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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH 1/3] fs/cachefiles: Remove wait_bit_key layout dependency From: David Howells To: linux-cachefs@redhat.com, linux-afs@lists.infradead.org Cc: "Matthew Wilcox (Oracle)" , Christoph Hellwig , linux-mm@kvack.org, dhowells@redhat.com, "Matthew Wilcox (Oracle)" , Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Date: Tue, 23 Mar 2021 11:53:36 +0000 Message-ID: <161650041625.2445805.664163782892781172.stgit@warthog.procyon.org.uk> In-Reply-To: <161650040278.2445805.7652115256944270457.stgit@warthog.procyon.org.uk> References: <161650040278.2445805.7652115256944270457.stgit@warthog.procyon.org.uk> User-Agent: StGit/0.23 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Stat-Signature: mhgmc3kp4i3sbhau8byf3baf99qpnroa X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 9CB4F90009DE Received-SPF: none (redhat.com>: No applicable sender policy available) receiver=imf19; identity=mailfrom; envelope-from=""; helo=us-smtp-delivery-124.mimecast.com; client-ip=216.205.24.124 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616500425-667639 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: From: Matthew Wilcox (Oracle) 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remove that fragility A comment on the need to maintain structure layout equivalence was added by Linus[1] and that is no longer applicable.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) Reviewed-by: Christoph Hellwig Signed-off-by: David Howells 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] --- fs/cachefiles/rdwr.c | 7 +++---- include/linux/pagemap.h | 1 - 2 files changed, 3 insertions(+), 5 deletions(-) diff --git a/fs/cachefiles/rdwr.c b/fs/cachefiles/rdwr.c index e027c718ca01..8ffc40e84a59 100644 --- a/fs/cachefiles/rdwr.c +++ b/fs/cachefiles/rdwr.c @@ -24,17 +24,16 @@ 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 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); diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index 20225b067583..8f4daac6eb4b 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -559,7 +559,6 @@ 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 page *page; int bit_nr;