From: Mark Hemment <markhemm@googlemail.com>
To: NeilBrown <neilb@suse.de>
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: Mon, 24 Jan 2022 13:22:15 +0000 [thread overview]
Message-ID: <CANe_+UgUNS81Jho8gLc956LArQk9SzGETusRpzRW-_uPF-fqbg@mail.gmail.com> (raw)
In-Reply-To: <164299611281.26253.15560926531007295753.stgit@noble.brown>
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?
Cheers,
Mark
next prev parent reply other threads:[~2022-01-24 13:29 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 [this message]
2022-01-26 22:51 ` NeilBrown
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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