Messages in this thread | | | Date | Wed, 10 Jan 2007 18:29:43 -0500 | From | Shaya Potter <> | Subject | Re: [PATCH 01/24] Unionfs: Documentation |
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Josef Sipek wrote: > On Wed, Jan 10, 2007 at 05:12:15PM +0100, Jan Kara wrote: >> I see :). To me it just sounds as if you want to do remount-read-only >> for source filesystems, which is operation we support perfectly fine, >> and after that create union mount. But I agree you cannot do quite that >> since you need to have write access later from your union mount. So >> maybe it's not so easy as I thought. >> On the other hand, there was some effort to support read-only bind-mounts of >> read-write filesystems (there were even some patches floating around but >> I don't think they got merged) and that should be even closer to what >> you'd need... > > Since the RO flag is per-mount point, how do you guarantee that no one is > messing with the fs? (I haven't looked at the patches that do per mount > ro flag, but this would require some over-arching ro flag - in the > superblock most likely.)
I thought about it, wrote an email, then cancelled it as it won't work.
what I thought was that you could a limited unionfs case would be with X layers read-only and the top layer read-write, and what you would do is dynamically make read only bind mounts for the the X layers and since you control the top layer hide it from the system.
However, read only bind mounts are great if you want a limit a process to accessing the files read-only, as they won't have access to the other vfs_mounts, but it does nothing for the other vfs_mounts that are using that same file system. hence, does us no good. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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