[Devel] [PATCH RH9 v2 5/8] dm/dm-qcow2: add llseek_hole
Andrey Zhadchenko
andrey.zhadchenko at virtuozzo.com
Wed Aug 16 12:32:52 MSK 2023
Implement llseek_hole() for dm-qcow2 target.
Iterate over ranges with cluster granularity until hole or data is found.
To reduce code duplication, we should use already existing parse_metadata()
We can pretend that seek request is read request for metadata purposes
and than interpret parsing result in our favor.
Since parse_metadata() support request postponing (for example when the
requested L2 cluster is absent in RAM), we should create separate qio
list for our queries.
Feature: dm: implement SEEK_HOLE for dm-qcow2 and dm-ploop
https://jira.vzint.dev/browse/PSBM-145746
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
v2 major rework:
- move some code to new functions
- alloc seek qios dynamically
- handle chaining images with more care
- do not skip L2 if backing image exists
drivers/md/dm-qcow2-map.c | 257 +++++++++++++++++++++++++++++++++++
drivers/md/dm-qcow2-target.c | 1 +
drivers/md/dm-qcow2.h | 2 +
3 files changed, 260 insertions(+)
diff --git a/drivers/md/dm-qcow2-map.c b/drivers/md/dm-qcow2-map.c
index 8c1620c11137..b15caaff8c98 100644
--- a/drivers/md/dm-qcow2-map.c
+++ b/drivers/md/dm-qcow2-map.c
@@ -4000,6 +4000,14 @@ static void process_resubmit_qios(struct qcow2 *qcow2, struct list_head *qios)
}
}
+static void process_seek_qios(struct qcow2 *qcow, struct list_head *qios)
+{
+ struct qio *qio;
+
+ while ((qio = qio_list_pop(qios)) != NULL)
+ complete(qio->data);
+}
+
void do_qcow2_work(struct work_struct *ws)
{
struct qcow2 *qcow2 = container_of(ws, struct qcow2, worker);
@@ -4011,6 +4019,7 @@ void do_qcow2_work(struct work_struct *ws)
LIST_HEAD(cow_indexes_qios);
LIST_HEAD(cow_end_qios);
LIST_HEAD(resubmit_qios);
+ LIST_HEAD(seek_qios);
unsigned int pflags = current->flags;
current->flags |= PF_LOCAL_THROTTLE|PF_MEMALLOC_NOIO;
@@ -4023,6 +4032,7 @@ void do_qcow2_work(struct work_struct *ws)
list_splice_init(&qcow2->qios[QLIST_COW_INDEXES], &cow_indexes_qios);
list_splice_init(&qcow2->qios[QLIST_COW_END], &cow_end_qios);
list_splice_init(&qcow2->resubmit_qios, &resubmit_qios);
+ list_splice_init(&qcow2->qios[QLIST_SEEK], &seek_qios);
spin_unlock_irq(&qcow2->deferred_lock);
process_embedded_qios(qcow2, &embedded_qios, &deferred_qios);
@@ -4033,6 +4043,7 @@ void do_qcow2_work(struct work_struct *ws)
process_cow_indexes_write(qcow2, &cow_indexes_qios);
process_cow_end(qcow2, &cow_end_qios);
process_resubmit_qios(qcow2, &resubmit_qios);
+ process_seek_qios(qcow2, &seek_qios);
/* This actually submits batch of md writeback, initiated above */
submit_metadata_writeback(qcow2);
@@ -4255,3 +4266,249 @@ static void handle_cleanup_mask(struct qio *qio)
ext->cleanup_mask &= ~FREE_ALLOCATED_CLU;
}
}
+
+struct qio_data_llseek_hole {
+ struct completion compl;
+ struct qio *higher;
+ loff_t lim;
+};
+
+#define SEEK_QIO_DATA(qio) ((struct qio_data_llseek_hole *)qio->data)
+
+struct qio *alloc_seek_qio(struct qcow2 *qcow2, struct qio *parent, loff_t new_lim)
+{
+ struct qio_data_llseek_hole *data;
+ struct qio *qio;
+
+ qio = qcow2_alloc_qio(qcow2->tgt->qio_pool, true);
+ if (!qio)
+ return NULL;
+
+ qcow2_init_qio(qio, REQ_OP_READ, qcow2);
+ qio->queue_list_id = QLIST_SEEK;
+
