linux-kernel - Re: [PATCH 2/2] ext4: make use of sb_getblk

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Message-ID: <20150702141754.GA9456@thunk.org>
Date:	Thu, 2 Jul 2015 10:17:54 -0400
From:	Theodore Ts'o <tytso@....edu>
To:	Nikolay Borisov <kernel@...p.com>
Cc:	adilger.kernel@...ger.ca, linux-ext4@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] ext4: make use of sb_getblk_gfp

On Thu, Jul 02, 2015 at 09:16:34AM +0300, Nikolay Borisov wrote:
> 
> Just a question that popped to my mind after discussing with a colleague
> - Is GFP_NOFS enough here or should it be GFP_NOIO? Presumably the
> latter is a stronger guarantee that we are not going to hit any
> fs/writeback related code?

GFP_NOFS is fine here; file system code calls the I/O codepaths, but
device driver code doesn't call fs code.  Put another way, if there
are pages that are backed by a block device, which can be cleaned
without going through the FS code paths, it's fine to let that happen
while we are inside file system code.

						- Ted
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