ext4: protect i_disksize update by i_data_sem in direct write path

i_disksize update should be protected by i_data_sem, by either taking
the lock explicitly or by using ext4_update_i_disksize() helper. But the
i_disksize updates in ext4_direct_IO_write() are not protected at all,
which may be racing with i_disksize updates in writeback path in
delalloc buffer write path.

This is found by code inspection, and I didn't hit any i_disksize
corruption due to this bug. Thanks to Jan Kara for catching this bug and
suggesting the fix!

Reported-by: Jan Kara <jack@suse.cz>
Suggested-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eryu Guan <guaneryu@gmail.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@vger.kernel.org
Orabug: 28940828

commit 73fdad00b208b139cf43f3163fbc0f67e4c6047c upstream

Signed-off-by: Brian Maly <brian.maly@oracle.com>
Conflicts:
	fs/ext4/indirect.c
	code line mismatch

Signed-off-by: Shan Hai <shan.hai@oracle.com>
Reviewed-by: Ashish Samant <ashish.samant@oracle.com>
Signed-off-by: Brian Maly <brian.maly@oracle.com>

diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c
index e862df31ddda30c41f5ba15fc810b6bb8495e3ad..f5d37de17558be4a6a7d983905a5cc59c00d23a8 100644 (file)
--- a/fs/ext4/indirect.c
+++ b/fs/ext4/indirect.c
@@ -647,7 +647,6 @@ ssize_t ext4_ind_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
 {
        struct file *file = iocb->ki_filp;
        struct inode *inode = file->f_mapping->host;
-       struct ext4_inode_info *ei = EXT4_I(inode);
        handle_t *handle;
        ssize_t ret;
        int orphan = 0;
@@ -670,7 +669,7 @@ ssize_t ext4_ind_direct_IO(struct kiocb *iocb, struct iov_iter *iter,
                                goto out;
                        }
                        orphan = 1;
-                       ei->i_disksize = inode->i_size;
+                       ext4_update_i_disksize(inode, inode->i_size);
                        ext4_journal_stop(handle);
                }
        }
@@ -738,7 +737,7 @@ locked:
                if (ret > 0) {
                        loff_t end = offset + ret;
                        if (end > inode->i_size) {
-                               ei->i_disksize = end;
+                               ext4_update_i_disksize(inode, end);
                                i_size_write(inode, end);
                                /*
                                 * We're going to return a positive `ret'