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    SubjectRe: [PATCH 05/24] elevate write count open()'d files
    On Mon, Sep 17, 2007 at 11:27:24AM -0700, Dave Hansen wrote:
    > This is the first really tricky patch in the series. It
    > elevates the writer count on a mount each time a
    > non-special file is opened for write.
    > This is not completely apparent in the patch because the
    > two if() conditions in may_open() above the
    > mnt_want_write() call are, combined, equivalent to
    > special_file().
    > There is also an elevated count around the vfs_create()
    > call in open_namei(). The count needs to be kept elevated
    > all the way into the may_open() call. Otherwise, when the
    > write is dropped, a ro->rw transisition could occur. This
    > would lead to having rw access on the newly created file,
    > while the vfsmount is ro. That is bad.
    > Some filesystems forego the use of normal vfs calls to create
    > struct files. Make sure that these users elevate the mnt writer
    > count because they will get __fput(), and we need to make
    > sure they're balanced.


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