Messages in this thread | | | Date | Tue, 17 May 2022 18:32:07 +0800 | From | Gao Xiang <> | Subject | Re: [PATCH] erofs: support idmapped mounts |
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On Tue, May 17, 2022 at 11:22:03AM +0200, Christian Brauner wrote: > On Tue, May 17, 2022 at 05:15:02PM +0800, Gao Xiang wrote: > > Hi Christian, > > > > On Tue, May 17, 2022 at 11:06:22AM +0200, Christian Brauner wrote: > > > On Tue, May 17, 2022 at 03:32:10PM +0800, Chao Yu wrote: > > > > This patch enables idmapped mounts for erofs, since all dedicated helpers > > > > for this functionality existsm, so, in this patch we just pass down the > > > > user_namespace argument from the VFS methods to the relevant helpers. > > > > > > > > Simple idmap example on erofs image: > > > > > > > > 1. mkdir dir > > > > 2. touch dir/file > > > > 3. mkfs.erofs erofs.img dir > > > > 4. mount -t erofs -o loop erofs.img /mnt/erofs/ > > > > > > > > 5. ls -ln /mnt/erofs/ > > > > total 0 > > > > -rw-rw-r-- 1 1000 1000 0 May 17 15:26 file > > > > > > > > 6. mount-idmapped --map-mount b:0:1001:1 /mnt/erofs/ /mnt/scratch_erofs/ > > > > > > > > 7. ls -ln /mnt/scratch_erofs/ > > > > total 0 > > > > -rw-rw-r-- 1 65534 65534 0 May 17 15:26 file > > > > > > Your current example maps id 0 in the filesystem to id 1001 in the > > > mount. But since no files with id 0 exist in the filesystem you're > > > illustrating that unmapped ids are correctly reported as overflow{g,u}id. > > > > > > I think what you'd rather want to show is something like this: > > > > > > 5. ls -ln /mnt/erofs/ > > > total 0 > > > -rw-rw-r-- 1 1000 1000 0 May 17 15:26 file > > > > > > 6. mount-idmapped --map-mount b:1000:1001:1 /mnt/erofs/ /mnt/scratch_erofs/ > > > > > > 7. ls -ln /mnt/scratch_erofs/ > > > total 0 > > > -rw-rw-r-- 1 1001 1001 0 May 17 15:26 file > > > > > > where id 1000 in the filesystem maps to id 1001 in the mount.
Yeah, I just manually tested, although some steps assume user 1000 and some steps assume the root user. But it works.
I will rephrase such commit messages when applying later...
Thanks, Gao Xiang
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