exofs: Prepare for groups

* Rename _offset_dev_unit_off() to _calc_stripe_info()
  and recieve a struct for the output params

* In _prepare_for_striping we only need to call
  _calc_stripe_info() once. The other componets
  are easy to calculate from that. This code
  was inspired by what's done in truncate.

* Some code shifts that make sense now but will make
  more sense when group support is added.

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

diff --git a/fs/exofs/ios.c b/fs/exofs/ios.c
index 263052c..d28febd 100644 (file)
--- a/fs/exofs/ios.c
+++ b/fs/exofs/ios.c
@@ -259,28 +259,46 @@ int exofs_check_io(struct exofs_io_state *ios, u64 *resid)
        return acumulated_lin_err;
 }
 
-/* REMOVEME: After review
-   Some quoteing from the standard
-
-   L = logical offset into the file
-   W = number of data components in a stripe
-   S = W * stripe_unit (S is Stripe length)
-   N = L / S (N is the stripe Number)
-   C = (L-(N*S)) / stripe_unit (C is the component)
-   O = (N*stripe_unit)+(L%stripe_unit) (O is the object's offset)
-*/
-
-static void _offset_dev_unit_off(struct exofs_io_state *ios, u64 file_offset,
-                       u64 *obj_offset, unsigned *dev, unsigned *unit_off)
+/*
+ * L - logical offset into the file
+ *
+ * U - The number of bytes in a full stripe
+ *
+ *     U = stripe_unit * group_width
+ *
+ * N - The stripe number
+ *
+ *     N = L / U
+ *
+ * C - The component index coresponding to L
+ *
+ *     C = (L - (N*U)) / stripe_unit
+ *
+ * O - The component offset coresponding to L
+ *
+ *     (N*stripe_unit)+(L%stripe_unit)
+ */
+
+struct _striping_info {
+       u64 obj_offset;
+       unsigned dev;
+       unsigned unit_off;
+};
+
+static void _calc_stripe_info(struct exofs_io_state *ios, u64 file_offset,
+                             struct _striping_info *si)
 {
-       unsigned stripe_unit = ios->layout->stripe_unit;
-       unsigned stripe_length = stripe_unit * ios->layout->group_width;
-       u64 stripe_no = file_offset;
-       unsigned stripe_mod = do_div(stripe_no, stripe_length);
+       u32     stripe_unit = ios->layout->stripe_unit;
+       u32     group_width = ios->layout->group_width;
+       u32     U = stripe_unit * group_width;
+
+       u32     LmodU;
+       u64     N = div_u64_rem(file_offset, U, &LmodU);
 
-       *unit_off = stripe_mod % stripe_unit;
-       *obj_offset = stripe_no * stripe_unit + *unit_off;
-       *dev = stripe_mod / stripe_unit * ios->layout->mirrors_p1;
+       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;
 }
 
 static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_pg,
@@ -327,65 +345,88 @@ static int _add_stripe_unit(struct exofs_io_state *ios,  unsigned *cur_pg,
        return 0;
 }
 
-static int _prepare_for_striping(struct exofs_io_state *ios)
+static int _prepare_pages(struct exofs_io_state *ios,
+                         struct _striping_info *si)
 {
        u64 length = ios->length;
-       u64 offset = ios->offset;
        unsigned stripe_unit = ios->layout->stripe_unit;
+       unsigned mirrors_p1 = ios->layout->mirrors_p1;
+       unsigned dev = si->dev;
        unsigned comp = 0;
        unsigned stripes = 0;
        unsigned cur_pg = 0;
        int ret = 0;
 
-       if (!ios->pages) {
-               if (ios->kern_buff) {
-                       struct exofs_per_dev_state *per_dev = &ios->per_dev[0];
-                       unsigned unit_off;
-
-                       _offset_dev_unit_off(ios, offset, &per_dev->offset,
-                                            &per_dev->dev, &unit_off);
-                       /* no cross device without page array */
-                       BUG_ON((ios->layout->group_width > 1) &&
-                              (unit_off + length > stripe_unit));
-               }
-               ios->numdevs = ios->layout->mirrors_p1;
-               return 0;
-       }
-
        while (length) {
                struct exofs_per_dev_state *per_dev = &ios->per_dev[comp];
-               unsigned cur_len, page_off;
+               unsigned cur_len, page_off = 0;
 
