[dm-devel] [PATCH 5/5] dm flakey: introduce the random_read_corrupt and random_write_corrupt options
Mikulas Patocka
mpatocka at redhat.com
Tue Apr 18 19:58:33 UTC 2023
The random_read_corrupt and random_write_corrupt options corrupt random
byte in a bio with a given probability. The corruptions only happen in the
"down" interval.
Signed-off-by: Mikulas Patocka <mpatocka at redhat.com>
---
Documentation/admin-guide/device-mapper/dm-flakey.rst | 10 +
drivers/md/dm-flakey.c | 118 ++++++++++++++----
2 files changed, 108 insertions(+), 20 deletions(-)
Index: linux-2.6/drivers/md/dm-flakey.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-flakey.c
+++ linux-2.6/drivers/md/dm-flakey.c
@@ -16,6 +16,8 @@
#define DM_MSG_PREFIX "flakey"
+#define PROBABILITY_BASE 1000000000
+
#define all_corrupt_bio_flags_match(bio, fc) \
(((bio)->bi_opf & (fc)->corrupt_bio_flags) == (fc)->corrupt_bio_flags)
@@ -34,6 +36,8 @@ struct flakey_c {
unsigned int corrupt_bio_rw;
unsigned int corrupt_bio_value;
blk_opf_t corrupt_bio_flags;
+ unsigned int random_read_corrupt;
+ unsigned int random_write_corrupt;
};
enum feature_flag_bits {
@@ -54,10 +58,11 @@ static int parse_features(struct dm_arg_
const char *arg_name;
static const struct dm_arg _args[] = {
- {0, 7, "Invalid number of feature args"},
+ {0, 11, "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"},
+ {0, PROBABILITY_BASE, "Invalid random corrupt argument"},
};
/* No feature arguments supplied. */
@@ -170,6 +175,32 @@ static int parse_features(struct dm_arg_
continue;
}
+ if (!strcasecmp(arg_name, "random_read_corrupt")) {
+ if (!argc) {
+ ti->error = "Feature random_read_corrupt requires a parameter";
+ return -EINVAL;
+ }
+ r = dm_read_arg(_args + 4, as, &fc->random_read_corrupt, &ti->error);
+ if (r)
+ return r;
+ argc--;
+
+ continue;
+ }
+
+ if (!strcasecmp(arg_name, "random_write_corrupt")) {
+ if (!argc) {
+ ti->error = "Feature random_write_corrupt requires a parameter";
+ return -EINVAL;
+ }
+ r = dm_read_arg(_args + 4, as, &fc->random_write_corrupt, &ti->error);
+ if (r)
+ return r;
+ argc--;
+
+ continue;
+ }
+
ti->error = "Unrecognised flakey feature requested";
return -EINVAL;
}
@@ -184,7 +215,8 @@ static int parse_features(struct dm_arg_
}
if (!fc->corrupt_bio_byte && !test_bit(ERROR_READS, &fc->flags) &&
- !test_bit(DROP_WRITES, &fc->flags) && !test_bit(ERROR_WRITES, &fc->flags)) {
+ !test_bit(DROP_WRITES, &fc->flags) && !test_bit(ERROR_WRITES, &fc->flags) &&
+ !fc->random_read_corrupt && !fc->random_write_corrupt) {
set_bit(ERROR_WRITES, &fc->flags);
set_bit(ERROR_READS, &fc->flags);
}
@@ -306,28 +338,23 @@ static void flakey_map_bio(struct dm_tar
bio->bi_iter.bi_sector = flakey_map_sector(ti, bio->bi_iter.bi_sector);
}
-static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
+static void corrupt_bio_common(struct bio *bio, unsigned int corrupt_bio_byte, unsigned char corrupt_bio_value)
{
- unsigned int corrupt_bio_byte = fc->corrupt_bio_byte - 1;
-
struct bvec_iter iter;
struct bio_vec bvec;
- if (!bio_has_data(bio))
- return;
-
/*
* Overwrite the Nth byte of the bio's data, on whichever page
* it falls.
