On Thu, Dec 08 2016, Artur Paszkiewicz wrote: > On 12/07/2016 02:25 AM, NeilBrown wrote: >> On Tue, Dec 06 2016, Artur Paszkiewicz wrote: >> >>> The PPL signature is used to determine if the stored PPL is valid for a >>> given array. With IMSM, the PPL signature should match the >>> orig_family_num field of the superblock. To avoid passing this value >>> from userspace, it can be read from the IMSM MPB when initializing the >>> log. >> >> It is up to mdadm to determine if the PPL is valid. It would only tell >> the kernel that a PPL exists if it is valid... > > The kernel also has to know this value because it writes it to the PPL > header. So yet another sysfs attribute just for this value? How about > adding a directory similar to "bitmap" to hold all the PPL related > settings? There is only one PPL header (per device) - correct? md can read that header, change the few fields that it knows about, and write it back out again. Does it ever need to change the PPL signature? When a PPL is created, mdadm can write the initial header. Am I missing something? Thanks, NeilBrown
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