Messages in this thread | | | Date | Mon, 22 Nov 2004 13:53:54 -0800 | From | Andrew Morton <> | Subject | Re: [RFC][PATCH] problem of cont_prepare_write() |
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Anton Altaparmakov <aia21@cam.ac.uk> wrote: > > Would it be ok to modify i_size from prepare_write?
I think so - I seem to recall seeing that done somewhere else...
One thing to watch out for is when to bring the page uptodate. If the page is uptodate then the read() code just won't try to lock it at all. If you increase i_size AND set PG_uptodate too early you could open a window which allows read() to peek at uninitialised data.
But if you set the page uptodate only when its contents really are sane then things should work OK.
If you end up doing
memset(page, 0, N); SetPageUptodate(page);
then I think you'll need an smb_wmb() in between so the read() code sees the above two writes in the correct order. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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