From: Christoph Hellwig <hch@infradead.org>
To: Arun Rao <arun.rao.bl@gmail.com>
Cc: hch@infradead.org, Arun <arunraobalappa@gmail.com>,
lenb@kernel.org, linux-btrfs@vger.kernel.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-pm@vger.kernel.org, pavel@kernel.org, rafael@kernel.org
Subject: Re: [PATCH] docs/power: note Btrfs limitation with FIBMAP for swap file offset
Date: Fri, 15 May 2026 06:23:10 -0700 [thread overview]
Message-ID: <agcePmiiO08tVtNb@infradead.org> (raw)
In-Reply-To: <CA+2hknjQ1wLjXdhZWezW=9BwcUhoXhXR1Yi=N8bhce-Qe7+RFw@mail.gmail.com>
On Tue, May 12, 2026 at 03:12:44PM +0530, Arun Rao wrote:
> Understood. My intent was mainly to document the current behaviour
> observed by users on Btrfs systems where filefrag/FIBMAP-based
> guidance fails, and to point users toward the existing btrfs-progs
> tooling.
>
> That said, I understand the concern about encouraging users to rely on
> resume_offset-based workflows in general given the underlying
> fragility of file block mappings on moving or CoW filesystems.
Yes. Can you maybe extend the text a bit to generally warn about this?
I also realized that filefrag uses FIEMAP by default these days and not
just FIBMAP, which is what makes it so dangerous on btrfs. btrfs
smartly does not implement ->bmap, but it does implement FIEMAP in
this weird way mapping to the logical address space.
next prev parent reply other threads:[~2026-05-15 13:23 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-12 9:42 [PATCH] docs/power: note Btrfs limitation with FIBMAP for swap file offset Arun Rao
2026-05-15 13:23 ` Christoph Hellwig [this message]
[not found] <20260512063713.77200-1-arunraobalappa@gmail.com>
2026-05-12 8:01 ` Christoph Hellwig
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