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From: "Theodore Y. Ts'o" <>
To: Roman Gushchin <>
	Alexander Viro <>,
	Andreas Dilger <>,
	Andrew Perepechko <>,
	Gioh Kim <>, Jan Kara <>
Subject: Re: [PATCH v2] ext4: use non-movable memory for superblock readahead
Date: Thu, 9 Apr 2020 23:23:44 -0400	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

On Fri, Feb 28, 2020 at 04:14:11PM -0800, Roman Gushchin wrote:
> Since commit a8ac900b8163 ("ext4: use non-movable memory for the
> superblock") buffers for ext4 superblock were allocated using
> the sb_bread_unmovable() helper which allocated buffer heads
> out of non-movable memory blocks. It was necessarily to not block
> page migrations and do not cause cma allocation failures.
> However commit 85c8f176a611 ("ext4: preload block group descriptors")
> broke this by introducing pre-reading of the ext4 superblock.
> The problem is that __breadahead() is using __getblk() underneath,
> which allocates buffer heads out of movable memory.
> It resulted in page migration failures I've seen on a machine
> with an ext4 partition and a preallocated cma area.
> Fix this by introducing sb_breadahead_unmovable() and
> __breadahead_gfp() helpers which use non-movable memory for buffer
> head allocations and use them for the ext4 superblock readahead.

Applied, thanks.  Apologies for not picking this up earlier.

	 	  	    	    	    - Ted

  parent reply	other threads:[~2020-04-10  3:24 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-29  0:14 Roman Gushchin
2020-02-29  7:49 ` Andreas Dilger
2020-03-02 16:37   ` Roman Gushchin
2020-03-03 22:17   ` Roman Gushchin
2020-04-06 17:20   ` Roman Gushchin
2020-04-10  3:23 ` Theodore Y. Ts'o [this message]
2020-04-10 16:12   ` Roman Gushchin

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