Revert "Intel IOMMU: Avoid memory allocation failures in dma map api calls" (354bb65e) · Commits · 戴 / test

commit said Intel IOMMU Intel IOMMU driver needs memory during DMA map calls to setup its internal page tables and for other data structures. As we all know that these DMA map calls are mostly called in the interrupt context or with the spinlock held by the upper level drivers(network/storage drivers), so in order to avoid any memory allocation failure due to low memory issues, this patch makes memory allocation by temporarily setting PF_MEMALLOC flags for the current task before making memory allocation calls. We evaluated mempools as a backup when kmem_cache_alloc() fails and found that mempools are really not useful here because 1) We don't know for sure how much to reserve in advance 2) And mempools are not useful for GFP_ATOMIC case (as we call memory alloc functions with GFP_ATOMIC) (akpm: point 2 is wrong...) The above description doesn't justify to waste system emergency memory at all. Non MM subsystem must not use PF_MEMALLOC. Memory reclaim need few memory, anyone must not prevent it. Otherwise the system cause mysterious hang-up and/or OOM Killer invokation. Plus, akpm already pointed out what we should do. Then, this patch revert it. Cc: Keshavamurthy Anil S <anil.s.keshavamurthy@intel.com> Signed-off-by:

KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Signed-off-by:

David Woodhouse <David.Woodhouse@intel.com>

drivers/pci/intel-iommu.c

+3 −22

Original line number	Diff line number	Diff line
		@@ -387,33 +387,14 @@ static struct kmem_cache *iommu_domain_cache;
		static struct kmem_cache *iommu_devinfo_cache;
		static struct kmem_cache *iommu_iova_cache;

		static inline void iommu_kmem_cache_alloc(struct kmem_cache cachep)
		{
		unsigned int flags;
		void *vaddr;

		/* trying to avoid low memory issues */
		flags = current->flags & PF_MEMALLOC;
		current->flags \|= PF_MEMALLOC;
		vaddr = kmem_cache_alloc(cachep, GFP_ATOMIC);
		current->flags &= (~PF_MEMALLOC \| flags);
		return vaddr;
		}


		static inline void *alloc_pgtable_page(int node)
		{
		unsigned int flags;
		struct page *page;
		void *vaddr = NULL;

		/* trying to avoid low memory issues */
		flags = current->flags & PF_MEMALLOC;
		current->flags \|= PF_MEMALLOC;
		page = alloc_pages_node(node, GFP_ATOMIC \| __GFP_ZERO, 0);
		if (page)
		vaddr = page_address(page);
		current->flags &= (~PF_MEMALLOC \| flags);
		return vaddr;
		}

		@@ -424,7 +405,7 @@ static inline void free_pgtable_page(void *vaddr)

		static inline void *alloc_domain_mem(void)
		{
		return iommu_kmem_cache_alloc(iommu_domain_cache);
		return kmem_cache_alloc(iommu_domain_cache, GFP_ATOMIC);
		}

		static void free_domain_mem(void *vaddr)
		@@ -434,7 +415,7 @@ static void free_domain_mem(void *vaddr)

		static inline void * alloc_devinfo_mem(void)
		{
		return iommu_kmem_cache_alloc(iommu_devinfo_cache);
		return kmem_cache_alloc(iommu_devinfo_cache, GFP_ATOMIC);
		}

		static inline void free_devinfo_mem(void *vaddr)
		@@ -444,7 +425,7 @@ static inline void free_devinfo_mem(void *vaddr)

		struct iova *alloc_iova_mem(void)
		{
		return iommu_kmem_cache_alloc(iommu_iova_cache);
		return kmem_cache_alloc(iommu_iova_cache, GFP_ATOMIC);
		}

		void free_iova_mem(struct iova *iova)

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