summaryrefslogtreecommitdiffstats
path: root/drivers/md/raid10.c
diff options
context:
space:
mode:
Diffstat (limited to 'drivers/md/raid10.c')
-rw-r--r--drivers/md/raid10.c58
1 files changed, 40 insertions, 18 deletions
diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index de174ad6f8bd..70b58b4bcf89 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -38,21 +38,36 @@
* near_copies (stored in low byte of layout)
* far_copies (stored in second byte of layout)
* far_offset (stored in bit 16 of layout )
+ * use_far_sets (stored in bit 17 of layout )
*
- * The data to be stored is divided into chunks using chunksize.
- * Each device is divided into far_copies sections.
- * In each section, chunks are laid out in a style similar to raid0, but
- * near_copies copies of each chunk is stored (each on a different drive).
- * The starting device for each section is offset near_copies from the starting
- * device of the previous section.
- * Thus they are (near_copies*far_copies) of each chunk, and each is on a different
- * drive.
- * near_copies and far_copies must be at least one, and their product is at most
- * raid_disks.
+ * The data to be stored is divided into chunks using chunksize. Each device
+ * is divided into far_copies sections. In each section, chunks are laid out
+ * in a style similar to raid0, but near_copies copies of each chunk is stored
+ * (each on a different drive). The starting device for each section is offset
+ * near_copies from the starting device of the previous section. Thus there
+ * are (near_copies * far_copies) of each chunk, and each is on a different
+ * drive. near_copies and far_copies must be at least one, and their product
+ * is at most raid_disks.
*
* If far_offset is true, then the far_copies are handled a bit differently.
- * The copies are still in different stripes, but instead of be very far apart
- * on disk, there are adjacent stripes.
+ * The copies are still in different stripes, but instead of being very far
+ * apart on disk, there are adjacent stripes.
+ *
+ * The far and offset algorithms are handled slightly differently if
+ * 'use_far_sets' is true. In this case, the array's devices are grouped into
+ * sets that are (near_copies * far_copies) in size. The far copied stripes
+ * are still shifted by 'near_copies' devices, but this shifting stays confined
+ * to the set rather than the entire array. This is done to improve the number
+ * of device combinations that can fail without causing the array to fail.
+ * Example 'far' algorithm w/o 'use_far_sets' (each letter represents a chunk
+ * on a device):
+ * A B C D A B C D E
+ * ... ...
+ * D A B C E A B C D
+ * Example 'far' algorithm w/ 'use_far_sets' enabled (sets illustrated w/ []'s):
+ * [A B] [C D] [A B] [C D E]
+ * |...| |...| |...| | ... |
+ * [B A] [D C] [B A] [E C D]
*/
/*
@@ -551,14 +566,18 @@ static void __raid10_find_phys(struct geom *geo, struct r10bio *r10bio)
/* and calculate all the others */
for (n = 0; n < geo->near_copies; n++) {
int d = dev;
+ int set;
sector_t s = sector;
r10bio->devs[slot].devnum = d;
r10bio->devs[slot].addr = s;
slot++;
for (f = 1; f < geo->far_copies; f++) {
+ set = d / geo->far_set_size;
d += geo->near_copies;
- d %= geo->raid_disks;
+ d %= geo->far_set_size;
+ d += geo->far_set_size * set;
+
s += geo->stride;
r10bio->devs[slot].devnum = d;
r10bio->devs[slot].addr = s;
@@ -594,6 +613,8 @@ static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)
* or recovery, so reshape isn't happening
*/
struct geom *geo = &conf->geo;
+ int far_set_start = (dev / geo->far_set_size) * geo->far_set_size;
+ int far_set_size = geo->far_set_size;
offset = sector & geo->chunk_mask;
if (geo->far_offset) {
@@ -601,13 +622,13 @@ static sector_t raid10_find_virt(struct r10conf *conf, sector_t sector, int dev)
chunk = sector >> geo->chunk_shift;
fc = sector_div(chunk, geo->far_copies);
dev -= fc * geo->near_copies;
- if (dev < 0)
- dev += geo->raid_disks;
+ if (dev < far_set_start)
+ dev += far_set_size;
} else {
while (sector >= geo->stride) {
sector -= geo->stride;
- if (dev < geo->near_copies)
- dev += geo->raid_disks - geo->near_copies;
+ if (dev < (geo->near_copies + far_set_start))
+ dev += far_set_size - geo->near_copies;
else
dev -= geo->near_copies;
}
@@ -3438,7 +3459,7 @@ static int setup_geo(struct geom *geo, struct mddev *mddev, enum geo_type new)
disks = mddev->raid_disks + mddev->delta_disks;
break;
}
- if (layout >> 17)
+ if (layout >> 18)
return -1;
if (chunk < (PAGE_SIZE >> 9) ||
!is_power_of_2(chunk))
@@ -3450,6 +3471,7 @@ static int setup_geo(struct geom *geo, struct mddev *mddev, enum geo_type new)
geo->near_copies = nc;
geo->far_copies = fc;
geo->far_offset = fo;
+ geo->far_set_size = (layout & (1<<17)) ? disks / fc : disks;
geo->chunk_mask = chunk - 1;
geo->chunk_shift = ffz(~chunk);
return nc*fc;
OpenPOWER on IntegriCloud