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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>
This commit is contained in:
Mike Snitzer 2011-08-02 12:32:06 +01:00 committed by Alasdair G Kergon
parent b26f5e3d71
commit a3998799fb
2 changed files with 159 additions and 15 deletions
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19
Documentation/device-mapper/dm-flakey.txt
View File

@ -32,3 +32,22 @@ Optional feature parameters:
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

155
drivers/md/dm-flakey.c
View File

@ -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 @@ struct flakey_c {
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 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
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 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
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 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
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 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
*
* 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 @@ static void flakey_map_bio(struct dm_target *ti, struct bio *bio)
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 @@ map_bio:
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 @@ static int flakey_status(struct dm_target *ti, status_type_t type,
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 @@ static struct target_type flakey_target = {
.ctr = flakey_ctr,
.dtr = flakey_dtr,
.map = flakey_map,
.end_io = flakey_end_io,
.status = flakey_status,
.ioctl = flakey_ioctl,
.merge = flakey_merge,