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From: Gao Xiang <gaoxiang25@huawei.com>
To: "yukuai (C)" <yukuai3@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>, <hch@infradead.org>,
	<darrick.wong@oracle.com>, <linux-xfs@vger.kernel.org>,
	<linux-fsdevel@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
	<houtao1@huawei.com>, <zhengbin13@huawei.com>,
	<yi.zhang@huawei.com>
Subject: Re: [RFC] iomap: fix race between readahead and direct write
Date: Sun, 19 Jan 2020 11:01:25 +0800	[thread overview]
Message-ID: <20200119030123.GA223124@architecture4> (raw)
In-Reply-To: <64d617cc-e7fe-6848-03bb-aab3498c9a07@huawei.com>

On Sun, Jan 19, 2020 at 10:51:37AM +0800, yukuai (C) wrote:
> 
> 
> Then, there might be a problem in your implementation.
> if 'use_list' is set to true here:
> +	bool use_list = mapping->a_ops->readpages;
> 
> Your code do not call add_to_page_cache_lru for the page.

IMO, if use_list == true, it will call read_pages -> .readpages
and go just like the current implementation.

->.readahead is just alloc_page and then add_to_page_cache_lru
right after in time and in principle it saves some extra page
allocation.

Thanks,
Gao Xiang

> +		if (use_list) {
> +			page->index = page_offset;
> +			list_add(&page->lru, &page_pool);
> +		} else if (!add_to_page_cache_lru(page, mapping, page_offset,
> +					gfp_mask)) {
> +			if (nr_pages)
> +				read_pages(mapping, filp, &page_pool,
> +						page_offset - nr_pages,
> +						nr_pages);
> +			nr_pages = 0;
> +			continue;
> +		}
> 

  reply	other threads:[~2020-01-19  3:02 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-01-16  6:36 [RFC] iomap: fix race between readahead and direct write yu kuai
2020-01-16 15:32 ` Jan Kara
2020-01-17  9:39   ` yukuai (C)
2020-01-17 11:05     ` Jan Kara
2020-01-17 16:24       ` Darrick J. Wong
2020-01-19  1:25         ` yukuai (C)
2020-01-19  1:17       ` yukuai (C)
2020-01-20 11:42         ` Jan Kara
2020-01-18 23:08 ` Matthew Wilcox
2020-01-19  1:34   ` yukuai (C)
2020-01-19  1:42     ` Matthew Wilcox
2020-01-19  1:57       ` yukuai (C)
2020-01-19  2:51       ` yukuai (C)
2020-01-19  3:01         ` Gao Xiang [this message]
2020-01-19  3:15           ` yukuai (C)
2020-01-19  6:14         ` Matthew Wilcox
2020-01-19  6:55           ` yukuai (C)
2020-01-19  7:58             ` Matthew Wilcox
2020-01-19 11:21               ` yukuai (C)

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