+ data = kzalloc(sizeof(struct qio_data_llseek_hole), GFP_KERNEL);
+ if (!data) {
+ qcow2_free_qio(qio, qcow2->tgt->qio_pool);
+ return NULL;
+ }
+
+ qio->data = data;
+ init_completion(&data->compl);
+ data->lim = new_lim;
+
+ if (parent) {
+ data->higher = parent;
+ qio->bi_iter.bi_sector = parent->bi_iter.bi_sector;
+
+ if (to_bytes(qio->bi_iter.bi_sector) + parent->bi_iter.bi_size > new_lim)
+ qio->bi_iter.bi_size = new_lim - to_bytes(qio->bi_iter.bi_sector);
+ else
+ qio->bi_iter.bi_size = parent->bi_iter.bi_size;
+ }
+
+ return qio;
+}
+
+struct qio *free_seek_qio_ret_higher(struct qio *qio)
+{
+ struct qio *ret = SEEK_QIO_DATA(qio)->higher;
+
+ kfree(qio->data);
+ qcow2_free_qio(qio, qio->qcow2->tgt->qio_pool);
+
+ return ret;
+}
+
+static inline sector_t get_next_l2(struct qio *qio)
+{
+ struct qcow2 *qcow2 = qio->qcow2;
+ loff_t start, add;
+
+ start = to_bytes(qio->bi_iter.bi_sector);
+ add = qcow2->l2_entries - (start / qcow2->clu_size) % qcow2->l2_entries;
+
+ return qio->bi_iter.bi_sector + (qcow2->clu_size / to_bytes(1)) * add;
+}
+
+static inline sector_t get_next_clu(struct qio *qio)
+{
+ struct qcow2 *qcow2 = qio->qcow2;
+ loff_t offset;
+
+ offset = to_bytes(qio->bi_iter.bi_sector);
+ offset = (offset + qcow2->clu_size) / qcow2->clu_size;
+ offset *= qcow2->clu_size;
+
+ return to_sector(offset);
+}
+
+static inline void seek_qio_next_clu(struct qio *qio, struct qcow2_map *map)
+{
+ /*
+ * Whole L2 table is unmapped - skip to next l2 table,
+ * but only if there is no backing image
+ */
+ if (map && !(map->level & L2_LEVEL) && !qio->qcow2->lower)
+ qio->bi_iter.bi_sector = get_next_l2(qio);
+ else
+ qio->bi_iter.bi_sector = get_next_clu(qio);
+
+ qio->bi_iter.bi_size = qio->qcow2->clu_size;
+}
+
+static struct qio *advance_and_spawn_lower_seek_qio(struct qio *old_qio, u32 size)
+{
+ struct qio *new_qio;
+ loff_t start, old_end;
+
+ start = to_bytes(old_qio->bi_iter.bi_sector);
+ old_end = start + old_qio->bi_iter.bi_size;
+
+ if (old_end > old_qio->qcow2->lower->hdr.size)
+ size = old_qio->qcow2->lower->hdr.size - start;
+
+ new_qio = alloc_seek_qio(old_qio->qcow2->lower, old_qio, start + size);
+ if (!new_qio)
+ return NULL;
+
+ if (old_qio->bi_iter.bi_size == size) {
+ seek_qio_next_clu(old_qio, NULL);
+ } else {
+ old_qio->bi_iter.bi_sector += to_sector(size);
+ old_qio->bi_iter.bi_size -= size;
+ }
+
+ return new_qio;
+}
+
+int qcow2_llseek_hole_qio(struct qio *qio, int whence, loff_t *result)
+{
+ struct calc_front_bytes_ret arg;
+ struct qcow2_map map;
+ struct qio *qptr;
+ int ret;
+ u32 size;
+
+ while (1) {
+ if (to_bytes(qio->bi_iter.bi_sector) >= SEEK_QIO_DATA(qio)->lim) {
+ if (SEEK_QIO_DATA(qio)->higher) {
+ qio = free_seek_qio_ret_higher(qio);
+ continue;
+ }
+ ret = 0;
+ *result = (loff_t)-1;
+ break;
+ }
+
+ memset(&map, 0, sizeof(map));
+ map.qcow2 = qio->qcow2;
+ qptr = qio;
+
+ ret = parse_metadata(qio->qcow2, &qptr, &map);
+ if (ret < 0)
+ break;
+ if (qptr == NULL) {
+ /* one of metadata pages is not loaded and qio is postponed*/
+ wait_for_completion(&SEEK_QIO_DATA(qio)->compl);
+ reinit_completion(&SEEK_QIO_DATA(qio)->compl);
+ continue;
+ }
+
+calc_subclu:
+ size = calc_front_qio_bytes(qio->qcow2, qio, &map, &arg);
+
+ if (arg.unmapped && arg.try_lower) {
+ /*
+ * Check if the backing image is big enough, then advance current qio
