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btrfs: add fast path for single device io in __btrfs_map_block

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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: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Tested-by: Nikolay Borisov <nborisov@suse.com>
Tested-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Christoph Hellwig 2022-08-06 10:03:29 +02:00 • committed by David Sterba
parent 28793b194e
commit 03793cbbc8
1 changed files with 46 additions and 14 deletions
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60
fs/btrfs/volumes.c
View file

@ -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));