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dm flakey: add drop_writes

Browse source 
Add 'drop_writes' option to drop writes silently while the
device is 'down'.  Reads are not touched.

Signed-off-by: Mike Snitzer <[email protected]>
Signed-off-by: Alasdair G Kergon <[email protected]>
This commit is contained in:
Mike Snitzer 2011-08-02 12:32:05 +01:00 • committed by Alasdair G Kergon
commit b26f5e3d71
2 changed files with 78 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

65
drivers/md/dm-flakey.c
View file

@ -25,16 +25,22 @@ struct flakey_c {
sector_t start;
unsigned up_interval;
unsigned down_interval;
unsigned long flags;
};
static int parse_features(struct dm_arg_set *as, struct dm_target *ti)
enum feature_flag_bits {
DROP_WRITES
};
static int parse_features(struct dm_arg_set *as, struct flakey_c *fc,
struct dm_target *ti)
{
int r;
unsigned argc;
const char *arg_name;
static struct dm_arg _args[] = {
{0, 0, "Invalid number of feature args"},
{0, 1, "Invalid number of feature args"},
};
/* No feature arguments supplied. */
@ -49,6 +55,18 @@ static int parse_features(struct dm_arg_set *as, struct dm_target *ti)
arg_name = dm_shift_arg(as);
argc--;
/*
* drop_writes
*/
if (!strcasecmp(arg_name, "drop_writes")) {
if (test_and_set_bit(DROP_WRITES, &fc->flags)) {
ti->error = "Feature drop_writes duplicated";
return -EINVAL;
}
continue;
}
ti->error = "Unrecognised flakey feature requested";
r = -EINVAL;
}
@ -59,6 +77,9 @@ static int parse_features(struct dm_arg_set *as, struct dm_target *ti)
/*
* Construct a flakey mapping:
* <dev_path> <offset> <up interval> <down interval> [<#feature args> [<arg>]*]
*
* Feature args:
* [drop_writes]
*/
static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
{
@ -81,7 +102,7 @@ static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
return -EINVAL;
}
fc = kmalloc(sizeof(*fc), GFP_KERNEL);
fc = kzalloc(sizeof(*fc), GFP_KERNEL);
if (!fc) {
ti->error = "Cannot allocate linear context";
return -ENOMEM;
@ -114,7 +135,7 @@ static int flakey_ctr(struct dm_target *ti, unsigned int argc, char **argv)
goto bad;
}
r = parse_features(&as, ti);
r = parse_features(&as, fc, ti);
if (r)
goto bad;
@ -162,12 +183,31 @@ static int flakey_map(struct dm_target *ti, struct bio *bio,
{
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)
return -EIO;
if (elapsed % (fc->up_interval + fc->down_interval) >= fc->up_interval) {
rw = bio_data_dir(bio);
/*
* Drop writes. Map reads as normal.
*/
if (test_bit(DROP_WRITES, &fc->flags)) {
if (rw == WRITE) {
bio_endio(bio, 0);
return DM_MAPIO_SUBMITTED;
}
goto map_bio;
}
/*
* Default setting errors all I/O.
*/
return -EIO;
}
map_bio:
flakey_map_bio(ti, bio);
return DM_MAPIO_REMAPPED;
@ -176,7 +216,9 @@ static int flakey_map(struct dm_target *ti, struct bio *bio,
static int flakey_status(struct dm_target *ti, status_type_t type,
char *result, unsigned int maxlen)
{
unsigned sz = 0;
struct flakey_c *fc = ti->private;
unsigned drop_writes;
switch (type) {
case STATUSTYPE_INFO:
@ -184,9 +226,14 @@ static int flakey_status(struct dm_target *ti, status_type_t type,
break;
case STATUSTYPE_TABLE:
snprintf(result, maxlen, "%s %llu %u %u", fc->dev->name,
(unsigned long long)fc->start, fc->up_interval,
fc->down_interval);
DMEMIT("%s %llu %u %u ", fc->dev->name,
(unsigned long long)fc->start, fc->up_interval,
fc->down_interval);
drop_writes = test_bit(DROP_WRITES, &fc->flags);
DMEMIT("%u ", drop_writes);
if (drop_writes)
DMEMIT("drop_writes ");
break;
}
return 0;