f2fs: fix avoid race between truncate and background GC
Thread A Background GC
- f2fs_setattr isize to 0
- truncate_setsize
- gc_data_segment
- f2fs_get_read_data_page page #0
- set_page_dirty
- set_cold_data
- f2fs_truncate
- f2fs_setattr isize to 4k
- read 4k <--- hit data in cached page #0
Above race condition can cause read out invalid data in a truncated
page, fix it by i_gc_rwsem[WRITE] lock.
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 1e6cc68..45f043e 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -2199,8 +2199,12 @@
if (to > i_size) {
down_write(&F2FS_I(inode)->i_mmap_sem);
+ down_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
+
truncate_pagecache(inode, i_size);
f2fs_truncate_blocks(inode, i_size, true);
+
+ up_write(&F2FS_I(inode)->i_gc_rwsem[WRITE]);
up_write(&F2FS_I(inode)->i_mmap_sem);
}
}