Add prefetch property

ZFS prefetch is currently governed by the zfs_prefetch_disable
tunable. However, this is a module-wide settings - if a specific
dataset benefits from prefetch, while others have issue with it,
an optimal solution does not exists.

This commit introduce the "prefetch" tri-state property, which enable
granular control (at dataset/volume level) for prefetching.

This patch does not remove the zfs_prefetch_disable, which remains
a system-wide switch for enable/disable prefetch. However, to avoid
duplication, it would be preferable to deprecate and then remove
the module tunable.

Reviewed-by: Brian Behlendorf <[email protected]>
Reviewed-by: Alexander Motin <[email protected]>
Reviewed-by: Ameer Hamza <[email protected]>
Signed-off-by: Gionatan Danti <[email protected]>
Co-authored-by: Gionatan Danti <[email protected]>
Closes #15237 
Closes #15436 

0 files changed, 0 insertions, 0 deletions