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dm writecache: split up writecache_map() to improve code readability
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writecache_map() has grown too large and can be confusing to read given
all the goto statements.

Signed-off-by: Mike Snitzer <[email protected]>
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@snitm
snitm committed Aug 10, 2021
1 parent 99d26de commit cdd4d78
Showing 1 changed file with 187 additions and 151 deletions.
338 changes: 187 additions & 151 deletions drivers/md/dm-writecache.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1293,10 +1293,164 @@ static void writecache_offload_bio(struct dm_writecache *wc, struct bio *bio)
bio_list_add(&wc->flush_list, bio);
}

static int writecache_map(struct dm_target *ti, struct bio *bio)
enum wc_map_op {
WC_MAP_SUBMIT,
WC_MAP_REMAP,
WC_MAP_REMAP_ORIGIN,
WC_MAP_RETURN,
WC_MAP_ERROR,
};

static enum wc_map_op writecache_map_read(struct dm_writecache *wc, struct bio *bio)
{
enum wc_map_op map_op;
struct wc_entry *e;

read_next_block:
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
if (e && read_original_sector(wc, e) == bio->bi_iter.bi_sector) {
if (WC_MODE_PMEM(wc)) {
bio_copy_block(wc, bio, memory_data(wc, e));
if (bio->bi_iter.bi_size)
goto read_next_block;
map_op = WC_MAP_SUBMIT;
} else {
dm_accept_partial_bio(bio, wc->block_size >> SECTOR_SHIFT);
bio_set_dev(bio, wc->ssd_dev->bdev);
bio->bi_iter.bi_sector = cache_sector(wc, e);
if (!writecache_entry_is_committed(wc, e))
writecache_wait_for_ios(wc, WRITE);
map_op = WC_MAP_REMAP;
}
} else {
if (e) {
sector_t next_boundary =
read_original_sector(wc, e) - bio->bi_iter.bi_sector;
if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT)
dm_accept_partial_bio(bio, next_boundary);
}
map_op = WC_MAP_REMAP_ORIGIN;
}

return map_op;
}

static enum wc_map_op writecache_bio_copy_ssd(struct dm_writecache *wc, struct bio *bio,
struct wc_entry *e, bool search_used)
{
unsigned bio_size = wc->block_size;
sector_t start_cache_sec = cache_sector(wc, e);
sector_t current_cache_sec = start_cache_sec + (bio_size >> SECTOR_SHIFT);

while (bio_size < bio->bi_iter.bi_size) {
if (!search_used) {
struct wc_entry *f = writecache_pop_from_freelist(wc, current_cache_sec);
if (!f)
break;
write_original_sector_seq_count(wc, f, bio->bi_iter.bi_sector +
(bio_size >> SECTOR_SHIFT), wc->seq_count);
writecache_insert_entry(wc, f);
wc->uncommitted_blocks++;
} else {
struct wc_entry *f;
struct rb_node *next = rb_next(&e->rb_node);
if (!next)
break;
f = container_of(next, struct wc_entry, rb_node);
if (f != e + 1)
break;
if (read_original_sector(wc, f) !=
read_original_sector(wc, e) + (wc->block_size >> SECTOR_SHIFT))
break;
if (unlikely(f->write_in_progress))
break;
if (writecache_entry_is_committed(wc, f))
wc->overwrote_committed = true;
e = f;
}
bio_size += wc->block_size;
current_cache_sec += wc->block_size >> SECTOR_SHIFT;
}

bio_set_dev(bio, wc->ssd_dev->bdev);
bio->bi_iter.bi_sector = start_cache_sec;
dm_accept_partial_bio(bio, bio_size >> SECTOR_SHIFT);

if (unlikely(wc->uncommitted_blocks >= wc->autocommit_blocks)) {
wc->uncommitted_blocks = 0;
queue_work(wc->writeback_wq, &wc->flush_work);
} else {
writecache_schedule_autocommit(wc);
}

return WC_MAP_REMAP;
}

static enum wc_map_op writecache_map_write(struct dm_writecache *wc, struct bio *bio)
{
struct wc_entry *e;

