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From: "NeilBrown" <neilb@suse.de>
To: "Matthew Wilcox" <willy@infradead.org>
Cc: "Trond Myklebust" <trond.myklebust@hammerspace.com>,
	"Anna Schumaker" <anna.schumaker@netapp.com>,
	"Chuck Lever" <chuck.lever@oracle.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Mel Gorman" <mgorman@suse.de>,
	linux-nfs@vger.kernel.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 00/13] Repair SWAP-over-NFS
Date: Tue, 16 Nov 2021 14:55:39 +1100	[thread overview]
Message-ID: <163703493923.13692.11352680016082986967@noble.neil.brown.name> (raw)
In-Reply-To: <YZMlk2sVjt5viat2@casper.infradead.org>

On Tue, 16 Nov 2021, Matthew Wilcox wrote:
> On Tue, Nov 16, 2021 at 01:44:04PM +1100, NeilBrown wrote:
> > swap-over-NFS currently has a variety of problems.
> > 
> > Due to a newish test in generic_write_checks(), all writes to swap
> > currently fail.
> 
> And by "currently", you mean "for over two years" (August 2019).

That's about the time scale for "enterprise" releases...
Actually, the earliest patches that impacted swap-over-NFS was more like
4 years ago.  I didn't bother tracking Fixes: tags for everything that
was a fix, as I didn't think it would really help and might encourage
people to backport little bits of the series which I wouldn't recommend.

> Does swap-over-NFS (or any other network filesystem) actually have any
> users, and should we fix it or rip it out?
> 
> 
We have at least one user (why else would I be working on this?).  I
think we have more, though they are presumably still on an earlier
release.

I'd prefer "fix it" over "rip it out".

I don't think any other network filesystem supports swap, but it is
not trivial to grep for.. There must be a 'swap_activate' method, and it
must return 0.  There must also be a direct_IO that works.
The only other network filesystem with swap_activate is cifs.  It
returns 0, but direct_IO returns -EINVAL.

NeilBrown

      reply	other threads:[~2021-11-16  3:55 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-11-16  2:44 [PATCH 00/13] Repair SWAP-over-NFS NeilBrown
2021-11-16  2:44 ` [PATCH 09/13] SUNRPC: improve 'swap' handling: scheduling and PF_MEMALLOC NeilBrown
2021-11-16  2:44 ` [PATCH 11/13] NFS: swap-out must always use STABLE writes NeilBrown
2021-11-16  2:44 ` [PATCH 02/13] NFS: do not take i_rwsem for swap IO NeilBrown
2021-11-16  7:52   ` Christoph Hellwig
2021-11-16 21:50     ` NeilBrown
2021-11-17  5:49       ` Christoph Hellwig
2021-11-16  2:44 ` [PATCH 08/13] NFS: discard NFS_RPC_SWAPFLAGS and RPC_TASK_ROOTCREDS NeilBrown
2021-11-16  2:44 ` [PATCH 01/13] NFS: move generic_write_checks() call from nfs_file_direct_write() to nfs_file_write() NeilBrown
2021-11-16  2:44 ` [PATCH 07/13] SUNRPC: remove scheduling boost for "SWAPPER" tasks NeilBrown
2021-11-16  2:44 ` [PATCH 10/13] NFSv4: keep state manager thread active if swap is enabled NeilBrown
2021-11-16  2:44 ` [PATCH 04/13] SUNRPC/call_alloc: async tasks mustn't block waiting for memory NeilBrown
2021-11-16  2:44 ` [PATCH 05/13] SUNRPC/auth: " NeilBrown
2021-11-16  2:44 ` [PATCH 13/13] MM: use AIO for DIO writes to swap NeilBrown
2021-11-16  2:44 ` [PATCH 06/13] SUNRPC/xprt: async tasks mustn't block waiting for memory NeilBrown
2021-11-16  2:44 ` [PATCH 03/13] MM: reclaim mustn't enter FS for swap-over-NFS NeilBrown
2021-11-16  8:32   ` Christoph Hellwig
2021-11-16 21:35     ` NeilBrown
2021-11-17  5:50       ` Christoph Hellwig
2021-11-18  1:43   ` kernel test robot
2021-11-18  1:43     ` kernel test robot
2021-11-16  2:44 ` [PATCH 12/13] MM: use AIO/DIO for reads from SWP_FS_OPS swap-space NeilBrown
2021-11-16  8:31   ` Christoph Hellwig
2021-11-16 21:46     ` NeilBrown
2021-11-16  3:29 ` [PATCH 00/13] Repair SWAP-over-NFS Matthew Wilcox
2021-11-16  3:55   ` NeilBrown [this message]

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