* [PATCH v4 1/9] dmapool: fix boundary comparison
@ 2018-11-12 15:41 Tony Battersby
2018-11-13 6:13 ` Matthew Wilcox
0 siblings, 1 reply; 2+ messages in thread
From: Tony Battersby @ 2018-11-12 15:41 UTC (permalink / raw)
To: Matthew Wilcox, Christoph Hellwig, Marek Szyprowski, iommu, linux-mm
Cc: linux-scsi
Fix the boundary comparison when constructing the list of free blocks
for the case that 'size' is a power of two. Since 'boundary' is also a
power of two, that would make 'boundary' a multiple of 'size', in which
case a single block would never cross the boundary. This bug would
cause some of the allocated memory to be wasted (but not leaked).
Example:
size = 512
boundary = 2048
allocation = 4096
Address range
0 - 511
512 - 1023
1024 - 1535
1536 - 2047 *
2048 - 2559
2560 - 3071
3072 - 3583
3584 - 4095 *
Prior to this fix, the address ranges marked with "*" would not have
been used even though they didn't cross the given boundary.
Fixes: e34f44b3517f ("pool: Improve memory usage for devices which can't cross boundaries")
Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
---
Even though I described this as a "fix", it does not seem important
enough to Cc: stable from a strict reading of the stable kernel rules.
IOW, it is not "bothering" anyone.
--- linux/mm/dmapool.c.orig 2018-08-01 17:57:04.000000000 -0400
+++ linux/mm/dmapool.c 2018-08-01 17:57:16.000000000 -0400
@@ -210,7 +210,7 @@ static void pool_initialise_page(struct
do {
unsigned int next = offset + pool->size;
- if (unlikely((next + pool->size) >= next_boundary)) {
+ if (unlikely((next + pool->size) > next_boundary)) {
next = next_boundary;
next_boundary += pool->boundary;
}
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [PATCH v4 1/9] dmapool: fix boundary comparison
2018-11-12 15:41 [PATCH v4 1/9] dmapool: fix boundary comparison Tony Battersby
@ 2018-11-13 6:13 ` Matthew Wilcox
0 siblings, 0 replies; 2+ messages in thread
From: Matthew Wilcox @ 2018-11-13 6:13 UTC (permalink / raw)
To: Tony Battersby
Cc: Christoph Hellwig, Marek Szyprowski, iommu, linux-mm, linux-scsi
On Mon, Nov 12, 2018 at 10:41:34AM -0500, Tony Battersby wrote:
> Fixes: e34f44b3517f ("pool: Improve memory usage for devices which can't cross boundaries")
> Signed-off-by: Tony Battersby <tonyb@cybernetics.com>
Acked-by: Matthew Wilcox <willy@infradead.org>
^ permalink raw reply [flat|nested] 2+ messages in thread
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