| Message ID | 20240412142120.220087-3-david@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | s390: PG_arch_1+folio cleanups for uv+hugetlb | expand |
On Fri, 12 Apr 2024 16:21:12 +0200 David Hildenbrand <david@redhat.com> wrote: > Let's factor out handling of LRU cache draining and convert the if-else > chain to a switch-case. > > Signed-off-by: David Hildenbrand <david@redhat.com> it is a little ugly with the bool* parameter, but I can't think of a better/nicer way to do it Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com> > --- > 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;
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;
Let's factor out handling of LRU cache draining and convert the if-else chain to a switch-case. Signed-off-by: David Hildenbrand <david@redhat.com> --- arch/s390/kernel/uv.c | 66 ++++++++++++++++++++++++++----------------- 1 file changed, 40 insertions(+), 26 deletions(-)