Commit 03793cbb authored by Christoph Hellwig's avatar Christoph Hellwig Committed by David Sterba
Browse files

btrfs: add fast path for single device io in __btrfs_map_block 



There is no need for most of the btrfs_io_context when doing I/O to a
single device.  To support such I/O without the extra btrfs_io_context
allocation, turn the mirror_num argument into a pointer so that it can
be used to output the selected mirror number, and add an optional
argument that points to a btrfs_io_stripe structure, which will be
filled with a single extent if provided by the caller.

In that case the btrfs_io_context allocation can be skipped as all
information for the single device I/O is provided in the mirror_num
argument and the on-stack btrfs_io_stripe.  A caller that makes use of
this new argument will be added in the next commit.

Reviewed-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: default avatarAnand Jain <anand.jain@oracle.com>
Tested-by: default avatarNikolay Borisov <nborisov@suse.com>
Tested-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 28793b19

fs/btrfs/volumes.c

+46 −14
Original line number Diff line number Diff line
@@ -249,10 +249,10 @@ static int init_first_rw_device(struct btrfs_trans_handle *trans); 
static int btrfs_relocate_sys_chunks(struct btrfs_fs_info *fs_info);

static void btrfs_dev_stat_print_on_load(struct btrfs_device *device);

static int __btrfs_map_block(struct btrfs_fs_info *fs_info,

			     enum btrfs_map_op op,

			     u64 logical, u64 *length,

			     enum btrfs_map_op op, u64 logical, u64 *length,

			     struct btrfs_io_context **bioc_ret,

			     int mirror_num, int need_raid_map);

			     struct btrfs_io_stripe *smap,

			     int *mirror_num_ret, int need_raid_map);



/*

 * Device locking
@@ -6093,7 +6093,7 @@ static int get_extra_mirror_from_replace(struct btrfs_fs_info *fs_info, 
	int ret = 0;



	ret = __btrfs_map_block(fs_info, BTRFS_MAP_GET_READ_MIRRORS,

				logical, &length, &bioc, 0, 0);

				logical, &length, &bioc, NULL, NULL, 0);

	if (ret) {

		ASSERT(bioc == NULL);

		return ret;
@@ -6350,11 +6350,19 @@ int btrfs_get_io_geometry(struct btrfs_fs_info *fs_info, struct extent_map *em, 
	return 0;

}



static void set_io_stripe(struct btrfs_io_stripe *dst, const struct map_lookup *map,

		          u32 stripe_index, u64 stripe_offset, u64 stripe_nr)

{

	dst->dev = map->stripes[stripe_index].dev;

	dst->physical = map->stripes[stripe_index].physical +

			stripe_offset + stripe_nr * map->stripe_len;

}



static int __btrfs_map_block(struct btrfs_fs_info *fs_info,

			     enum btrfs_map_op op,

			     u64 logical, u64 *length,

			     enum btrfs_map_op op, u64 logical, u64 *length,

			     struct btrfs_io_context **bioc_ret,

			     int mirror_num, int need_raid_map)

			     struct btrfs_io_stripe *smap,

			     int *mirror_num_ret, int need_raid_map)

{

	struct extent_map *em;

	struct map_lookup *map;
@@ -6365,6 +6373,7 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, 
	int data_stripes;

	int i;

	int ret = 0;

	int mirror_num = (mirror_num_ret ? *mirror_num_ret : 0);

	int num_stripes;

	int max_errors = 0;

	int tgtdev_indexes = 0;
@@ -6525,6 +6534,29 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, 
		tgtdev_indexes = num_stripes;

	}



	/*

	 * If this I/O maps to a single device, try to return the device and

	 * physical block information on the stack instead of allocating an

	 * I/O context structure.

	 */

	if (smap && num_alloc_stripes == 1 &&

	    !((map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) && mirror_num > 1) &&

	    (!need_full_stripe(op) || !dev_replace_is_ongoing ||

	     !dev_replace->tgtdev)) {

		if (patch_the_first_stripe_for_dev_replace) {

			smap->dev = dev_replace->tgtdev;

			smap->physical = physical_to_patch_in_first_stripe;

			*mirror_num_ret = map->num_stripes + 1;

		} else {

			set_io_stripe(smap, map, stripe_index, stripe_offset,

				      stripe_nr);

			*mirror_num_ret = mirror_num;

		}

		*bioc_ret = NULL;

		ret = 0;

		goto out;

	}



	bioc = alloc_btrfs_io_context(fs_info, num_alloc_stripes, tgtdev_indexes);

	if (!bioc) {

		ret = -ENOMEM;
@@ -6532,9 +6564,8 @@ static int __btrfs_map_block(struct btrfs_fs_info *fs_info, 
	}



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

		bioc->stripes[i].physical = map->stripes[stripe_index].physical +

			stripe_offset + stripe_nr * map->stripe_len;

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

		set_io_stripe(&bioc->stripes[i], map, stripe_index, stripe_offset,

			      stripe_nr);

		stripe_index++;

	}
@@ -6602,7 +6633,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, 
		      struct btrfs_io_context **bioc_ret, int mirror_num)

{

	return __btrfs_map_block(fs_info, op, logical, length, bioc_ret,

				 mirror_num, 0);

				 NULL, &mirror_num, 0);

}



/* For Scrub/replace */
@@ -6610,7 +6641,8 @@ int btrfs_map_sblock(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, 
		     u64 logical, u64 *length,

		     struct btrfs_io_context **bioc_ret)

{

	return __btrfs_map_block(fs_info, op, logical, length, bioc_ret, 0, 1);

	return __btrfs_map_block(fs_info, op, logical, length, bioc_ret,

				 NULL, NULL, 1);

}



/*
@@ -6820,8 +6852,8 @@ void btrfs_submit_bio(struct btrfs_fs_info *fs_info, struct bio *bio, int mirror 
	struct btrfs_io_context *bioc = NULL;



	btrfs_bio_counter_inc_blocked(fs_info);

	ret = __btrfs_map_block(fs_info, btrfs_op(bio), logical,

				&map_length, &bioc, mirror_num, 1);

	ret = __btrfs_map_block(fs_info, btrfs_op(bio), logical, &map_length,

				&bioc, NULL, &mirror_num, 1);

	if (ret) {

		btrfs_bio_counter_dec(fs_info);

		btrfs_bio_end_io(btrfs_bio(bio), errno_to_blk_status(ret));