shmem: convert shmem_write_end() to use a folio

Use a folio internally to shmem_write_end() which saves a number of calls
to compound_head() and lets us get rid of the custom code to zero out the
rest of a THP and supports folios of arbitrary size.

Link: https://lkml.kernel.org/r/20230112131031.1209553-1-willy@infradead.org
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: William Kucharski <william.kucharski@oracle.com>
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/shmem.c b/mm/shmem.c
index bc5c156..c5048c6 100644 (file)
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -2578,33 +2578,23 @@ shmem_write_end(struct file *file, struct address_space *mapping,
                        loff_t pos, unsigned len, unsigned copied,
                        struct page *page, void *fsdata)
 {
+       struct folio *folio = page_folio(page);
        struct inode *inode = mapping->host;
 
        if (pos + copied > inode->i_size)
                i_size_write(inode, pos + copied);
 
-       if (!PageUptodate(page)) {
-               struct page *head = compound_head(page);
-               if (PageTransCompound(page)) {
-                       int i;
-
-                       for (i = 0; i < HPAGE_PMD_NR; i++) {
-                               if (head + i == page)
-                                       continue;
-                               clear_highpage(head + i);
-                               flush_dcache_page(head + i);
-                       }
-               }
-               if (copied < PAGE_SIZE) {
-                       unsigned from = pos & (PAGE_SIZE - 1);
-                       zero_user_segments(page, 0, from,
-                                       from + copied, PAGE_SIZE);
+       if (!folio_test_uptodate(folio)) {
+               if (copied < folio_size(folio)) {
+                       size_t from = offset_in_folio(folio, pos);
+                       folio_zero_segments(folio, 0, from,
+                                       from + copied, folio_size(folio));
                }
-               SetPageUptodate(head);
+               folio_mark_uptodate(folio);
        }
-       set_page_dirty(page);
-       unlock_page(page);
-       put_page(page);
+       folio_mark_dirty(folio);
+       folio_unlock(folio);
+       folio_put(folio);
 
        return copied;
 }