Re: [PATCH 1/5] freepgt: free_pgtables use vma list

[Hugh Dickins <hugh@veritas.com>]

Many thanks for the testing.

On Mon, 21 Mar 2005, David S. Miller wrote:
> 
> This adjustment of addr relative to floor is very
> strange, it can advance "addr" (and thus "start")
> past the end of the VMA we are unmapping.

Not strange, it's just trying to skip a pointless iteration.

> In fact, it is miraculious that this free_pud_range()
> calling loop terminates properly!  Actually, it is
> no mystery, since the next PGD address is the same
> for both the original and adjusted value of "addr".
> So the loop terminates after the first iteration.

Miraculous indeed, I hadn't realized those do {} while () loops
were as robust as that.  But it's certainly wrong to have been
calling them once in this case, even if they did recover.

> Anyways, there's the full analysis, what do you make
> of this Hugh? :-)

Much better than I deserve.  Silly me.  This patch should fix it.

[PATCH 6/5] freepgt: fix addr,end check

Fix placing of free_p?d_range's check for addr against end.

Signed-off-by: Hugh Dickins <hugh@veritas.com>

--- freepgt5/mm/memory.c	2005-03-22 04:28:40.000000000 +0000
+++ freepgt6/mm/memory.c	2005-03-22 05:11:05.000000000 +0000
@@ -127,11 +127,6 @@ static inline void free_pmd_range(struct
 	unsigned long next;
 	unsigned long start;
 
-	if (end - 1 > ceiling - 1)
-		end -= PMD_SIZE;
-	if (addr > end - 1)
-		return;
-
 	start = addr;
 	pmd = pmd_offset(pud, addr);
 	do {
@@ -202,7 +197,9 @@ void free_pgd_range(struct mmu_gather **
 			return;
 	}
 	ceiling &= PMD_MASK;
-	if (addr > ceiling - 1)
+	if (end - 1 > ceiling - 1)
+		end -= PMD_SIZE;
+	if (addr > end - 1)
 		return;
 
 	start = addr;