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Subject[PATCH v4 4/5] mm: cma: add list of currently allocated CMA buffers to debugfs
Date
When CONFIG_CMA_BUFFER_LIST is configured a file is added to debugfs:
/sys/kernel/debug/cma/cma-<N>/buffers contains a list of currently allocated
CMA buffers for each CMA region (N stands for number of CMA region).

Format is:
<base_phys_addr> - <end_phys_addr> (<size> kB), allocated by <PID> (<comm>)

When CONFIG_CMA_ALLOC_STACKTRACE is configured then stack traces are saved when
the allocations are made. The stack traces are added to cma/cma-<N>/buffers
for each buffer list entry.

Example:

root@debian:/sys/kernel/debug/cma# cat cma-0/buffers
0x2f400000 - 0x2f417000 (92 kB), allocated by pid 1 (swapper/0)
[<c1142c4b>] cma_alloc+0x1bb/0x200
[<c143d28a>] dma_alloc_from_contiguous+0x3a/0x40
[<c10079d9>] dma_generic_alloc_coherent+0x89/0x160
[<c14456ce>] dmam_alloc_coherent+0xbe/0x100
[<c1487312>] ahci_port_start+0xe2/0x210
[<c146e0e0>] ata_host_start.part.28+0xc0/0x1a0
[<c1473650>] ata_host_activate+0xd0/0x110
[<c14881bf>] ahci_host_activate+0x3f/0x170
[<c14854e4>] ahci_init_one+0x764/0xab0
[<c12e415f>] pci_device_probe+0x6f/0xd0
[<c14378a8>] driver_probe_device+0x68/0x210
[<c1437b09>] __driver_attach+0x79/0x80
[<c1435eef>] bus_for_each_dev+0x4f/0x80
[<c143749e>] driver_attach+0x1e/0x20
[<c1437197>] bus_add_driver+0x157/0x200
[<c14381bd>] driver_register+0x5d/0xf0
<...>

Signed-off-by: Stefan Strogin <stefan.strogin@gmail.com>
---
mm/Kconfig | 17 +++++
mm/cma.c | 7 ++
mm/cma.h | 14 ++++
mm/cma_debug.c | 206 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
4 files changed, 243 insertions(+), 1 deletion(-)

diff --git a/mm/Kconfig b/mm/Kconfig
index 390214d..5ee2388 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -523,6 +523,23 @@ config CMA_DEBUGFS
help
Turns on the DebugFS interface for CMA.

+config CMA_BUFFER_LIST
+ bool "List of currently allocated CMA buffers in debugfs"
+ depends on CMA_DEBUGFS
+ help
+ /sys/kernel/debug/cma/cma-<N>/buffers contains a list of currently
+ allocated CMA buffers for each CMA region (N stands for number of
+ CMA region).
+ Format is:
+ <base_phys_addr> - <end_phys_addr> (<size> kB), allocated by <PID> (<comm>)
+
+config CMA_ALLOC_STACKTRACE
+ bool "Add stack trace to CMA buffer list"
+ depends on CMA_BUFFER_LIST && STACKTRACE
+ help
+ Add stack traces saved at the moment of allocation for each buffer
+ listed in /sys/kernel/debug/cma/cma-<N>/buffers.
+
config CMA_AREAS
int "Maximum count of the CMA areas"
depends on CMA
diff --git a/mm/cma.c b/mm/cma.c
index 77960af..faf8eac 100644
--- a/mm/cma.c
+++ b/mm/cma.c
@@ -133,6 +133,10 @@ static int __init cma_activate_area(struct cma *cma)
INIT_HLIST_HEAD(&cma->mem_head);
spin_lock_init(&cma->mem_head_lock);
#endif
+#ifdef CONFIG_CMA_BUFFER_LIST
+ INIT_LIST_HEAD(&cma->buffer_list);
+ mutex_init(&cma->list_lock);
+#endif

return 0;

@@ -416,6 +420,8 @@ struct page *cma_alloc(struct cma *cma, unsigned int count, unsigned int align)
start = bitmap_no + mask + 1;
}

+ if (page)
+ cma_buffer_list_add(cma, pfn, count);
trace_cma_alloc(cma, page, count);

pr_debug("%s(): returned %p\n", __func__, page);
@@ -451,6 +457,7 @@ bool cma_release(struct cma *cma, const struct page *pages, unsigned int count)
free_contig_range(pfn, count);
cma_clear_bitmap(cma, pfn, count);
trace_cma_release(cma, pfn, count);
+ cma_buffer_list_del(cma, pfn, count);

return true;
}
diff --git a/mm/cma.h b/mm/cma.h
index 1132d73..e174272 100644
--- a/mm/cma.h
+++ b/mm/cma.h
@@ -1,6 +1,8 @@
#ifndef __MM_CMA_H__
#define __MM_CMA_H__

+#include <linux/sched.h>
+
struct cma {
unsigned long base_pfn;
unsigned long count;
@@ -11,8 +13,20 @@ struct cma {
struct hlist_head mem_head;
spinlock_t mem_head_lock;
#endif
+#ifdef CONFIG_CMA_BUFFER_LIST
+ struct list_head buffer_list;
+ struct mutex list_lock;
+#endif
};

