For READ, caller normally hopes to get what they request, other than
full stripe map.
In this case, we should remove unrelated stripe map, just like the
following case:
32K 96K
|<-request range->|
0 64k 128K
RAID0: | Data 1 | Data 2 |
disk1 disk2
Before this patch, we return the full stripe:
Stripe 0: Logical 0, Physical X, Len 64K, Dev disk1
Stripe 1: Logical 64k, Physical Y, Len 64K, Dev disk2
After this patch, we limit the stripe result to the request range:
Stripe 0: Logical 32K, Physical X+32K, Len 32K, Dev disk1
Stripe 1: Logical 64k, Physical Y, Len 32K, Dev disk2
And if it's a RAID5/6 stripe, we just handle it like RAID0, ignoring
parities.
This should make caller easier to use.
Signed-off-by: Qu Wenruo <quwen...@cn.fujitsu.com>
---
volumes.c | 103 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 102 insertions(+), 1 deletion(-)
diff --git a/volumes.c b/volumes.c
index 985e5661..e61ddcd6 100644
--- a/volumes.c
+++ b/volumes.c
@@ -1737,6 +1737,107 @@ static int fill_full_map_block(struct map_lookup *map,
u64 start, u64 length,
return 0;
}
+static void del_one_stripe(struct btrfs_map_block *map_block, int i)
+{
+ int cur_nr = map_block->num_stripes;
+ int size_left = (cur_nr - 1 - i) * sizeof(struct btrfs_map_stripe);
+
+ memmove(&map_block->stripes[i], &map_block->stripes[i + 1], size_left);
+ map_block->num_stripes--;
+}
+
+static void remove_unrelated_stripes(struct map_lookup *map,
+ int rw, u64 start, u64 length,
+ struct btrfs_map_block *map_block)
+{
+ int i = 0;
+ /*
+ * RAID5/6 write must use full stripe.
+ * No need to do anything.
+ */
+ if (map->type & (BTRFS_BLOCK_GROUP_RAID5 | BTRFS_BLOCK_GROUP_RAID6) &&
+ rw == WRITE)
+ return;
+
+ /*
+ * For RAID0/1/10/DUP, whatever read/write, we can remove unrelated
+ * stripes without causing anything wrong.
+ * RAID5/6 READ is just like RAID0, we don't care parity unless we need
+ * to recovery.
+ * For recovery, rw should be set to WRITE.
+ */
+ while (i < map_block->num_stripes) {
+ struct btrfs_map_stripe *stripe;
+ u64 orig_logical; /* Original stripe logical start */
+ u64 orig_end; /* Original stripe logical end */
+
+ stripe = &map_block->stripes[i];
+
+ /*
+ * For READ, we don't really care parity
+ */
+ if (stripe->logical == BTRFS_RAID5_P_STRIPE ||
+ stripe->logical == BTRFS_RAID6_Q_STRIPE) {
+ del_one_stripe(map_block, i);
+ continue;
+ }
+ /* Completely unrelated stripe */
+ if (stripe->logical >= start + length ||
+ stripe->logical + stripe->length <= start) {
+ del_one_stripe(map_block, i);
+ continue;
+ }
+ /* Covered stripe, modify its logical and physical */
+ orig_logical = stripe->logical;
+ orig_end = stripe->logical + stripe->length;
+ if (start + length <= orig_end) {
+ /*
+ * |<--range-->|
+ * | stripe |
+ * Or
+ * |<range>|
+ * | stripe |
+ */
+ stripe->logical = max(orig_logical, start);
+ stripe->length = start + length;
+ stripe->physical += stripe->logical - orig_logical;
+ } else if (start >= orig_logical) {
+ /*
+ * |<-range--->|
+ * | stripe |
+ * Or
+ * |<range>|
+ * | stripe |
+ */
+ stripe->logical = start;
+ stripe->length = min(orig_end, start + length);
+ stripe->physical += stripe->logical - orig_logical;
+ }
+ /*
+ * Remaining case:
+ * |<----range----->|
+ * | stripe |
+ * No need to do any modification
+ */
+ i++;
+ }
+
+ /* Recaculate map_block size */
+ map_block->start = 0;
+ map_block->length = 0;
+ for (i = 0; i < map_block->num_stripes; i++) {
+ struct btrfs_map_stripe *stripe;
+
+ stripe = &map_block->stripes[i];
+ if (stripe->logical > map_block->start)
+ map_block->start = stripe->logical;
+ if (stripe->logical + stripe->length >
+ map_block->start + map_block->length)
+ map_block->length = stripe->logical + stripe->length -
+ map_block->start;
+ }
+}
+
int __btrfs_map_block_v2(struct btrfs_fs_info *fs_info, int rw, u64 logical,
u64 length, struct btrfs_map_block **map_ret)
{
@@ -1772,7 +1873,7 @@ int __btrfs_map_block_v2(struct btrfs_fs_info *fs_info,
int rw, u64 logical,
free(map_block);
return ret;
}
- /* TODO: Remove unrelated map_stripes for READ operation */
+ remove_unrelated_stripes(map, rw, logical, length, map_block);
*map_ret = map_block;
return 0;
--
2.13.0
--
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