Messages in this thread | | | Date | Tue, 21 Feb 2006 10:33:40 -0500 | From | "Jun'ichi Nomura" <> | Subject | Re: [PATCH 1/3] sysfs representation of stacked devices (dm/md common) |
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Thanks Alasdair and Neil,
Alasdair G Kergon wrote: > Test with trees of devices too - where a whole tree is suspended -
Suspending maps in the tree and reload one of them? I'll try that.
> I don't think you can allocate anywhere in dm_swap_table() > without PF_MEMALLOC (which I recently removed and am reluctant > to reinstate).
I understand your reluctance and I don't want to revive it either. I think moving sysfs_add_link() outside of dm_swap_table() solves this. Am I right? Or do you want to eliminate the possibility that sysfs_remove_symlink() may require memory allocation in future?
Anyway, I'll seek for bd_claim based approach.
> Have you considered if anything is feasible based around bd_claim()? > Doesn't it make more sense for the links to be set up at table > load time - i.e. superset of both tables if present?
I think it makes sense. But I have difficulty with it.
What I once thought was extending bd_claim() like: bd_claim_with_owner(bdev, void *holder, struct kobject *owner) where "owner" is a kobject for "slaves" directory. We may have the object embedded in gendisk structure. Then we can create symlinks like: /sys/block/<bdev>/holders/<owner> --> /sys/block/<owner> /sys/block/<owner>/slaves/<bdev> --> /sys/block/<bdev>
This should work for md.
However, dm needs more for its flexibility. Because multiple dm devices can hold one device and one dm device can hold a device twice (i.e. current table and new table), we need to reference-count per relationship basis, not per slave device. This might be solved by allocating management struct in bd_claim() to reference-counting the relationship. I'll try this. Comments are welcome.
-- Jun'ichi Nomura, NEC Solutions (America), Inc. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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