Patch "fs/cachefiles: Remove wait_bit_key layout dependency" has been added to the 5.11-stable tree

Patch "fs/cachefiles: Remove wait_bit_key layout dependency" has been added to the 5.11-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    fs/cachefiles: Remove wait_bit_key layout dependency

to the 5.11-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     fs-cachefiles-remove-wait_bit_key-layout-dependency.patch
and it can be found in the queue-5.11 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


From 39f985c8f667c80a3d1eb19d31138032fa36b09e Mon Sep 17 00:00:00 2001
From: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Date: Sat, 20 Mar 2021 05:40:38 +0000
Subject: fs/cachefiles: Remove wait_bit_key layout dependency

From: Matthew Wilcox (Oracle) <willy@infradead.org>

commit 39f985c8f667c80a3d1eb19d31138032fa36b09e upstream.

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

A comment on the need to maintain structure layout equivalence was added by
Linus[1] and that is no longer applicable.

Fixes: 62906027091f ("mm: add PageWaiters indicating tasks are waiting for a page bit")
Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: kafs-testing@auristor.com
cc: linux-cachefs@redhat.com
cc: linux-mm@kvack.org
Link: https://lore.kernel.org/r/20210320054104.1300774-2-willy@infradead.org/
Link: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3510ca20ece0150af6b10c77a74ff1b5c198e3e2 [1]
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/cachefiles/rdwr.c    |    7 +++----
 include/linux/pagemap.h |    1 -
 2 files changed, 3 insertions(+), 5 deletions(-)

--- a/fs/cachefiles/rdwr.c
+++ b/fs/cachefiles/rdwr.c
@@ -24,17 +24,16 @@ static int cachefiles_read_waiter(wait_q
 		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 wait_page_key *key = _key;
 	struct page *page = wait->private;
 
 	ASSERT(key);
 
 	_enter("{%lu},%u,%d,{%p,%u}",
 	       monitor->netfs_page->index, mode, sync,
-	       key->flags, key->bit_nr);
+	       key->page, key->bit_nr);
 
-	if (key->flags != &page->flags ||
-	    key->bit_nr != PG_locked)
+	if (key->page != page || key->bit_nr != PG_locked)
 		return 0;
 
 	_debug("--- monitor %p %lx ---", page, page->flags);
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -559,7 +559,6 @@ static inline pgoff_t linear_page_index(
 	return pgoff;
 }
 
-/* This has the same layout as wait_bit_key - see fs/cachefiles/rdwr.c */
 struct wait_page_key {
 	struct page *page;
 	int bit_nr;


Patches currently in stable-queue which might be from willy@infradead.org are

queue-5.11/fs-cachefiles-remove-wait_bit_key-layout-dependency.patch