f2fs: Avoid double lock for cp_rwsem during checkpoint

There could be a scenario where f2fs_sync_node_pages gets
called during checkpoint, which in turn tries to flush
inline data and calls iput(). This results in deadlock as
iput() tries to hold cp_rwsem, which is already held at the
beginning by checkpoint->block_operations().

Call stack :

Thread A		Thread B
f2fs_write_checkpoint()
- block_operations(sbi)
 - f2fs_lock_all(sbi);
  - down_write(&sbi->cp_rwsem);

                        - open()
                         - igrab()
                        - write() write inline data
                        - unlink()
- f2fs_sync_node_pages()
 - if (is_inline_node(page))
  - flush_inline_data()
   - ilookup()
     page = f2fs_pagecache_get_page()
     if (!page)
      goto iput_out;
     iput_out:
			-close()
			-iput()
       iput(inode);
       - f2fs_evict_inode()
        - f2fs_truncate_blocks()
         - f2fs_lock_op()
           - down_read(&sbi->cp_rwsem);

Fixes: 2049d4fcb057 ("f2fs: avoid multiple node page writes due to inline_data")
Signed-off-by: Sayali Lokhande <sayalil@codeaurora.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 49 insertions, 2 deletions

diff --git a/fs/f2fs/node.c b/fs/f2fs/node.c
index 1db8cabf727e..e632de10aeda 100644
--- a/fs/f2fs/node.c
+++ b/fs/f2fs/node.c
@@ -1807,6 +1807,53 @@ static bool flush_dirty_inode(struct page *page)
 	return true;
 }
 
+int f2fs_flush_inline_data(struct f2fs_sb_info *sbi)
+{
+	pgoff_t index = 0;
+	struct pagevec pvec;
+	int nr_pages;
+	int ret = 0;
+
+	pagevec_init(&pvec);
+
+	while ((nr_pages = pagevec_lookup_tag(&pvec,
+			NODE_MAPPING(sbi), &index, PAGECACHE_TAG_DIRTY))) {
+		int i;
+
+		for (i = 0; i < nr_pages; i++) {
+			struct page *page = pvec.pages[i];
+
+			if (!IS_DNODE(page))
+				continue;
+
+			lock_page(page);
+
+			if (unlikely(page->mapping != NODE_MAPPING(sbi))) {
+continue_unlock:
+				unlock_page(page);
+				continue;
+			}
+
+			if (!PageDirty(page)) {
+				/* someone wrote it for us */
+				goto continue_unlock;
+			}
+
+			/* flush inline_data, if it's async context. */
+			if (is_inline_node(page)) {
+				clear_inline_node(page);
+				unlock_page(page);
+				flush_inline_data(sbi, ino_of_node(page));
+				continue;
+			}
+			unlock_page(page);
+		}
+		pagevec_release(&pvec);
+		cond_resched();
+	}
+	return ret;
+}
+
 int f2fs_sync_node_pages(struct f2fs_sb_info *sbi,
 				struct writeback_control *wbc,
 				bool do_balance, enum iostat_type io_type)
@@ -1870,8 +1917,8 @@ continue_unlock:
 				goto continue_unlock;
 			}
 
-			/* flush inline_data */
-			if (is_inline_node(page)) {
+			/* flush inline_data, if it's async context. */
+			if (do_balance && is_inline_node(page)) {
 				clear_inline_node(page);
 				unlock_page(page);
 				flush_inline_data(sbi, ino_of_node(page));