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Date:   Fri, 14 Feb 2020 14:59:41 +0100
From:   David Sterba <dsterba@suse.cz>
To:     Johannes Thumshirn <johannes.thumshirn@wdc.com>
Cc:     David Sterba <dsterba@suse.cz>,
        Nikolay Borisov <nborisov@suse.com>,
        Josef Bacik <josef@toxicpanda.com>,
        "linux-btrfs @ vger . kernel . org" <linux-btrfs@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH v8 4/8] btrfs: use the page-cache for super block reading
Message-ID: <20200214135941.GW2902@twin.jikos.cz>
Reply-To: dsterba@suse.cz
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        Johannes Thumshirn <johannes.thumshirn@wdc.com>,
        Nikolay Borisov <nborisov@suse.com>,
        Josef Bacik <josef@toxicpanda.com>,
        "linux-btrfs @ vger . kernel . org" <linux-btrfs@vger.kernel.org>,
        Christoph Hellwig <hch@lst.de>
References: <20200213152436.13276-1-johannes.thumshirn@wdc.com>
 <20200213152436.13276-5-johannes.thumshirn@wdc.com>
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On Fri, Feb 14, 2020 at 12:24:32AM +0900, Johannes Thumshirn wrote:
> -	bh = __bread(bdev, bytenr / BTRFS_BDEV_BLOCKSIZE, BTRFS_SUPER_INFO_SIZE);
> -	/*
> -	 * If we fail to read from the underlying devices, as of now
> -	 * the best option we have is to mark it EIO.
> -	 */
> -	if (!bh)
> -		return -EIO;
> +	page = read_cache_page_gfp(mapping, bytenr >> PAGE_SHIFT, GFP_NOFS);
> +	if (IS_ERR(page))
> +		return ERR_PTR(-ENOMEM);

This should be 'return page', read_cache_page_gfp can return more
errors than just ENOMEM.