| Message ID | 1700620625-70866-1-git-send-email-alibuda@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | [net,v4] net/smc: avoid data corruption caused by decline | expand |
On 2023/11/22 10:37, D. Wythe wrote: > From: "D. Wythe" <alibuda@linux.alibaba.com> > > We found a data corruption issue during testing of SMC-R on Redis > applications. > > The benchmark has a low probability of reporting a strange error as > shown below. > > "Error: Protocol error, got "\xe2" as reply type byte" > > Finally, we found that the retrieved error data was as follows: > > 0xE2 0xD4 0xC3 0xD9 0x04 0x00 0x2C 0x20 0xA6 0x56 0x00 0x16 0x3E 0x0C > 0xCB 0x04 0x02 0x01 0x00 0x00 0x20 0x00 0x00 0x00 0x00 0x00 0x00 0x00 > 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xE2 > > It is quite obvious that this is a SMC DECLINE message, which means that > the applications received SMC protocol message. > We found that this was caused by the following situations: > > client server > ¦ clc proposal > -------------> > ¦ clc accept > <------------- > ¦ clc confirm > -------------> > wait llc confirm > send llc confirm > ¦failed llc confirm > ¦ x------ > (after 2s)timeout > wait llc confirm rsp > > wait decline > > (after 1s) timeout > (after 2s) timeout > ¦ decline > --------------> > ¦ decline > <-------------- > > As a result, a decline message was sent in the implementation, and this > message was read from TCP by the already-fallback connection. > > This patch double the client timeout as 2x of the server value, > With this simple change, the Decline messages should never cross or > collide (during Confirm link timeout). > > This issue requires an immediate solution, since the protocol updates > involve a more long-term solution. > > Fixes: 0fb0b02bd6fd ("net/smc: adapt SMC client code to use the LLC flow") > Signed-off-by: D. Wythe <alibuda@linux.alibaba.com> > --- LGTM, thanks. Reviewed-by: Wen Gu <guwen@linux.alibaba.com> > net/smc/af_smc.c | 8 ++++++-- > 1 file changed, 6 insertions(+), 2 deletions(-) > > diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c > index abd2667..8615cc0 100644 > --- a/net/smc/af_smc.c > +++ b/net/smc/af_smc.c > @@ -598,8 +598,12 @@ static int smcr_clnt_conf_first_link(struct smc_sock *smc) > struct smc_llc_qentry *qentry; > int rc; > > - /* receive CONFIRM LINK request from server over RoCE fabric */ > - qentry = smc_llc_wait(link->lgr, NULL, SMC_LLC_WAIT_TIME, > + /* Receive CONFIRM LINK request from server over RoCE fabric. > + * Increasing the client's timeout by twice as much as the server's > + * timeout by default can temporarily avoid decline messages of > + * both sides crossing or colliding > + */ > + qentry = smc_llc_wait(link->lgr, NULL, 2 * SMC_LLC_WAIT_TIME, > SMC_LLC_CONFIRM_LINK); > if (!qentry) { > struct smc_clc_msg_decline dclc;
On 22.11.23 03:37, D. Wythe wrote: > From: "D. Wythe" <alibuda@linux.alibaba.com> > > We found a data corruption issue during testing of SMC-R on Redis > applications. > > The benchmark has a low probability of reporting a strange error as > shown below. > > "Error: Protocol error, got "\xe2" as reply type byte" > > Finally, we found that the retrieved error data was as follows: > > 0xE2 0xD4 0xC3 0xD9 0x04 0x00 0x2C 0x20 0xA6 0x56 0x00 0x16 0x3E 0x0C > 0xCB 0x04 0x02 0x01 0x00 0x00 0x20 0x00 0x00 0x00 0x00 0x00 0x00 0x00 > 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0x00 0xE2 > > It is quite obvious that this is a SMC DECLINE message, which means that > the applications received SMC protocol message. > We found that this was caused by the following situations: > > client server > ¦ clc proposal > -------------> > ¦ clc accept > <------------- > ¦ clc confirm > -------------> > wait llc confirm > send llc confirm > ¦failed llc confirm > ¦ x------ > (after 2s)timeout > wait llc confirm rsp > > wait decline > > (after 1s) timeout > (after 2s) timeout > ¦ decline > --------------> > ¦ decline > <-------------- > > As a result, a decline message was sent in the implementation, and this > message was read from TCP by the already-fallback connection. > > This patch double the client timeout as 2x of the server value, > With this simple change, the Decline messages should never cross or > collide (during Confirm link timeout). > > This issue requires an immediate solution, since the protocol updates > involve a more long-term solution. > > Fixes: 0fb0b02bd6fd ("net/smc: adapt SMC client code to use the LLC flow") > Signed-off-by: D. Wythe <alibuda@linux.alibaba.com> > --- Looks good to me! Thank you, D.Wythe! Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Hello: This patch was applied to netdev/net.git (main) by David S. Miller <davem@davemloft.net>: On Wed, 22 Nov 2023 10:37:05 +0800 you wrote: > From: "D. Wythe" <alibuda@linux.alibaba.com> > > We found a data corruption issue during testing of SMC-R on Redis > applications. > > The benchmark has a low probability of reporting a strange error as > shown below. > > [...] Here is the summary with links: - [net,v4] net/smc: avoid data corruption caused by decline https://git.kernel.org/netdev/net/c/e6d71b437abc You are awesome, thank you!
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index abd2667..8615cc0 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -598,8 +598,12 @@ static int smcr_clnt_conf_first_link(struct smc_sock *smc) struct smc_llc_qentry *qentry; int rc; - /* receive CONFIRM LINK request from server over RoCE fabric */ - qentry = smc_llc_wait(link->lgr, NULL, SMC_LLC_WAIT_TIME, + /* Receive CONFIRM LINK request from server over RoCE fabric. + * Increasing the client's timeout by twice as much as the server's + * timeout by default can temporarily avoid decline messages of + * both sides crossing or colliding + */ + qentry = smc_llc_wait(link->lgr, NULL, 2 * SMC_LLC_WAIT_TIME, SMC_LLC_CONFIRM_LINK); if (!qentry) { struct smc_clc_msg_decline dclc;