From: "Mkrtchyan, Tigran" <tigran.mkrtchyan@desy.de>
To: Trond Myklebust <trondmy@gmail.com>
Cc: Olga Kornievskaia <aglo@umich.edu>,
linux-nfs <linux-nfs@vger.kernel.org>
Subject: Re: [PATCH v2 00/28] Fix up soft mounts for NFSv4.x
Date: Wed, 3 Apr 2019 22:51:27 +0200 (CEST) [thread overview]
Message-ID: <995086222.2639035.1554324687132.JavaMail.zimbra@desy.de> (raw)
In-Reply-To: <1778bf6d42f956d0226fe05683b385654b4c0109.camel@gmail.com>
Hi Trond,
----- Original Message -----
> From: "Trond Myklebust" <trondmy@gmail.com>
> To: "Olga Kornievskaia" <aglo@umich.edu>
> Cc: "linux-nfs" <linux-nfs@vger.kernel.org>
> Sent: Tuesday, April 2, 2019 8:28:38 PM
> Subject: Re: [PATCH v2 00/28] Fix up soft mounts for NFSv4.x
> On Mon, 2019-04-01 at 12:54 -0400, Olga Kornievskaia wrote:
>> On Fri, Mar 29, 2019 at 6:02 PM Trond Myklebust <trondmy@gmail.com>
>> wrote:
>> > This patchset aims to make soft mounts a viable option for NFSv4
>> > clients
>> > by minimising the risk of false positive timeouts, while allowing
>> > for
>> > faster failover of reads and writes once a timeout is actually
>> > observed.
>> >
>> > The patches rely on the NFS server correctly implementing the
>> > contract
>> > specified in RFC7530 section 3.1.1 with respect to not dropping
>> > requests
>> > while the transport connection is up. When this is the case, the
>> > client
>> > can safely assume that if the request has not received a reply
>> > after
>> > transmitting a RPC request, it is not because the request was
>> > dropped,
>> > but rather is due to congestion, or slow processing on the server.
>> > IOW: as long as the connection remains up, there is no need for
>> > requests
>> > to time out.
>> >
>> > The patches break down roughly as follows:
>> > - A set of patches to clean up the RPC engine timeouts, and ensure
>> > they
>> > are accurate.
>> > - A set of patches to change the 'soft' mount semantics for
>> > NFSv4.x.
>> > - A set of patches to add a new 'softerr' mount option that works
>> > like
>> > soft, but explicitly signals timeouts using the ETIMEDOUT error
>> > code
>> > rather than using EIO. This allows applications to tune their
>> > behaviour (e.g. by failing over to a different server) if a
>> > timeout
>> > occurs.
>>
>> I'm just curious why would an application be aware of a different
>> server to connect to and an NFS layer would not be? I'm also curious
>> wouldn't it break application that typically expect to get an EIO
>> errors? Do all system calls allow to return ETIMEDOUT error?
>
> This is why it is a separate mount option. ...and actually most
> applications blow up when they get EIO as well. However you can imagine
> an application that might decide to retry if it hits an ETIMEDOUT,
> while failing if it hits an EIO.
What is the reason of introducing new error code for IO operations, which
is not in the list of POSIX specified values for read(2) and write(2). Is
there expected application behavior change compared to EAGAIN?
I would like to use the opportunity to bring the topic of O_NONBLOCK open(2)
flag for offline files.
Tigran.
>
> Cheers
> Trond
next prev parent reply other threads:[~2019-04-03 20:57 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-29 21:59 [PATCH v2 00/28] Fix up soft mounts for NFSv4.x Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 01/28] SUNRPC: Fix up task signalling Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 02/28] SUNRPC: Refactor rpc_restart_call/rpc_restart_call_prepare Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 03/28] SUNRPC: Refactor xprt_request_wait_receive() Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 04/28] SUNRPC: Refactor rpc_sleep_on() Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 05/28] SUNRPC: Remove unused argument 'action' from rpc_sleep_on_priority() Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 06/28] SUNRPC: Add function rpc_sleep_on_timeout() Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 07/28] SUNRPC: Fix up tracking of timeouts Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 08/28] SUNRPC: Simplify queue timeouts using timer_reduce() Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 09/28] SUNRPC: Declare RPC timers as TIMER_DEFERRABLE Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 10/28] SUNRPC: Ensure that the transport layer respect major timeouts Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 11/28] SUNRPC: Add tracking of RPC level errors Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 12/28] SUNRPC: Make "no retrans timeout" soft tasks behave like softconn for timeouts Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 13/28] SUNRPC: Start the first major timeout calculation at task creation Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 14/28] SUNRPC: Ensure to ratelimit the "server not responding" syslog messages Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 15/28] SUNRPC: Add the 'softerr' rpc_client flag Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 16/28] NFS: Consider ETIMEDOUT to be a fatal error Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 17/28] NFS: Move internal constants out of uapi/linux/nfs_mount.h Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 18/28] NFS: Add a mount option "softerr" to allow clients to see ETIMEDOUT errors Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 19/28] NFS: Don't interrupt file writeout due to fatal errors Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 20/28] NFS: Don't call generic_error_remove_page() while holding locks Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 21/28] NFS: Don't inadvertently clear writeback errors Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 22/28] NFS: Replace custom error reporting mechanism with generic one Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 23/28] NFS: Fix up NFS I/O subrequest creation Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 24/28] NFS: Remove unused argument from nfs_create_request() Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 25/28] pNFS: Add tracking to limit the number of pNFS retries Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 26/28] NFS: Allow signal interruption of NFS4ERR_DELAYed operations Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 27/28] NFS: Add a helper to return a pointer to the open context of a struct nfs_page Trond Myklebust
2019-03-29 21:59 ` [PATCH v2 28/28] NFS: Remove redundant open context from nfs_page Trond Myklebust
2019-04-05 19:42 ` Anna Schumaker
2019-04-06 14:14 ` Trond Myklebust
2019-04-08 17:11 ` Anna Schumaker
2019-04-08 18:13 ` Trond Myklebust
2019-04-08 18:15 ` Anna Schumaker
2019-04-01 16:27 ` [PATCH v2 25/28] pNFS: Add tracking to limit the number of pNFS retries Olga Kornievskaia
2019-04-02 18:23 ` Trond Myklebust
2019-04-01 16:54 ` [PATCH v2 00/28] Fix up soft mounts for NFSv4.x Olga Kornievskaia
2019-04-02 18:28 ` Trond Myklebust
2019-04-03 20:51 ` Mkrtchyan, Tigran [this message]
2019-04-03 21:13 ` Trond Myklebust
2019-04-03 21:59 ` Mkrtchyan, Tigran
2019-04-03 22:10 ` Trond Myklebust
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