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Date: Wed, 22 Oct 2025 06:39:30 +0200
From: Christoph Hellwig <hch@lst.de>
To: Dave Chinner <david@fromorbit.com>
Cc: Kundan Kumar <kundan.kumar@samsung.com>, jaegeuk@kernel.org,
	chao@kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org,
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	anuj20.g@samsung.com, vishak.g@samsung.com, joshi.k@samsung.com
Subject: Re: [PATCH v2 00/16] Parallelizing filesystem writeback
Message-ID: <20251022043930.GC2371@lst.de>
References: <CGME20251014120958epcas5p267c3c9f9dbe6ffc53c25755327de89f9@epcas5p2.samsung.com> <20251014120845.2361-1-kundan.kumar@samsung.com> <aPa7xozr7YbZX0W4@dread.disaster.area>
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On Tue, Oct 21, 2025 at 09:46:30AM +1100, Dave Chinner wrote:
> Not necessarily. The allocator can (and will) select different AGs
> for an inode as the file grows and the AGs run low on space. Once
> they select a different AG for an inode, they don't tend to return
> to the original AG because allocation targets are based on
> contiguous allocation w.r.t. existing adjacent extents, not the AG
> the inode is located in.

Also, as pointed out in the last discussion of this for the RT
subvolume there is zero relation between the AG the inode is in
and the data placement.