f2fs crypto: fix racing of accessing encrypted page among

 different competitors

Since we use different page cache (normally inode's page cache for R/W
and meta inode's page cache for GC) to cache the same physical block
which is belong to an encrypted inode. Writeback of these two page
cache should be exclusive, but now we didn't handle writeback state
well, so there may be potential racing problem:

a)
kworker:				f2fs_gc:
 - f2fs_write_data_pages
  - f2fs_write_data_page
   - do_write_data_page
    - write_data_page
     - f2fs_submit_page_mbio
(page#1 in inode's page cache was queued
in f2fs bio cache, and be ready to write
to new blkaddr)
					 - gc_data_segment
					  - move_encrypted_block
					   - pagecache_get_page
					(page#2 in meta inode's page cache
					was cached with the invalid datas
					of physical block located in new
					blkaddr)
					   - f2fs_submit_page_mbio
					(page#1 was submitted, later, page#2
					with invalid data will be submitted)

b)
f2fs_gc:
 - gc_data_segment
  - move_encrypted_block
   - f2fs_submit_page_mbio
(page#1 in meta inode's page cache was
queued in f2fs bio cache, and be ready
to write to new blkaddr)
					user thread:
					 - f2fs_write_begin
					  - f2fs_submit_page_bio
					(we submit the request to block layer
					to update page#2 in inode's page cache
					with physical block located in new
					blkaddr, so here we may read gabbage
					data from new blkaddr since GC hasn't
					writebacked the page#1 yet)

This patch fixes above potential racing problem for encrypted inode.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 10 insertions, 2 deletions

diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c
index 3f19634e2aa5..af7c24caeef9 100644
--- a/fs/f2fs/gc.c
+++ b/fs/f2fs/gc.c
@@ -559,8 +559,16 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
 	if (err)
 		goto out;
 
-	if (unlikely(dn.data_blkaddr == NULL_ADDR))
+	if (unlikely(dn.data_blkaddr == NULL_ADDR)) {
+		ClearPageUptodate(page);
 		goto put_out;
+	}
+
+	/*
+	 * don't cache encrypted data into meta inode until previous dirty
+	 * data were writebacked to avoid racing between GC and flush.
+	 */
+	f2fs_wait_on_page_writeback(page, DATA);
 
 	get_node_info(fio.sbi, dn.nid, &ni);
 	set_summary(&sum, dn.nid, dn.ofs_in_node, ni.version);
@@ -589,7 +597,7 @@ static void move_encrypted_block(struct inode *inode, block_t bidx)
 		goto put_page_out;
 
 	set_page_dirty(fio.encrypted_page);
-	f2fs_wait_on_page_writeback(fio.encrypted_page, META);
+	f2fs_wait_on_page_writeback(fio.encrypted_page, DATA);
 	if (clear_page_dirty_for_io(fio.encrypted_page))
 		dec_page_count(fio.sbi, F2FS_DIRTY_META);