+
+out_retry:
+ put_page(page);
+ if (vmf->flags & FAULT_FLAG_VMA_LOCK)
+ vma_end_read(vma);
+ if (fault_flag_allow_retry_first(vmf->flags)) {
+ err = VM_FAULT_RETRY;
+ } else {
+ /* Replay the fault. */
+ err = 0;
Hello!
Unfortunately, if the page continues to be pinned, it seems like fault will continue to occur.
I guess it makes system stability issue. (but I'm not familiar with that, so please let me know if I'm mistaken!)
How about migrating the page when migration problem repeats.
Yes, I had the same though in the previous iteration of the series, the
page was migrated out of the VMA if tag storage couldn't be reserved.
Only short term pins are allowed on MIGRATE_CMA pages, so I expect that the
pin will be released before the fault is replayed. Because of this, and
because it makes the code simpler, I chose not to migrate the page if tag
storage couldn't be reserved.
There are still some cases that are theoretically problematic:
vmsplice() can pin pages forever and doesn't use FOLL_LONGTERM yet.
All these things also affect other users that rely on movability (e.g.,
CMA, memory hotunplug).
--
Cheers,
David / dhildenb
