The patch titled
Subject: iov_iter: add copy_page_to_iter_atomic()
has been added to the -mm mm-unstable branch. Its filename is
iov_iter-add-copy_page_to_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_iter-add-copy_page_to_iter_atomic.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Subject: iov_iter: add copy_page_to_iter_atomic()
Date: Tue, 21 Mar 2023 20:54:32 +0000
Provide an atomic context equivalent for copy_page_to_iter(). This
eschews the might_fault() check copies memory in the same way that
copy_page_from_iter_atomic() does.
This functions assumes a non-compound page, however this mimics the
existing behaviour of copy_page_from_iter_atomic(). I am keeping the
behaviour consistent between the two, deferring any such change to an
explicit folio-fication effort.
This is being added in order that an iteratable form of vread() can be
implemented with known prefaulted pages to avoid the need for mutex
locking.
Link: https://lkml.kernel.org/r/31482908634cbb68adafedb65f0b21888c194a1b.1679431886.git.lstoakes@xxxxxxxxx
Signed-off-by: Lorenzo Stoakes <lstoakes@xxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: David Hildenbrand <david@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Liu Shixin <liushixin2@xxxxxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/uio.h | 2 ++
lib/iov_iter.c | 28 ++++++++++++++++++++++++++++
2 files changed, 30 insertions(+)
--- a/include/linux/uio.h~iov_iter-add-copy_page_to_iter_atomic
+++ a/include/linux/uio.h
@@ -154,6 +154,8 @@ static inline struct iovec iov_iter_iove
size_t copy_page_from_iter_atomic(struct page *page, unsigned offset,
size_t bytes, struct iov_iter *i);
+size_t copy_page_to_iter_atomic(struct page *page, unsigned 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);
--- a/lib/iov_iter.c~iov_iter-add-copy_page_to_iter_atomic
+++ a/lib/iov_iter.c
@@ -821,6 +821,34 @@ size_t copy_page_from_iter_atomic(struct
}
EXPORT_SYMBOL(copy_page_from_iter_atomic);
+size_t copy_page_to_iter_atomic(struct page *page, unsigned offset, size_t bytes,
+ struct iov_iter *i)
+{
+ char *kaddr = kmap_local_page(page);
+ char *p = kaddr + offset;
+ size_t copied = 0;
+
+ if (!page_copy_sane(page, offset, bytes) ||
+ WARN_ON_ONCE(i->data_source))
+ goto out;
+
+ if (unlikely(iov_iter_is_pipe(i))) {
+ copied = copy_page_to_iter_pipe(page, offset, bytes, i);
+ goto out;
+ }
+
+ iterate_and_advance(i, bytes, base, len, off,
+ copyout(base, p + off, len),
+ memcpy(base, p + off, len)
+ )
+ copied = bytes;
+
+out:
+ kunmap_local(kaddr);
+ return copied;
+}
+EXPORT_SYMBOL(copy_page_to_iter_atomic);
+
static void pipe_advance(struct iov_iter *i, size_t size)
{
struct pipe_inode_info *pipe = i->pipe;
_
Patches currently in -mm which might be from lstoakes@xxxxxxxxx are
mm-prefer-xxx_page-alloc-free-functions-for-order-0-pages.patch
mm-refactor-do_fault_around.patch
mm-pefer-fault_around_pages-to-fault_around_bytes.patch
maintainers-add-myself-as-vmalloc-reviewer.patch
mm-remove-unused-vmf_insert_mixed_prot.patch
mm-remove-vmf_insert_pfn_xxx_prot-for-huge-page-table-entries.patch
drm-ttm-remove-comment-referencing-now-removed-vmf_insert_mixed_prot.patch
mm-mmap-vma_merge-further-improve-prev-next-vma-naming.patch
mm-mmap-vma_merge-set-next-to-null-if-not-applicable.patch
mm-mmap-vma_merge-extend-invariants-avoid-invalid-res-vma.patch
mm-mmap-vma_merge-init-cleanup-be-explicit-about-the-non-mergeable-case.patch
fs-proc-kcore-avoid-bounce-buffer-for-ktext-data.patch
fs-proc-kcore-convert-read_kcore-to-read_kcore_iter.patch
iov_iter-add-copy_page_to_iter_atomic.patch
mm-vmalloc-convert-vread-to-vread_iter.patch
