exofs: groups support

* _calc_stripe_info() changes to accommodate for grouping
  calculations. Returns additional information

* old _prepare_pages() becomes _prepare_one_group()
  which stores pages belonging to one device group.

* New _prepare_for_striping iterates on all groups calling
  _prepare_one_group().

* Enable mounting of groups data_maps (group_width != 0)

[QUESTION]
what is faster A or B;
A.	x += stride;
	x = x % width + first_x;

B	x += stride
	if (x < last_x)
		x = first_x;

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

3 files changed, 141 insertions, 37 deletions

diff --git a/fs/exofs/exofs.h b/fs/exofs/exofs.h
index acfebd36de83..59b8bf2825c7 100644
--- a/fs/exofs/exofs.h
+++ b/fs/exofs/exofs.h
@@ -63,6 +63,8 @@ struct exofs_layout {
         unsigned mirrors_p1;
 
         unsigned group_width;
+        u64      group_depth;
+        unsigned group_count;
 
         enum exofs_inode_layout_gen_functions lay_func;
 
@@ -132,6 +134,7 @@ struct exofs_io_state {
         struct page             **pages;
         unsigned                nr_pages;
         unsigned                pgbase;
+        unsigned                pages_consumed;
 
         /* Attributes */
         unsigned                in_attr_len;
diff --git a/fs/exofs/ios.c b/fs/exofs/ios.c
index d28febdf54ab..5293bc411d17 100644
--- a/fs/exofs/ios.c
+++ b/fs/exofs/ios.c
@@ -262,25 +262,50 @@ int exofs_check_io(struct exofs_io_state *ios, u64 *resid)
 /*
  * L - logical offset into the file
  *
- * U - The number of bytes in a full stripe
+ * U - The number of bytes in a stripe within a group
  *
  *      U = stripe_unit * group_width
  *
- * N - The stripe number
+ * T - The number of bytes striped within a group of component objects
+ *     (before advancing to the next group)
  *
- *      N = L / U
+ *      T = stripe_unit * group_width * group_depth
+ *
+ * S - The number of bytes striped across all component objects
+ *     before the pattern repeats
+ *
+ *      S = stripe_unit * group_width * group_depth * group_count
+ *
+ * M - The "major" (i.e., across all components) stripe number
+ *
+ *      M = L / S
+ *
+ * G - Counts the groups from the beginning of the major stripe
+ *
+ *      G = (L - (M * S)) / T   [or (L % S) / T]
+ *
+ * H - The byte offset within the group
+ *
+ *      H = (L - (M * S)) % T   [or (L % S) % T]
+ *
+ * N - The "minor" (i.e., across the group) stripe number
+ *
+ *      N = H / U
  *
  * C - The component index coresponding to L
  *
- *      C = (L - (N*U)) / stripe_unit
+ *      C = (H - (N * U)) / stripe_unit + G * group_width
+ *      [or (L % U) / stripe_unit + G * group_width]
  *
  * O - The component offset coresponding to L
  *
- *      (N*stripe_unit)+(L%stripe_unit)
+ *      O = L % stripe_unit + N * stripe_unit + M * group_depth * stripe_unit
  */
-
 struct _striping_info {
         u64 obj_offset;
+        u64 group_length;
+        u64 total_group_length;
+        u64 Major;
         unsigned dev;
         unsigned unit_off;
 };
@@ -290,15 +315,35 @@ static void _calc_stripe_info(struct exofs_io_state *ios, u64 file_offset,
 {
         u32     stripe_unit = ios->layout->stripe_unit;
         u32     group_width = ios->layout->group_width;
+        u64     group_depth = ios->layout->group_depth;
+
         u32     U = stripe_unit * group_width;
+        u64     T = U * group_depth;
+        u64     S = T * ios->layout->group_count;
+        u64     M = div64_u64(file_offset, S);
+
+        /*
+        G = (L - (M * S)) / T
+        H = (L - (M * S)) % T
+        */
+        u64     LmodS = file_offset - M * S;
+        u32     G = div64_u64(LmodS, T);
+        u64     H = LmodS - G * T;
+
+        u32     N = div_u64(H, U);
+
+        /* "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;
 
-        u32     LmodU;
-        u64     N = div_u64_rem(file_offset, U, &LmodU);
+        div_u64_rem(file_offset, stripe_unit, &si->unit_off);
 
