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    SubjectRe: [RFC v2 0/5] Non-blockling buffered fs read (page cache only)
    Date
    Jonathan Corbet <corbet@lwn.net> writes:

    > On Fri, 19 Sep 2014 13:33:14 -0400
    > Milosz Tanski <milosz@adfin.com> wrote:
    >
    >> > - Non-blocking I/O has long been supported with a well-understood set
    >> > of operations - O_NONBLOCK and fcntl(). Why do we need a different
    >> > mechanism here - one that's only understood in the context of
    >> > buffered file I/O? I assume you didn't want to implement support
    >> > for poll() and all that, but is that a good enough reason to add a
    >> > new Linux-specific non-blocking I/O technique?
    >>
    >> I realized that I didn't answer this question well in my other long
    >> email. O_NONBLOCK doesn't work on files under any commonly used OS,
    >> and people have gotten use to this behavior so I doubt we could change
    >> that without breaking a lot of folks applications.
    >
    > So I'm not contesting this, but I am genuinely curious: do you think
    > there are applications out there requesting non-blocking behavior on
    > regular files that will then break if they actually get non-blocking
    > behavior? I don't suppose you have an example?

    Hi, Jon,

    Back when I tried to introduct O_NONBLOCK for regular files, the squid
    proxy actually broke. Software that dealt with burning optical media
    also broke. See my mail message here for more details:
    https://lkml.org/lkml/2014/9/15/942

    Cheers,
    Jeff


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