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From: Matthew Wilcox <willy@infradead.org>
To: David Howells <dhowells@redhat.com>
Cc: trond.myklebust@primarydata.com, darrick.wong@oracle.com,
	hch@lst.de, jlayton@kernel.org, sfrench@samba.org,
	torvalds@linux-foundation.org, linux-nfs@vger.kernel.org,
	linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] mm: Make swap_readpage() for SWP_FS_OPS use ->direct_IO() not ->readpage()
Date: Thu, 12 Aug 2021 14:00:14 +0100	[thread overview]
Message-ID: <YRUbXoMzWVX9X/Vf@casper.infradead.org> (raw)
In-Reply-To: <162876947840.3068428.12591293664586646085.stgit@warthog.procyon.org.uk>

On Thu, Aug 12, 2021 at 12:57:58PM +0100, David Howells wrote:

I'm not quite sure why we need the refcount.

> +	refcount_set(&ki->ki_refcnt, 2);
> +	init_sync_kiocb(&ki->iocb, swap_file);
> +	ki->page = page;
> +	ki->iocb.ki_flags = IOCB_DIRECT | IOCB_SWAP;
> +	ki->iocb.ki_pos	= page_file_offset(page);
> +	ki->iocb.ki_filp = get_file(swap_file);
> +	if (!synchronous)
> +		ki->iocb.ki_complete = swapfile_read_complete;
> +
> +	iov_iter_bvec(&to, READ, &bv, 1, PAGE_SIZE);
> +	ret = swap_file->f_mapping->a_ops->direct_IO(&ki->iocb, &to);

After submitting the IO here ...

> +	if (ret != -EIOCBQUEUED)
> +		swapfile_read_complete(&ki->iocb, ret, 0);

We only touch the 'ki' here ... if the caller didn't call read_complete

> +	swapfile_put_kiocb(ki);

Except for here, which is only touched in order to put the refcount.

So why can't swapfile_read_complete() do the work of freeing the ki?


  parent reply	other threads:[~2021-08-12 13:02 UTC|newest]

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-12 11:57 [PATCH 0/2] mm: Fix NFS swapfiles and use DIO read for swapfiles David Howells
2021-08-12 11:57 ` [PATCH 1/2] nfs: Fix write to swapfile failure due to generic_write_checks() David Howells
2021-08-12 11:57 ` [PATCH 2/2] mm: Make swap_readpage() for SWP_FS_OPS use ->direct_IO() not ->readpage() David Howells
2021-08-12 12:21   ` Christoph Hellwig
2021-08-12 12:57   ` David Howells
2021-08-12 15:39     ` Matthew Wilcox
2021-08-12 17:02       ` Christoph Hellwig
2021-08-12 17:48         ` Darrick J. Wong
2021-08-12 18:14           ` Matthew Wilcox
2021-08-12 20:13             ` Theodore Ts'o
2021-08-13  6:54           ` Christoph Hellwig
2021-08-12 13:00   ` Matthew Wilcox [this message]
2021-08-12 13:23   ` David Howells
2021-08-12 13:37   ` David Howells
2021-08-12 13:50     ` Matthew Wilcox
2021-08-12 14:16     ` David Howells
2021-08-12 12:18 ` [PATCH 0/2] mm: Fix NFS swapfiles and use DIO read for swapfiles Christoph Hellwig

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