Re: how text page of executable are shared ?

[Andrea Arcangeli <andrea@suse.de>]

On Tue, 28 Mar 2000, Mark Hahn wrote:

>in shrink_mmap:
>                /*
>                 * We can't free pages unless there's just one user
>                 * (count == 2 because we added one ourselves above).
>                 */
>                if (page_count(page) != 2)
>                        goto cache_unlock_continue;
>
>is this wrong, since the page cache holds a reference?

That is right. At that point the miniumum count is 2 (there you could
say also:

	if (page_count < 2)
		BUG()

if you want).

1 reference is in the page cache and 1 reference is for the additional
get_page that shrink_mmap does to avoid the page to be freed under it.
Thus if the page count is 2 we can go ahead and release the page. If the
page count is != 2 (that means >2) we can't play with such page since
somebody else is using it.

Andrea

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