f2fs: introduce mode=lfs mount option

This mount option is to enable original log-structured filesystem forcefully.
So, there should be no random writes for main area.

Especially, this supports host-managed SMR device.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c
index 5f655d0c5b1f..607ef4397330 100644
--- a/fs/f2fs/data.c
+++ b/fs/f2fs/data.c
@@ -1710,6 +1710,8 @@ static ssize_t f2fs_direct_IO(struct kiocb *iocb, struct iov_iter *iter)
 
         if (f2fs_encrypted_inode(inode) && S_ISREG(inode->i_mode))
                 return 0;
+        if (test_opt(F2FS_I_SB(inode), LFS))
+                return 0;
 
         trace_f2fs_direct_IO_enter(inode, offset, count, iov_iter_rw(iter));