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From: David Howells <dhowells@redhat.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: dhowells@redhat.com, hch@lst.de, trond.myklebust@primarydata.com,
	Jens Axboe <axboe@kernel.dk>,
	"Darrick J. Wong" <djwong@kernel.org>,
	linux-block@vger.kernel.org, linux-xfs@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
	darrick.wong@oracle.com, viro@zeniv.linux.org.uk,
	jlayton@kernel.org, torvalds@linux-foundation.org,
	linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 9/9] mm: Remove swap BIO paths and only use DIO paths
Date: Sat, 25 Sep 2021 16:36:42 +0100	[thread overview]
Message-ID: <2396106.1632584202@warthog.procyon.org.uk> (raw)
In-Reply-To: <YU84rYOyyXDP3wjp@casper.infradead.org>

Matthew Wilcox <willy@infradead.org> wrote:

> On Fri, Sep 24, 2021 at 06:19:23PM +0100, David Howells wrote:
> > Delete the BIO-generating swap read/write paths and always use ->swap_rw().
> > This puts the mapping layer in the filesystem.
> 
> Is SWP_FS_OPS now unused after this patch?

Ummm.  Interesting question - it's only used in swap_set_page_dirty():

int swap_set_page_dirty(struct page *page)
{
	struct swap_info_struct *sis = page_swap_info(page);

	if (data_race(sis->flags & SWP_FS_OPS)) {
		struct address_space *mapping = sis->swap_file->f_mapping;

		VM_BUG_ON_PAGE(!PageSwapCache(page), page);
		return mapping->a_ops->set_page_dirty(page);
	} else {
		return __set_page_dirty_no_writeback(page);
	}
}


> Also, do we still need ->swap_activate and ->swap_deactivate?

f2fs does quite a lot of work in its ->swap_activate(), as does btrfs.  I'm
not sure how necessary it is.  cifs looks like it intends to use it, but it's
not fully implemented yet.  zonefs and nfs do some checking, including hole
checking in nfs's case.  nfs also does some setting up for the sunrpc
transport.

btrfs, cifs, f2fs and nfs all supply ->swap_deactivate() to undo the effects
of the activation.

David


  parent reply	other threads:[~2021-09-25 15:36 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-09-24 17:17 [RFC][PATCH v3 0/9] mm: Use DIO for swap and fix NFS swapfiles David Howells
2021-09-24 17:18 ` [PATCH v3 1/9] mm: Remove the callback func argument from __swap_writepage() David Howells
2021-09-24 17:18 ` [PATCH v3 2/9] mm: Add 'supports' field to the address_space_operations to list features David Howells
2021-09-24 20:10   ` Matthew Wilcox
2021-09-24 17:18 ` [PATCH v3 3/9] mm: Make swap_readpage() void David Howells
2021-09-24 22:07   ` Matthew Wilcox
2021-09-24 17:18 ` [PATCH v3 4/9] Introduce IOCB_SWAP kiocb flag to trigger REQ_SWAP David Howells
2021-09-26 21:56   ` Dave Chinner
2021-09-24 17:18 ` [PATCH v3 5/9] mm: Make swap_readpage() for SWP_FS_OPS use ->swap_rw() not ->readpage() David Howells
2021-09-24 17:18 ` [PATCH v3 6/9] mm: Make __swap_writepage() do async DIO if asked for it David Howells
2021-09-24 17:19 ` [PATCH v3 7/9] nfs: Fix write to swapfile failure due to generic_write_checks() David Howells
2021-09-24 17:19 ` [PATCH v3 8/9] block, btrfs, ext4, xfs: Implement swap_rw David Howells
2021-09-24 17:19 ` [PATCH v3 9/9] mm: Remove swap BIO paths and only use DIO paths David Howells
2021-09-25 14:56   ` Matthew Wilcox
2021-09-25 15:36   ` David Howells [this message]
2021-09-25 17:09     ` Matthew Wilcox
2021-09-26 23:08       ` Damien Le Moal
2021-09-27  1:25         ` Dave Chinner
2021-09-27  1:41           ` Damien Le Moal
2021-09-27 20:03     ` David Sterba
2021-09-25 23:42 ` [RFC][PATCH v3 0/9] mm: Use DIO for swap and fix NFS swapfiles Dave Chinner
2021-09-26  3:10   ` Matthew Wilcox
2021-09-26 22:36     ` Dave Chinner
2021-09-27 20:07 ` David Sterba
2021-09-28  3:11 ` NeilBrown
2021-09-30 15:54   ` Steve French
2021-09-30 15:54     ` Steve French
2021-09-29 15:45 ` David Howells

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