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From: Gao Xiang <xiang@kernel.org>
To: Giuseppe Scrivano <gscrivan@redhat.com>
Cc: linux-erofs@lists.ozlabs.org, linux-fsdevel@vger.kernel.org,
	linux-api@vger.kernel.org, Christian Brauner <brauner@kernel.org>
Subject: Re: [PATCH 2/2] erofs: add ioctl to retrieve the backing source file descriptor
Date: Wed, 8 Jul 2026 20:51:40 +0800	[thread overview]
Message-ID: <ak5H3N5c0ccCwv6i@debian> (raw)
In-Reply-To: <20260708093446.3370200-3-gscrivan@redhat.com>

Hi Giuseppe,

On Wed, Jul 08, 2026 at 11:34:27AM +0200, Giuseppe Scrivano wrote:
> Add EROFS_IOC_GET_SOURCE_FD ioctl that returns a file descriptor to the
> backing image file for file-backed erofs mounts.
> 
> Returns -ENOENT for block-device-backed erofs mounts where there is no
> backing file.
> 
> The UAPI constant is defined in include/uapi/linux/erofs.h.
> 
> Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

Thanks for the patch!

The functionality is indeed useful to users, but similar to overlayfs
one, I'm not sure if the interface is the best way. Since after we add
this to EROFS, we will support this way forever.

I wonder if there could be a way as a common vfs uapi to get source
fds, but I don't have better ideas for now... (that is why I suggested
to Cc linux-api too..)

Thanks,
Gao Xiang

  reply	other threads:[~2026-07-08 12:51 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-07-08  9:34 [PATCH 0/2] erofs: fd-based source and backing file introspection Giuseppe Scrivano
2026-07-08  9:34 ` [PATCH 1/2] erofs: accept source file descriptor via fsconfig Giuseppe Scrivano
2026-07-08 12:45   ` Gao Xiang
2026-07-08  9:34 ` [PATCH 2/2] erofs: add ioctl to retrieve the backing source file descriptor Giuseppe Scrivano
2026-07-08 12:51   ` Gao Xiang [this message]
2026-07-08 14:55   ` Andy Lutomirski
2026-07-08 15:20     ` Giuseppe Scrivano

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