[PATCH 3/3] dma debug: flag copy-on-write events to pagesundergoing dma

From: Dan Williams
Date: Tue Dec 17 2013 - 19:16:21 EST

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Record actively mapped pages and provide an api for other parts of the kernel
to check that a given page is dma inactive before taking action. Verified to
catch the misuse of the dma-api in the NET_DMA implementation.

Cc: Vinod Koul <vinod.koul@xxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
---
include/linux/dma-debug.h | 6 ++
lib/dma-debug.c | 130 +++++++++++++++++++++++++++++++++++++++++----
mm/memory.c | 3 +
3 files changed, 126 insertions(+), 13 deletions(-)

diff --git a/include/linux/dma-debug.h b/include/linux/dma-debug.h
index fc0e34ce038f..fe8cb610deac 100644
--- a/include/linux/dma-debug.h
+++ b/include/linux/dma-debug.h
@@ -85,6 +85,8 @@ extern void debug_dma_sync_sg_for_device(struct device *dev,

extern void debug_dma_dump_mappings(struct device *dev);

+extern void debug_dma_assert_idle(struct page *page);
+
#else /* CONFIG_DMA_API_DEBUG */

static inline void dma_debug_add_bus(struct bus_type *bus)
@@ -183,6 +185,10 @@ static inline void debug_dma_dump_mappings(struct device *dev)
{
}

+static inline void debug_dma_assert_idle(struct page *page)
+{
+}
+
#endif /* CONFIG_DMA_API_DEBUG */

#endif /* __DMA_DEBUG_H */
diff --git a/lib/dma-debug.c b/lib/dma-debug.c
index d87a17a819d0..f67ae111cd2f 100644
--- a/lib/dma-debug.c
+++ b/lib/dma-debug.c
@@ -57,7 +57,8 @@ struct dma_debug_entry {
struct list_head list;
struct device *dev;
int type;
- phys_addr_t paddr;
+ unsigned long pfn;
+ size_t offset;
u64 dev_addr;
u64 size;
int direction;
@@ -372,6 +373,11 @@ static void hash_bucket_del(struct dma_debug_entry *entry)
list_del(&entry->list);
}

+static unsigned long long phys_addr(struct dma_debug_entry *entry)
+{
+ return page_to_phys(pfn_to_page(entry->pfn)) + entry->offset;
+}
+
/*
* Dump mapping entries for debugging purposes
*/
@@ -389,9 +395,9 @@ void debug_dma_dump_mappings(struct device *dev)
list_for_each_entry(entry, &bucket->list, list) {
if (!dev || dev == entry->dev) {
dev_info(entry->dev,
- "%s idx %d P=%Lx D=%Lx L=%Lx %s %s\n",
+ "%s idx %d P=%Lx N=%lx D=%Lx L=%Lx %s %s\n",
type2name[entry->type], idx,
- (unsigned long long)entry->paddr,
+ phys_addr(entry), entry->pfn,
entry->dev_addr, entry->size,
dir2name[entry->direction],
maperr2str[entry->map_err_type]);
@@ -403,6 +409,83 @@ void debug_dma_dump_mappings(struct device *dev)
}
EXPORT_SYMBOL(debug_dma_dump_mappings);

