On 12/17/15 8:01 PM, Christoph Anton Mitterer wrote: > On Fri, 2015-12-18 at 09:29 +0800, Qu Wenruo wrote: >> Given that nothing in the documentation implies that the block >>> device itself >>> must remain unchanged on a read-only mount, I don't see any problem >>> which >>> needs fixing. MS_RDONLY rejects user IO; that's all. >> >> And thanks for the info provided by Karel, it's clear that at least >> mount(8) itself already has explain on what ro will do and what it >> won't do. > > I wouldn't really agree, here. At least not from the non-developer side > (and one should hope filesystems and their manpages aren't only made > for fs-devlopers). > > The manpage says: >> ro Mount the filesystem read-only. >> rw Mount the filesystem read-write. > > IMHO, that leaves absolutely unclear, what this actually means, > especially given that most end-users will probably consider the > filesystem and its device being basically "the same". <lots of words snipped> Karel pointed out that recent mount(8) says: > -r, --read-only > Mount the filesystem read-only. A synonym is -o ro. > > Note that, depending on the filesystem type, state and > kernel behavior, the system may still write to the device. For > example, ext3 and ext4 will replay the journal if the > filesystem is dirty. To prevent this kind of write access, you > may want to mount an ext3 or ext4 filesystem with the ro,noload > mount options or set the block device itself to read-only > mode, see the blockdev(8) command. which should leave nothing to the imagination. -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
