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s390/uv: gmap_make_secure() cleanups for further changes

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

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20240508182955.358628-3-david@redhat.com
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Alexander Gordeev <agordeev@linux.ibm.com>
This commit is contained in:
David Hildenbrand 2024-05-08 20:29:47 +02:00 committed by Alexander Gordeev
parent 3f29f6537f
commit 68ad4743be
1 changed files with 40 additions and 26 deletions
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66
arch/s390/kernel/uv.c
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@ -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 @@ unlock:
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;