*/
bio_for_each_segment(bvec, bio, iter) {
if (bio_iter_len(bio, iter) > corrupt_bio_byte) {
- char *segment = bvec_kmap_local(&bvec);
- segment[corrupt_bio_byte] = fc->corrupt_bio_value;
+ unsigned char *segment = bvec_kmap_local(&bvec);
+ segment[corrupt_bio_byte] = corrupt_bio_value;
kunmap_local(segment);
DMDEBUG("Corrupting data bio=%p by writing %u to byte %u "
"(rw=%c bi_opf=%u bi_sector=%llu size=%u)\n",
- bio, fc->corrupt_bio_value, fc->corrupt_bio_byte,
+ bio, corrupt_bio_value, corrupt_bio_byte,
(bio_data_dir(bio) == WRITE) ? 'w' : 'r', bio->bi_opf,
(unsigned long long)bio->bi_iter.bi_sector, bio->bi_iter.bi_size);
break;
@@ -336,6 +363,30 @@ static void corrupt_bio_data(struct bio
}
}
+static void corrupt_bio_data(struct bio *bio, struct flakey_c *fc)
+{
+ unsigned int corrupt_bio_byte = fc->corrupt_bio_byte - 1;
+
+ if (!bio_has_data(bio))
+ return;
+
+ corrupt_bio_common(bio, corrupt_bio_byte, fc->corrupt_bio_value);
+}
+
+static void corrupt_bio_random(struct bio *bio)
+{
+ unsigned int corrupt_byte;
+ unsigned char corrupt_value;
+
+ if (!bio_has_data(bio))
+ return;
+
+ corrupt_byte = get_random_u32() % bio->bi_iter.bi_size;
+ corrupt_value = get_random_u8();
+
+ corrupt_bio_common(bio, corrupt_byte, corrupt_value);
+}
+
static void clone_free(struct bio *clone)
{
struct folio_iter fi;
@@ -434,6 +485,7 @@ static int flakey_map(struct dm_target *
/* Are we alive ? */
elapsed = (jiffies - fc->start_time) / HZ;
if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
+ bool corrupt_fixed, corrupt_random;
/*
* Flag this bio as submitted while down.
*/
@@ -463,16 +515,28 @@ static int flakey_map(struct dm_target *
/*
* Corrupt matching writes.
*/
+ corrupt_fixed = false;
+ corrupt_random = false;
if (fc->corrupt_bio_byte && fc->corrupt_bio_rw == WRITE) {
- if (all_corrupt_bio_flags_match(bio, fc)) {
- struct bio *clone = clone_bio(ti, fc, bio);
- if (clone) {
+ if (all_corrupt_bio_flags_match(bio, fc))
+ corrupt_fixed = true;
+ }
+ if (fc->random_write_corrupt) {
+ u64 rnd = get_random_u64();
+ u32 rem = do_div(rnd, PROBABILITY_BASE);
+ if (rem < fc->random_write_corrupt)
+ corrupt_random = true;
+ }
+ if (corrupt_fixed || corrupt_random) {
+ struct bio *clone = clone_bio(ti, fc, bio);
+ if (clone) {
+ if (corrupt_fixed)
corrupt_bio_data(clone, fc);
- submit_bio(clone);
- return DM_MAPIO_SUBMITTED;
- }
- }
- goto map_bio;
+ if (corrupt_random)
+ corrupt_bio_random(clone);
+ submit_bio(clone);
+ return DM_MAPIO_SUBMITTED;
+ }
}
}
@@ -501,6 +565,12 @@ static int flakey_end_io(struct dm_targe
corrupt_bio_data(bio, fc);
}
}
+ if (fc->random_read_corrupt) {
+ u64 rnd = get_random_u64();
+ u32 rem = do_div(rnd, PROBABILITY_BASE);
+ if (rem < fc->random_read_corrupt)
+ corrupt_bio_random(bio);
+ }
if (test_bit(ERROR_READS, &fc->flags)) {
/*
* Error read during the down_interval if drop_writes
@@ -533,7 +603,10 @@ static void flakey_status(struct dm_targ
error_reads = test_bit(ERROR_READS, &fc->flags);
drop_writes = test_bit(DROP_WRITES, &fc->flags);
error_writes = test_bit(ERROR_WRITES, &fc->flags);
- DMEMIT(" %u", error_reads + drop_writes + error_writes + (fc->corrupt_bio_byte > 0) * 5);
+ DMEMIT(" %u", error_reads + drop_writes + error_writes +
+ (fc->corrupt_bio_byte > 0) * 5 +
+ (fc->random_read_corrupt > 0) * 2 +
+ (fc->random_write_corrupt > 0) * 2);
if (error_reads)
DMEMIT(" error_reads");
@@ -548,6 +621,11 @@ static void flakey_status(struct dm_targ
(fc->corrupt_bio_rw == WRITE) ? 'w' : 'r',
fc->corrupt_bio_value, fc->corrupt_bio_flags);
+ if (fc->random_read_corrupt > 0)
+ DMEMIT(" %u", fc->random_read_corrupt);
+ if (fc->random_write_corrupt > 0)
+ DMEMIT(" %u", fc->random_write_corrupt);
+
break;
case STATUSTYPE_IMA:
Index: linux-2.6/Documentation/admin-guide/device-mapper/dm-flakey.rst
===================================================================
--- linux-2.6.orig/Documentation/admin-guide/device-mapper/dm-flakey.rst
+++ linux-2.6/Documentation/admin-guide/device-mapper/dm-flakey.rst
@@ -67,6 +67,16 @@ Optional feature parameters:
Perform the replacement only if bio->bi_opf has all the
selected flags set.
+ random_read_corrupt <probability>
+ During <down interval>, replace random byte in a read bio
+ with a random value. probability is an integer between
+ 0 and 1000000000 meaning 0% to 100% probability of corruption.
+
+ random_write_corrupt <probability>
+ During <down interval>, replace random byte in a write bio
+ with a random value. probability is an integer between
+ 0 and 1000000000 meaning 0% to 100% probability of corruption.
+
Examples:
Replaces the 32nd byte of READ bios with the value 1::
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