Let's factor out handling of LRU cache draining and convert the if-else chain to a switch-case. Reviewed-by: Claudio Imbrenda <imbrenda@xxxxxxxxxxxxx> Signed-off-by: David Hildenbrand <david@xxxxxxxxxx> --- arch/s390/kernel/uv.c | 66 ++++++++++++++++++++++++++----------------- 1 file changed, 40 insertions(+), 26 deletions(-) diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c index 016993e9eb72..25fe28d189df 100644 --- a/arch/s390/kernel/uv.c +++ b/arch/s390/kernel/uv.c @@ -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 */ - goto again; - } else if (rc == -ENXIO) { + return -EAGAIN; + case -EBUSY: + /* Additional folio references. */ + if (drain_lru(&drain_lru_called)) + goto again; + return -EAGAIN; + case -ENXIO: if (gmap_fault(gmap, gaddr, FAULT_FLAG_WRITE)) return -EFAULT; return -EAGAIN; -- 2.45.0