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    SubjectRe: make getdents/readdir POSIX compliant wrt mount-point dirent.d ino
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    Ulrich Drepper <drepper <at> gmail.com> writes:

    > I guess that this is really a difficult way to solve. I wouldn't want
    > to pay for something which is hardly ever really used.
    >
    > But there are programs out there which would like to use the inode
    > uniqueness. Therefore the next best thing to do is perhaps to return
    > a flag in the getdents information (in d_type, perhaps) to indicate
    > that this is a mount point and/or that there are multiple ways to
    > access the file in question. Then programs which can use the inode
    > information can be watching for this flag and enter the slow path only
    > if it's set.

    An alternative to a flag in d_type might be setting d_ino to a sentinel value
    (there is plenty of existing code that refuses to use a readdir entry with d_ino
    of 0, so it would have to be something else; but maybe -1 would work). But I
    definitely like your idea of making it obvious to the application (whether by
    d_ino or d_type) when it is necessary to use lstat to validate the inode number,
    and promising that if the flag is not set then d_ino is correct.

    --
    Eric Blake




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