+ * and spawn a new one for lower image
+ */
+ if (to_bytes(qio->bi_iter.bi_sector) < qio->qcow2->lower->hdr.size) {
+ struct qio *new_qio;
+
+ new_qio = advance_and_spawn_lower_seek_qio(qio, size);
+ if (!new_qio) {
+ ret = -ENOMEM;
+ break;
+ }
+
+ qio = new_qio;
+ continue;
+ }
+ }
+
+ if (whence & SEEK_HOLE) {
+ if (arg.zeroes || arg.unmapped) {
+ *result = to_bytes(qio->bi_iter.bi_sector);
+ ret = 0;
+ break;
+ } else if (size != qio->bi_iter.bi_size) {
+ /*
+ * range starts with data subclusters and after that
+ * some subclusters are zero or unmapped
+ */
+ *result = to_bytes(qio->bi_iter.bi_sector) + size;
+ ret = 0;
+ break;
+ }
+ }
+
+ if (whence & SEEK_DATA) {
+ if (!arg.zeroes && !arg.unmapped) {
+ *result = to_bytes(qio->bi_iter.bi_sector);
+ ret = 0;
+ break;
+ } else if (size != qio->bi_iter.bi_size) {
+ /*
+ * range starts with zero or unmapped subclusters
+ * but after that it still can be unmapped or zero
+ * We do not need to parse metadata again but we should
+ * skip this sublusters and look onto next ones
+ */
+ qio->bi_iter.bi_sector += to_sector(size);
+ qio->bi_iter.bi_size -= size;
+ goto calc_subclu;
+ }
+ }
+
+ seek_qio_next_clu(qio, &map);
+ }
+
+ while (qio)
+ qio = free_seek_qio_ret_higher(qio);
+
+ return ret;
+}
+
+loff_t qcow2_llseek_hole(struct dm_target *ti, loff_t offset, int whence)
+{
+ struct qcow2 *qcow2 = to_qcow2_target(ti)->top;
+ loff_t result = -EINVAL;
+ struct qio *qio;
+ int ret;
+
+ qio = alloc_seek_qio(qcow2, NULL, qcow2->hdr.size);
+ if (!qio)
+ return -ENOMEM;
+
+ qio->bi_iter.bi_sector = to_sector(offset);
+ qio->bi_iter.bi_size = qcow2->clu_size -
+ to_bytes(qio->bi_iter.bi_sector) % qcow2->clu_size;
+
+ ret = qcow2_llseek_hole_qio(qio, whence, &result);
+ /* In case of error remap ENXIO as it have special meaning for llseek */
+ if (ret < 0)
+ return (ret == -ENXIO) ? -EINVAL : ret;
+
+ if (result >= 0 && result < offset)
+ result = offset;
+
+ if (result == (loff_t)-1) {
+ if (whence & SEEK_HOLE)
+ result = qcow2->hdr.size;
+ if (whence & SEEK_DATA)
+ result = -ENXIO;
+ }
+
+ return result;
+}
diff --git a/drivers/md/dm-qcow2-target.c b/drivers/md/dm-qcow2-target.c
index 24ace08a03a0..a59d6e757dad 100644
--- a/drivers/md/dm-qcow2-target.c
+++ b/drivers/md/dm-qcow2-target.c
@@ -1019,6 +1019,7 @@ static struct target_type qcow2_target = {
.resume = qcow2_resume,
.clone_and_map_rq = qcow2_clone_and_map,
.message = qcow2_message,
+ .llseek_hole = qcow2_llseek_hole,
};
static int __init dm_qcow2_init(void)
diff --git a/drivers/md/dm-qcow2.h b/drivers/md/dm-qcow2.h
index aec64c23dbae..4c4f4a0c0c8c 100644
--- a/drivers/md/dm-qcow2.h
+++ b/drivers/md/dm-qcow2.h
@@ -151,6 +151,7 @@ enum {
QLIST_COW_DATA,
QLIST_COW_INDEXES,
QLIST_COW_END,
+ QLIST_SEEK,
QLIST_COUNT,
QLIST_INVALID = QLIST_COUNT,
@@ -299,6 +300,7 @@ int qcow2_message(struct dm_target *ti, unsigned int argc, char **argv,
char *result, unsigned int maxlen);
int qcow2_clone_and_map(struct dm_target *ti, struct request *rq,
union map_info *info, struct request **clone);
+loff_t qcow2_llseek_hole(struct dm_target *ti, loff_t offset, int whence);
void do_qcow2_work(struct work_struct *ws);
void do_qcow2_fsync_work(struct work_struct *ws);
--
2.39.3
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