f2fs: count the number of inmemory pages

This patch adds counting # of inmemory pages in the page cache.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/debug.c b/fs/f2fs/debug.c
index 40b679c..4e2e39c 100644
--- a/fs/f2fs/debug.c
+++ b/fs/f2fs/debug.c
@@ -39,6 +39,7 @@
 	si->ndirty_dent = get_pages(sbi, F2FS_DIRTY_DENTS);
 	si->ndirty_dirs = sbi->n_dirty_dirs;
 	si->ndirty_meta = get_pages(sbi, F2FS_DIRTY_META);
+	si->inmem_pages = get_pages(sbi, F2FS_INMEM_PAGES);
 	si->total_count = (int)sbi->user_block_count / sbi->blocks_per_seg;
 	si->rsvd_segs = reserved_segments(sbi);
 	si->overp_segs = overprovision_segments(sbi);
@@ -249,6 +250,8 @@
 		seq_printf(s, "\nExtent Hit Ratio: %d / %d\n",
 			   si->hit_ext, si->total_ext);
 		seq_puts(s, "\nBalancing F2FS Async:\n");
+		seq_printf(s, "  - inmem: %4d\n",
+			   si->inmem_pages);
 		seq_printf(s, "  - nodes: %4d in %4d\n",
 			   si->ndirty_node, si->node_pages);
 		seq_printf(s, "  - dents: %4d in dirs:%4d\n",