GFS2: Use inode_newsize_ok and get_write_access in fallocate

gfs2_fallocate wasn't checking inode_newsize_ok nor get_write_access.
Split out the context setup and inode locking pieces into a separate
function to make it more clear and add these missing calls.

inode_newsize_ok is called conditional on FALLOC_FL_KEEP_SIZE as there
is no need to enforce a file size limit if it isn't going to change.

Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

fs/gfs2/file.c

@@ -797,8 +797,7 @@ static void calc_max_reserv(struct gfs2_inode *ip, loff_t max, loff_t *len,
 	}
 }
 
-static long gfs2_fallocate(struct file *file, int mode, loff_t offset,
-			   loff_t len)
+static long __gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 {
 	struct inode *inode = file_inode(file);
 	struct gfs2_sbd *sdp = GFS2_SB(inode);
@@ -812,14 +811,9 @@ static long gfs2_fallocate(struct file *file, int mode, loff_t offset,
 	loff_t bsize_mask = ~((loff_t)sdp->sd_sb.sb_bsize - 1);
 	loff_t next = (offset + len - 1) >> sdp->sd_sb.sb_bsize_shift;
 	loff_t max_chunk_size = UINT_MAX & bsize_mask;
-	struct gfs2_holder gh;
 
 	next = (next + 1) << sdp->sd_sb.sb_bsize_shift;
 
-	/* We only support the FALLOC_FL_KEEP_SIZE mode */
-	if (mode & ~FALLOC_FL_KEEP_SIZE)
-		return -EOPNOTSUPP;
-
 	offset &= bsize_mask;
 
 	len = next - offset;
@@ -830,17 +824,6 @@ static long gfs2_fallocate(struct file *file, int mode, loff_t offset,
 	if (bytes == 0)
 		bytes = sdp->sd_sb.sb_bsize;
 
-	error = gfs2_rs_alloc(ip);
-	if (error)
-		return error;
-
-	mutex_lock(&inode->i_mutex);
-
-	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
-	error = gfs2_glock_nq(&gh);
-	if (unlikely(error))
-		goto out_uninit;
-
 	gfs2_size_hint(file, offset, len);
 
 	while (len > 0) {
@@ -853,8 +836,7 @@ static long gfs2_fallocate(struct file *file, int mode, loff_t offset,
 		}
 		error = gfs2_quota_lock_check(ip);
 		if (error)
-			goto out_unlock;
-
+			return error;
 retry:
 		gfs2_write_calc_reserv(ip, bytes, &data_blocks, &ind_blocks);
 
@@ -898,18 +880,58 @@ retry:
 
 	if (error == 0)
 		error = generic_write_sync(file, pos, count);
-	goto out_unlock;
+	return error;
 
 out_trans_fail:
 	gfs2_inplace_release(ip);
 out_qunlock:
 	gfs2_quota_unlock(ip);
+	return error;
+}
+
+static long gfs2_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
+{
+	struct inode *inode = file_inode(file);
+	struct gfs2_inode *ip = GFS2_I(inode);
+	struct gfs2_holder gh;
+	int ret;
+
+	if (mode & ~FALLOC_FL_KEEP_SIZE)
+		return -EOPNOTSUPP;
+
+	mutex_lock(&inode->i_mutex);
+
+	gfs2_holder_init(ip->i_gl, LM_ST_EXCLUSIVE, 0, &gh);
+	ret = gfs2_glock_nq(&gh);
+	if (ret)
+		goto out_uninit;
+
+	if (!(mode & FALLOC_FL_KEEP_SIZE) &&
+	    (offset + len) > inode->i_size) {
+		ret = inode_newsize_ok(inode, offset + len);
+		if (ret)
+			goto out_unlock;
+	}
+
+	ret = get_write_access(inode);
+	if (ret)
+		goto out_unlock;
+
+	ret = gfs2_rs_alloc(ip);
+	if (ret)
+		goto out_putw;
+
+	ret = __gfs2_fallocate(file, mode, offset, len);
+	if (ret)
+		gfs2_rs_deltree(ip->i_res);
+out_putw:
+	put_write_access(inode);
 out_unlock:
 	gfs2_glock_dq(&gh);
 out_uninit:
 	gfs2_holder_uninit(&gh);
 	mutex_unlock(&inode->i_mutex);
-	return error;
+	return ret;
 }
 
 #ifdef CONFIG_GFS2_FS_LOCKING_DLM