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    SubjectRe: [PATCH] support O_DIRECT in tmpfs/ramfs
    Hua Zhong wrote:
    > Hi,
    >
    > A while ago there was a discussion about supporting direct-io on tmpfs.
    >
    > Here is a simple patch that does it.
    >
    > 1. A new fs flag FS_RAM_BASED is added and the O_DIRECT flag is ignored
    > if this flag is set (suggestions on a better name?)
    >
    > 2. Specify FS_RAM_BASED for tmpfs and ramfs.
    >
    > 3. When EINVAL is returned only a fput is done. I changed it to go
    > through cleanup_all. But there is still a cleanup problem:
    >
    > If a new file is created and then EINVAL is returned due to O_DIRECT,
    > the file is still left on the disk. I am not exactly sure how to fix
    > it other than adding another fs flag so we could check O_DIRECT
    > support at a much earlier stage. Comments on how to fix it?

    This would seem to create two different sets of O_DIRECT semantics,
    wouldn't it? I think that it would be possible to develop an application
    using one of these FS_RAM_BASED file systems as the testbed, but then be
    surprised when the application failed to work on other file systems such
    as ext3.

    ps
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