Compression option in inode should not be changed after they have
been used, however, it may happen in below race case:
Thread A Thread B
- f2fs_ioc_set_compress_option
- check f2fs_is_mmap_file()
- check get_dirty_pages()
- check F2FS_HAS_BLOCKS()
- f2fs_file_mmap
- set_inode_flag(FI_MMAP_FILE)
- fault
- do_page_mkwrite
- f2fs_vm_page_mkwrite
- f2fs_get_block_locked
- fault_dirty_shared_page
- set_page_dirty
- update i_compress_algorithm
- update i_log_cluster_size
- update i_cluster_size
Avoid such race condition by covering f2fs_file_mmap() w/ i_sem lock,
meanwhile add mmap file check condition in f2fs_may_compress() as well.
Fixes: e1e8debec6 ("f2fs: add F2FS_IOC_SET_COMPRESS_OPTION ioctl")
Signed-off-by: Chao Yu <chao@kernel.org>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
b5ab3276eb