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>

diff --git a/Documentation/device-mapper/delay.txt b/Documentation/device-mapper/delay.txt
index 4b1d22a44ce42d19cb54442d4e608b3f61a7e1e9..6426c45273cbbaf16b169332111538dcf46e3b44 100644 (file)
--- a/Documentation/device-mapper/delay.txt
+++ b/Documentation/device-mapper/delay.txt
@@ -5,7 +5,8 @@ Device-Mapper's "delay" target delays reads and/or writes
 and maps them to different devices.
 
 Parameters:
-    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>]
+    <device> <offset> <delay> [<write_device> <write_offset> <write_delay>
+                              [<flush_device> <flush_offset> <flush_delay>]]
 
 With separate write parameters, the first set is only used for reads.
 Offsets are specified in sectors.

diff --git a/drivers/md/dm-delay.c b/drivers/md/dm-delay.c
index c5ebe56bc28b1a7d7713e7529d42c2f84aa824fe..2fb7bb4304ad7f0ade6eb10ccd02d07f36271acf 100644 (file)
--- a/drivers/md/dm-delay.c
+++ b/drivers/md/dm-delay.c
@@ -34,6 +34,7 @@ struct delay_c {
 
        struct delay_class read;
        struct delay_class write;
+       struct delay_class flush;
 
        int argc;
 };
@@ -126,6 +127,8 @@ static void delay_dtr(struct dm_target *ti)
                dm_put_device(ti, dc->read.dev);
        if (dc->write.dev)
                dm_put_device(ti, dc->write.dev);
+       if (dc->flush.dev)
+               dm_put_device(ti, dc->flush.dev);
 
        mutex_destroy(&dc->timer_lock);
 
@@ -171,8 +174,8 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
        struct delay_c *dc;
        int ret;
 
-       if (argc != 3 && argc != 6) {
-               ti->error = "Requires exactly 3 or 6 arguments";
+       if (argc != 3 && argc != 6 && argc != 9) {
+               ti->error = "Requires exactly 3, 6 or 9 arguments";
                return -EINVAL;
        }
 
@@ -196,6 +199,9 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 
        if (argc == 3) {
                ret = delay_class_ctr(ti, &dc->write, argv);
+               if (ret)
+                       goto bad;
+               ret = delay_class_ctr(ti, &dc->flush, argv);
                if (ret)
                        goto bad;
                goto out;
@@ -204,6 +210,16 @@ static int delay_ctr(struct dm_target *ti, unsigned int argc, char **argv)
        ret = delay_class_ctr(ti, &dc->write, argv + 3);
        if (ret)
                goto bad;
+       if (argc == 6) {
+               ret = delay_class_ctr(ti, &dc->flush, argv + 3);
+               if (ret)
+                       goto bad;
+               goto out;
+       }
+
+       ret = delay_class_ctr(ti, &dc->flush, argv + 6);
+       if (ret)
+               goto bad;
 
 out:
        dc->kdelayd_wq = alloc_workqueue("kdelayd", WQ_MEM_RECLAIM, 0);
@@ -269,7 +285,10 @@ static int delay_map(struct dm_target *ti, struct bio *bio)
        struct dm_delay_info *delayed = dm_per_bio_data(bio, sizeof(struct dm_delay_info));
 
        if (bio_data_dir(bio) == WRITE) {
-               c = &dc->write;
+               if (unlikely(bio->bi_opf & REQ_PREFLUSH))
+                       c = &dc->flush;
+               else
+                       c = &dc->write;
        } else {
                c = &dc->read;
        }
@@ -292,7 +311,7 @@ static void delay_status(struct dm_target *ti, status_type_t type,
 
        switch (type) {
        case STATUSTYPE_INFO:
-               DMEMIT("%u %u", dc->read.ops, dc->write.ops);
+               DMEMIT("%u %u %u", dc->read.ops, dc->write.ops, dc->flush.ops);
                break;
 
        case STATUSTYPE_TABLE:
@@ -301,6 +320,10 @@ static void delay_status(struct dm_target *ti, status_type_t type,
                        DMEMIT(" ");
                        DMEMIT_DELAY_CLASS(&dc->write);
                }
+               if (dc->argc >= 9) {
+                       DMEMIT(" ");
+                       DMEMIT_DELAY_CLASS(&dc->flush);
+               }
                break;
        }
 }
@@ -317,6 +340,9 @@ static int delay_iterate_devices(struct dm_target *ti,
        ret = fn(ti, dc->write.dev, dc->write.start, ti->len, data);
        if (ret)
                goto out;
+       ret = fn(ti, dc->flush.dev, dc->flush.start, ti->len, data);
+       if (ret)
+               goto out;
 
 out:
        return ret;