In commit c749d9b7ebbc (iov_iter: fix copy_page_from_iter_atomic() if
KMAP_LOCAL_FORCE_MAP), Hugh correctly noted that if KMAP_LOCAL_FORCE_MAP
is enabled, we must limit ourselves to PAGE_SIZE bytes per call
to kmap_local(). The same problem exists in memcpy_from_folio(),
memcpy_to_folio(), folio_zero_tail(), folio_fill_tail() and
memcpy_from_file_folio(), so add folio_test_partial_kmap() to do this
more succinctly.
Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Fixes: 00cdf76012ab (mm: add memcpy_from_file_folio())
Cc: stable@xxxxxxxxxxxxxxx
---
include/linux/highmem.h | 10 +++++-----
include/linux/page-flags.h | 7 +++++++
2 files changed, 12 insertions(+), 5 deletions(-)
diff --git a/include/linux/highmem.h b/include/linux/highmem.h
index 5c6bea81a90e..c698f8415675 100644
--- a/include/linux/highmem.h
+++ b/include/linux/highmem.h
@@ -461,7 +461,7 @@ static inline void memcpy_from_folio(char *to, struct folio *folio,
const char *from = kmap_local_folio(folio, offset);
size_t chunk = len;
- if (folio_test_highmem(folio) &&
+ if (folio_test_partial_kmap(folio) &&
chunk > PAGE_SIZE - offset_in_page(offset))
chunk = PAGE_SIZE - offset_in_page(offset);
memcpy(to, from, chunk);
@@ -489,7 +489,7 @@ static inline void memcpy_to_folio(struct folio *folio, size_t offset,
char *to = kmap_local_folio(folio, offset);
size_t chunk = len;
- if (folio_test_highmem(folio) &&
+ if (folio_test_partial_kmap(folio) &&
chunk > PAGE_SIZE - offset_in_page(offset))
chunk = PAGE_SIZE - offset_in_page(offset);
memcpy(to, from, chunk);
@@ -522,7 +522,7 @@ static inline __must_check void *folio_zero_tail(struct folio *folio,
{
size_t len = folio_size(folio) - offset;
- if (folio_test_highmem(folio)) {
+ if (folio_test_partial_kmap(folio)) {
size_t max = PAGE_SIZE - offset_in_page(offset);
while (len > max) {
@@ -560,7 +560,7 @@ static inline void folio_fill_tail(struct folio *folio, size_t offset,
VM_BUG_ON(offset + len > folio_size(folio));
- if (folio_test_highmem(folio)) {
+ if (folio_test_partial_kmap(folio)) {
size_t max = PAGE_SIZE - offset_in_page(offset);
while (len > max) {
@@ -597,7 +597,7 @@ static inline size_t memcpy_from_file_folio(char *to, struct folio *folio,
size_t offset = offset_in_folio(folio, pos);
char *from = kmap_local_folio(folio, offset);
- if (folio_test_highmem(folio)) {
+ if (folio_test_partial_kmap(folio)) {
offset = offset_in_page(offset);
len = min_t(size_t, len, PAGE_SIZE - offset);
} else
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index e6a21b62dcce..3b814ce08331 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -615,6 +615,13 @@ FOLIO_FLAG(dropbehind, FOLIO_HEAD_PAGE)
PAGEFLAG_FALSE(HighMem, highmem)
#endif
+/* Does kmap_local_folio() only allow access to one page of the folio? */
+#ifdef CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP
+#define folio_test_partial_kmap(f) true
+#else
+#define folio_test_partial_kmap(f) folio_test_highmem(f)
+#endif
+
#ifdef CONFIG_SWAP
static __always_inline bool folio_test_swapcache(const struct folio *folio)
{
--
2.47.2
