Subject: [PATCH] mm: dmapool: use provided gfp flags for all dma_alloc_coherent() calls

From: [email-masked] (Soeren Moch)
Date: Mon, 12 Nov 2012 10:48:02 +0100

On 11.11.2012 18:22, Andrew Lunn wrote:
 > On Thu, Nov 08, 2012 at 07:38:57AM +0100, Marek Szyprowski wrote:
 >> dmapool always calls dma_alloc_coherent() with GFP_ATOMIC flag, 
regardless
 >> the flags provided by the caller. This causes excessive pruning of
 >> emergency memory pools without any good reason. This patch changes 
the code
 >> to correctly use gfp flags provided by the dmapool caller. This should
 >> solve the dmapool usage on ARM architecture, where GFP_ATOMIC DMA
 >> allocations can be served only from the special, very limited memory 
pool.
 >>
 >> Reported-by: Soren Moch <[email-masked]>
Please use
Reported-by: Soeren Moch <[email-masked]>

 >> Reported-by: Thomas Petazzoni <[email-masked]>
 >> Signed-off-by: Marek Szyprowski <[email-masked]>
 >
 > Tested-by: Andrew Lunn <[email-masked]>
 >
 > I tested this on a Kirkwood QNAP after removing the call to
 > init_dma_coherent_pool_size().
 >
 >     Andrew

Tested-by: Soeren Moch <[email-masked]>

Now I had a chance to test this patch on my Kirkwood guruplug
system with linux-3.6.6 . It is running much better now, but with the
original 256K coherent pool size I still see errors after several hours
of runtime:

Nov 12 09:42:32 guru kernel: ERROR: 256 KiB atomic DMA coherent pool is 
too small!
Nov 12 09:42:32 guru kernel: Please increase it with coherent_pool= 
kernel parameter!

   Soeren

 >> ---
 >>  mm/dmapool.c |   27 +++++++--------------------
 >>  1 file changed, 7 insertions(+), 20 deletions(-)
 >>
 >> diff --git a/mm/dmapool.c b/mm/dmapool.c
 >> index c5ab33b..86de9b2 100644
 >> --- a/mm/dmapool.c
 >> +++ b/mm/dmapool.c
 >> @@ -62,8 +62,6 @@ struct dma_page {        /* cacheable header for 
'allocation' bytes */
 >>      unsigned int offset;
 >>  };
 >>
 >> -#define    POOL_TIMEOUT_JIFFIES    ((100 /* msec */ * HZ) / 1000)
 >> -
 >>  static DEFINE_MUTEX(pools_lock);
 >>
 >>  static ssize_t
 >> @@ -227,7 +225,6 @@ static struct dma_page *pool_alloc_page(struct 
dma_pool *pool, gfp_t mem_flags)
 >>          memset(page->vaddr, POOL_POISON_FREED, pool->allocation);
 >>  #endif
 >>          pool_initialise_page(pool, page);
 >> -        list_add(&page->page_list, &pool->page_list);
 >>          page->in_use = 0;
 >>          page->offset = 0;
 >>      } else {
 >> @@ -315,30 +312,21 @@ void *dma_pool_alloc(struct dma_pool *pool, 
gfp_t mem_flags,
 >>      might_sleep_if(mem_flags & __GFP_WAIT);
 >>
 >>      spin_lock_irqsave(&pool->lock, flags);
 >> - restart:
 >>      list_for_each_entry(page, &pool->page_list, page_list) {
 >>          if (page->offset < pool->allocation)
 >>              goto ready;
 >>      }
 >> -    page = pool_alloc_page(pool, GFP_ATOMIC);
 >> -    if (!page) {
 >> -        if (mem_flags & __GFP_WAIT) {
 >> -            DECLARE_WAITQUEUE(wait, current);
 >>
 >> -            __set_current_state(TASK_UNINTERRUPTIBLE);
 >> -            __add_wait_queue(&pool->waitq, &wait);
 >> -            spin_unlock_irqrestore(&pool->lock, flags);
 >> +    /* pool_alloc_page() might sleep, so temporarily drop 
&pool->lock */
 >> +    spin_unlock_irqrestore(&pool->lock, flags);
 >>
 >> -            schedule_timeout(POOL_TIMEOUT_JIFFIES);
 >> +    page = pool_alloc_page(pool, mem_flags);
 >> +    if (!page)
 >> +        return NULL;
 >>
 >> -            spin_lock_irqsave(&pool->lock, flags);
 >> -            __remove_wait_queue(&pool->waitq, &wait);
 >> -            goto restart;
 >> -        }
 >> -        retval = NULL;
 >> -        goto done;
 >> -    }
 >> +    spin_lock_irqsave(&pool->lock, flags);
 >>
 >> +    list_add(&page->page_list, &pool->page_list);
 >>   ready:
 >>      page->in_use++;
 >>      offset = page->offset;
 >> @@ -348,7 +336,6 @@ void *dma_pool_alloc(struct dma_pool *pool, 
gfp_t mem_flags,
 >>  #ifdef    DMAPOOL_DEBUG
 >>      memset(retval, POOL_POISON_ALLOCATED, pool->size);
 >>  #endif
 >> - done:
 >>      spin_unlock_irqrestore(&pool->lock, flags);
 >>      return retval;
 >>  }
 >> --
 >> 1.7.9.5
 >>