On Fri, Oct 24, 2014 at 7:42 AM, Laurent Pinchart
[off-list ref] wrote:

Hi Michal,

On Thursday 23 October 2014 18:53:36 Michal Nazarewicz wrote:

quoted

On Thu, Oct 23 2014, Laurent Pinchart wrote:

quoted

If activation of the CMA area fails its mutex won't be initialized,
leading to an oops at allocation time when trying to lock the mutex. Fix
this by failing allocation if the area hasn't been successfully actived,
and detect that condition by moving the CMA bitmap allocation after page
block reservation completion.

Signed-off-by: Laurent Pinchart
[off-list ref]

Cc: <redacted>  # v3.17
Acked-by: Michal Nazarewicz <redacted>

This patch is good, but how about add a active field in cma struct?
use cma->active to check whether cma is actived successfully.
I think it will make code more clear and readable.
Just my little opinion.

quoted

As a matter of fact, this is present in kernels earlier than 3.17 but in
the 3.17 the code has been moved from drivers/base/dma-contiguous.c to
mm/cma.c so this might require separate stable patch.  I can track this
and prepare a patch if you want.

That could be done, but I'm not sure if it's really worth it. The bug only
occurs when the CMA zone activation fails. I've ran into that case due to a
bug introduced in v3.18-rc1, but this shouldn't be the case for older kernel
versions.

If you think the fix should be backported to stable kernels older than v3.17
please feel free to cook up a patch.

quoted

quoted

---

 mm/cma.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

diff --git a/mm/cma.c b/mm/cma.c
index 963bc4a..16c6650 100644
--- a/mm/cma.c
+++ b/mm/cma.c

@@ -93,11 +93,6 @@ static int __init cma_activate_area(struct cma *cma)
    unsigned i = cma->count >> pageblock_order;
    struct zone *zone;

-   cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
-
-   if (!cma->bitmap)
-           return -ENOMEM;
-
    WARN_ON_ONCE(!pfn_valid(pfn));
    zone = page_zone(pfn_to_page(pfn));

@@ -114,17 +109,17 @@ static int __init cma_activate_area(struct cma *cma)
                     * to be in the same zone.
                     */
                    if (page_zone(pfn_to_page(pfn)) != zone)
-                           goto err;
+                           return -EINVAL;
            }
            init_cma_reserved_pageblock(pfn_to_page(base_pfn));
    } while (--i);

+   cma->bitmap = kzalloc(bitmap_size, GFP_KERNEL);
+   if (!cma->bitmap)
+           return -ENOMEM;
+
    mutex_init(&cma->lock);
    return 0;
-
-err:
-   kfree(cma->bitmap);
-   return -EINVAL;
 }

 static int __init cma_init_reserved_areas(void)

@@ -313,7 +308,7 @@ struct page *cma_alloc(struct cma *cma, int count,

unsigned int align)
    struct page *page = NULL;
    int ret;

-   if (!cma || !cma->count)
+   if (!cma || !cma->count || !cma->bitmap)
            return NULL;

    pr_debug("%s(cma %p, count %d, align %d)\n", __func__, (void *)cma,

--
Regards,

Laurent Pinchart

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