
+ unsigned corrupt_bio_flags;
};
enum feature_flag_bits {
@@ -40,7 +47,10 @@
const char *arg_name;
static struct dm_arg _args[] = {
- {0, 1, "Invalid number of feature args"},
+ {0, 6, "Invalid number of feature args"},
+ {1, UINT_MAX, "Invalid corrupt bio byte"},
+ {0, 255, "Invalid corrupt value to write into bio byte (0-255)"},
+ {0, UINT_MAX, "Invalid corrupt bio flags mask"},
};
/* No feature arguments supplied. */
@@ -49,9 +59,9 @@
r = dm_read_arg_group(_args, as, &argc, &ti->error);
if (r)
- return -EINVAL;
+ return r;
- while (argc && !r) {
+ while (argc) {
arg_name = dm_shift_arg(as);
argc--;
@@ -67,11 +77,61 @@
continue;
}
+ /*
+ * corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>
+ */
+ if (!strcasecmp(arg_name, "corrupt_bio_byte")) {
+ if (!argc)
+ ti->error = "Feature corrupt_bio_byte requires parameters";
+
+ r = dm_read_arg(_args + 1, as, &fc->corrupt_bio_byte, &ti->error);
+ if (r)
+ return r;
+ argc--;
+
+ /*
+ * Direction r or w?
+ */
+ arg_name = dm_shift_arg(as);
+ if (!strcasecmp(arg_name, "w"))
+ fc->corrupt_bio_rw = WRITE;
+ else if (!strcasecmp(arg_name, "r"))
+ fc->corrupt_bio_rw = READ;
+ else {
+ ti->error = "Invalid corrupt bio direction (r or w)";
+ return -EINVAL;
+ }
+ argc--;
+
+ /*
+ * Value of byte (0-255) to write in place of correct one.
+ */
+ r = dm_read_arg(_args + 2, as, &fc->corrupt_bio_value, &ti->error);
+ if (r)
+ return r;
+ argc--;
+
+ /*
+ * Only corrupt bios with these flags set.
+ */
+ r = dm_read_arg(_args + 3, as, &fc->corrupt_bio_flags, &ti->error);
+ if (r)
+ return r;
+ argc--;
+
+ continue;
+ }
+
ti->error = "Unrecognised flakey feature requested";
- r = -EINVAL;
+ return -EINVAL;
}
- return r;
+ if (test_bit(DROP_WRITES, &fc->flags) && (fc->corrupt_bio_rw == WRITE)) {
+ ti->error = "drop_writes is incompatible with corrupt_bio_byte with the WRITE flag set";
+ return -EINVAL;
+ }
+
+ return 0;
}
/*
@@ -80,6 +140,11 @@
*
* Feature args:
* [drop_writes]
+ * [corrupt_bio_byte <Nth_byte> <direction> <value> <bio_flags>]
+ *
+ * Nth_byte starts from 1 for the first byte.
+ * Direction is r for READ or w for WRITE.
+ * bio_flags is ignored if 0.
*/
static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
@@ -178,31 +243,64 @@
bio->bi_sector = flakey_map_sector(ti, bio->bi_sector);
}
+static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
+{
+ unsigned bio_bytes = bio_cur_bytes(bio);
+ char *data = bio_data(bio);
+
+ /*
+ * Overwrite the Nth byte of the data returned.
+ */
+ if (data && bio_bytes >= fc->corrupt_bio_byte) {
+ data[fc->corrupt_bio_byte - 1] = fc->corrupt_bio_value;
+
+ DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
+ "(rw=%c bi_rw=%lu bi_sector=%llu cur_bytes=%u)\n",
+ bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
+ (bio_data_dir(bio) == WRITE) ? 'w' : 'r',
+ bio->bi_rw, (unsigned long long)bio->bi_sector, bio_bytes);
+ }
+}
+
static int flakey_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
struct flakey_c *fc = ti->private;
unsigned elapsed;
- unsigned rw;
/* Are we alive ? */
elapsed = (jiffies - fc->start_time) / HZ;
if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
- rw = bio_data_dir(bio);
+ /*
+ * Flag this bio as submitted while down.
+ */
+ map_context->ll = 1;
/*
- * Drop writes. Map reads as normal.
+ * Map reads as normal.
+ */
+ if (bio_data_dir(bio) == READ)
+ goto map_bio;
+
+ /*
+ * Drop writes?
*/
if (test_bit(DROP_WRITES, &fc->flags)) {
- if (rw == WRITE) {
- bio_endio(bio, 0);
- return DM_MAPIO_SUBMITTED;
- }
+ bio_endio(bio, 0);
+ return DM_MAPIO_SUBMITTED;
+ }
+
+ /*
+ * Corrupt matching writes.
+ */
+ if (fc->corrupt_bio_byte && (fc->corrupt_bio_rw == WRITE)) {
+ if (all_corrupt_bio_flags_match(bio, fc))
+ corrupt_bio_data(bio, fc);
goto map_bio;
}
/*
- * Default setting errors all I/O.
+ * By default, error all I/O.
*/
return -EIO;
}
@@ -213,6 +311,24 @@
return DM_MAPIO_REMAPPED;
}
+static int flakey_end_io(struct dm_target *ti, struct bio *bio,
+ int error, union map_info *map_context)
+{
+ struct flakey_c *fc = ti->private;
+ unsigned bio_submitted_while_down = map_context->ll;
+
+ /*
+ * Corrupt successful READs while in down state.
+ * If flags were specified, only corrupt those that match.
+ */
+ if (!error && bio_submitted_while_down &&
+ (bio_data_dir(bio) == READ) && (fc->corrupt_bio_rw == READ) &&
+ all_corrupt_bio_flags_match(bio, fc))
+ corrupt_bio_data(bio, fc);
+
+ return error;
+}
+
static int flakey_status(struct dm_target *ti, status_type_t type,
char *result, unsigned int maxlen)
{
@@ -231,9 +347,17 @@
fc->down_interval);
drop_writes = test_bit(DROP_WRITES, &fc->flags);
- DMEMIT("%u ", drop_writes);
+ DMEMIT("%u ", drop_writes + (fc->corrupt_bio_byte > 0) * 5);
+
if (drop_writes)
DMEMIT("drop_writes ");
+
+ if (fc->corrupt_bio_byte)
+ DMEMIT("corrupt_bio_byte %u %c %u %u ",
+ fc->corrupt_bio_byte,
+ (fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
+ fc->corrupt_bio_value, fc->corrupt_bio_flags);
+
break;
}
return 0;
@@ -275,6 +399,7 @@
.ctr = flakey_ctr,
.dtr = flakey_dtr,
.map = flakey_map,
+ .end_io = flakey_end_io,
.status = flakey_status,
.ioctl = flakey_ioctl,
.merge = flakey_merge,