diff mbox series

[v3,1/8] iov_iter: Handle compound highmem pages in copy_page_from_iter_atomic()

Message ID 20230612203910.724378-2-willy@infradead.org (mailing list archive)
State Superseded, archived
Headers show
Series Create large folios in iomap buffered write path | expand

Commit Message

Matthew Wilcox (Oracle) June 12, 2023, 8:39 p.m. UTC 
copy_page_from_iter_atomic() already handles !highmem compound
pages correctly, but if we are passed a highmem compound page,
each base page needs to be mapped & unmapped individually.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
---
 lib/iov_iter.c | 43 ++++++++++++++++++++++++++++---------------
 1 file changed, 28 insertions(+), 15 deletions(-)

Comments

Christoph Hellwig June 13, 2023, 4:52 a.m. UTC | #1 
Looks good:
Matthew Wilcox (Oracle) July 10, 2023, 3:36 a.m. UTC | #2 
On Mon, Jun 12, 2023 at 09:52:52PM -0700, Christoph Hellwig wrote:
> Looks good:
> 

I'm assuming this was intended to have
Reviewed-by: Christoph Hellwig <hch@lst.de>

after it, so I'm taking the liverty of adding that.
diff mbox series

Patch

diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 960223ed9199..1a3fbda0c508 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -857,24 +857,37 @@  size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
 }
 EXPORT_SYMBOL(iov_iter_zero);
 
-size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,
-				  struct iov_iter *i)
+size_t copy_page_from_iter_atomic(struct page *page, unsigned offset,
+		size_t bytes, struct iov_iter *i)
 {
-	char *kaddr = kmap_atomic(page), *p = kaddr + offset;
-	if (!page_copy_sane(page, offset, bytes)) {
-		kunmap_atomic(kaddr);
+	size_t n, copied = 0;
+
+	if (!page_copy_sane(page, offset, bytes))
 		return 0;
-	}
-	if (WARN_ON_ONCE(!i->data_source)) {
-		kunmap_atomic(kaddr);
+	if (WARN_ON_ONCE(!i->data_source))
 		return 0;
-	}
-	iterate_and_advance(i, bytes, base, len, off,
-		copyin(p + off, base, len),
-		memcpy_from_iter(i, p + off, base, len)
-	)
-	kunmap_atomic(kaddr);
-	return bytes;
+
+	do {
+		char *kaddr;
+
+		n = bytes - copied;
+		if (PageHighMem(page)) {
+			page += offset / PAGE_SIZE;
+			offset %= PAGE_SIZE;
+			n = min_t(size_t, n, PAGE_SIZE - offset);
+		}
+
+		kaddr = kmap_atomic(page) + offset;
+		iterate_and_advance(i, n, base, len, off,
+			copyin(kaddr + off, base, len),
+			memcpy_from_iter(i, kaddr + off, base, len)
+		)
+		kunmap_atomic(kaddr);
+		copied += n;
+		offset += n;
+	} while (PageHighMem(page) && copied != bytes && n > 0);
+
+	return copied;
 }
 EXPORT_SYMBOL(copy_page_from_iter_atomic);