-        si->unit_off = LmodU % stripe_unit;
-        si->obj_offset = N * stripe_unit + si->unit_off;
-        si->dev = LmodU / stripe_unit;
-        si->dev *= ios->layout->mirrors_p1;
+        si->obj_offset = si->unit_off + (N * stripe_unit) +
+                                  (M * group_depth * stripe_unit);
+
+        si->group_length = T - H;
+        si->total_group_length = T;
+        si->Major = M;
 }
 
 static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_pg,
@@ -345,16 +390,17 @@ static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_pg,
         return 0;
 }
 
-static int _prepare_pages(struct exofs_io_state *ios,
-                          struct _striping_info *si)
+static int _prepare_one_group(struct exofs_io_state *ios, u64 length,
+                              struct _striping_info *si, unsigned first_comp)
 {
-        u64 length = ios->length;
         unsigned stripe_unit = ios->layout->stripe_unit;
         unsigned mirrors_p1 = ios->layout->mirrors_p1;
+        unsigned devs_in_group = ios->layout->group_width * mirrors_p1;
         unsigned dev = si->dev;
-        unsigned comp = 0;
-        unsigned stripes = 0;
-        unsigned cur_pg = 0;
+        unsigned first_dev = dev - (dev % devs_in_group);
+        unsigned comp = first_comp + (dev - first_dev);
+        unsigned max_comp = ios->numdevs ? ios->numdevs - mirrors_p1 : 0;
+        unsigned cur_pg = ios->pages_consumed;
         int ret = 0;
 
         while (length) {
@@ -377,10 +423,11 @@ static int _prepare_pages(struct exofs_io_state *ios,
                                 cur_len = stripe_unit;
                         }
 
-                        stripes++;
+                        if (max_comp < comp)
+                                max_comp = comp;
 
                         dev += mirrors_p1;
-                        dev %= ios->layout->s_numdevs;
+                        dev = (dev % devs_in_group) + first_dev;
                 } else {
                         cur_len = stripe_unit;
                 }
@@ -393,18 +440,24 @@ static int _prepare_pages(struct exofs_io_state *ios,
                         goto out;
 
                 comp += mirrors_p1;
-                comp %= ios->layout->s_numdevs;
+                comp = (comp % devs_in_group) + first_comp;
 
                 length -= cur_len;
         }
 out:
-        ios->numdevs = stripes * mirrors_p1;
+        ios->numdevs = max_comp + mirrors_p1;
+        ios->pages_consumed = cur_pg;
         return ret;
 }
 
 static int _prepare_for_striping(struct exofs_io_state *ios)
 {
+        u64 length = ios->length;
         struct _striping_info si;
+        unsigned devs_in_group = ios->layout->group_width *
+                                 ios->layout->mirrors_p1;
+        unsigned first_comp = 0;
+        int ret = 0;
 
         _calc_stripe_info(ios, ios->offset, &si);
 
@@ -424,7 +477,31 @@ static int _prepare_for_striping(struct exofs_io_state *ios)
                 return 0;
         }
 
-        return _prepare_pages(ios, &si);
+        while (length) {
+                if (length < si.group_length)
+                        si.group_length = length;
+
+                ret = _prepare_one_group(ios, si.group_length, &si, first_comp);
+                if (unlikely(ret))
+                        goto out;
+
+                length -= si.group_length;
+
+                si.group_length = si.total_group_length;
+                si.unit_off = 0;
+                ++si.Major;
+                si.obj_offset = si.Major * ios->layout->stripe_unit *
+                                                ios->layout->group_depth;
+
+                si.dev = (si.dev - (si.dev % devs_in_group)) + devs_in_group;
+                si.dev %= ios->layout->s_numdevs;
+
+                first_comp += devs_in_group;
+                first_comp %= ios->layout->s_numdevs;
+        }
+
+out:
+        return ret;
 }
 
 int exofs_sbi_create(struct exofs_io_state *ios)
@@ -482,6 +559,9 @@ static int _sbi_write_mirror(struct exofs_io_state *ios, int cur_comp)
         unsigned last_comp = cur_comp + ios->layout->mirrors_p1;
         int ret = 0;
 
+        if (ios->pages && !master_dev->length)
+                return 0; /* Just an empty slot */
+
         for (; cur_comp < last_comp; ++cur_comp, ++dev) {
                 struct exofs_per_dev_state *per_dev = &ios->per_dev[cur_comp];
                 struct osd_request *or;
@@ -580,6 +660,9 @@ static int _sbi_read_mirror(struct exofs_io_state *ios, unsigned cur_comp)
         struct exofs_per_dev_state *per_dev = &ios->per_dev[cur_comp];
         unsigned first_dev = (unsigned)ios->obj.id;
 
