Messages in this thread | | | Date | Wed, 10 Jan 2007 20:51:57 -0800 | From | Andrew Morton <> | Subject | Re: O_DIRECT question |
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On Thu, 11 Jan 2007 10:57:06 +0800 Aubrey <aubreylee@gmail.com> wrote:
> Hi all, > > Opening file with O_DIRECT flag can do the un-buffered read/write access. > So if I need un-buffered access, I have to change all of my > applications to add this flag. What's more, Some scripts like "cp > oldfile newfile" still use pagecache and buffer. > Now, my question is, is there a existing way to mount a filesystem > with O_DIRECT flag? so that I don't need to change anything in my > system. If there is no option so far, What is the right way to achieve > my purpose?
Not possible, basically.
O_DIRECT reads and writes must be aligned to the device's block size (usually 512 bytes) in memory addresses, file offsets and read/write request sizes. Very few applications will bother to do that and will hence fail if their files are automagically opened with O_DIRECT.
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