linux-kernel - [PATCH v3 25/25] cachefiles: Switch to wait_page

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Date:   Thu, 28 Jan 2021 07:04:04 +0000
From:   "Matthew Wilcox (Oracle)" <willy@...radead.org>
To:     linux-fsdevel@...r.kernel.org, linux-mm@...ck.org
Cc:     "Matthew Wilcox (Oracle)" <willy@...radead.org>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v3 25/25] cachefiles: Switch to wait_page_key

Cachefiles was relying on wait_page_key and wait_bit_key being the
same layout, which is fragile.  Now that wait_page_key is exposed in
the pagemap.h header, we can remove that fragility.  Also switch it
to use the folio directly instead of the page.

Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
---
 fs/cachefiles/rdwr.c    | 13 ++++++-------
 include/linux/pagemap.h |  1 -
 2 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c
index e027c718ca01..b1dbc484a9c7 100644
--- a/fs/cachefiles/rdwr.c
+++ b/fs/cachefiles/rdwr.c
@@ -24,22 +24,21 @@ static int cachefiles_read_waiter(wait_queue_entry_t *wait, unsigned mode,
 		container_of(wait, struct cachefiles_one_read, monitor);
 	struct cachefiles_object *object;
 	struct fscache_retrieval *op = monitor->op;
-	struct wait_bit_key *key = _key;
-	struct page *page = wait->private;
+	struct wait_page_key *key = _key;
+	struct folio *folio = wait->private;
 
 	ASSERT(key);
 
 	_enter("{%lu},%u,%d,{%p,%u}",
 	       monitor->netfs_page->index, mode, sync,
-	       key->flags, key->bit_nr);
+	       key->folio, key->bit_nr);
 
-	if (key->flags != &page->flags ||
-	    key->bit_nr != PG_locked)
+	if (key->folio != folio || key->bit_nr != PG_locked)
 		return 0;
 
-	_debug("--- monitor %p %lx ---", page, page->flags);
+	_debug("--- monitor %p %lx ---", folio, folio->page.flags);
 
-	if (!PageUptodate(page) && !PageError(page)) {
+	if (!FolioUptodate(folio) && !FolioError(folio)) {
 		/* unlocked, not uptodate and not erronous? */
 		_debug("page probably truncated");
 	}
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index f0a601f6d68c..e8d8c66b027e 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -592,7 +592,6 @@ static inline pgoff_t linear_page_index(struct vm_area_struct *vma,
 	return pgoff;
 }
 
-/* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
 struct wait_page_key {
 	struct folio *folio;
 	int bit_nr;
-- 
2.29.2