Commit ec9ef7a1 authored by Li Zefan's avatar Li Zefan
Browse files

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: default avatarLi Zefan <lizf@cn.fujitsu.com>
parent de11cc12

fs/btrfs/volumes.c

+31 −64
Original line number Diff line number Diff line
@@ -3024,80 +3024,47 @@ static int __btrfs_map_block(struct btrfs_mapping_tree *map_tree, int rw, 
	atomic_set(&bbio->error, 0);



	if (rw & REQ_DISCARD) {

		int factor = 0;

		int sub_stripes = 0;

		u64 stripes_per_dev = 0;

		u32 remaining_stripes = 0;



		if (map->type &

		    (BTRFS_BLOCK_GROUP_RAID0 | BTRFS_BLOCK_GROUP_RAID10)) {

			if (map->type & BTRFS_BLOCK_GROUP_RAID0)

				sub_stripes = 1;

			else

				sub_stripes = map->sub_stripes;



			factor = map->num_stripes / sub_stripes;

			stripes_per_dev = div_u64_rem(stripe_nr_end -

						      stripe_nr_orig,

						      factor,

						      &remaining_stripes);

		}



		for (i = 0; i < num_stripes; i++) {

			bbio->stripes[i].physical =

				map->stripes[stripe_index].physical +

				stripe_offset + stripe_nr * map->stripe_len;

			bbio->stripes[i].dev = map->stripes[stripe_index].dev;



			if (map->type & BTRFS_BLOCK_GROUP_RAID0) {

				u64 stripes;

				u32 last_stripe = 0;

				int j;



				div_u64_rem(stripe_nr_end - 1,

					    map->num_stripes,

					    &last_stripe);



				for (j = 0; j < map->num_stripes; j++) {

					u32 test;



					div_u64_rem(stripe_nr_end - 1 - j,

						    map->num_stripes, &test);

					if (test == stripe_index)

						break;

				}

				stripes = stripe_nr_end - 1 - j;

				do_div(stripes, map->num_stripes);

				bbio->stripes[i].length = map->stripe_len *

					(stripes - stripe_nr + 1);



				if (i == 0) {

			if (map->type & (BTRFS_BLOCK_GROUP_RAID0 |

					 BTRFS_BLOCK_GROUP_RAID10)) {

				bbio->stripes[i].length = stripes_per_dev *

							  map->stripe_len;

				if (i / sub_stripes < remaining_stripes)

					bbio->stripes[i].length +=

						map->stripe_len;

				if (i < sub_stripes)

					bbio->stripes[i].length -=

						stripe_offset;

					stripe_offset = 0;

				}

				if (stripe_index == last_stripe)

				if ((i / sub_stripes + 1) %

				    sub_stripes == remaining_stripes)

					bbio->stripes[i].length -=

						stripe_end_offset;

			} else if (map->type & BTRFS_BLOCK_GROUP_RAID10) {

				u64 stripes;

				int j;

				int factor = map->num_stripes /

					     map->sub_stripes;

				u32 last_stripe = 0;



				div_u64_rem(stripe_nr_end - 1,

					    factor, &last_stripe);

				last_stripe *= map->sub_stripes;



				for (j = 0; j < factor; j++) {

					u32 test;



					div_u64_rem(stripe_nr_end - 1 - j,

						    factor, &test);



					if (test ==

					    stripe_index / map->sub_stripes)

						break;

				}

				stripes = stripe_nr_end - 1 - j;

				do_div(stripes, factor);

				bbio->stripes[i].length = map->stripe_len *

					(stripes - stripe_nr + 1);



				if (i < map->sub_stripes) {

					bbio->stripes[i].length -=

						stripe_offset;

					if (i == map->sub_stripes - 1)

				if (i == sub_stripes - 1)

					stripe_offset = 0;

				}

				if (stripe_index >= last_stripe &&

				    stripe_index <= (last_stripe +

						     map->sub_stripes - 1)) {

					bbio->stripes[i].length -=

						stripe_end_offset;

				}

			} else

				bbio->stripes[i].length = *length;

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