ocfs2: fix disk file size and memory file size mismatch

When doing append direct write in an already allocated cluster, and fast
path in ocfs2_dio_get_block() is triggered, function
ocfs2_dio_end_io_write() will be skipped as there is no context
allocated.

As a result, the disk file size will not be changed as it should be.
The solution is to skip fast path when we are about to change file size.

Fixes: af1310367f41 ("ocfs2: fix sparse file & data ordering issue in direct io.")
Signed-off-by: Ryan Ding <ryan.ding@oracle.com>
Acked-by: Junxiao Bi <junxiao.bi@oracle.com>
Cc: Joseph Qi <joseph.qi@huawei.com>
Cc: Mark Fasheh <mfasheh@suse.de>
Cc: Joel Becker <jlbec@evilplan.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ocfs2/aops.c

@@ -2167,6 +2167,12 @@ static int ocfs2_dio_get_block(struct inode *inode, sector_t iblock,
 	mlog(0, "get block of %lu at %llu:%u req %u\n",
 			inode->i_ino, pos, len, total_len);
 
+	/*
+	 * Because we need to change file size in ocfs2_dio_end_io_write(), or
+	 * we may need to add it to orphan dir. So can not fall to fast path
+	 * while file size will be changed.
+	 */
+	if (pos + total_len <= i_size_read(inode)) {
 		down_read(&oi->ip_alloc_sem);
 		/* This is the fast path for re-write. */
 		ret = ocfs2_get_block(inode, iblock, bh_result, create);
@@ -2180,6 +2186,7 @@ static int ocfs2_dio_get_block(struct inode *inode, sector_t iblock,
 
 		/* Clear state set by ocfs2_get_block. */
 		bh_result->b_state = 0;
+	}
 
 	dwc = ocfs2_dio_alloc_write_ctx(bh_result, &first_get_block);
 	if (unlikely(dwc == NULL)) {