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    SubjectRe: [PATCHSET] Refactor barrier=/nobarrier flags from fs to block layer
    On 01/26/2011 02:12 AM, Darrick J. Wong wrote:
    > Hello,
    > From what I can tell, most of the filesystems that know how to issue commands
    > to flush the write cache also have some mechanism for the user to override
    > whether or not the filesystem actually issues those flushes. Unfortunately,
    > the term "barrier" is obsolete having been changed into flushes in 2.6.36, and
    > many of the filesystems implement the mount options with slightly different
    > syntaxes (barrier=[0|1|none|flush], nobarrier, etc).
    > This patchset adds to the block layer a sysfs knob that an administrator can
    > use to disable flushes, and removes the mount options from the filesystem code.
    > As a starting point, I'm removing the mount options and flush toggle from
    > jbd2/ext4.
    > Anyway, I'm looking for some feedback about refactoring the barrier/flush
    > control knob into the block layer. It sounds like we want a knob that picks
    > the safest option (issue flushes when supported) unless the administrator
    > decides that it is appropriate to do otherwise. I suspect that there are good
    > arguments for not having a knob at all, and good arguments for a safe knob.
    > However, since I don't see the barrier options being removed en masse, I'm
    > assuming that we still want a knob somewhere. Do we need the ignore_fua knob
    > too? Is this the proper way to deprecate mount options out of filesystems?
    > --D

    Just to be clear, I strongly object to remove the mount options.

    "Barrier" and "poke a control knob in the block" layer are both equally
    mysterious and meaningless to real users, so I do not see this as a gain,


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