                if (!per_dev->length) {
-                       unsigned unit_off;
+                       per_dev->dev = dev;
+                       if (dev < si->dev) {
+                               per_dev->offset = si->obj_offset + stripe_unit -
+                                                                  si->unit_off;
+                               cur_len = stripe_unit;
+                       } else if (dev == si->dev) {
+                               per_dev->offset = si->obj_offset;
+                               cur_len = stripe_unit - si->unit_off;
+                               page_off = si->unit_off & ~PAGE_MASK;
+                               BUG_ON(page_off && (page_off != ios->pgbase));
+                       } else { /* dev > si->dev */
+                               per_dev->offset = si->obj_offset - si->unit_off;
+                               cur_len = stripe_unit;
+                       }
 
-                       _offset_dev_unit_off(ios, offset, &per_dev->offset,
-                                            &per_dev->dev, &unit_off);
                        stripes++;
-                       cur_len = min_t(u64, stripe_unit - unit_off, length);
-                       offset += cur_len;
-                       page_off = unit_off & ~PAGE_MASK;
-                       BUG_ON(page_off != ios->pgbase);
+
+                       dev += mirrors_p1;
+                       dev %= ios->layout->s_numdevs;
                } else {
-                       cur_len = min_t(u64, stripe_unit, length);
-                       page_off = 0;
+                       cur_len = stripe_unit;
                }
+               if (cur_len >= length)
+                       cur_len = length;
 
                ret = _add_stripe_unit(ios, &cur_pg, page_off , per_dev,
                                       cur_len);
                if (unlikely(ret))
                        goto out;
 
-               comp += ios->layout->mirrors_p1;
+               comp += mirrors_p1;
                comp %= ios->layout->s_numdevs;
 
                length -= cur_len;
        }
 out:
-       ios->numdevs = stripes * ios->layout->mirrors_p1;
+       ios->numdevs = stripes * mirrors_p1;
        return ret;
 }
 
+static int _prepare_for_striping(struct exofs_io_state *ios)
+{
+       struct _striping_info si;
+
+       _calc_stripe_info(ios, ios->offset, &si);
+
+       if (!ios->pages) {
+               if (ios->kern_buff) {
+                       struct exofs_per_dev_state *per_dev = &ios->per_dev[0];
+
+                       per_dev->offset = si.obj_offset;
+                       per_dev->dev = si.dev;
+
+                       /* no cross device without page array */
+                       BUG_ON((ios->layout->group_width > 1) &&
+                              (si.unit_off + ios->length >
+                               ios->layout->stripe_unit));
+               }
+               ios->numdevs = ios->layout->mirrors_p1;
+               return 0;
+       }
+
+       return _prepare_pages(ios, &si);
+}
+
 int exofs_sbi_create(struct exofs_io_state *ios)
 {
        int i, ret;
@@ -648,9 +689,7 @@ int exofs_oi_truncate(struct exofs_i_info *oi, u64 size)
                struct osd_attr attr;
                __be64 newsize;
        } *size_attrs;
-       u64 this_obj_size;
-       unsigned dev;
-       unsigned unit_off;
+       struct _striping_info si;
        int i, ret;
 
        ret = exofs_get_io_state(&sbi->layout, &ios);
@@ -668,19 +707,19 @@ int exofs_oi_truncate(struct exofs_i_info *oi, u64 size)
        ios->cred = oi->i_cred;
 
        ios->numdevs = ios->layout->s_numdevs;
-       _offset_dev_unit_off(ios, size, &this_obj_size, &dev, &unit_off);
+       _calc_stripe_info(ios, size, &si);
 
        for (i = 0; i < ios->layout->group_width; ++i) {
                struct exofs_trunc_attr *size_attr = &size_attrs[i];
                u64 obj_size;
 
-               if (i < dev)
-                       obj_size = this_obj_size +
-                                       ios->layout->stripe_unit - unit_off;
-               else if (i == dev)
-                       obj_size = this_obj_size;
-               else /* i > dev */
-                       obj_size = this_obj_size - unit_off;
+               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;
 
                size_attr->newsize = cpu_to_be64(obj_size);
                size_attr->attr = g_attr_logical_length;