[PATCH 3/4] erofs: insert to managed cache after adding to pcl

[Gao Xiang via Linux-erofs]

From: Gao Xiang <hsiang...@redhat.com>

Previously, it could be some concern to call add_to_page_cache_lru()
with page->mapping == Z_EROFS_MAPPING_STAGING (!= NULL).

In contrast, page->private is used instead now, so partially revert
commit 5ddcee1f3a1c ("erofs: get rid of __stagingpage_alloc helper")
with some adaption for simplicity.

Signed-off-by: Gao Xiang <hsiang...@redhat.com>
---
 fs/erofs/zdata.c | 23 +++++++----------------
 1 file changed, 7 insertions(+), 16 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index afeadf413c2c..edd7325570e1 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1071,28 +1071,19 @@ static struct page *pickup_page_for_submission(struct 
z_erofs_pcluster *pcl,
        put_page(page);
 out_allocpage:
        page = erofs_allocpage(pagepool, gfp | __GFP_NOFAIL);
-       if (!tocache || add_to_page_cache_lru(page, mc, index + nr, gfp)) {
-               /* turn into temporary page if fails */
-               set_page_private(page, Z_EROFS_SHORTLIVED_PAGE);
-               tocache = false;
-       }
-
        if (oldpage != cmpxchg(&pcl->compressed_pages[nr], oldpage, page)) {
-               if (tocache) {
-                       /* since it added to managed cache successfully */
-                       unlock_page(page);
-                       put_page(page);
-               } else {
-                       list_add(&page->lru, pagepool);
-               }
+               list_add(&page->lru, pagepool);
                cond_resched();
                goto repeat;
        }
 
-       if (tocache) {
-               set_page_private(page, (unsigned long)pcl);
-               SetPagePrivate(page);
+       if (!tocache || add_to_page_cache_lru(page, mc, index + nr, gfp)) {
+               /* turn into temporary page if fails */
+               set_page_private(page, Z_EROFS_SHORTLIVED_PAGE);
+               goto out;
        }
+       set_page_private(page, (unsigned long)pcl);
+       SetPagePrivate(page);
 out:   /* the only exit (for tracing and debugging) */
        return page;
 }
-- 
2.24.0