ext4: Add markers for better debuggability

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 56142ac..4cac8da 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1351,6 +1351,10 @@
  	pgoff_t index;
 	unsigned from, to;
 
+	trace_mark(ext4_write_begin,
+		   "dev %s ino %lu pos %llu len %u flags %u",
+		   inode->i_sb->s_id, inode->i_ino,
+		   (unsigned long long) pos, len, flags);
  	index = pos >> PAGE_CACHE_SHIFT;
 	from = pos & (PAGE_CACHE_SIZE - 1);
 	to = from + len;
@@ -1422,6 +1426,10 @@
 	struct inode *inode = mapping->host;
 	int ret = 0, ret2;
 
+	trace_mark(ext4_ordered_write_end,
+		   "dev %s ino %lu pos %llu len %u copied %u",
+		   inode->i_sb->s_id, inode->i_ino,
+		   (unsigned long long) pos, len, copied);
 	ret = ext4_jbd2_file_inode(handle, inode);
 
 	if (ret == 0) {
@@ -1460,6 +1468,10 @@
 	int ret = 0, ret2;
 	loff_t new_i_size;
 
+	trace_mark(ext4_writeback_write_end,
+		   "dev %s ino %lu pos %llu len %u copied %u",
+		   inode->i_sb->s_id, inode->i_ino,
+		   (unsigned long long) pos, len, copied);
 	new_i_size = pos + copied;
 	if (new_i_size > EXT4_I(inode)->i_disksize) {
 		ext4_update_i_disksize(inode, new_i_size);
@@ -1495,6 +1507,10 @@
 	unsigned from, to;
 	loff_t new_i_size;
 
+	trace_mark(ext4_journalled_write_end,
+		   "dev %s ino %lu pos %llu len %u copied %u",
+		   inode->i_sb->s_id, inode->i_ino,
+		   (unsigned long long) pos, len, copied);
 	from = pos & (PAGE_CACHE_SIZE - 1);
 	to = from + len;
 
@@ -2311,6 +2327,9 @@
 	struct buffer_head *page_bufs;
 	struct inode *inode = page->mapping->host;
 
+	trace_mark(ext4_da_writepage,
+		   "dev %s ino %lu page_index %lu",
+		   inode->i_sb->s_id, inode->i_ino, page->index);
 	size = i_size_read(inode);
 	if (page->index == size >> PAGE_CACHE_SHIFT)
 		len = size & ~PAGE_CACHE_MASK;
@@ -2421,6 +2440,20 @@
 	int needed_blocks, ret = 0, nr_to_writebump = 0;
 	struct ext4_sb_info *sbi = EXT4_SB(mapping->host->i_sb);
 
+	trace_mark(ext4_da_writepages,
+		   "dev %s ino %lu nr_t_write %ld "
+		   "pages_skipped %ld range_start %llu "
+		   "range_end %llu nonblocking %d "
+		   "for_kupdate %d for_reclaim %d "
+		   "for_writepages %d range_cyclic %d",
+		   inode->i_sb->s_id, inode->i_ino,
+		   wbc->nr_to_write, wbc->pages_skipped,
+		   (unsigned long long) wbc->range_start,
+		   (unsigned long long) wbc->range_end,
+		   wbc->nonblocking, wbc->for_kupdate,
+		   wbc->for_reclaim, wbc->for_writepages,
+		   wbc->range_cyclic);
+
 	/*
 	 * No pages to write? This is mainly a kludge to avoid starting
 	 * a transaction for special inodes like journal inode on last iput()
@@ -2539,6 +2572,14 @@
 	if (!no_nrwrite_index_update)
 		wbc->no_nrwrite_index_update = 0;
 	wbc->nr_to_write -= nr_to_writebump;
+	trace_mark(ext4_da_writepage_result,
+		   "dev %s ino %lu ret %d pages_written %d "
+		   "pages_skipped %ld congestion %d "
+		   "more_io %d no_nrwrite_index_update %d",
+		   inode->i_sb->s_id, inode->i_ino, ret,
+		   pages_written, wbc->pages_skipped,
+		   wbc->encountered_congestion, wbc->more_io,
+		   wbc->no_nrwrite_index_update);
 	return ret;
 }
 
@@ -2590,6 +2631,11 @@
 					len, flags, pagep, fsdata);
 	}
 	*fsdata = (void *)0;
+
+	trace_mark(ext4_da_write_begin,
+		   "dev %s ino %lu pos %llu len %u flags %u",
+		   inode->i_sb->s_id, inode->i_ino,
+		   (unsigned long long) pos, len, flags);
 retry:
 	/*
 	 * With delayed allocation, we don't log the i_disksize update
@@ -2679,6 +2725,10 @@
 		}
 	}
 
+	trace_mark(ext4_da_write_end,
+		   "dev %s ino %lu pos %llu len %u copied %u",
+		   inode->i_sb->s_id, inode->i_ino,
+		   (unsigned long long) pos, len, copied);
 	start = pos & (PAGE_CACHE_SIZE - 1);
 	end = start + copied - 1;
 
@@ -2892,6 +2942,9 @@
 	loff_t size = i_size_read(inode);
 	loff_t len;
 
+	trace_mark(ext4_normal_writepage,
+		   "dev %s ino %lu page_index %lu",
+		   inode->i_sb->s_id, inode->i_ino, page->index);
 	J_ASSERT(PageLocked(page));
 	if (page->index == size >> PAGE_CACHE_SHIFT)
 		len = size & ~PAGE_CACHE_MASK;
@@ -2977,6 +3030,9 @@
 	loff_t size = i_size_read(inode);
 	loff_t len;
 
+	trace_mark(ext4_journalled_writepage,
+		   "dev %s ino %lu page_index %lu",
+		   inode->i_sb->s_id, inode->i_ino, page->index);
 	J_ASSERT(PageLocked(page));
 	if (page->index == size >> PAGE_CACHE_SHIFT)
 		len = size & ~PAGE_CACHE_MASK;