exofs: Fix truncate for the raid-groups case

In the general raid-group case the truncate was wrong in that
it did not also fix the object length of the neighboring groups.

There are two bad cases in the old code:
1. Space that should be freed was not.
2. If a file That was big is truncated small, then made bigger
   again, the holes would not contain zeros but could expose old data.
   (If the growing of the file expands to more than a full
    groups cycle + group size (> S + T))

Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>

fs/exofs/ios.c

@@ -305,20 +305,21 @@ int exofs_check_io(struct exofs_io_state *ios, u64 *resid)
 struct _striping_info {
 	u64 obj_offset;
 	u64 group_length;
+	u64 M; /* for truncate */
 	unsigned dev;
 	unsigned unit_off;
 };
 
-static void _calc_stripe_info(struct exofs_io_state *ios, u64 file_offset,
+static void _calc_stripe_info(struct exofs_layout *layout, u64 file_offset,
 			      struct _striping_info *si)
 {
-	u32	stripe_unit = ios->layout->stripe_unit;
-	u32	group_width = ios->layout->group_width;
-	u64	group_depth = ios->layout->group_depth;
+	u32	stripe_unit = layout->stripe_unit;
+	u32	group_width = layout->group_width;
+	u64	group_depth = layout->group_depth;
 
 	u32	U = stripe_unit * group_width;
 	u64	T = U * group_depth;
-	u64	S = T * ios->layout->group_count;
+	u64	S = T * layout->group_count;
 	u64	M = div64_u64(file_offset, S);
 
 	/*
@@ -333,14 +334,15 @@ static void _calc_stripe_info(struct exofs_io_state *ios, u64 file_offset,
 
 	/* "H - (N * U)" is just "H % U" so it's bound to u32 */
 	si->dev = (u32)(H - (N * U)) / stripe_unit + G * group_width;
-	si->dev *= ios->layout->mirrors_p1;
+	si->dev *= layout->mirrors_p1;
 
 	div_u64_rem(file_offset, stripe_unit, &si->unit_off);
 
 	si->obj_offset = si->unit_off + (N * stripe_unit) +
 				  (M * group_depth * stripe_unit);
 
 	si->group_length = T - H;
+	si->M = M;
 }
 
 static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_pg,
@@ -454,7 +456,7 @@ static int _prepare_for_striping(struct exofs_io_state *ios)
 		if (ios->kern_buff) {
 			struct exofs_per_dev_state *per_dev = &ios->per_dev[0];
 
-			_calc_stripe_info(ios, ios->offset, &si);
+			_calc_stripe_info(ios->layout, ios->offset, &si);
 			per_dev->offset = si.obj_offset;
 			per_dev->dev = si.dev;
 
@@ -468,7 +470,7 @@ static int _prepare_for_striping(struct exofs_io_state *ios)
 	}
 
 	while (length) {
-		_calc_stripe_info(ios, offset, &si);
+		_calc_stripe_info(ios->layout, offset, &si);
 
 		if (length < si.group_length)
 			si.group_length = length;
@@ -745,6 +747,31 @@ static int _truncate_mirrors(struct exofs_io_state *ios, unsigned cur_comp,
 	return 0;
 }
 
+struct _trunc_info {
+	struct _striping_info si;
+	u64 prev_group_obj_off;
+	u64 next_group_obj_off;
+
+	unsigned first_group_dev;
+	unsigned nex_group_dev;
+	unsigned max_devs;
+};
+
+void _calc_trunk_info(struct exofs_layout *layout, u64 file_offset,
+		       struct _trunc_info *ti)
+{
+	unsigned stripe_unit = layout->stripe_unit;
+
+	_calc_stripe_info(layout, file_offset, &ti->si);
+
+	ti->prev_group_obj_off = ti->si.M * stripe_unit;
+	ti->next_group_obj_off = ti->si.M ? (ti->si.M - 1) * stripe_unit : 0;
+
+	ti->first_group_dev = ti->si.dev - (ti->si.dev % layout->group_width);
+	ti->nex_group_dev = ti->first_group_dev + layout->group_width;
+	ti->max_devs = layout->group_width * layout->group_count;
+}
+
 int exofs_oi_truncate(struct exofs_i_info *oi, u64 size)
 {
 	struct exofs_sb_info *sbi = oi->vfs_inode.i_sb->s_fs_info;
@@ -753,14 +780,16 @@ int exofs_oi_truncate(struct exofs_i_info *oi, u64 size)
 		struct osd_attr attr;
 		__be64 newsize;
 	} *size_attrs;
-	struct _striping_info si;
+	struct _trunc_info ti;
 	int i, ret;
 
 	ret = exofs_get_io_state(&sbi->layout, &ios);
 	if (unlikely(ret))
 		return ret;
 
-	size_attrs = kcalloc(ios->layout->group_width, sizeof(*size_attrs),
+	_calc_trunk_info(ios->layout, size, &ti);
+
+	size_attrs = kcalloc(ti.max_devs, sizeof(*size_attrs),
 			     GFP_KERNEL);
 	if (unlikely(!size_attrs)) {
 		ret = -ENOMEM;
@@ -769,26 +798,30 @@ int exofs_oi_truncate(struct exofs_i_info *oi, u64 size)
 
 	ios->obj.id = exofs_oi_objno(oi);
 	ios->cred = oi->i_cred;
-
 	ios->numdevs = ios->layout->s_numdevs;
-	_calc_stripe_info(ios, size, &si);
 
-	for (i = 0; i < ios->layout->group_width; ++i) {
+	for (i = 0; i < ti.max_devs; ++i) {
 		struct exofs_trunc_attr *size_attr = &size_attrs[i];
 		u64 obj_size;
 
-		if (i < si.dev)
-			obj_size = si.obj_offset +
-					ios->layout->stripe_unit - si.unit_off;
-		else if (i == si.dev)
-			obj_size = si.obj_offset;
-		else /* i > si.dev */
-			obj_size = si.obj_offset - si.unit_off;
+		if (i < ti.first_group_dev)
+			obj_size = ti.prev_group_obj_off;
+		else if (i >= ti.nex_group_dev)
+			obj_size = ti.next_group_obj_off;
+		else if (i < ti.si.dev) /* dev within this group */
+			obj_size = ti.si.obj_offset +
+				      ios->layout->stripe_unit - ti.si.unit_off;
+		else if (i == ti.si.dev)
+			obj_size = ti.si.obj_offset;
+		else /* i > ti.dev */
+			obj_size = ti.si.obj_offset - ti.si.unit_off;
 
 		size_attr->newsize = cpu_to_be64(obj_size);
 		size_attr->attr = g_attr_logical_length;
 		size_attr->attr.val_ptr = &size_attr->newsize;
 
+		EXOFS_DBGMSG("trunc(0x%llx) obj_offset=0x%llx dev=%d\n",
+			     _LLU(ios->obj.id), _LLU(obj_size), i);
 		ret = _truncate_mirrors(ios, i * ios->layout->mirrors_p1,
 					&size_attr->attr);
 		if (unlikely(ret))