From: "NeilBrown" <neilb@suse.de>
To: "Mark Hemment" <markhemm@googlemail.com>
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>,
"Christoph Hellwig" <hch@infradead.org>,
"David Howells" <dhowells@redhat.com>,
linux-nfs@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 14/23] NFS: swap IO handling is slightly different for O_DIRECT IO
Date: Thu, 27 Jan 2022 09:51:41 +1100 [thread overview]
Message-ID: <164323750168.5493.12090358551960276049@noble.neil.brown.name> (raw)
In-Reply-To: <CANe_+UgUNS81Jho8gLc956LArQk9SzGETusRpzRW-_uPF-fqbg@mail.gmail.com>
On Tue, 25 Jan 2022, Mark Hemment wrote:
> On Mon, 24 Jan 2022 at 03:53, NeilBrown <neilb@suse.de> wrote:
> >
> > 1/ Taking the i_rwsem for swap IO triggers lockdep warnings regarding
> > possible deadlocks with "fs_reclaim". These deadlocks could, I believe,
> > eventuate if a buffered read on the swapfile was attempted.
> >
> > We don't need coherence with the page cache for a swap file, and
> > buffered writes are forbidden anyway. There is no other need for
> > i_rwsem during direct IO. So never take it for swap_rw()
> >
> > 2/ generic_write_checks() explicitly forbids writes to swap, and
> > performs checks that are not needed for swap. So bypass it
> > for swap_rw().
> >
> > Signed-off-by: NeilBrown <neilb@suse.de>
> > ---
> > fs/nfs/direct.c | 30 +++++++++++++++++++++---------
> > fs/nfs/file.c | 4 ++--
> > include/linux/nfs_fs.h | 4 ++--
> > 3 files changed, 25 insertions(+), 13 deletions(-)
> >
> ...
> > @@ -943,7 +954,8 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter)
> > pos >> PAGE_SHIFT, end);
> > }
> >
> > - nfs_end_io_direct(inode);
> > + if (!swap)
> > + nfs_end_io_direct(inode);
>
> Just above this code diff, there is;
> if (mapping->nrpages) {
> invalidate_inode_pages2_range(mapping,
> pos >> PAGE_SHIFT, end);
> }
>
> This invalidation looks strange/wrong for a NFS swap write. Should it
> be disabled for the swap case?
Yes, I think it should - particularly as we don't take the mutex in the
swap case. Thanks!
This change improves the look of the code too :-)
Thanks,
NeilBrown
next prev parent reply other threads:[~2022-01-26 22:51 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-24 3:48 [PATCH 00/23 V3] Repair SWAP-over_NFS NeilBrown
2022-01-24 3:48 ` [PATCH 05/23] MM: reclaim mustn't enter FS for SWP_FS_OPS swap-space NeilBrown
2022-01-24 7:31 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 03/23] MM: drop swap_set_page_dirty NeilBrown
2022-01-24 7:28 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 14/23] NFS: swap IO handling is slightly different for O_DIRECT IO NeilBrown
2022-01-24 8:58 ` Christoph Hellwig
2022-01-24 13:22 ` Mark Hemment
2022-01-26 22:51 ` NeilBrown [this message]
2022-01-24 3:48 ` [PATCH 22/23] NFS: swap-out must always use STABLE writes NeilBrown
2022-01-26 3:45 ` Trond Myklebust
2022-01-26 21:42 ` NeilBrown
2022-01-24 3:48 ` [PATCH 23/23] SUNRPC: lock against ->sock changing during sysfs read NeilBrown
2022-01-24 3:48 ` [PATCH 08/23] DOC: update documentation for swap_activate and swap_rw NeilBrown
2022-01-24 8:50 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 07/23] MM: perform async writes to SWP_FS_OPS swap-space using ->swap_rw NeilBrown
2022-01-24 8:49 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 02/23] MM: extend block-plugging to cover all swap reads with read-ahead NeilBrown
2022-01-24 7:27 ` Christoph Hellwig
2022-01-26 21:47 ` NeilBrown
2022-01-26 23:09 ` Hugh Dickins
2022-01-27 0:32 ` NeilBrown
2022-01-24 3:48 ` [PATCH 16/23] SUNRPC/auth: async tasks mustn't block waiting for memory NeilBrown
2022-01-24 3:48 ` [PATCH 04/23] MM: move responsibility for setting SWP_FS_OPS to ->swap_activate NeilBrown
2022-01-24 7:30 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 06/23] MM: introduce ->swap_rw and use it for reads from SWP_FS_OPS swap-space NeilBrown
2022-01-24 8:48 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 15/23] SUNRPC/call_alloc: async tasks mustn't block waiting for memory NeilBrown
2022-01-24 3:48 ` [PATCH 20/23] SUNRPC: improve 'swap' handling: scheduling and PF_MEMALLOC NeilBrown
2022-01-24 3:48 ` [PATCH 01/23] MM: create new mm/swap.h header file NeilBrown
2022-02-07 13:51 ` Geert Uytterhoeven
2022-01-24 3:48 ` [PATCH 09/23] MM: submit multipage reads for SWP_FS_OPS swap-space NeilBrown
2022-01-24 8:25 ` kernel test robot
2022-01-24 8:52 ` Christoph Hellwig
2022-01-24 9:27 ` kernel test robot
2022-01-24 13:16 ` Mark Hemment
2022-01-26 22:04 ` NeilBrown
2022-02-08 11:07 ` Geert Uytterhoeven
2022-01-24 3:48 ` [PATCH 12/23] NFS: remove IS_SWAPFILE hack NeilBrown
2022-01-24 8:56 ` Christoph Hellwig
2022-01-24 3:48 ` [PATCH 19/23] NFS: discard NFS_RPC_SWAPFLAGS and RPC_TASK_ROOTCREDS NeilBrown
2022-01-24 3:48 ` [PATCH 17/23] SUNRPC/xprt: async tasks mustn't block waiting for memory NeilBrown
2022-01-24 3:48 ` [PATCH 18/23] SUNRPC: remove scheduling boost for "SWAPPER" tasks NeilBrown
2022-01-24 3:48 ` [PATCH 21/23] NFSv4: keep state manager thread active if swap is enabled NeilBrown
2022-01-24 3:48 ` [PATCH 11/23] VFS: Add FMODE_CAN_ODIRECT file flag NeilBrown
2022-01-24 8:56 ` Christoph Hellwig
2022-01-26 22:14 ` NeilBrown
2022-01-24 3:48 ` [PATCH 10/23] MM: submit multipage write for SWP_FS_OPS swap-space NeilBrown
2022-01-24 8:55 ` Christoph Hellwig
2022-01-24 10:29 ` kernel test robot
2022-01-24 3:48 ` [PATCH 13/23] NFS: rename nfs_direct_IO and use as ->swap_rw NeilBrown
2022-01-24 8:57 ` Christoph Hellwig
2022-02-07 17:55 ` [PATCH 00/23 V3] Repair SWAP-over_NFS Geert Uytterhoeven
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