diff mbox series

SUNRPC: Flush dcache only when receiving more seeking

Message ID 20200918125052.2493006-1-zhe.he@windriver.com
State New
Headers show
Series SUNRPC: Flush dcache only when receiving more seeking | expand

Commit Message

He Zhe Sept. 18, 2020, 12:50 p.m. UTC
From: He Zhe <zhe.he@windriver.com>

commit ca07eda33e01 ("SUNRPC: Refactor svc_recvfrom()") introduces
svc_flush_bvec to after sock_recvmsg, but sometimes we receive less than we
seek, which triggers the following warning.

WARNING: CPU: 0 PID: 18266 at include/linux/bvec.h:101 bvec_iter_advance+0x44/0xa8
Attempted to advance past end of bvec iter
Modules linked in: sch_fq_codel openvswitch nsh nf_conncount nf_nat
nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4
CPU: 1 PID: 18266 Comm: nfsd Not tainted 5.9.0-rc5 #1
Hardware name: Xilinx Zynq Platform
[<80112ec0>] (unwind_backtrace) from [<8010c3a8>] (show_stack+0x18/0x1c)
[<8010c3a8>] (show_stack) from [<80755214>] (dump_stack+0x9c/0xd0)
[<80755214>] (dump_stack) from [<80125e64>] (__warn+0xdc/0xf4)
[<80125e64>] (__warn) from [<80126244>] (warn_slowpath_fmt+0x84/0xac)
[<80126244>] (warn_slowpath_fmt) from [<80c88514>] (bvec_iter_advance+0x44/0xa8)
[<80c88514>] (bvec_iter_advance) from [<80c88940>] (svc_tcp_read_msg+0x10c/0x1bc)
[<80c88940>] (svc_tcp_read_msg) from [<80c895d4>] (svc_tcp_recvfrom+0x98/0x63c)
[<80c895d4>] (svc_tcp_recvfrom) from [<80c97bf4>] (svc_handle_xprt+0x48c/0x4f8)
[<80c97bf4>] (svc_handle_xprt) from [<80c98038>] (svc_recv+0x94/0x1e0)
[<80c98038>] (svc_recv) from [<804747cc>] (nfsd+0xf0/0x168)
[<804747cc>] (nfsd) from [<80148a0c>] (kthread+0x144/0x154)
[<80148a0c>] (kthread) from [<80100114>] (ret_from_fork+0x14/0x20)

Fixes: ca07eda33e01 ("SUNRPC: Refactor svc_recvfrom()")
Cc: <stable@vger.kernel.org> # 5.8+
Signed-off-by: He Zhe <zhe.he@windriver.com>
---
 net/sunrpc/svcsock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Chuck Lever Sept. 18, 2020, 4:23 p.m. UTC | #1
> On Sep 18, 2020, at 8:50 AM, zhe.he@windriver.com wrote:
> 
> From: He Zhe <zhe.he@windriver.com>
> 
> commit ca07eda33e01 ("SUNRPC: Refactor svc_recvfrom()") introduces
> svc_flush_bvec to after sock_recvmsg, but sometimes we receive less than we
> seek, which triggers the following warning.
> 
> WARNING: CPU: 0 PID: 18266 at include/linux/bvec.h:101 bvec_iter_advance+0x44/0xa8
> Attempted to advance past end of bvec iter
> Modules linked in: sch_fq_codel openvswitch nsh nf_conncount nf_nat
> nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4
> CPU: 1 PID: 18266 Comm: nfsd Not tainted 5.9.0-rc5 #1
> Hardware name: Xilinx Zynq Platform
> [<80112ec0>] (unwind_backtrace) from [<8010c3a8>] (show_stack+0x18/0x1c)
> [<8010c3a8>] (show_stack) from [<80755214>] (dump_stack+0x9c/0xd0)
> [<80755214>] (dump_stack) from [<80125e64>] (__warn+0xdc/0xf4)
> [<80125e64>] (__warn) from [<80126244>] (warn_slowpath_fmt+0x84/0xac)
> [<80126244>] (warn_slowpath_fmt) from [<80c88514>] (bvec_iter_advance+0x44/0xa8)
> [<80c88514>] (bvec_iter_advance) from [<80c88940>] (svc_tcp_read_msg+0x10c/0x1bc)
> [<80c88940>] (svc_tcp_read_msg) from [<80c895d4>] (svc_tcp_recvfrom+0x98/0x63c)
> [<80c895d4>] (svc_tcp_recvfrom) from [<80c97bf4>] (svc_handle_xprt+0x48c/0x4f8)
> [<80c97bf4>] (svc_handle_xprt) from [<80c98038>] (svc_recv+0x94/0x1e0)
> [<80c98038>] (svc_recv) from [<804747cc>] (nfsd+0xf0/0x168)
> [<804747cc>] (nfsd) from [<80148a0c>] (kthread+0x144/0x154)
> [<80148a0c>] (kthread) from [<80100114>] (ret_from_fork+0x14/0x20)
> 
> Fixes: ca07eda33e01 ("SUNRPC: Refactor svc_recvfrom()")
> Cc: <stable@vger.kernel.org> # 5.8+
> Signed-off-by: He Zhe <zhe.he@windriver.com>
> ---
> net/sunrpc/svcsock.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
> index d5805fa1d066..ea3bc9635448 100644
> --- a/net/sunrpc/svcsock.c
> +++ b/net/sunrpc/svcsock.c
> @@ -277,7 +277,7 @@ static ssize_t svc_tcp_read_msg(struct svc_rqst *rqstp, size_t buflen,
> 		buflen -= seek;
> 	}
> 	len = sock_recvmsg(svsk->sk_sock, &msg, MSG_DONTWAIT);
> -	if (len > 0)
> +	if (len > (seek & PAGE_MASK))

I don't understand how this addresses the WARNING. Can you provide
an example set of inputs that trigger the issue?

