swiotlb: add debugfs to track swiotlb buffer usage

The device driver will not be able to do dma operations once swiotlb buffer
is full, either because the driver is using so many IO TLB blocks inflight,
or because there is memory leak issue in device driver. To export the
swiotlb buffer usage via debugfs would help the user estimate the size of
swiotlb buffer to pre-allocate or analyze device driver memory leak issue.

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Orabug: 29582587
(cherry picked from commit 71602fe6d4e9291af105adfef8e893b57c735906)
Signed-off-by: Brian Maly <brian.maly@oracle.com>
Conflicts:
  debugfs_create_ulong() is not available. debugfs_create_file() is used instead.

Signed-off-by: Dongli Zhang <dongli.zhang@oracle.com>
Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>

diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 6210202148a56356220025eb16313e42a95b634c..f41f1be70367c4c318ffa1a221ded6e2ec8f7f11 100644 (file)
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -29,6 +29,9 @@
 #include <linux/ctype.h>
 #include <linux/highmem.h>
 #include <linux/gfp.h>
+#ifdef CONFIG_DEBUG_FS
+#include <linux/debugfs.h>
+#endif
 
 #include <asm/io.h>
 #include <asm/dma.h>
@@ -68,6 +71,11 @@ static phys_addr_t io_tlb_start, io_tlb_end;
  */
 static unsigned long io_tlb_nslabs;
 
+/*
+ * The number of used IO TLB block
+ */
+static unsigned long io_tlb_used;
+
 /*
  * When the IOMMU overflows we return a fallback buffer. This sets the size.
  */
@@ -517,6 +525,7 @@ not_found:
                dev_warn(hwdev, "swiotlb buffer is full (sz: %zd bytes)\n", size);
        return SWIOTLB_MAP_ERROR;
 found:
+       io_tlb_used += nslots;
        spin_unlock_irqrestore(&io_tlb_lock, flags);
 
        /*
@@ -588,6 +597,8 @@ void swiotlb_tbl_unmap_single(struct device *hwdev, phys_addr_t tlb_addr,
                 */
                for (i = index - 1; (OFFSET(i, IO_TLB_SEGSIZE) != IO_TLB_SEGSIZE -1) && io_tlb_list[i]; i--)
                        io_tlb_list[i] = ++count;
+
+               io_tlb_used -= nslots;
        }
        spin_unlock_irqrestore(&io_tlb_lock, flags);
 }
@@ -993,3 +1004,72 @@ swiotlb_dma_supported(struct device *hwdev, u64 mask)
        return phys_to_dma(hwdev, io_tlb_end - 1) <= mask;
 }
 EXPORT_SYMBOL(swiotlb_dma_supported);
+
+#ifdef CONFIG_DEBUG_FS
+
+static int swiotlb_io_tlb_nslabs_show(struct seq_file *m, void *v)
+{
+       seq_printf(m, "%lu\n", io_tlb_nslabs);
+       return 0;
+}
+
+static int swiotlb_io_tlb_nslabs_open(struct inode *inode, struct file *filp)
+{
+       return single_open(filp, swiotlb_io_tlb_nslabs_show, NULL);
+}
+
+static const struct file_operations swiotlb_io_tlb_nslabs_fops = {
+       .open           = swiotlb_io_tlb_nslabs_open,
+       .read           = seq_read,
+       .llseek         = seq_lseek,
+       .release        = single_release,
+};
+
+static int swiotlb_io_tlb_used_show(struct seq_file *m, void *v)
+{
+       seq_printf(m, "%lu\n", io_tlb_used);
+       return 0;
+}
+
+static int swiotlb_io_tlb_used_open(struct inode *inode, struct file *filp)
+{
+       return single_open(filp, swiotlb_io_tlb_used_show, NULL);
+}
+
+static const struct file_operations swiotlb_io_tlb_used_fops = {
+       .open           = swiotlb_io_tlb_used_open,
+       .read           = seq_read,
+       .llseek         = seq_lseek,
+       .release        = single_release,
+};
+
+static int __init swiotlb_create_debugfs(void)
+{
+       static struct dentry *d_swiotlb_usage;
+       struct dentry *ent;
+
+       d_swiotlb_usage = debugfs_create_dir("swiotlb", NULL);
+
+       if (!d_swiotlb_usage)
+               return -ENOMEM;
+
+       ent = debugfs_create_file("io_tlb_nslabs", 0400, d_swiotlb_usage,
+                                 NULL, &swiotlb_io_tlb_nslabs_fops);
+       if (!ent)
+               goto fail;
+
+       ent = debugfs_create_file("io_tlb_used", 0400, d_swiotlb_usage,
+                                 NULL, &swiotlb_io_tlb_used_fops);
+       if (!ent)
+               goto fail;
+
+       return 0;
+
+fail:
+       debugfs_remove_recursive(d_swiotlb_usage);
+       return -ENOMEM;
+}
+
+late_initcall(swiotlb_create_debugfs);
+
+#endif