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    SubjectRe: PATCH: killing read_ahead[]


    Alexander Viro wrote:
    >
    > On Wed, 25 Oct 2000, Jeff V. Merkey wrote:
    >
    > > Al,
    > >
    > > Thanks. I'll print this one out and post it on the wall for tonight's
    > > debugging session.
    > [snip]
    > > > (e.g. generic_commit_write have to mess with i_size value to update the
    > ^^^^^^^
    > Ugh. s/have/doesn't have/, indeed. Sorry.

    Wrong syntax:

    :%s/have/doesn't have/gc

    :-)

    >
    > As for tonight's debugging session... I love your optimism, but I would
    > really like to see comments from Linus. For one thing, patch intersects
    > with Rik's one, so I wouldn't expect that to be over tonight (and that's
    > completely aside of the chances that Linus will say "no" to that idea).
    > Linus?
    >
    > ObDevices: the last time when we were talking about the devices-in-pagecache
    > the things stopped on the ->i_size accesses and related ugliness. IMO the
    > main reason of that ugliness was in the attempts to _move_ the i_size to
    > address_space. Which was a patently bad idea. How about mirroring it
    > there? Notice that atomicity is not an issue - we don't have it when we
    > set/modify long long anyway. Said that, I really think that caching the
    > values of these expressions makes sense regardless of device handling.

    In reality, the file has already been extended in prepare_write() and
    the fs's should
    always make this assumption. If the write fails, it should be treated
    as an I/O error. i_size should be assumed to have been extended at this
    point (since the space on the device has
    already been allocated.

    The way aroud this is to enforce i_size updates in prepare_write()
    (this is where I return, "out of space" return codes, and the other FS's
    would probably be ok with some minor
    changes.).

    :-)

    Jeff
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