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>

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 7f3fa79..22c45e9 100644 (file)
--- 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;