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dm: Allow dm_call_pr to be used for path searches

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The specs state that if you send a reserve down a path that is already
the holder success must be returned and if it goes down a path that
is not the holder reservation conflict must be returned. Windows
failover clustering will send a second reservation and expects that a
device returns success. The problem for multipathing is that for an
All Registrants reservation, we can send the reserve down any path but
for all other reservation types there is one path that is the holder.

To handle this we could add PR state to dm but that can get nasty.
Look at target_core_pr.c for an example of the type of things we'd
have to track. It will also get more complicated because other
initiators can change the state so we will have to add in async
event/sense handling.

This commit, and the 3 commits that follow, tries to keep dm simple
and keep just doing passthrough. This commit modifies dm_call_pr to be
able to find the first usable path that can execute our pr_op then
return. When dm_pr_reserve is converted to dm_call_pr in the next
commit for the normal case we will use the same path for every
reserve.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Mike Christie 2022-07-17 17:45:05 -05:00 committed by Mike Snitzer
parent e120a5f1e7
commit 8dd87f3c52
1 changed files with 38 additions and 12 deletions
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50
drivers/md/dm.c
View file

@ -3077,10 +3077,11 @@ struct dm_pr {
u64 new_key;
u32 flags;
bool fail_early;
int ret;
};
static int dm_call_pr(struct block_device *bdev, iterate_devices_callout_fn fn,
void *data)
struct dm_pr *pr)
{
struct mapped_device *md = bdev->bd_disk->private_data;
struct dm_table *table;
@ -3105,7 +3106,8 @@ static int dm_call_pr(struct block_device *bdev, iterate_devices_callout_fn fn,
if (!ti->type->iterate_devices)
goto out;
ret = ti->type->iterate_devices(ti, fn, data);
ti->type->iterate_devices(ti, fn, pr);
ret = 0;
out:
dm_put_live_table(md, srcu_idx);
return ret;
@ -3119,10 +3121,24 @@ static int __dm_pr_register(struct dm_target *ti, struct dm_dev *dev,
{
struct dm_pr *pr = data;
const struct pr_ops *ops = dev->bdev->bd_disk->fops->pr_ops;
int ret;
if (!ops || !ops->pr_register)
return -EOPNOTSUPP;
return ops->pr_register(dev->bdev, pr->old_key, pr->new_key, pr->flags);
if (!ops || !ops->pr_register) {
pr->ret = -EOPNOTSUPP;
return -1;
}
ret = ops->pr_register(dev->bdev, pr->old_key, pr->new_key, pr->flags);
if (!ret)
return 0;
if (!pr->ret)
pr->ret = ret;
if (pr->fail_early)
return -1;
return 0;
}
static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
@ -3133,19 +3149,29 @@ static int dm_pr_register(struct block_device *bdev, u64 old_key, u64 new_key,
.new_key = new_key,
.flags = flags,
.fail_early = true,
.ret = 0,
};
int ret;
ret = dm_call_pr(bdev, __dm_pr_register, &pr);
if (ret && new_key) {
/* unregister all paths if we failed to register any path */
pr.old_key = new_key;
pr.new_key = 0;
pr.flags = 0;
pr.fail_early = false;
dm_call_pr(bdev, __dm_pr_register, &pr);
if (ret) {
/* Didn't even get to register a path */
return ret;
}
if (!pr.ret)
return 0;
ret = pr.ret;
if (!new_key)
return ret;
/* unregister all paths if we failed to register any path */
pr.old_key = new_key;
pr.new_key = 0;
pr.flags = 0;
pr.fail_early = false;
(void) dm_call_pr(bdev, __dm_pr_register, &pr);
return ret;
}