+        if (ios->pages && !per_dev->length)
+                return 0; /* Just an empty slot */
+
         first_dev = per_dev->dev + first_dev % ios->layout->mirrors_p1;
         or = osd_start_request(exofs_ios_od(ios, first_dev), GFP_KERNEL);
         if (unlikely(!or)) {
diff --git a/fs/exofs/super.c b/fs/exofs/super.c
index 8f4e4b37a578..6cf5e4e84d61 100644
--- a/fs/exofs/super.c
+++ b/fs/exofs/super.c
@@ -323,11 +323,7 @@ static int _read_and_match_data_map(struct exofs_sb_info *sbi, unsigned numdevs,
         sbi->data_map.odm_raid_algorithm  =
                                 le32_to_cpu(dt->dt_data_map.cb_raid_algorithm);
 
-/* FIXME: Only raid0 !group_width/depth for now. if not so, do not mount */
-        if (sbi->data_map.odm_group_width || sbi->data_map.odm_group_depth) {
-                EXOFS_ERR("Group width/depth not supported\n");
-                return -EINVAL;
-        }
+/* FIXME: Only raid0 for now. if not so, do not mount */
         if (sbi->data_map.odm_num_comps != numdevs) {
                 EXOFS_ERR("odm_num_comps(%u) != numdevs(%u)\n",
                           sbi->data_map.odm_num_comps, numdevs);
@@ -343,14 +339,6 @@ static int _read_and_match_data_map(struct exofs_sb_info *sbi, unsigned numdevs,
                 return -EINVAL;
         }
 
-        stripe_length = sbi->data_map.odm_stripe_unit *
-                        (numdevs / (sbi->data_map.odm_mirror_cnt + 1));
-        if (stripe_length >= (1ULL << 32)) {
-                EXOFS_ERR("Total Stripe length(0x%llx)"
-                          " >= 32bit is not supported\n", _LLU(stripe_length));
-                return -EINVAL;
-        }
-
         if (0 != (sbi->data_map.odm_stripe_unit & ~PAGE_MASK)) {
                 EXOFS_ERR("Stripe Unit(0x%llx)"
                           " must be Multples of PAGE_SIZE(0x%lx)\n",
@@ -360,8 +348,36 @@ static int _read_and_match_data_map(struct exofs_sb_info *sbi, unsigned numdevs,
 
         sbi->layout.stripe_unit = sbi->data_map.odm_stripe_unit;
         sbi->layout.mirrors_p1 = sbi->data_map.odm_mirror_cnt + 1;
-        sbi->layout.group_width = sbi->data_map.odm_num_comps /
+
+        if (sbi->data_map.odm_group_width) {
+                sbi->layout.group_width = sbi->data_map.odm_group_width;
+                sbi->layout.group_depth = sbi->data_map.odm_group_depth;
+                if (!sbi->layout.group_depth) {
+                        EXOFS_ERR("group_depth == 0 && group_width != 0\n");
+                        return -EINVAL;
+                }
+                sbi->layout.group_count = sbi->data_map.odm_num_comps /
+                                                sbi->layout.mirrors_p1 /
+                                                sbi->data_map.odm_group_width;
+        } else {
+                if (sbi->data_map.odm_group_depth) {
+                        printk(KERN_NOTICE "Warning: group_depth ignored "
+                                "group_width == 0 && group_depth == %d\n",
+                                sbi->data_map.odm_group_depth);
+                        sbi->data_map.odm_group_depth = 0;
+                }
+                sbi->layout.group_width = sbi->data_map.odm_num_comps /
                                                         sbi->layout.mirrors_p1;
+                sbi->layout.group_depth = -1;
+                sbi->layout.group_count = 1;
+        }
+
+        stripe_length = (u64)sbi->layout.group_width * sbi->layout.stripe_unit;
+        if (stripe_length >= (1ULL << 32)) {
+                EXOFS_ERR("Total Stripe length(0x%llx)"
+                          " >= 32bit is not supported\n", _LLU(stripe_length));
+                return -EINVAL;
+        }
 
         return 0;
 }
@@ -540,6 +556,8 @@ static int exofs_fill_super(struct super_block *sb, void *data, int silent)
         sbi->layout.stripe_unit = PAGE_SIZE;
         sbi->layout.mirrors_p1 = 1;
         sbi->layout.group_width = 1;
+        sbi->layout.group_depth = -1;
+        sbi->layout.group_count = 1;
         sbi->layout.s_ods[0] = od;
         sbi->layout.s_numdevs = 1;
         sbi->layout.s_pid = opts->pid;