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Message-ID: <20140722073005.GT3935@laptop> Date: Tue, 22 Jul 2014 09:30:05 +0200 From: Peter Zijlstra <peterz@...radead.org> To: Gioh Kim <gioh.kim@....com> Cc: Alexander Viro <viro@...iv.linux.org.uk>, Andrew Morton <akpm@...ux-foundation.org>, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>, Jan Kara <jack@...e.cz>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, Theodore Ts'o <tytso@....edu>, Andreas Dilger <adilger.kernel@...ger.ca>, linux-ext4@...r.kernel.org Subject: Re: [PATCH 0/2] new API to allocate buffer-cache for superblock in non-movable area On Tue, Jul 22, 2014 at 02:18:47PM +0900, Gioh Kim wrote: > Hello, > > This patch try to solve problem that a long-lasting page cache of > ext4 superblock disturbs page migration. > > I've been testing CMA feature on my ARM-based platform > and found some pages for page caches cannot be migrated. > Some of them are page caches of superblock of ext4 filesystem. > > Current ext4 reads superblock with sb_bread(). sb_bread() allocates page > from movable area. But the problem is that ext4 hold the page until > it is unmounted. If root filesystem is ext4 the page cannot be migrated forever. > > I introduce a new API for allocating page from non-movable area. > It is useful for ext4 and others that want to hold page cache for a long time. There's no word on why you can't teach ext4 to still migrate that page. For all I know it might be impossible, but at least mention why. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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