From: Chen Anqing <[email protected]>
To: Ilya Dryomov <[email protected]>
Cc: Jeff Layton <[email protected]>,
Sage Weil <[email protected]>,
Jakub Kicinski <[email protected]>,
[email protected],
[email protected],
[email protected],
[email protected]
Subject: [PATCH] libceph: we should take compound page into account also
Date: Fri, 27 Mar 2020 04:36:30 -0400
Message-Id: <[email protected]>
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 <[email protected]>
---
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;
--
2.18.2
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On Fri, Mar 27, 2020 at 9:36 AM <[email protected]> wrote:
>
> From: Chen Anqing <[email protected]>
> To: Ilya Dryomov <[email protected]>
> Cc: Jeff Layton <[email protected]>,
> Sage Weil <[email protected]>,
> Jakub Kicinski <[email protected]>,
> [email protected],
> [email protected],
> [email protected],
> [email protected]
> Subject: [PATCH] libceph: we should take compound page into account also
> Date: Fri, 27 Mar 2020 04:36:30 -0400
> Message-Id: <[email protected]>
> 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 <[email protected]>
> ---
> 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