On Wed, Aug 19, 2015 at 10:21:44AM +0200, Karel Zak wrote: > > It seems that ext4_remount() allows to enable the option by MS_LAZYTIME, > but there is no sb->s_flags &= ~MS_LAZYTIME at all. It seems like a > regression, because old string based solution (handle_mount_opt()) contains: > > case Opt_nolazytime: > sb->s_flags &= ~MS_LAZYTIME; > return 1; > > > From my point of view, a2fd66d06 commit is insufficient, for ext4_remount() > we also need "else" for MS_LAZYTIME: > > if (*flags & MS_LAZYTIME) > sb->s_flags |= MS_LAZYTIME; > else > sb->s_flags &= ~MS_LAZYTIME; > > > The another possibility is that "lazytime" is possible enable only -- > if yes, then handle_mount_opt() should be fixed to not provide > Opt_nolazytime. Yeah, I noticed this when I coded up a2fd66d06, but the problem is that if you are using an older version of mount, then a command which does *not* mention lazytime will silently ending up disabling lazttime. (This a generic problem any time we migrate whether mount program or the kernel is supposed to parse a particular mount option where we toggle state by the presence or absence of a MS_XXX bit; so we could also solve this problem by burning another mount option bit for MS_NOLAZYTIME, but we don't have any bits left.) So the question is which is worse. Causing people who are using newer kernels, but older versions of mount, and who want to use lazytime, to have to specify it on every single "mount -o remount" command (and this includes someone who sets lazytime using rootflags, and now needs to start hacking systemd binaries since there is no longer a shell program to remount file systems read-write --- why I hate systemd, but that's a rant for another forum), or make it impossible for people who are using newer versions of mount who want to disable lazytime. I *think* the number of people who would want to disable lazytime is smaller, which why I made the decision that I did, so my thinking was to leave it this way until the next version of Debian stable ships, and then change the kernel to allow the newer versions of mount to disable lazytime at that point. I suppose I could set up make this be switchable, so people could specify ext4.support_older_mount=1 on the boot command-line option, but this seems really ugly, and then people would need to remember to remove said ugly command-line option from their grub config file when they update to a newer mount command. Blargh; no really good solutions here. Does anyone have any thoughts or suggestions about how to handle this better? - Ted -- 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