+/* memory usage is constrained by the maximum number of available
+ * dma-debug entries
+ */
+static RADIX_TREE(dma_active_pfn, GFP_NOWAIT);
+static DEFINE_SPINLOCK(radix_lock);
+
+static void __active_pfn_inc_overlap(struct dma_debug_entry *entry)
+{
+ unsigned long pfn = entry->pfn;
+ int i;
+
+ for (i = 0; i < RADIX_TREE_MAX_TAGS; i++)
+ if (radix_tree_tag_get(&dma_active_pfn, pfn, i) == 0) {
+ radix_tree_tag_set(&dma_active_pfn, pfn, i);
+ return;
+ }
+ pr_debug("DMA-API: max overlap count (%d) reached for pfn 0x%lx\n",
+ RADIX_TREE_MAX_TAGS, pfn);
+}
+
+static void __active_pfn_dec_overlap(struct dma_debug_entry *entry)
+{
+ unsigned long pfn = entry->pfn;
+ int i;
+
+ for (i = RADIX_TREE_MAX_TAGS - 1; i >= 0; i--)
+ if (radix_tree_tag_get(&dma_active_pfn, pfn, i)) {
+ radix_tree_tag_clear(&dma_active_pfn, pfn, i);
+ return;
+ }
+ radix_tree_delete(&dma_active_pfn, pfn);
+}
+
+static int active_pfn_insert(struct dma_debug_entry *entry)
+{
+ unsigned long flags;
+ int rc;
+
+ spin_lock_irqsave(&radix_lock, flags);
+ rc = radix_tree_insert(&dma_active_pfn, entry->pfn, entry);
+ if (rc == -EEXIST)
+ __active_pfn_inc_overlap(entry);
+ spin_unlock_irqrestore(&radix_lock, flags);
+
+ return rc;
+}
+
+static void active_pfn_remove(struct dma_debug_entry *entry)
+{
+ unsigned long flags;
+
+ spin_lock_irqsave(&radix_lock, flags);
+ __active_pfn_dec_overlap(entry);
+ spin_unlock_irqrestore(&radix_lock, flags);
+}
+
+void debug_dma_assert_idle(struct page *page)
+{
+ unsigned long flags;
+ struct dma_debug_entry *entry;
+
+ if (!page)
+ return;
+
+ spin_lock_irqsave(&radix_lock, flags);
+ entry = radix_tree_lookup(&dma_active_pfn, page_to_pfn(page));
+ spin_unlock_irqrestore(&radix_lock, flags);
+
+ if (!entry)
+ return;
+
+ err_printk(entry->dev, entry,
+ "DMA-API: cpu touching an active dma mapped page "
+ "[pfn=0x%lx]\n", entry->pfn);
+}
+EXPORT_SYMBOL_GPL(debug_dma_assert_idle);
+
/*
* Wrapper function for adding an entry to the hash.
* This function takes care of locking itself.
@@ -411,10 +494,22 @@ static void add_dma_entry(struct dma_debug_entry *entry)
{
struct hash_bucket *bucket;
unsigned long flags;
+ int rc;

bucket = get_hash_bucket(entry, &flags);
hash_bucket_add(bucket, entry);
put_hash_bucket(bucket, &flags);
+
+ rc = active_pfn_insert(entry);
+ if (rc == -ENOMEM) {
+ pr_err("DMA-API: pfn tracking out of memory - "
+ "disabling dma-debug\n");
+ global_disable = true;
+ }
+
+ /* TODO: report -EEXIST errors as overlapping mappings are not
+ * supported by the DMA API
+ */
}

static struct dma_debug_entry *__dma_entry_alloc(void)
@@ -469,6 +564,8 @@ static void dma_entry_free(struct dma_debug_entry *entry)
{
unsigned long flags;

+ active_pfn_remove(entry);
+
/*
* add to beginning of the list - this way the entries are
* more likely cache hot when they are reallocated.
@@ -895,15 +992,15 @@ static void check_unmap(struct dma_debug_entry *ref)
ref->dev_addr, ref->size,
type2name[entry->type], type2name[ref->type]);
} else if ((entry->type == dma_debug_coherent) &&
- (ref->paddr != entry->paddr)) {
+ (phys_addr(ref) != phys_addr(entry))) {
err_printk(ref->dev, entry, "DMA-API: device driver frees "
"DMA memory with different CPU address "
"[device address=0x%016llx] [size=%llu bytes] "
"[cpu alloc address=0x%016llx] "
"[cpu free address=0x%016llx]",
ref->dev_addr, ref->size,
- (unsigned long long)entry->paddr,
- (unsigned long long)ref->paddr);
+ phys_addr(entry),
+ phys_addr(ref));
}

if (ref->sg_call_ents && ref->type == dma_debug_sg &&
@@ -1052,7 +1149,8 @@ void debug_dma_map_page(struct device *dev, struct page *page, size_t offset,

