On 8/21/23 14:07, Alexander Atanasov wrote:
On 16.08.23 12:32, Andrey Zhadchenko wrote:
Add new function to target_type, so any dm devices may realize it
Implement intermediate llseek_hole() on device-mapper layer, do some
simple
checks.
Feature: dm: implement SEEK_HOLE for dm-qcow2 and dm-ploop
https://jira.vzint.dev/browse/PSBM-145746
Signed-off-by: Andrey Zhadchenko <andrey.zhadche...@virtuozzo.com>
---
v2: fix return and goto inconsistency
drivers/md/dm.c | 41 +++++++++++++++++++++++++++++++++++
include/linux/device-mapper.h | 4 ++++
2 files changed, 45 insertions(+)
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index 7e5c61a75eeb..d592c023b090 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -484,6 +484,45 @@ static int dm_blk_ioctl(struct block_device
*bdev, fmode_t mode,
return r;
}
+static loff_t dm_llseek_hole(struct block_device *bdev, loff_t
offset, int whence)
+{
+ struct mapped_device *md = bdev->bd_disk->private_data;
+ struct dm_table *table;
+ struct dm_target *ti;
+ int srcu_idx;
+ loff_t ret;
+
+ table = dm_get_live_table(md, &srcu_idx);
+ if (!table || !dm_table_get_size(table))
+ return -ENOTTY;
+
+ /*
+ * For now we only support devices that have a single target.
+ * But probably it is not hard to break it to a few requests to a
different
+ * targets
+ */
+ if (table->num_targets != 1)
+ return -EOPNOTSUPP;
multipath, tracking and push_backup are all possible targets (that get
used) so any combination can increase the count - shouldn't this be TODO?
Maybe I am mistaken, but I always thought that table->num_targets is
amount of targets within single device. e.g. linear dm made by two
devices concatenation will have two as the number of targets. And I
think dm-ploop and dm-qcow2 num targets is always one, at least for now
+ ti = dm_table_get_target(table, 0);
+
+ if (dm_suspended_md(md)) {
+ ret = -EAGAIN;
+ goto out;
+ }
+
+ if (!ti->type->llseek_hole) {
+ ret = -EINVAL;
EOPNOTSUPP - may be swap with num_targets != 1 error - which will be
EINVAL due to the argument - while here it is not supported - not an
issue with the arguments ?
-EINVAL is here to preserve default SEEK_DATA or SEEK_HOLE behavior with
block devices. Previously fixed_size_llseek() was called in all cases
and returned -EINVAL when seeking holes or data. So dm devices without
llseek_hole implementation should return this value too.
The same comment goes for 3/8 patch.
+ goto out;
+ }
+
+ ret = ti->type->llseek_hole(ti, offset, whence);
+
+out:
+ dm_put_live_table(md, srcu_idx);
+ return ret;
+}
+
u64 dm_start_time_ns_from_clone(struct bio *bio)
{
return jiffies_to_nsecs(clone_to_tio(bio)->io->start_time);
@@ -3255,6 +3294,7 @@ static const struct block_device_operations
dm_blk_dops = {
.getgeo = dm_blk_getgeo,
.report_zones = dm_blk_report_zones,
.pr_ops = &dm_pr_ops,
+ .llseek_hole = &dm_llseek_hole,
Why &dm_llseek_hole and not just dm_llseek_hole - like the other
function assignments?
.owner = THIS_MODULE
};
@@ -3264,6 +3304,7 @@ static const struct block_device_operations
dm_rq_blk_dops = {
.ioctl = dm_blk_ioctl,
.getgeo = dm_blk_getgeo,
.pr_ops = &dm_pr_ops,
+ .llseek_hole = &dm_llseek_hole,
ditto
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