Commit 68ad4743 authored by David Hildenbrand's avatar David Hildenbrand Committed by Alexander Gordeev
Browse files

s390/uv: gmap_make_secure() cleanups for further changes 



Let's factor out handling of LRU cache draining and convert the if-else
chain to a switch-case.

Reviewed-by: default avatarClaudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20240508182955.358628-3-david@redhat.com


Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
parent 3f29f653

arch/s390/kernel/uv.c

+40 −26
Original line number Diff line number Diff line
@@ -266,6 +266,36 @@ static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_str 
	return atomic_read(&mm->context.protected_count) > 1;

}



/*

 * Drain LRU caches: the local one on first invocation and the ones of all

 * CPUs on successive invocations. Returns "true" on the first invocation.

 */

static bool drain_lru(bool *drain_lru_called)

{

	/*

	 * If we have tried a local drain and the folio refcount

	 * still does not match our expected safe value, try with a

	 * system wide drain. This is needed if the pagevecs holding

	 * the page are on a different CPU.

	 */

	if (*drain_lru_called) {

		lru_add_drain_all();

		/* We give up here, don't retry immediately. */

		return false;

	}

	/*

	 * We are here if the folio refcount does not match the

	 * expected safe value. The main culprits are usually

	 * pagevecs. With lru_add_drain() we drain the pagevecs

	 * on the local CPU so that hopefully the refcount will

	 * reach the expected safe value.

	 */

	lru_add_drain();

	*drain_lru_called = true;

	/* The caller should try again immediately */

	return true;

}



/*

 * Requests the Ultravisor to make a page accessible to a guest.

 * If it's brought in the first time, it will be cleared. If
@@ -275,7 +305,7 @@ static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_str 
int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb)

{

	struct vm_area_struct *vma;

	bool local_drain = false;

	bool drain_lru_called = false;

	spinlock_t *ptelock;

	unsigned long uaddr;

	struct folio *folio;
@@ -331,37 +361,21 @@ int gmap_make_secure(struct gmap *gmap, unsigned long gaddr, void *uvcb) 
out:

	mmap_read_unlock(gmap->mm);



	if (rc == -EAGAIN) {

	switch (rc) {

	case -EAGAIN:

		/*

		 * If we are here because the UVC returned busy or partial

		 * completion, this is just a useless check, but it is safe.

		 */

		folio_wait_writeback(folio);

		folio_put(folio);

	} else if (rc == -EBUSY) {

		/*

		 * If we have tried a local drain and the folio refcount

		 * still does not match our expected safe value, try with a

		 * system wide drain. This is needed if the pagevecs holding

		 * the page are on a different CPU.

		 */

		if (local_drain) {

			lru_add_drain_all();

			/* We give up here, and let the caller try again */

		return -EAGAIN;

		}

		/*

		 * We are here if the folio refcount does not match the

		 * expected safe value. The main culprits are usually

		 * pagevecs. With lru_add_drain() we drain the pagevecs

		 * on the local CPU so that hopefully the refcount will

		 * reach the expected safe value.

		 */

		lru_add_drain();

		local_drain = true;

		/* And now we try again immediately after draining */

	case -EBUSY:

		/* Additional folio references. */

		if (drain_lru(&drain_lru_called))

			goto again;

	} else if (rc == -ENXIO) {

		return -EAGAIN;

	case -ENXIO:

		if (gmap_fault(gmap, gaddr, FAULT_FLAG_WRITE))

			return -EFAULT;

		return -EAGAIN;