+#ifdef CONFIG_CMA_BUFFER_LIST
+extern int cma_buffer_list_add(struct cma *cma, unsigned long pfn, int count);
+extern void cma_buffer_list_del(struct cma *cma, unsigned long pfn, int count);
+#else
+#define cma_buffer_list_add(cma, pfn, count) { }
+#define cma_buffer_list_del(cma, pfn, count) { }
+#endif
+
extern struct cma cma_areas[MAX_CMA_AREAS];
extern unsigned cma_area_count;

diff --git a/mm/cma_debug.c b/mm/cma_debug.c
index ec915e6..20bad2d 100644
--- a/mm/cma_debug.c
+++ b/mm/cma_debug.c
@@ -2,6 +2,7 @@
* CMA DebugFS Interface
*
* Copyright (c) 2015 Sasha Levin <sasha.levin@oracle.com>
+ * Copyright (c) 2015 Stefan Strogin <stefan.strogin@gmail.com>
*/


@@ -10,7 +11,8 @@
#include <linux/list.h>
#include <linux/kernel.h>
#include <linux/slab.h>
-#include <linux/mm_types.h>
+#include <linux/mm.h>
+#include <linux/stacktrace.h>

#include "cma.h"

@@ -20,8 +22,119 @@ struct cma_mem {
unsigned long n;
};

+#ifdef CONFIG_CMA_BUFFER_LIST
+struct cma_buffer {
+ unsigned long pfn;
+ unsigned long count;
+ pid_t pid;
+ char comm[TASK_COMM_LEN];
+#ifdef CONFIG_CMA_ALLOC_STACKTRACE
+ unsigned long trace_entries[16];
+ unsigned int nr_entries;
+#endif
+ struct list_head list;
+};
+#endif /* CONFIG_CMA_BUFFER_LIST */
+
static struct dentry *cma_debugfs_root;

+#ifdef CONFIG_CMA_BUFFER_LIST
+/* Must be called under cma->list_lock */
+static int __cma_buffer_list_add(struct cma *cma, unsigned long pfn, int count)
+{
+ struct cma_buffer *cmabuf;
+#ifdef CONFIG_CMA_ALLOC_STACKTRACE
+ struct stack_trace trace;
+#endif
+
+ cmabuf = kmalloc(sizeof(*cmabuf), GFP_KERNEL);
+ if (!cmabuf) {
+ pr_warn("%s(page %p, count %d): failed to allocate buffer list entry\n",
+ __func__, pfn_to_page(pfn), count);
+ return -ENOMEM;
+ }
+
+#ifdef CONFIG_CMA_ALLOC_STACKTRACE
+ trace.nr_entries = 0;
+ trace.max_entries = ARRAY_SIZE(cmabuf->trace_entries);
+ trace.entries = &cmabuf->trace_entries[0];
+ trace.skip = 2;
+ save_stack_trace(&trace);
+ cmabuf->nr_entries = trace.nr_entries;
+#endif
+ cmabuf->pfn = pfn;
+ cmabuf->count = count;
+ cmabuf->pid = task_pid_nr(current);
+ get_task_comm(cmabuf->comm, current);
+
+ list_add_tail(&cmabuf->list, &cma->buffer_list);
+
+ return 0;
+}
+
+/**
+ * cma_buffer_list_add() - add a new entry to a list of allocated buffers
+ * @cma: Contiguous memory region for which the allocation is performed.
+ * @pfn: Base PFN of the allocated buffer.
+ * @count: Number of allocated pages.
+ *
+ * This function adds a new entry to the list of allocated contiguous memory
+ * buffers in a CMA region.
+ */
+int cma_buffer_list_add(struct cma *cma, unsigned long pfn, int count)
+{
+ int ret;
+
+ mutex_lock(&cma->list_lock);
+ ret = __cma_buffer_list_add(cma, pfn, count);
+ mutex_unlock(&cma->list_lock);
+
+ return ret;
+}
+
+/**
+ * cma_buffer_list_del() - delete an entry from a list of allocated buffers
+ * @cma: Contiguous memory region for which the allocation was performed.
+ * @pfn: Base PFN of the released buffer.
+ * @count: Number of pages.
+ *
+ * This function deletes a list entry added by cma_buffer_list_add().
+ */
+void cma_buffer_list_del(struct cma *cma, unsigned long pfn, int count)
+{
+ struct cma_buffer *cmabuf, *tmp;
+ int found = 0;
+ unsigned long buf_end_pfn, free_end_pfn = pfn + count;
+
+ mutex_lock(&cma->list_lock);
+ list_for_each_entry_safe(cmabuf, tmp, &cma->buffer_list, list) {
+
+ buf_end_pfn = cmabuf->pfn + cmabuf->count;
+ if (pfn <= cmabuf->pfn && free_end_pfn >= buf_end_pfn) {
+ list_del(&cmabuf->list);
+ kfree(cmabuf);
+ found = 1;
+ } else if (pfn <= cmabuf->pfn && free_end_pfn < buf_end_pfn) {
+ cmabuf->count -= free_end_pfn - cmabuf->pfn;
+ cmabuf->pfn = free_end_pfn;
+ found = 1;
+ } else if (pfn > cmabuf->pfn && pfn < buf_end_pfn) {
+ if (free_end_pfn < buf_end_pfn)
+ __cma_buffer_list_add(cma, free_end_pfn,
+ buf_end_pfn - free_end_pfn);
+ cmabuf->count = pfn - cmabuf->pfn;
+ found = 1;
+ }
+ }
+ mutex_unlock(&cma->list_lock);
+
+ if (!found)
+ pr_err("%s(page %p, count %d): couldn't find buffer list entry\n",
+ __func__, pfn_to_page(pfn), count);
+
+}
+#endif /* CONFIG_CMA_BUFFER_LIST */
+
static int cma_debugfs_get(void *data, u64 *val)
{
unsigned long *p = data;
@@ -127,6 +240,93 @@ static int cma_alloc_write(void *data, u64 val)

