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[71.69.161.161]) by smtp.gmail.com with ESMTPSA id af79cd13be357-7e87e0224c1sm122738985a.6.2025.08.15.08.06.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 Aug 2025 08:06:47 -0700 (PDT) From: Sohan Kunkerkar To: miklos@szeredi.hu, amir73il@gmail.com Cc: linux-unionfs@vger.kernel.org, linux-kernel@vger.kernel.org, Sohan Kunkerkar Subject: [PATCH] overlayfs: add FS_ALLOW_IDMAP flag to enable idmapped mounts Date: Fri, 15 Aug 2025 11:06:29 -0400 Message-ID: <20250815150629.2097562-1-sohank2602@gmail.com> X-Mailer: git-send-email 2.50.1 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" OverlayFS already has comprehensive support for idmapped mounts through its ovl_copyattr() function and proper mnt_idmap() handling throughout the codebase. The infrastructure correctly maps UIDs/GIDs from idmapped upper and lower layers. However, the filesystem was missing the FS_ALLOW_IDMAP flag, which caused mount_setattr() calls with MOUNT_ATTR_IDMAP to fail with -EINVAL. This change enables idmapped mount support by adding the FS_ALLOW_IDMAP flag to the overlayfs file_system_type, allowing containers and other applications to use idmapped mounts with overlay filesystems. Signed-off-by: Sohan Kunkerkar --- fs/overlayfs/super.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c index e19940d64..c628f9179 100644 --- a/fs/overlayfs/super.c +++ b/fs/overlayfs/super.c @@ -1516,7 +1516,7 @@ struct file_system_type ovl_fs_type =3D { .name =3D "overlay", .init_fs_context =3D ovl_init_fs_context, .parameters =3D ovl_parameter_spec, - .fs_flags =3D FS_USERNS_MOUNT, + .fs_flags =3D FS_USERNS_MOUNT | FS_ALLOW_IDMAP, .kill_sb =3D kill_anon_super, }; MODULE_ALIAS_FS("overlay"); --=20 2.50.1