ceph: Convert ceph_readdir_cache_control to store a folio

Pass a folio around instead of a page.  This removes an access to
page->index and a few hidden calls to compound_head().

Signed-off-by: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Link: https://lore.kernel.org/r/20250217185119.430193-5-willy@infradead.org
Tested-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Reviewed-by: Viacheslav Dubeyko <Slava.Dubeyko@ibm.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: Matthew Wilcox (Oracle)

fs/ceph/dir.c

@@ -141,17 +141,18 @@ __dcache_find_get_entry(struct dentry *parent, u64 idx,
 	if (ptr_pos >= i_size_read(dir))
 		return NULL;
 
-	if (!cache_ctl->page || ptr_pgoff != cache_ctl->page->index) {
+	if (!cache_ctl->folio || ptr_pgoff != cache_ctl->folio->index) {
 		ceph_readdir_cache_release(cache_ctl);
-		cache_ctl->page = find_lock_page(&dir->i_data, ptr_pgoff);
-		if (!cache_ctl->page) {
-			doutc(cl, " page %lu not found\n", ptr_pgoff);
+		cache_ctl->folio = filemap_lock_folio(&dir->i_data, ptr_pgoff);
+		if (IS_ERR(cache_ctl->folio)) {
+			cache_ctl->folio = NULL;
+			doutc(cl, " folio %lu not found\n", ptr_pgoff);
 			return ERR_PTR(-EAGAIN);
 		}
 		/* reading/filling the cache are serialized by
-		   i_rwsem, no need to use page lock */
-		unlock_page(cache_ctl->page);
-		cache_ctl->dentries = kmap(cache_ctl->page);
+		   i_rwsem, no need to use folio lock */
+		folio_unlock(cache_ctl->folio);
+		cache_ctl->dentries = kmap_local_folio(cache_ctl->folio, 0);
 	}
 
 	cache_ctl->index = idx & idx_mask;

fs/ceph/inode.c

@@ -1845,10 +1845,9 @@ static int readdir_prepopulate_inodes_only(struct ceph_mds_request *req,
 
 void ceph_readdir_cache_release(struct ceph_readdir_cache_control *ctl)
 {
-	if (ctl->page) {
-		kunmap(ctl->page);
-		put_page(ctl->page);
-		ctl->page = NULL;
+	if (ctl->folio) {
+		folio_release_kmap(ctl->folio, ctl->dentries);
+		ctl->folio = NULL;
 	}
 }
 
@@ -1862,20 +1861,23 @@ static int fill_readdir_cache(struct inode *dir, struct dentry *dn,
 	unsigned idx = ctl->index % nsize;
 	pgoff_t pgoff = ctl->index / nsize;
 
-	if (!ctl->page || pgoff != ctl->page->index) {
+	if (!ctl->folio || pgoff != ctl->folio->index) {
 		ceph_readdir_cache_release(ctl);
+		fgf_t fgf = FGP_LOCK;
+
 		if (idx == 0)
-			ctl->page = grab_cache_page(&dir->i_data, pgoff);
-		else
-			ctl->page = find_lock_page(&dir->i_data, pgoff);
-		if (!ctl->page) {
+			fgf |= FGP_ACCESSED | FGP_CREAT;
+
+		ctl->folio = __filemap_get_folio(&dir->i_data, pgoff,
+				fgf, mapping_gfp_mask(&dir->i_data));
+		if (!ctl->folio) {
 			ctl->index = -1;
 			return idx == 0 ? -ENOMEM : 0;
 		}
 		/* reading/filling the cache are serialized by
-		 * i_rwsem, no need to use page lock */
-		unlock_page(ctl->page);
-		ctl->dentries = kmap(ctl->page);
+		 * i_rwsem, no need to use folio lock */
+		folio_unlock(ctl->folio);
+		ctl->dentries = kmap_local_folio(ctl->folio, 0);
 		if (idx == 0)
 			memset(ctl->dentries, 0, PAGE_SIZE);
 	}

fs/ceph/super.h

@@ -903,7 +903,7 @@ ceph_find_rw_context(struct ceph_file_info *cf)
 }
 
 struct ceph_readdir_cache_control {
-	struct page  *page;
+	struct folio *folio;
 	struct dentry **dentries;
 	int index;
 };