entry->dev = dev;
entry->type = dma_debug_page;
- entry->paddr = page_to_phys(page) + offset;
+ entry->pfn = page_to_pfn(page);
+ entry->offset = offset,
entry->dev_addr = dma_addr;
entry->size = size;
entry->direction = direction;
@@ -1148,7 +1246,8 @@ void debug_dma_map_sg(struct device *dev, struct scatterlist *sg,

entry->type = dma_debug_sg;
entry->dev = dev;
- entry->paddr = sg_phys(s);
+ entry->pfn = page_to_pfn(sg_page(s));
+ entry->offset = s->offset,
entry->size = sg_dma_len(s);
entry->dev_addr = sg_dma_address(s);
entry->direction = direction;
@@ -1198,7 +1297,8 @@ void debug_dma_unmap_sg(struct device *dev, struct scatterlist *sglist,
struct dma_debug_entry ref = {
.type = dma_debug_sg,
.dev = dev,
- .paddr = sg_phys(s),
+ .pfn = page_to_pfn(sg_page(s)),
+ .offset = s->offset,
.dev_addr = sg_dma_address(s),
.size = sg_dma_len(s),
.direction = dir,
@@ -1233,7 +1333,8 @@ void debug_dma_alloc_coherent(struct device *dev, size_t size,

entry->type = dma_debug_coherent;
entry->dev = dev;
- entry->paddr = virt_to_phys(virt);
+ entry->pfn = page_to_pfn(virt_to_page(virt));
+ entry->offset = (size_t) virt & PAGE_MASK;
entry->size = size;
entry->dev_addr = dma_addr;
entry->direction = DMA_BIDIRECTIONAL;
@@ -1248,7 +1349,8 @@ void debug_dma_free_coherent(struct device *dev, size_t size,
struct dma_debug_entry ref = {
.type = dma_debug_coherent,
.dev = dev,
- .paddr = virt_to_phys(virt),
+ .pfn = page_to_pfn(virt_to_page(virt)),
+ .offset = (size_t) virt & PAGE_MASK,
.dev_addr = addr,
.size = size,
.direction = DMA_BIDIRECTIONAL,
@@ -1356,7 +1458,8 @@ void debug_dma_sync_sg_for_cpu(struct device *dev, struct scatterlist *sg,
struct dma_debug_entry ref = {
.type = dma_debug_sg,
.dev = dev,
- .paddr = sg_phys(s),
+ .pfn = page_to_pfn(sg_page(s)),
+ .offset = s->offset,
.dev_addr = sg_dma_address(s),
.size = sg_dma_len(s),
.direction = direction,
@@ -1388,7 +1491,8 @@ void debug_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sg,
struct dma_debug_entry ref = {
.type = dma_debug_sg,
.dev = dev,
- .paddr = sg_phys(s),
+ .pfn = page_to_pfn(sg_page(s)),
+ .offset = s->offset,
.dev_addr = sg_dma_address(s),
.size = sg_dma_len(s),
.direction = direction,
diff --git a/mm/memory.c b/mm/memory.c
index 5d9025f3b3e1..c89788436f81 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -59,6 +59,7 @@
#include <linux/gfp.h>
#include <linux/migrate.h>
#include <linux/string.h>
+#include <linux/dma-debug.h>

#include <asm/io.h>
#include <asm/pgalloc.h>
@@ -2559,6 +2560,8 @@ static inline int pte_unmap_same(struct mm_struct *mm, pmd_t *pmd,

static inline void cow_user_page(struct page *dst, struct page *src, unsigned long va, struct vm_area_struct *vma)
{
+ debug_dma_assert_idle(src);
+
/*
* If the source page was a PFN mapping, we don't have
* a "struct page" for it. We do a best-effort copy by

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Next message: Rafael J. Wysocki: "Re: [PATCH] libata, freezer: avoid block device removal while system is frozen"
Previous message: Dan Williams: "[PATCH 2/3] net_dma: remove"
In reply to: Dan Williams: "[PATCH 2/3] net_dma: remove"
Messages sorted by: [ date ] [ thread ] [ subject ] [ author ]