do {
bool found_entry = false;
bool search_used = false;
if (writecache_has_error(wc))
return WC_MAP_ERROR;
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, 0);
if (e) {
if (!writecache_entry_is_committed(wc, e)) {
search_used = true;
goto bio_copy;
}
if (!WC_MODE_PMEM(wc) && !e->write_in_progress) {
wc->overwrote_committed = true;
search_used = true;
goto bio_copy;
}
found_entry = true;
} else {
if (unlikely(wc->cleaner) ||
(wc->metadata_only && !(bio->bi_opf & REQ_META)))
goto direct_write;
}
e = writecache_pop_from_freelist(wc, (sector_t)-1);
if (unlikely(!e)) {
if (!WC_MODE_PMEM(wc) && !found_entry) {
direct_write:
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
if (e) {
sector_t next_boundary = read_original_sector(wc, e) - bio->bi_iter.bi_sector;
BUG_ON(!next_boundary);
if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT) {
dm_accept_partial_bio(bio, next_boundary);
}
}
return WC_MAP_REMAP_ORIGIN;
}
writecache_wait_on_freelist(wc);
continue;
}
write_original_sector_seq_count(wc, e, bio->bi_iter.bi_sector, wc->seq_count);
writecache_insert_entry(wc, e);
wc->uncommitted_blocks++;
bio_copy:
if (WC_MODE_PMEM(wc))
bio_copy_block(wc, bio, memory_data(wc, e));
else
return writecache_bio_copy_ssd(wc, bio, e, search_used);
} while (bio->bi_iter.bi_size);

if (unlikely(bio->bi_opf & REQ_FUA || wc->uncommitted_blocks >= wc->autocommit_blocks))
writecache_flush(wc);
else
writecache_schedule_autocommit(wc);

return WC_MAP_SUBMIT;
}

static int writecache_map(struct dm_target *ti, struct bio *bio)
{
struct dm_writecache *wc = ti->private;
enum wc_map_op map_op = WC_MAP_ERROR;

bio->bi_private = NULL;

Expand Down Expand Up @@ -1342,167 +1496,49 @@ static int writecache_map(struct dm_target *ti, struct bio *bio)
}
}

if (bio_data_dir(bio) == READ) {
read_next_block:
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
if (e && read_original_sector(wc, e) == bio->bi_iter.bi_sector) {
if (WC_MODE_PMEM(wc)) {
bio_copy_block(wc, bio, memory_data(wc, e));
if (bio->bi_iter.bi_size)
goto read_next_block;
goto unlock_submit;
} else {
dm_accept_partial_bio(bio, wc->block_size >> SECTOR_SHIFT);
bio_set_dev(bio, wc->ssd_dev->bdev);
bio->bi_iter.bi_sector = cache_sector(wc, e);
if (!writecache_entry_is_committed(wc, e))
writecache_wait_for_ios(wc, WRITE);
goto unlock_remap;
}
} else {
if (e) {
sector_t next_boundary =
read_original_sector(wc, e) - bio->bi_iter.bi_sector;
if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT) {
dm_accept_partial_bio(bio, next_boundary);
}
}
goto unlock_remap_origin;
}
} else {
do {
bool found_entry = false;
bool search_used = false;
if (writecache_has_error(wc))
goto unlock_error;
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, 0);
if (e) {
if (!writecache_entry_is_committed(wc, e)) {
search_used = true;
goto bio_copy;
}
if (!WC_MODE_PMEM(wc) && !e->write_in_progress) {
wc->overwrote_committed = true;
search_used = true;
goto bio_copy;
}
found_entry = true;
} else {
if (unlikely(wc->cleaner) ||
(wc->metadata_only && !(bio->bi_opf & REQ_META)))
goto direct_write;
}
e = writecache_pop_from_freelist(wc, (sector_t)-1);
if (unlikely(!e)) {
if (!WC_MODE_PMEM(wc) && !found_entry) {
direct_write:
e = writecache_find_entry(wc, bio->bi_iter.bi_sector, WFE_RETURN_FOLLOWING);
if (e) {
sector_t next_boundary = read_original_sector(wc, e) - bio->bi_iter.bi_sector;
BUG_ON(!next_boundary);
if (next_boundary < bio->bi_iter.bi_size >> SECTOR_SHIFT) {
dm_accept_partial_bio(bio, next_boundary);
}
}
goto unlock_remap_origin;
}
writecache_wait_on_freelist(wc);
continue;
}
write_original_sector_seq_count(wc, e, bio->bi_iter.bi_sector, wc->seq_count);
writecache_insert_entry(wc, e);
wc->uncommitted_blocks++;
bio_copy:
if (WC_MODE_PMEM(wc)) {
bio_copy_block(wc, bio, memory_data(wc, e));
} else {
unsigned bio_size = wc->block_size;
sector_t start_cache_sec = cache_sector(wc, e);
sector_t current_cache_sec = start_cache_sec + (bio_size >> SECTOR_SHIFT);

