Messages in this thread | | | Date | Wed, 17 Dec 2014 08:20:21 +0000 | From | Al Viro <> | Subject | Re: [PATCH 2/8] swap: lock i_mutex for swap_writepage direct_IO |
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On Wed, Dec 17, 2014 at 12:06:10AM -0800, Christoph Hellwig wrote:
> > This seems to be more or less equivalent to doing a fcntl(F_SETFL) to > > add the O_DIRECT flag to swap_file (which is a struct file *). Swapoff > > calls filp_close on swap_file, so I don't see why it's necessary to > > clear the flag. > > filp_lose doesn't nessecarily destroy the file structure, there might be > other reference to it, e.g. from dup() or descriptor passing.
Where the hell would those other references come from? We open the damn thing in sys_swapon(), never put it into descriptor tables, etc. and the only reason why we use filp_close() instead of fput() is that we would miss ->flush() otherwise.
Said that, why not simply *open* it with O_DIRECT to start with and be done with that? It's not as if those guys came preopened by caller - swapon(2) gets a pathname and does opening itself.
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