writeback: add some debug inode list counters to bdi stats

Add some debug entries to be able to inspect the internal state of
the writeback details.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 34 insertions, 4 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 7f3fa79f25c0..22c45e932e3a 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -52,9 +52,29 @@ static void bdi_debug_init(void)
 static int bdi_debug_stats_show(struct seq_file *m, void *v)
 {
         struct backing_dev_info *bdi = m->private;
+        struct bdi_writeback *wb;
         unsigned long background_thresh;
         unsigned long dirty_thresh;
         unsigned long bdi_thresh;
+        unsigned long nr_dirty, nr_io, nr_more_io, nr_wb;
+        struct inode *inode;
+
+        /*
+         * inode lock is enough here, the bdi->wb_list is protected by
+         * RCU on the reader side
+         */
+        nr_wb = nr_dirty = nr_io = nr_more_io = 0;
+        spin_lock(&inode_lock);
+        list_for_each_entry(wb, &bdi->wb_list, list) {
+                nr_wb++;
+                list_for_each_entry(inode, &wb->b_dirty, i_list)
+                        nr_dirty++;
+                list_for_each_entry(inode, &wb->b_io, i_list)
+                        nr_io++;
+                list_for_each_entry(inode, &wb->b_more_io, i_list)
+                        nr_more_io++;
+        }
+        spin_unlock(&inode_lock);
 
         get_dirty_limits(&background_thresh, &dirty_thresh, &bdi_thresh, bdi);
 
@@ -64,12 +84,22 @@ static int bdi_debug_stats_show(struct seq_file *m, void *v)
                    "BdiReclaimable:   %8lu kB\n"
                    "BdiDirtyThresh:   %8lu kB\n"
                    "DirtyThresh:      %8lu kB\n"
-                   "BackgroundThresh: %8lu kB\n",
+                   "BackgroundThresh: %8lu kB\n"
+                   "WriteBack threads:%8lu\n"
+                   "b_dirty:          %8lu\n"
+                   "b_io:             %8lu\n"
+                   "b_more_io:        %8lu\n"
+                   "bdi_list:         %8u\n"
+                   "state:            %8lx\n"
+                   "wb_mask:          %8lx\n"
+                   "wb_list:          %8u\n"
+                   "wb_cnt:           %8u\n",
                    (unsigned long) K(bdi_stat(bdi, BDI_WRITEBACK)),
                    (unsigned long) K(bdi_stat(bdi, BDI_RECLAIMABLE)),
-                   K(bdi_thresh),
-                   K(dirty_thresh),
-                   K(background_thresh));
+                   K(bdi_thresh), K(dirty_thresh),
+                   K(background_thresh), nr_wb, nr_dirty, nr_io, nr_more_io,
+                   !list_empty(&bdi->bdi_list), bdi->state, bdi->wb_mask,
+                   !list_empty(&bdi->wb_list), bdi->wb_cnt);
 #undef K
 
         return 0;