Hugh Dickins wrote:
On Tue, 9 May 2006, Rafael J. Wysocki wrote:
On Tuesday 09 May 2006 09:33, Andrew Morton wrote:
task_struct.mm can sometimes be NULL. This function assumes that it will
never be NULL. That makes it a somewhat risky interface. Are we sure it
can never be NULL?
Well, now it's only called for task == current, but I can add a check.
Better fold it into the (renamed and recommented) page_to_copy,
applying only to current.
The "use" of page_table_lock there is totally bogus. Normally you
need down_read(¤t->mm->mmap_sem) to walk that vma chain; but
I'm guessing you have everything sufficiently frozen here that you
don't need that.
I have to admit that I suggested making this change, because the
function was sufficently generic looking. I guess the mm == NULL
case should logically return 0... unless you did that, making
page_mapped_by_task use current still leaves the burden of ensuring
->mm != NULL on the caller.
But I don't much mind which way the consensus goes.
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