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>
diff --git a/fs/exofs/ios.c b/fs/exofs/ios.c
index d28febd..5293bc4 100644
--- a/fs/exofs/ios.c
+++ b/fs/exofs/ios.c
@@ -262,25 +262,50 @@
/*
* 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 @@
{
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);
- u32 LmodU;
- u64 N = div_u64_rem(file_offset, U, &LmodU);
+ /*
+ 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;
- si->unit_off = LmodU % stripe_unit;
- si->obj_offset = N * stripe_unit + si->unit_off;
- si->dev = LmodU / stripe_unit;
+ 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;
+
+ 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->total_group_length = T;
+ si->Major = M;
}
static int _add_stripe_unit(struct exofs_io_state *ios, unsigned *cur_pg,
@@ -345,16 +390,17 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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)) {