iomap: Copy larger chunks from userspace

If we have a large folio, we can copy in larger chunks than PAGE_SIZE.
Start at the maximum page cache size and shrink by half every time we
hit the "we are short on memory" problem.

Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
index 00e0e94..608cd2e 100644 (file)
--- a/fs/iomap/buffered-io.c
+++ b/fs/iomap/buffered-io.c
@@ -769,6 +769,7 @@ static size_t iomap_write_end(struct iomap_iter *iter, loff_t pos, size_t len,
 static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 {
        loff_t length = iomap_length(iter);
+       size_t chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
        loff_t pos = iter->pos;
        ssize_t written = 0;
        long status = 0;
@@ -777,15 +778,12 @@ static loff_t iomap_write_iter(struct iomap_iter *iter, struct iov_iter *i)
 
        do {
                struct folio *folio;
-               struct page *page;
-               unsigned long offset;   /* Offset into pagecache page */
-               unsigned long bytes;    /* Bytes to write to page */
+               size_t offset;          /* Offset into folio */
+               size_t bytes;           /* Bytes to write to folio */
                size_t copied;          /* Bytes copied from user */
 
-               offset = offset_in_page(pos);
-               bytes = min_t(unsigned long, PAGE_SIZE - offset,
-                                               iov_iter_count(i));
-again:
+               offset = pos & (chunk - 1);
+               bytes = min(chunk - offset, iov_iter_count(i));
                status = balance_dirty_pages_ratelimited_flags(mapping,
                                                               bdp_flags);
                if (unlikely(status))
@@ -815,12 +813,14 @@ again:
                if (iter->iomap.flags & IOMAP_F_STALE)
                        break;
 
-               page = folio_file_page(folio, pos >> PAGE_SHIFT);
-               if (mapping_writably_mapped(mapping))
-                       flush_dcache_page(page);
+               offset = offset_in_folio(folio, pos);
+               if (bytes > folio_size(folio) - offset)
+                       bytes = folio_size(folio) - offset;
 
-               copied = copy_page_from_iter_atomic(page, offset, bytes, i);
+               if (mapping_writably_mapped(mapping))
+                       flush_dcache_folio(folio);
 
+               copied = copy_folio_from_iter_atomic(folio, offset, bytes, i);
                status = iomap_write_end(iter, pos, bytes, copied, folio);
 
                if (unlikely(copied != status))
@@ -836,11 +836,13 @@ again:
                         */
                        if (copied)
                                bytes = copied;
-                       goto again;
+                       if (chunk > PAGE_SIZE)
+                               chunk /= 2;
+               } else {
+                       pos += status;
+                       written += status;
+                       length -= status;
                }
-               pos += status;
-               written += status;
-               length -= status;
        } while (iov_iter_count(i) && length);
 
        if (status == -EAGAIN) {