Also this change introduces a mixed-sign comparison, so NACK on
this particular patch unless it can be demonstrated that the
implicit type conversion here is benign (I don't think it is,
but I haven't thought through it).


> 		svc_flush_bvec(bvec, len, seek);
> 
> 	/* If we read a full record, then assume there may be more
> -- 
> 2.17.1
> 

--
Chuck Lever
He Zhe Sept. 19, 2020, 1:15 p.m. UTC | #2
On 9/19/20 12:23 AM, Chuck Lever wrote:
>
>> On Sep 18, 2020, at 8:50 AM, zhe.he@windriver.com wrote:
>>
>> From: He Zhe <zhe.he@windriver.com>
>>
>> commit ca07eda33e01 ("SUNRPC: Refactor svc_recvfrom()") introduces
>> svc_flush_bvec to after sock_recvmsg, but sometimes we receive less than we
>> seek, which triggers the following warning.
>>
>> WARNING: CPU: 0 PID: 18266 at include/linux/bvec.h:101 bvec_iter_advance+0x44/0xa8
>> Attempted to advance past end of bvec iter
>> Modules linked in: sch_fq_codel openvswitch nsh nf_conncount nf_nat
>> nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4
>> CPU: 1 PID: 18266 Comm: nfsd Not tainted 5.9.0-rc5 #1
>> Hardware name: Xilinx Zynq Platform
>> [<80112ec0>] (unwind_backtrace) from [<8010c3a8>] (show_stack+0x18/0x1c)
>> [<8010c3a8>] (show_stack) from [<80755214>] (dump_stack+0x9c/0xd0)
>> [<80755214>] (dump_stack) from [<80125e64>] (__warn+0xdc/0xf4)
>> [<80125e64>] (__warn) from [<80126244>] (warn_slowpath_fmt+0x84/0xac)
>> [<80126244>] (warn_slowpath_fmt) from [<80c88514>] (bvec_iter_advance+0x44/0xa8)
>> [<80c88514>] (bvec_iter_advance) from [<80c88940>] (svc_tcp_read_msg+0x10c/0x1bc)
>> [<80c88940>] (svc_tcp_read_msg) from [<80c895d4>] (svc_tcp_recvfrom+0x98/0x63c)
>> [<80c895d4>] (svc_tcp_recvfrom) from [<80c97bf4>] (svc_handle_xprt+0x48c/0x4f8)
>> [<80c97bf4>] (svc_handle_xprt) from [<80c98038>] (svc_recv+0x94/0x1e0)
>> [<80c98038>] (svc_recv) from [<804747cc>] (nfsd+0xf0/0x168)
>> [<804747cc>] (nfsd) from [<80148a0c>] (kthread+0x144/0x154)
>> [<80148a0c>] (kthread) from [<80100114>] (ret_from_fork+0x14/0x20)
>>
>> Fixes: ca07eda33e01 ("SUNRPC: Refactor svc_recvfrom()")
>> Cc: <stable@vger.kernel.org> # 5.8+
>> Signed-off-by: He Zhe <zhe.he@windriver.com>
>> ---
>> net/sunrpc/svcsock.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
>> index d5805fa1d066..ea3bc9635448 100644
>> --- a/net/sunrpc/svcsock.c
>> +++ b/net/sunrpc/svcsock.c
>> @@ -277,7 +277,7 @@ static ssize_t svc_tcp_read_msg(struct svc_rqst *rqstp, size_t buflen,
>> 		buflen -= seek;
>> 	}
>> 	len = sock_recvmsg(svsk->sk_sock, &msg, MSG_DONTWAIT);
>> -	if (len > 0)
>> +	if (len > (seek & PAGE_MASK))
> I don't understand how this addresses the WARNING. Can you provide
> an example set of inputs that trigger the issue?

I was trying to meet the not warning condition in bvec_iter_advance to make
the flushing meaningful.

svc_flush_bvec
    bvec_iter_advance
        WARN_ONCE(bytes > iter->bi_size,...

Here are my steps:
mkdir /root/mount_point/
mount /dev/sda1 /root/mount_point/
systemctl restart nfs-server
exportfs
mount -vvv -t nfs 127.0.0.1:/root/mount_point/ /mnt
cp /bin/bash ./bash.tmp

>
> Also this change introduces a mixed-sign comparison, so NACK on
> this particular patch unless it can be demonstrated that the
> implicit type conversion here is benign (I don't think it is,
> but I haven't thought through it).

Thanks, I didn't notice the different types. What about this?
if (len > 0 && (size_t)len > (seek & PAGE_MASK))


Zhe

>
>
>> 		svc_flush_bvec(bvec, len, seek);
>>
>> 	/* If we read a full record, then assume there may be more
>> -- 
>> 2.17.1
>>
> --
> Chuck Lever
>
>
>
diff mbox series

Patch

diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index d5805fa1d066..ea3bc9635448 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -277,7 +277,7 @@  static ssize_t svc_tcp_read_msg(struct svc_rqst *rqstp, size_t buflen,
 		buflen -= seek;
 	}
 	len = sock_recvmsg(svsk->sk_sock, &msg, MSG_DONTWAIT);
-	if (len > 0)
+	if (len > (seek & PAGE_MASK))
 		svc_flush_bvec(bvec, len, seek);
 
 	/* If we read a full record, then assume there may be more