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SubjectRe: dm: pass up rotational flag
On Wed, May 25 2011 at  4:50pm -0400,
Mandeep Singh Baines <msb@chromium.org> wrote:

> Allow the NONROT flag to be passed through to linear mappings if all
> underlying device are non-rotational. Tools like ureadahead will
> schedule IOs differently based on the rotational flag.
>
> With this patch, I see boot time go from 7.75 s to 7.46 s on my device.
>
> Suggested-by: J. Richard Barnette <jrbarnette@chromium.org>
> Signed-off-by: Mandeep Singh Baines <msb@chromium.org>
> Cc: Neil Brown <neilb@suse.de>
> Cc: Mike Snitzer <snitzer@redhat.com>
> Cc: Jens Axboe <jaxboe@fusionio.com>
> Cc: Martin K. Petersen <martin.petersen@oracle.com>
> Cc: Alasdair G Kergon <agk@redhat.com>
> Cc: dm-devel@redhat.com

Thanks for doing this, looks good in general.

Just a few small nits:
- rename device_nonrot to device_is_nonrot
- rename dm_table_all_nonrot to dm_table_is_nonrot
- add missing whitespace in dm_table_set_restrictions
- move ti declaration outside of dm_table_is_nonrot's while loop
- dm doesn't use 'true' or 'false' bool returns even though we have
functions that return bool -- odd but best to keep consistent for now

I'll respond with v2 that folds these changes in and my Signed-off-by
---
drivers/md/dm-table.c | 18 ++++++++++--------
1 files changed, 10 insertions(+), 8 deletions(-)
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 40c6071..a173828 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -1177,28 +1177,29 @@ static void dm_table_set_integrity(struct dm_table *t)
blk_get_integrity(template_disk));
}

-static int device_nonrot(struct dm_target *ti, struct dm_dev *dev,
- sector_t start, sector_t len, void *data)
+static int device_is_nonrot(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data)
{
struct request_queue *q = bdev_get_queue(dev->bdev);

return q && blk_queue_nonrot(q);
}

-static bool dm_table_all_nonrot(struct dm_table *t)
+static bool dm_table_is_nonrot(struct dm_table *t)
{
+ struct dm_target *ti;
unsigned i = 0;

/* Ensure that all underlying device are non rotational. */
while (i < dm_table_get_num_targets(t)) {
- struct dm_target *ti = dm_table_get_target(t, i++);
+ ti = dm_table_get_target(t, i++);

if (!ti->type->iterate_devices ||
- !ti->type->iterate_devices(ti, device_nonrot, NULL))
- return false;
+ !ti->type->iterate_devices(ti, device_is_nonrot, NULL))
+ return 0;
}

- return true;
+ return 1;
}

void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
@@ -1213,7 +1214,8 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
else
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
- if (!dm_table_all_nonrot(t))
+
+ if (!dm_table_is_nonrot(t))
queue_flag_clear_unlocked(QUEUE_FLAG_NONROT, q);
else
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);

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