Merge tag 'fuse-fixes-6.14-rc4' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse

Pull fuse fixes from Miklos Szeredi:

This contains a fix for fuse readahead.

* tag 'fuse-fixes-6.14-rc4' of ssh://gitolite.kernel.org/pub/scm/linux/kernel/git/mszeredi/fuse:
  fuse: revert back to __readahead_folio() for readahead

Link: https://lore.kernel.org/r/CAJfpegv=+M4hy=hfBKEgBN8vfWULWT9ApbQzCnPopnMqyjpkzA@mail.gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>

Author: brauner

fs/fuse/dev.c

@@ -838,6 +838,12 @@ static int fuse_check_folio(struct folio *folio)
 	return 0;
 }
 
+/*
+ * Attempt to steal a page from the splice() pipe and move it into the
+ * pagecache. If successful, the pointer in @pagep will be updated. The
+ * folio that was originally in @pagep will lose a reference and the new
+ * folio returned in @pagep will carry a reference.
+ */
 static int fuse_try_move_page(struct fuse_copy_state *cs, struct page **pagep)
 {
 	int err;

fs/fuse/file.c

@@ -955,8 +955,10 @@ static void fuse_readpages_end(struct fuse_mount *fm, struct fuse_args *args,
 		fuse_invalidate_atime(inode);
 	}
 
-	for (i = 0; i < ap->num_folios; i++)
+	for (i = 0; i < ap->num_folios; i++) {
 		folio_end_read(ap->folios[i], !err);
+		folio_put(ap->folios[i]);
+	}
 	if (ia->ff)
 		fuse_file_put(ia->ff, false);
 
@@ -1048,7 +1050,14 @@ static void fuse_readahead(struct readahead_control *rac)
 		ap = &ia->ap;
 
 		while (ap->num_folios < cur_pages) {
-			folio = readahead_folio(rac);
+			/*
+			 * This returns a folio with a ref held on it.
+			 * The ref needs to be held until the request is
+			 * completed, since the splice case (see
+			 * fuse_try_move_page()) drops the ref after it's
+			 * replaced in the page cache.
+			 */
+			folio = __readahead_folio(rac);
 			ap->folios[ap->num_folios] = folio;
 			ap->descs[ap->num_folios].length = folio_size(folio);
 			ap->num_folios++;