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Message-ID: <625bd9c98ad4fd49d7df678f0186129226f77d7d.1747264138.git.ackerleytng@google.com>
Date: Wed, 14 May 2025 16:42:18 -0700
From: Ackerley Tng <ackerleytng@...gle.com>
To: kvm@...r.kernel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
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Subject: [RFC PATCH v2 39/51] KVM: guest_memfd: Merge and truncate on fallocate(PUNCH_HOLE)
Merge and truncate on fallocate(PUNCH_HOLE), but if the file is being
closed, defer merging to folio_put() callback.
Change-Id: Iae26987756e70c83f3b121edbc0ed0bc105eec0d
Signed-off-by: Ackerley Tng <ackerleytng@...gle.com>
---
virt/kvm/guest_memfd.c | 76 +++++++++++++++++++++++++++++++++++++-----
1 file changed, 68 insertions(+), 8 deletions(-)
diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c
index cb426c1dfef8..04b1513c2998 100644
--- a/virt/kvm/guest_memfd.c
+++ b/virt/kvm/guest_memfd.c
@@ -859,6 +859,35 @@ static int kvm_gmem_restructure_folios_in_range(struct inode *inode,
return ret;
}
+static long kvm_gmem_merge_truncate_indices(struct inode *inode, pgoff_t index,
+ size_t nr_pages)
+{
+ struct folio *f;
+ pgoff_t unused;
+ long num_freed;
+
+ unmap_mapping_pages(inode->i_mapping, index, nr_pages, false);
+
+ if (!kvm_gmem_has_safe_refcount(inode->i_mapping, index, nr_pages, &unused))
+ return -EAGAIN;
+
+ f = filemap_get_folio(inode->i_mapping, index);
+ if (IS_ERR(f))
+ return 0;
+
+ /* Leave just filemap's refcounts on the folio. */
+ folio_put(f);
+
+ WARN_ON(kvm_gmem_merge_folio_in_filemap(inode, f));
+
+ num_freed = folio_nr_pages(f);
+ folio_lock(f);
+ truncate_inode_folio(inode->i_mapping, f);
+ folio_unlock(f);
+
+ return num_freed;
+}
+
#else
static inline int kvm_gmem_try_split_folio_in_filemap(struct inode *inode,
@@ -874,6 +903,12 @@ static int kvm_gmem_restructure_folios_in_range(struct inode *inode,
return 0;
}
+static long kvm_gmem_merge_truncate_indices(struct inode *inode, pgoff_t index,
+ size_t nr_pages)
+{
+ return 0;
+}
+
#endif
#else
@@ -1182,8 +1217,10 @@ static long kvm_gmem_truncate_indices(struct address_space *mapping,
*
* Removes folios beginning @index for @nr_pages from filemap in @inode, updates
* inode metadata.
+ *
+ * Return: 0 on success and negative error otherwise.
*/
-static void kvm_gmem_truncate_inode_aligned_pages(struct inode *inode,
+static long kvm_gmem_truncate_inode_aligned_pages(struct inode *inode,
pgoff_t index,
size_t nr_pages)
{
@@ -1191,19 +1228,34 @@ static void kvm_gmem_truncate_inode_aligned_pages(struct inode *inode,
long num_freed;
pgoff_t idx;
void *priv;
+ long ret;
priv = kvm_gmem_allocator_private(inode);
nr_per_huge_page = kvm_gmem_allocator_ops(inode)->nr_pages_in_folio(priv);
+ ret = 0;
num_freed = 0;
for (idx = index; idx < index + nr_pages; idx += nr_per_huge_page) {
- num_freed += kvm_gmem_truncate_indices(
- inode->i_mapping, idx, nr_per_huge_page);
+ if (mapping_exiting(inode->i_mapping) ||
+ !kvm_gmem_has_some_shared(inode, idx, nr_per_huge_page)) {
+ num_freed += kvm_gmem_truncate_indices(
+ inode->i_mapping, idx, nr_per_huge_page);
+ } else {
+ ret = kvm_gmem_merge_truncate_indices(inode, idx,
+ nr_per_huge_page);
+ if (ret < 0)
+ break;
+
+ num_freed += ret;
+ ret = 0;
+ }
}
spin_lock(&inode->i_lock);
inode->i_blocks -= (num_freed << PAGE_SHIFT) / 512;
spin_unlock(&inode->i_lock);
+
+ return ret;
}
/**
@@ -1252,8 +1304,10 @@ static void kvm_gmem_zero_range(struct address_space *mapping,
*
* Removes full (huge)pages from the filemap and zeroing incomplete
* (huge)pages. The pages in the range may be split.
+ *
+ * Return: 0 on success and negative error otherwise.
*/
-static void kvm_gmem_truncate_inode_range(struct inode *inode, loff_t lstart,
+static long kvm_gmem_truncate_inode_range(struct inode *inode, loff_t lstart,
loff_t lend)
{
pgoff_t full_hpage_start;
@@ -1263,6 +1317,7 @@ static void kvm_gmem_truncate_inode_range(struct inode *inode, loff_t lstart,
pgoff_t start;
pgoff_t end;
void *priv;
+ long ret;
priv = kvm_gmem_allocator_private(inode);
nr_per_huge_page = kvm_gmem_allocator_ops(inode)->nr_pages_in_folio(priv);
@@ -1279,10 +1334,11 @@ static void kvm_gmem_truncate_inode_range(struct inode *inode, loff_t lstart,
kvm_gmem_zero_range(inode->i_mapping, start, zero_end);
}
+ ret = 0;
if (full_hpage_end > full_hpage_start) {
nr_pages = full_hpage_end - full_hpage_start;
- kvm_gmem_truncate_inode_aligned_pages(inode, full_hpage_start,
- nr_pages);
+ ret = kvm_gmem_truncate_inode_aligned_pages(
+ inode, full_hpage_start, nr_pages);
}
if (end > full_hpage_end && end > full_hpage_start) {
@@ -1290,6 +1346,8 @@ static void kvm_gmem_truncate_inode_range(struct inode *inode, loff_t lstart,
kvm_gmem_zero_range(inode->i_mapping, zero_start, end);
}
+
+ return ret;
}
static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
@@ -1298,6 +1356,7 @@ static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
pgoff_t start = offset >> PAGE_SHIFT;
pgoff_t end = (offset + len) >> PAGE_SHIFT;
struct kvm_gmem *gmem;
+ long ret;
/*
* Bindings must be stable across invalidation to ensure the start+end
@@ -1308,8 +1367,9 @@ static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
list_for_each_entry(gmem, gmem_list, entry)
kvm_gmem_invalidate_begin_and_zap(gmem, start, end);
+ ret = 0;
if (kvm_gmem_has_custom_allocator(inode)) {
- kvm_gmem_truncate_inode_range(inode, offset, offset + len);
+ ret = kvm_gmem_truncate_inode_range(inode, offset, offset + len);
} else {
/* Page size is PAGE_SIZE, so use optimized truncation function. */
truncate_inode_pages_range(inode->i_mapping, offset, offset + len - 1);
@@ -1320,7 +1380,7 @@ static long kvm_gmem_punch_hole(struct inode *inode, loff_t offset, loff_t len)
filemap_invalidate_unlock(inode->i_mapping);
- return 0;
+ return ret;
}
static long kvm_gmem_allocate(struct inode *inode, loff_t offset, loff_t len)
--
2.49.0.1045.g170613ef41-goog
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