DEFINE_SIMPLE_ATTRIBUTE(cma_alloc_fops, NULL, cma_alloc_write, "%llu\n");

+#ifdef CONFIG_CMA_BUFFER_LIST
+static void *s_start(struct seq_file *seq, loff_t *ppos)
+{
+ struct cma *cma = seq->private;
+ struct cma_buffer *cmabuf;
+ loff_t n = *ppos;
+
+ mutex_lock(&cma->list_lock);
+ cmabuf = list_first_entry(&cma->buffer_list, typeof(*cmabuf), list);
+ list_for_each_entry(cmabuf, &cma->buffer_list, list)
+ if (n-- == 0)
+ return cmabuf;
+
+ return 0;
+}
+
+static int s_show(struct seq_file *seq, void *p)
+{
+ struct cma_buffer *cmabuf = p;
+#ifdef CONFIG_CMA_ALLOC_STACKTRACE
+ struct stack_trace trace;
+#endif
+
+ seq_printf(seq, "0x%llx - 0x%llx (%lu kB), allocated by pid %u (%s)\n",
+ (unsigned long long)PFN_PHYS(cmabuf->pfn),
+ (unsigned long long)PFN_PHYS(cmabuf->pfn +
+ cmabuf->count),
+ (cmabuf->count * PAGE_SIZE) >> 10, cmabuf->pid,
+ cmabuf->comm);
+
+#ifdef CONFIG_CMA_ALLOC_STACKTRACE
+ trace.nr_entries = cmabuf->nr_entries;
+ trace.entries = &cmabuf->trace_entries[0];
+ seq_print_stack_trace(seq, &trace, 0);
+ seq_putc(seq, '\n');
+#endif
+
+ return 0;
+}
+
+static void *s_next(struct seq_file *seq, void *p, loff_t *ppos)
+{
+ struct cma *cma = seq->private;
+ struct cma_buffer *cmabuf = (struct cma_buffer *)p, *next;
+
+ ++*ppos;
+ next = list_next_entry(cmabuf, list);
+ if (&next->list != &cma->buffer_list)
+ return next;
+
+ return 0;
+}
+
+static void s_stop(struct seq_file *seq, void *p)
+{
+ struct cma *cma = seq->private;
+
+ mutex_unlock(&cma->list_lock);
+}
+
+static const struct seq_operations cma_buffers_sops = {
+ .start = s_start,
+ .show = s_show,
+ .next = s_next,
+ .stop = s_stop,
+};
+
+static int cma_buffers_open(struct inode *inode, struct file *file)
+{
+ int ret = seq_open(file, &cma_buffers_sops);
+
+ if (ret == 0) {
+ struct seq_file *seq = file->private_data;
+
+ seq->private = inode->i_private;
+ }
+ return ret;
+}
+
+static const struct file_operations cma_buffers_fops = {
+ .open = cma_buffers_open,
+ .read = seq_read,
+ .llseek = seq_lseek,
+ .release = seq_release,
+};
+#endif /* CONFIG_CMA_BUFFER_LIST */
+
static void cma_debugfs_add_one(struct cma *cma, int idx)
{
struct dentry *tmp;
@@ -149,6 +349,10 @@ static void cma_debugfs_add_one(struct cma *cma, int idx)
&cma->count, &cma_debugfs_fops);
debugfs_create_file("order_per_bit", S_IRUGO, tmp,
&cma->order_per_bit, &cma_debugfs_fops);
+#ifdef CONFIG_CMA_BUFFER_LIST
+ debugfs_create_file("buffers", S_IRUGO, tmp, cma,
+ &cma_buffers_fops);
+#endif

u32s = DIV_ROUND_UP(cma_bitmap_maxno(cma), BITS_PER_BYTE * sizeof(u32));
debugfs_create_u32_array("bitmap", S_IRUGO, tmp, (u32*)cma->bitmap, u32s);
--
2.1.0


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