Re:
From: Ilya Dryomov <idryomov@gmail.com>
Date: 2020-03-27 08:59:54
Also in:
ceph-devel, lkml
On Fri, Mar 27, 2020 at 9:36 AM [off-list ref] wrote:
quoted hunk
From: Chen Anqing <redacted> To: Ilya Dryomov <idryomov@gmail.com> Cc: Jeff Layton <jlayton@kernel.org>, Sage Weil [off-list ref], Jakub Kicinski [off-list ref], ceph-devel@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, chenanqing@oppo.com Subject: [PATCH] libceph: we should take compound page into account also Date: Fri, 27 Mar 2020 04:36:30 -0400 Message-Id: [off-list ref] X-Mailer: git-send-email 2.18.2 the patch is occur at a real crash,which slab is come from a compound page,so we need take the compound page into account also. fixed commit 7e241f647dc7 ("libceph: fall back to sendmsg for slab pages")' Signed-off-by: Chen Anqing <redacted> --- net/ceph/messenger.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)diff --git a/net/ceph/messenger.c b/net/ceph/messenger.c index f8ca5edc5f2c..e08c1c334cd9 100644 --- a/net/ceph/messenger.c +++ b/net/ceph/messenger.c@@ -582,7 +582,7 @@ static int ceph_tcp_sendpage(struct socket *sock, struct page *page, * coalescing neighboring slab objects into a single frag which * triggers one of hardened usercopy checks. */ - if (page_count(page) >= 1 && !PageSlab(page)) + if (page_count(page) >= 1 && !PageSlab(compound_head(page))) sendpage = sock->ops->sendpage; else sendpage = sock_no_sendpage;
Hi Chen,
AFAICT compound pages should already be taken into account, because
PageSlab is defined as:
__PAGEFLAG(Slab, slab, PF_NO_TAIL)
#define __PAGEFLAG(uname, lname, policy) \
TESTPAGEFLAG(uname, lname, policy) \
__SETPAGEFLAG(uname, lname, policy) \
__CLEARPAGEFLAG(uname, lname, policy)
#define TESTPAGEFLAG(uname, lname, policy) \
static __always_inline int Page##uname(struct page *page) \
{ return test_bit(PG_##lname, &policy(page, 0)->flags); }
and PF_NO_TAIL policy is defined as:
#define PF_NO_TAIL(page, enforce) ({ \
VM_BUG_ON_PGFLAGS(enforce && PageTail(page), page); \
PF_POISONED_CHECK(compound_head(page)); })
So compound_head() is called behind the scenes.
Could you please explain what crash did you observe in more detail?
Perhaps you backported this patch to an older kernel?
Thanks,
Ilya