KVM: guest_memfd: return folio from __kvm_gmem_get_pfn()

Right now this is simply more consistent and avoids use of pfn_to_page()
and put_page().  It will be put to more use in upcoming patches, to
ensure that the up-to-date flag is set at the very end of both the
kvm_gmem_get_pfn() and kvm_gmem_populate() flows.

Reviewed-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 1c509c3512614666f6cf592766ca4e5c3a8b9266..522e1b28e7aeae2b3b2d23b0503f024d796e81ff 100644 (file)
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -541,34 +541,34 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot)
        fput(file);
 }
 
-static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
-                      gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prepare)
+static struct folio *
+__kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
+                  gfn_t gfn, kvm_pfn_t *pfn, int *max_order, bool prepare)
 {
        pgoff_t index = gfn - slot->base_gfn + slot->gmem.pgoff;
        struct kvm_gmem *gmem = file->private_data;
        struct folio *folio;
        struct page *page;
-       int r;
 
        if (file != slot->gmem.file) {
                WARN_ON_ONCE(slot->gmem.file);
-               return -EFAULT;
+               return ERR_PTR(-EFAULT);
        }
 
        gmem = file->private_data;
        if (xa_load(&gmem->bindings, index) != slot) {
                WARN_ON_ONCE(xa_load(&gmem->bindings, index));
-               return -EIO;
+               return ERR_PTR(-EIO);
        }
 
        folio = kvm_gmem_get_folio(file_inode(file), index, prepare);
        if (IS_ERR(folio))
-               return PTR_ERR(folio);
+               return folio;
 
        if (folio_test_hwpoison(folio)) {
                folio_unlock(folio);
                folio_put(folio);
-               return -EHWPOISON;
+               return ERR_PTR(-EHWPOISON);
        }
 
        page = folio_file_page(folio, index);
@@ -577,25 +577,25 @@ static int __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
        if (max_order)
                *max_order = 0;
 
-       r = 0;
-
        folio_unlock(folio);
-
-       return r;
+       return folio;
 }
 
 int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
                     gfn_t gfn, kvm_pfn_t *pfn, int *max_order)
 {
        struct file *file = kvm_gmem_get_file(slot);
-       int r;
+       struct folio *folio;
 
        if (!file)
                return -EFAULT;
 
-       r = __kvm_gmem_get_pfn(file, slot, gfn, pfn, max_order, true);
+       folio = __kvm_gmem_get_pfn(file, slot, gfn, pfn, max_order, true);
        fput(file);
-       return r;
+       if (IS_ERR(folio))
+               return PTR_ERR(folio);
+
+       return 0;
 }
 EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
 
@@ -625,6 +625,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
 
        npages = min_t(ulong, slot->npages - (start_gfn - slot->base_gfn), npages);
        for (i = 0; i < npages; i += (1 << max_order)) {
+               struct folio *folio;
                gfn_t gfn = start_gfn + i;
                kvm_pfn_t pfn;
 
@@ -633,9 +634,11 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
                        break;
                }
 
-               ret = __kvm_gmem_get_pfn(file, slot, gfn, &pfn, &max_order, false);
-               if (ret)
+               folio = __kvm_gmem_get_pfn(file, slot, gfn, &pfn, &max_order, false);
+               if (IS_ERR(folio)) {
+                       ret = PTR_ERR(folio);
                        break;
+               }
 
                if (!IS_ALIGNED(gfn, (1 << max_order)) ||
                    (npages - i) < (1 << max_order))
@@ -644,7 +647,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
                p = src ? src + i * PAGE_SIZE : NULL;
                ret = post_populate(kvm, gfn, pfn, p, max_order, opaque);
 
-               put_page(pfn_to_page(pfn));
+               folio_put(folio);
                if (ret)
                        break;
        }