dm delay: add flush as a third class of IO
Add a new class for dm-delay that delays flush requests. Previously, flushes were delayed as writes, but it caused problems if the user needed to create a device with one or a few slow sectors for the purpose of testing - all flushes would be forwarded to this device and delayed, and that skews the test results. Fix this by allowing to select 0 delay for flushes. Signed-off-by: Mikulas Patocka <mpatocka@redhat.com> Signed-off-by: Mike Snitzer <snitzer@redhat.com>
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@ -5,7 +5,8 @@ Device-Mapper's "delay" target delays reads and/or writes
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and maps them to different devices.
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Parameters:
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<device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
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<device> <offset> <delay> [<write_device> <write_offset> <write_delay>
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[<flush_device> <flush_offset> <flush_delay>]]
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With separate write parameters, the first set is only used for reads.
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Offsets are specified in sectors.
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@ -34,6 +34,7 @@ struct delay_c {
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struct delay_class read;
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struct delay_class write;
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struct delay_class flush;
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int argc;
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};
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@ -126,6 +127,8 @@ static void delay_dtr(struct dm_target *ti)
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dm_put_device(ti, dc->read.dev);
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if (dc->write.dev)
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dm_put_device(ti, dc->write.dev);
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if (dc->flush.dev)
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dm_put_device(ti, dc->flush.dev);
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mutex_destroy(&dc->timer_lock);
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@ -171,8 +174,8 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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struct delay_c *dc;
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int ret;
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if (argc != 3 && argc != 6) {
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ti->error = "Requires exactly 3 or 6 arguments";
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if (argc != 3 && argc != 6 && argc != 9) {
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ti->error = "Requires exactly 3, 6 or 9 arguments";
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return -EINVAL;
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}
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@ -196,6 +199,9 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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if (argc == 3) {
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ret = delay_class_ctr(ti, &dc->write, argv);
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if (ret)
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goto bad;
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ret = delay_class_ctr(ti, &dc->flush, argv);
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if (ret)
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goto bad;
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goto out;
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@ -204,6 +210,16 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
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ret = delay_class_ctr(ti, &dc->write, argv + 3);
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if (ret)
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goto bad;
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if (argc == 6) {
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ret = delay_class_ctr(ti, &dc->flush, argv + 3);
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if (ret)
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goto bad;
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goto out;
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}
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ret = delay_class_ctr(ti, &dc->flush, argv + 6);
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if (ret)
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goto bad;
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out:
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dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
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@ -269,6 +285,9 @@ static int delay_map(struct dm_target *ti, struct bio *bio)
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struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
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if (bio_data_dir(bio) == WRITE) {
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if (unlikely(bio->bi_opf & REQ_PREFLUSH))
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c = &dc->flush;
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else
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c = &dc->write;
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} else {
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c = &dc->read;
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@ -292,7 +311,7 @@ static void delay_status(struct dm_target *ti, status_type_t type,
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switch (type) {
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case STATUSTYPE_INFO:
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DMEMIT("%u %u", dc->read.ops, dc->write.ops);
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DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);
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break;
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case STATUSTYPE_TABLE:
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@ -301,6 +320,10 @@ static void delay_status(struct dm_target *ti, status_type_t type,
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DMEMIT(" ");
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DMEMIT_DELAY_CLASS(&dc->write);
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}
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if (dc->argc >= 9) {
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DMEMIT(" ");
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DMEMIT_DELAY_CLASS(&dc->flush);
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}
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break;
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}
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}
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@ -317,6 +340,9 @@ static int delay_iterate_devices(struct dm_target *ti,
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ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);
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if (ret)
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goto out;
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ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);
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if (ret)
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goto out;
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out:
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return ret;
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