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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