iommu/iova: Manage the depot list size

mainline inclusion
from mainline-v6.7-rc1
commit 233045378dbbc0a7346127d19a54d4f91e0bd855
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8KS9A
CVE: NA

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=233045378dbbc0a7346127d19a54d4f91e0bd855



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Automatically scaling the depot up to suit the peak capacity of a
workload is all well and good, but it would be nice to have a way to
scale it back down again if the workload changes. To that end, add
backround reclaim that will gradually free surplus magazines if the
depot size remains above a reasonable threshold for long enough.

Reviewed-by: Jerry Snitselaar <jsnitsel@redhat.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/03170665c56d89c6ce6081246b47f68d4e483308.1694535580.git.robin.murphy@arm.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Zhang Zekun <zhangzekun11@huawei.com>