while (bio_size < bio->bi_iter.bi_size) {
if (!search_used) {
struct wc_entry *f = writecache_pop_from_freelist(wc, current_cache_sec);
if (!f)
break;
write_original_sector_seq_count(wc, f, bio->bi_iter.bi_sector +
(bio_size >> SECTOR_SHIFT), wc->seq_count);
writecache_insert_entry(wc, f);
wc->uncommitted_blocks++;
} else {
struct wc_entry *f;
struct rb_node *next = rb_next(&e->rb_node);
if (!next)
break;
f = container_of(next, struct wc_entry, rb_node);
if (f != e + 1)
break;
if (read_original_sector(wc, f) !=
read_original_sector(wc, e) + (wc->block_size >> SECTOR_SHIFT))
break;
if (unlikely(f->write_in_progress))
break;
if (writecache_entry_is_committed(wc, f))
wc->overwrote_committed = true;
e = f;
}
bio_size += wc->block_size;
current_cache_sec += wc->block_size >> SECTOR_SHIFT;
}

bio_set_dev(bio, wc->ssd_dev->bdev);
bio->bi_iter.bi_sector = start_cache_sec;
dm_accept_partial_bio(bio, bio_size >> SECTOR_SHIFT);

if (unlikely(wc->uncommitted_blocks >= wc->autocommit_blocks)) {
wc->uncommitted_blocks = 0;
queue_work(wc->writeback_wq, &wc->flush_work);
} else {
writecache_schedule_autocommit(wc);
}
goto unlock_remap;
}
} while (bio->bi_iter.bi_size);

if (unlikely(bio->bi_opf & REQ_FUA ||
wc->uncommitted_blocks >= wc->autocommit_blocks))
writecache_flush(wc);
else
writecache_schedule_autocommit(wc);
goto unlock_submit;
}
if (bio_data_dir(bio) == READ)
map_op = writecache_map_read(wc, bio);
else
map_op = writecache_map_write(wc, bio);

switch (map_op) {
case WC_MAP_REMAP_ORIGIN:
unlock_remap_origin:
if (likely(wc->pause != 0)) {
if (bio_op(bio) == REQ_OP_WRITE) {
dm_iot_io_begin(&wc->iot, 1);
bio->bi_private = (void *)2;
if (likely(wc->pause != 0)) {
if (bio_op(bio) == REQ_OP_WRITE) {
dm_iot_io_begin(&wc->iot, 1);
bio->bi_private = (void *)2;
}
}
}
bio_set_dev(bio, wc->dev->bdev);
wc_unlock(wc);
return DM_MAPIO_REMAPPED;
bio_set_dev(bio, wc->dev->bdev);
wc_unlock(wc);
return DM_MAPIO_REMAPPED;

case WC_MAP_REMAP:
unlock_remap:
/* make sure that writecache_end_io decrements bio_in_progress: */
bio->bi_private = (void *)1;
atomic_inc(&wc->bio_in_progress[bio_data_dir(bio)]);
wc_unlock(wc);
return DM_MAPIO_REMAPPED;
/* make sure that writecache_end_io decrements bio_in_progress: */
bio->bi_private = (void *)1;
atomic_inc(&wc->bio_in_progress[bio_data_dir(bio)]);
wc_unlock(wc);
return DM_MAPIO_REMAPPED;

case WC_MAP_SUBMIT:
unlock_submit:
wc_unlock(wc);
bio_endio(bio);
return DM_MAPIO_SUBMITTED;
wc_unlock(wc);
bio_endio(bio);
return DM_MAPIO_SUBMITTED;

case WC_MAP_RETURN:
unlock_return:
wc_unlock(wc);
return DM_MAPIO_SUBMITTED;
wc_unlock(wc);
return DM_MAPIO_SUBMITTED;

case WC_MAP_ERROR:
unlock_error:
wc_unlock(wc);
bio_io_error(bio);
return DM_MAPIO_SUBMITTED;
wc_unlock(wc);
bio_io_error(bio);
return DM_MAPIO_SUBMITTED;
}
}

static int writecache_end_io(struct dm_target *ti, struct bio *bio, blk_status_t *status)
Expand Down

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