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Btrfs: simplfy calculation of stripe length for discard operation
For btrfs raid, while discarding a range of space, we'll need to know the start offset and length to discard for each device, and it's done in btrfs_map_block(). However the calculation is a bit complex for raid0 and raid10, so I reimplement it based on a fact that: dev1 dev2 dev3 (raid0) ----------------------------------- s0 s3 s6 s1 s4 s7 s2 s5 Each device has (total_stripes / nr_dev) stripes, or plus one. Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
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1 changed files with 32 additions and 65 deletions
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@ -3024,80 +3024,47 @@ static int __btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw,
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atomic_set(&bbio->error, 0);
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if (rw & REQ_DISCARD) {
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int factor = 0;
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int sub_stripes = 0;
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u64 stripes_per_dev = 0;
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u32 remaining_stripes = 0;
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if (map->type &
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(BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID10)) {
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if (map->type & BTRFS_BLOCK_GROUP_RAID0)
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sub_stripes = 1;
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else
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sub_stripes = map->sub_stripes;
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factor = map->num_stripes / sub_stripes;
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stripes_per_dev = div_u64_rem(stripe_nr_end -
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stripe_nr_orig,
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factor,
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&remaining_stripes);
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}
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for (i = 0; i < num_stripes; i++) {
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bbio->stripes[i].physical =
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map->stripes[stripe_index].physical +
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stripe_offset + stripe_nr * map->stripe_len;
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bbio->stripes[i].dev = map->stripes[stripe_index].dev;
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if (map->type & BTRFS_BLOCK_GROUP_RAID0) {
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u64 stripes;
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u32 last_stripe = 0;
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int j;
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div_u64_rem(stripe_nr_end - 1,
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map->num_stripes,
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&last_stripe);
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for (j = 0; j < map->num_stripes; j++) {
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u32 test;
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div_u64_rem(stripe_nr_end - 1 - j,
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map->num_stripes, &test);
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if (test == stripe_index)
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break;
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}
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stripes = stripe_nr_end - 1 - j;
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do_div(stripes, map->num_stripes);
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bbio->stripes[i].length = map->stripe_len *
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(stripes - stripe_nr + 1);
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if (i == 0) {
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if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |
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BTRFS_BLOCK_GROUP_RAID10)) {
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bbio->stripes[i].length = stripes_per_dev *
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map->stripe_len;
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if (i / sub_stripes < remaining_stripes)
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bbio->stripes[i].length +=
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map->stripe_len;
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if (i < sub_stripes)
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bbio->stripes[i].length -=
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stripe_offset;
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if ((i / sub_stripes + 1) %
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sub_stripes == remaining_stripes)
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bbio->stripes[i].length -=
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stripe_end_offset;
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if (i == sub_stripes - 1)
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stripe_offset = 0;
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}
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if (stripe_index == last_stripe)
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bbio->stripes[i].length -=
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stripe_end_offset;
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} else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {
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u64 stripes;
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int j;
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int factor = map->num_stripes /
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map->sub_stripes;
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u32 last_stripe = 0;
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div_u64_rem(stripe_nr_end - 1,
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factor, &last_stripe);
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last_stripe *= map->sub_stripes;
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for (j = 0; j < factor; j++) {
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u32 test;
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div_u64_rem(stripe_nr_end - 1 - j,
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factor, &test);
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if (test ==
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stripe_index / map->sub_stripes)
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break;
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}
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stripes = stripe_nr_end - 1 - j;
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do_div(stripes, factor);
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bbio->stripes[i].length = map->stripe_len *
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(stripes - stripe_nr + 1);
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if (i < map->sub_stripes) {
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bbio->stripes[i].length -=
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stripe_offset;
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if (i == map->sub_stripes - 1)
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stripe_offset = 0;
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}
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if (stripe_index >= last_stripe &&
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stripe_index <= (last_stripe +
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map->sub_stripes - 1)) {
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bbio->stripes[i].length -=
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stripe_end_offset;
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}
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} else
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bbio->stripes[i].length = *length;
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