Re: [PATCH 2/2] ext4: make use of sb_getblk_gfp

From: Theodore Ts'o
Date: Thu Jul 02 2015 - 10:18:08 EST


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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