[PATCH 05/12] KVM: guest_memfd: return locked folio from __kvm_gmem_get_pfn

Paolo Bonzini
2024-07-11T22:28:05Z

Allow testing the up-to-date flag in the caller without taking the
lock again.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
virt/kvm/guest_memfd.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index 76139332f2f3..9271aba9b7b3 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -59,6 +59,7 @@ static int kvm_gmem_prepare_folio(struct inode *inode, pgoff_t index, struct fol
return 0;
}

+/* Returns a locked folio on success. */
static struct folio *kvm_gmem_get_folio(struct inode *inode, pgoff_t index, bool prepare)
{
struct folio *folio;
@@ -551,6 +552,7 @@ void kvm_gmem_unbind(struct kvm_memory_slot *slot)
fput(file);
}

+/* Returns a locked folio on success. */
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)
@@ -584,7 +586,6 @@ __kvm_gmem_get_pfn(struct file *file, struct kvm_memory_slot *slot,
if (max_order)
*max_order = 0;

- folio_unlock(folio);
return folio;
}

@@ -602,6 +603,7 @@ int kvm_gmem_get_pfn(struct kvm *kvm, struct kvm_memory_slot *slot,
if (IS_ERR(folio))
return PTR_ERR(folio);

+ folio_unlock(folio);
return 0;
}
EXPORT_SYMBOL_GPL(kvm_gmem_get_pfn);
@@ -647,6 +649,7 @@ long kvm_gmem_populate(struct kvm *kvm, gfn_t start_gfn, void __user *src, long
break;
}

+ folio_unlock(folio);
if (!IS_ALIGNED(gfn, (1 << max_order)) ||
(npages - i) < (1 << max_order))
max_order = 0;
--
2.43.0