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Go Back   Linux Archive > Redhat > Device-mapper Development

 
 
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Old 06-27-2011, 07:53 PM
Mike Snitzer
 
Default dm flakey: add corrupt_bio_byte feature

Add 'corrupt_bio_byte' feature that will write 0 to the specified Nth
byte of each bio (when the device is "down").

Signed-off-by: Mike Snitzer <snitzer@redhat.com>
---
drivers/md/dm-flakey.c | 35 +++++++++++++++++++++++++++++++++--
1 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/drivers/md/dm-flakey.c b/drivers/md/dm-flakey.c
index 618f313..b26f61d 100644
--- a/drivers/md/dm-flakey.c
+++ b/drivers/md/dm-flakey.c
@@ -27,6 +27,7 @@ struct flakey_c {
unsigned up_interval;
unsigned down_interval;
unsigned long flags;
+ unsigned corrupt_bio_byte;
};

enum feature_flag_bits {
@@ -41,7 +42,8 @@ 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, 3, "invalid number of feature args"},
+ {1, UINT_MAX, "invalid corrupt bio byte value"},
};

r = dm_read_arg(_args, dm_shift_arg(as), &argc, &ti->error);
@@ -55,6 +57,15 @@ static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
arg_name = dm_shift_arg(as);
argc--;

+ /* corrupt_bio_byte <Nth byte> */
+ if (!strnicmp(arg_name, MESG_STR("corrupt_bio_byte")) &&
+ (argc >= 1)) {
+ r = dm_read_arg(_args + 1, dm_shift_arg(as),
+ &fc->corrupt_bio_byte, &ti->error);
+ argc--;
+ continue;
+ }
+
if (!strnicmp(arg_name, MESG_STR("drop_writes"))) {
set_bit(DROP_WRITES, &fc->flags);
continue;
@@ -172,6 +183,16 @@ 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);
+
+ /* write 0 to the specified Nth byte of the bio */
+ if (data && bio_bytes >= fc->corrupt_bio_byte)
+ data[fc->corrupt_bio_byte-1] = 0;
+}
+
static int flakey_map(struct dm_target *ti, struct bio *bio,
union map_info *map_context)
{
@@ -182,6 +203,12 @@ static int flakey_map(struct dm_target *ti, struct bio *bio,
elapsed = (jiffies - fc->start_time) / HZ;
if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
unsigned rw = bio_data_dir(bio);
+ if (fc->corrupt_bio_byte) {
+ /* corrupt writes but don't touch reads */
+ if (rw == WRITE)
+ corrupt_bio_data(bio, fc);
+ goto map_bio;
+ }
if (test_bit(DROP_WRITES, &fc->flags)) {
/* drop writes but don't error reads */
if (rw == WRITE) {
@@ -218,7 +245,11 @@ 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) * 2);
+
+ if (fc->corrupt_bio_byte)
+ DMEMIT("corrupt_bio_byte %u ", fc->corrupt_bio_byte);
if (drop_writes)
DMEMIT("drop_writes ");
break;
--
1.7.1

--
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