The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.
To reproduce the conflict and resubmit, you may use the following commands:
git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x 97dfbbd135cb5e4426f37ca53a8fa87eaaa4e376 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2025052622-segment-presuming-e4c6@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^..
Possible dependencies:
thanks,
greg k-h
------------------ original commit in Linus's tree ------------------
From 97dfbbd135cb5e4426f37ca53a8fa87eaaa4e376 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" willy@infradead.org Date: Wed, 14 May 2025 18:06:02 +0100 Subject: [PATCH] highmem: add folio_test_partial_kmap()
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.
Link: https://lkml.kernel.org/r/20250514170607.3000994-2-willy@infradead.org Fixes: 00cdf76012ab ("mm: add memcpy_from_file_folio()") Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org Cc: Al Viro viro@zeniv.linux.org.uk Cc: Hugh Dickins hughd@google.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org
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) {