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Commit 5f141126 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba
Browse files

btrfs: Introduce btrfs_io_geometry infrastructure 



Add a structure that holds various parameters for IO calculations and a
helper that fills the values. This will help further refactoring and
reduction of functions that in some way open-coded the calculations.

Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent c9d713d5

fs/btrfs/volumes.c

+96 −0
Original line number Diff line number Diff line
@@ -5915,6 +5915,102 @@ static bool need_full_stripe(enum btrfs_map_op op) 
	return (op == BTRFS_MAP_WRITE || op == BTRFS_MAP_GET_READ_MIRRORS);

}



/*

 * btrfs_get_io_geometry - calculates the geomery of a particular (address, len)

 *		       tuple. This information is used to calculate how big a

 *		       particular bio can get before it straddles a stripe.

 *

 * @fs_info - the filesystem

 * @logical - address that we want to figure out the geometry of

 * @len	    - the length of IO we are going to perform, starting at @logical

 * @op      - type of operation - write or read

 * @io_geom - pointer used to return values

 *

 * Returns < 0 in case a chunk for the given logical address cannot be found,

 * usually shouldn't happen unless @logical is corrupted, 0 otherwise.

 */

int btrfs_get_io_geometry(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,

		      u64 logical, u64 len, struct btrfs_io_geometry *io_geom)

{

	struct extent_map *em;

	struct map_lookup *map;

	u64 offset;

	u64 stripe_offset;

	u64 stripe_nr;

	u64 stripe_len;

	u64 raid56_full_stripe_start = (u64)-1;

	int data_stripes;



	ASSERT(op != BTRFS_MAP_DISCARD);



	em = btrfs_get_chunk_map(fs_info, logical, len);

	if (IS_ERR(em))

		return PTR_ERR(em);



	map = em->map_lookup;

	/* Offset of this logical address in the chunk */

	offset = logical - em->start;

	/* Len of a stripe in a chunk */

	stripe_len = map->stripe_len;

	/* Stripe wher this block falls in */

	stripe_nr = div64_u64(offset, stripe_len);

	/* Offset of stripe in the chunk */

	stripe_offset = stripe_nr * stripe_len;

	if (offset < stripe_offset) {

		btrfs_crit(fs_info,

"stripe math has gone wrong, stripe_offset=%llu offset=%llu start=%llu logical=%llu stripe_len=%llu",

			stripe_offset, offset, em->start, logical, stripe_len);

		free_extent_map(em);

		return -EINVAL;

	}



	/* stripe_offset is the offset of this block in its stripe */

	stripe_offset = offset - stripe_offset;

	data_stripes = nr_data_stripes(map);



	if (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) {

		u64 max_len = stripe_len - stripe_offset;



		/*

		 * In case of raid56, we need to know the stripe aligned start

		 */

		if (map->type & BTRFS_BLOCK_GROUP_RAID56_MASK) {

			unsigned long full_stripe_len = stripe_len * data_stripes;

			raid56_full_stripe_start = offset;



			/*

			 * Allow a write of a full stripe, but make sure we

			 * don't allow straddling of stripes

			 */

			raid56_full_stripe_start = div64_u64(raid56_full_stripe_start,

					full_stripe_len);

			raid56_full_stripe_start *= full_stripe_len;



			/*

			 * For writes to RAID[56], allow a full stripeset across

			 * all disks. For other RAID types and for RAID[56]

			 * reads, just allow a single stripe (on a single disk).

			 */

			if (op == BTRFS_MAP_WRITE) {

				max_len = stripe_len * data_stripes -

					  (offset - raid56_full_stripe_start);

			}

		}

		len = min_t(u64, em->len - offset, max_len);

	} else {

		len = em->len - offset;

	}



	io_geom->len = len;

	io_geom->offset = offset;

	io_geom->stripe_len = stripe_len;

	io_geom->stripe_nr = stripe_nr;

	io_geom->stripe_offset = stripe_offset;

	io_geom->raid56_stripe_offset = raid56_full_stripe_start;



	return 0;

}



static int __btrfs_map_block(struct btrfs_fs_info *fs_info,

			     enum btrfs_map_op op,

			     u64 logical, u64 *length,

fs/btrfs/volumes.h

+17 −0
Original line number Diff line number Diff line
@@ -23,6 +23,21 @@ struct btrfs_pending_bios { 
	struct bio *tail;

};



struct btrfs_io_geometry {

	/* remaining bytes before crossing a stripe */

	u64 len;

	/* offset of logical address in chunk */

	u64 offset;

	/* length of single IO stripe */

	u64 stripe_len;

	/* number of stripe where address falls */

	u64 stripe_nr;

	/* offset of address in stripe */

	u64 stripe_offset;

	/* offset of raid56 stripe into the chunk */

	u64 raid56_stripe_offset;

};



/*

 * Use sequence counter to get consistent device stat data on

 * 32-bit processors.
@@ -413,6 +428,8 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, 
int btrfs_map_sblock(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,

		     u64 logical, u64 *length,

		     struct btrfs_bio **bbio_ret);

int btrfs_get_io_geometry(struct btrfs_fs_info *fs_info, enum btrfs_map_op op,

			  u64 logical, u64 len, struct btrfs_io_geometry *io_geom);

int btrfs_rmap_block(struct btrfs_fs_info *fs_info, u64 chunk_start,

		     u64 physical, u64 **logical, int *naddrs, int *stripe_len);

int btrfs_read_sys_array(struct btrfs_fs_info *fs_info);