+ iov-remove-copy_page_from_iter_atomic.patch added to mm-new branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: iov: remove copy_page_from_iter_atomic()
has been added to the -mm mm-new branch.  Its filename is
     iov-remove-copy_page_from_iter_atomic.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/iov-remove-copy_page_from_iter_atomic.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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patches, and acceptance into mm-new is a notification for others take
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------------------------------------------------------
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Subject: iov: remove copy_page_from_iter_atomic()
Date: Wed, 14 May 2025 18:06:04 +0100

All callers now use copy_folio_from_iter_atomic(), so convert
copy_page_from_iter_atomic().  While I'm in there, use kmap_local_folio()
and pagefault_disable() instead of kmap_atomic().  That allows preemption
and/or task migration to happen during the copy_from_user().  Also use the
new folio_test_partial_kmap() predicate instead of open-coding it.

Link: https://lkml.kernel.org/r/20250514170607.3000994-4-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Hugh Dickins <hughd@google.com>
Cc: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/uio.h |   10 ++--------
 lib/iov_iter.c      |   29 +++++++++++++----------------
 2 files changed, 15 insertions(+), 24 deletions(-)

--- a/include/linux/uio.h~iov-remove-copy_page_from_iter_atomic
+++ a/include/linux/uio.h
@@ -176,8 +176,6 @@ static inline size_t iov_length(const st
 	return ret;
 }
 
-size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
-				  size_t bytes, struct iov_iter *i);
 void iov_iter_advance(struct iov_iter *i, size_t bytes);
 void iov_iter_revert(struct iov_iter *i, size_t bytes);
 size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t bytes);
@@ -187,6 +185,8 @@ size_t copy_page_to_iter(struct page *pa
 			 struct iov_iter *i);
 size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
 			 struct iov_iter *i);
+size_t copy_folio_from_iter_atomic(struct folio *folio, size_t offset,
+		size_t bytes, struct iov_iter *i);
 
 size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i);
 size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i);
@@ -204,12 +204,6 @@ static inline size_t copy_folio_from_ite
 	return copy_page_from_iter(&folio->page, offset, bytes, i);
 }
 
-static inline size_t copy_folio_from_iter_atomic(struct folio *folio,
-		size_t offset, size_t bytes, struct iov_iter *i)
-{
-	return copy_page_from_iter_atomic(&folio->page, offset, bytes, i);
-}
-
 size_t copy_page_to_iter_nofault(struct page *page, unsigned offset,
 				 size_t bytes, struct iov_iter *i);
 
--- a/lib/iov_iter.c~iov-remove-copy_page_from_iter_atomic
+++ a/lib/iov_iter.c
@@ -457,38 +457,35 @@ size_t iov_iter_zero(size_t bytes, struc
 }
 EXPORT_SYMBOL(iov_iter_zero);
 
-size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
+size_t copy_folio_from_iter_atomic(struct folio *folio, size_t offset,
 		size_t bytes, struct iov_iter *i)
 {
 	size_t n, copied = 0;
-	bool uses_kmap = IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) ||
-			 PageHighMem(page);
 
-	if (!page_copy_sane(page, offset, bytes))
+	if (!page_copy_sane(&folio->page, offset, bytes))
 		return 0;
 	if (WARN_ON_ONCE(!i->data_source))
 		return 0;
 
 	do {
-		char *p;
+		char *to = kmap_local_folio(folio, offset);
 
 		n = bytes - copied;
-		if (uses_kmap) {
-			page += offset / PAGE_SIZE;
-			offset %= PAGE_SIZE;
-			n = min_t(size_t, n, PAGE_SIZE - offset);
-		}
-
-		p = kmap_atomic(page) + offset;
-		n = __copy_from_iter(p, n, i);
-		kunmap_atomic(p);
+		if (folio_test_partial_kmap(folio) &&
+		    n > PAGE_SIZE - offset_in_page(offset))
+			n = PAGE_SIZE - offset_in_page(offset);
+
+		pagefault_disable();
+		n = __copy_from_iter(to, n, i);
+		pagefault_enable();
+		kunmap_local(to);
 		copied += n;
 		offset += n;
-	} while (uses_kmap && copied != bytes && n > 0);
+	} while (copied != bytes && n > 0);
 
 	return copied;
 }
-EXPORT_SYMBOL(copy_page_from_iter_atomic);
+EXPORT_SYMBOL(copy_folio_from_iter_atomic);
 
 static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
 {
_

Patches currently in -mm which might be from willy@infradead.org are

highmem-add-folio_test_partial_kmap.patch
mm-rename-page-index-to-page-__folio_index.patch
ntfs3-use-folios-more-in-ntfs_compress_write.patch
iov-remove-copy_page_from_iter_atomic.patch