[Devel] [PATCH VZ10 v2 01/10] drivers/md/dm-qcow2: fix revert_cluster_alloc() for ext_l2 case
Pavel Tikhomirov
ptikhomirov at virtuozzo.com
Wed Aug 19 13:27:37 MSK 2026
On 8/12/26 22:19, Andrey Zhadchenko wrote:
> This function walks over all changed u64 values in md. With ext_l2
> half of them holds subcluster description. Firstly it reverts these
> values to saved pe_page, which is fine, but then it tries to revert
> r1r2 changes. It makes no sense when the value is a subcluster
> description.
> Teach the function to skip subcluster descriptions: do it based on
> a new lx_level in struct wb_desc. Add new argument to
> prepare_l_entry_update() and set it there.
> The warning also could have tripped for ext_l2 entries, so drop
> it entirely.
> The function effectively reverts not only cluster alloc, so rename
> it to revert_l_entries_update() to mimic prepare_l_entries_update.
prepare_l_entrie(s)_update is probably a misspelled prepare_l_entry_update
>
> Feature: dm-qcow2: block device over QCOW2 files driver
> https://virtuozzo.atlassian.net/browse/VSTOR-139406
> Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
> ---
> drivers/md/dm-qcow2-map.c | 28 ++++++++++++++++++----------
> drivers/md/dm-qcow2-target.c | 2 +-
> drivers/md/dm-qcow2.h | 1 +
> 3 files changed, 20 insertions(+), 11 deletions(-)
>
> diff --git a/drivers/md/dm-qcow2-map.c b/drivers/md/dm-qcow2-map.c
> index db21efb45e17a..2cd8e174049f8 100644
> --- a/drivers/md/dm-qcow2-map.c
> +++ b/drivers/md/dm-qcow2-map.c
> @@ -1297,18 +1297,19 @@ static void do_md_page_read_complete(int ret, struct qcow2 *qcow2,
> }
>
> /* Be careful with dirty_or_writeback()/etc! Check races. */
> -static void revert_clusters_alloc(struct qcow2 *qcow2, struct wb_desc *wbd)
> +static void revert_l_entries_update(struct qcow2 *qcow2, struct wb_desc *wbd)
> {
> struct qcow2_map_item r1, r2;
> struct page *pe_page;
> + bool skip_odd;
> u64 pos, old;
> int i, ret;
>
> + skip_odd = qcow2->ext_l2 && wbd->lx_level == L2_LEVEL;
> +
> lockdep_assert_held(&qcow2->md_pages_lock);
> for_each_set_bit(i, wbd->changed_indexes, LX_INDEXES_PER_PAGE) {
> pos = get_u64_from_be_page(wbd->md->page, i);
> - WARN_ON_ONCE(!(pos & ~LX_REFCOUNT_EXACTLY_ONE) ||
> - !(pos & LX_REFCOUNT_EXACTLY_ONE));
>
> /* Here we restore prealloced and compressed clu mappings */
> pe_page = wbd->pe_page;
> @@ -1321,6 +1322,9 @@ static void revert_clusters_alloc(struct qcow2 *qcow2, struct wb_desc *wbd)
> }
>
> set_u64_to_be_page(wbd->md->page, i, 0);
> + if (skip_odd && (i & 1))
> + continue; /* pos contains ext_l2 part of L2 entry */
> +
> spin_unlock(&qcow2->md_pages_lock);
> pos &= ~LX_REFCOUNT_EXACTLY_ONE;
>
> @@ -1369,7 +1373,7 @@ static void complete_wbd(struct qcow2 *qcow2, struct wb_desc *wbd)
> unsigned long flags;
>
> spin_lock_irqsave(&qcow2->md_pages_lock, flags);
> - revert_clusters_alloc(qcow2, wbd);
> + revert_l_entries_update(qcow2, wbd);
> clear_writeback_status(qcow2, wbd->md, wbd->ret,
> &wait_list, &end_list);
> spin_unlock_irqrestore(&qcow2->md_pages_lock, flags);
> @@ -2433,7 +2437,7 @@ static loff_t allocate_cluster(struct qcow2 *qcow2, struct qio *qio,
> #define LU_IGN_CHANGED_IND (1 << 3)
> static int prepare_l_entry_update(struct qcow2 *qcow2, struct qio *qio,
> struct md_page *md, u32 index_in_page,
> - u64 *pval, u32 arg_mask)
> + u64 *pval, u32 arg_mask, u8 lx_level)
> {
> bool wants_pe_page = (arg_mask & LU_WANTS_PE_PAGE);
> struct wb_desc *new_wbd = NULL;
> @@ -2453,6 +2457,7 @@ static int prepare_l_entry_update(struct qcow2 *qcow2, struct qio *qio,
> if (!new_wbd)
> return -ENOMEM;
> new_wbd->md = md;
> + new_wbd->lx_level = lx_level;
> } else if (wants_pe_page && !md->wbd->pe_page) {
> pe_page = alloc_page(GFP_NOIO|__GFP_ZERO);
> if (!pe_page)
> @@ -2515,7 +2520,8 @@ static int prepare_l1l2_allocation(struct qcow2 *qcow2, struct qio *qio,
> /* Allocate cluster for L2 entries, and prepare L1 update */
> ret = prepare_l_entry_update(qcow2, qio, map->l1.md,
> map->l1.index_in_page, &val,
> - LU_SET_ONE_MASK|LU_WANTS_ALLOC);
> + LU_SET_ONE_MASK|LU_WANTS_ALLOC,
> + L1_LEVEL);
> if (ret <= 0)
> return ret;
>
> @@ -2541,7 +2547,8 @@ static int prepare_l1l2_allocation(struct qcow2 *qcow2, struct qio *qio,
>
> ret = prepare_l_entry_update(qcow2, qio, map->l2.md,
> map->l2.index_in_page,
> - &map->data_clu_pos, arg_mask);
> + &map->data_clu_pos, arg_mask,
> + L2_LEVEL);
> if (ret <= 0)
> return ret;
>
> @@ -2562,7 +2569,7 @@ static int prepare_l1l2_allocation(struct qcow2 *qcow2, struct qio *qio,
>
> return prepare_l_entry_update(qcow2, qio, map->l2.md,
> map->l2.index_in_page + 1,
> - &val, arg_mask);
> + &val, arg_mask, L2_LEVEL);
> }
>
> /*
> @@ -3975,7 +3982,7 @@ static void process_cow_indexes_write(struct qcow2 *qcow2,
> ret = prepare_l_entry_update(qcow2, qio, lx_md,
> ext->lx_index_in_page,
> &ext->allocated_clu_pos,
> - arg_mask);
> + arg_mask, ext->cow_level);
> if (ret < 0) {
> qio->bi_status = errno_to_blk_status(ret);
> qio_endio(qio);
> @@ -3986,7 +3993,8 @@ static void process_cow_indexes_write(struct qcow2 *qcow2,
> arg_mask &= ~LU_SET_ONE_MASK;
> ret = prepare_l_entry_update(qcow2, qio, lx_md,
> ext->lx_index_in_page + 1,
> - &ext->new_ext_l2, arg_mask);
> + &ext->new_ext_l2, arg_mask,
> + L2_LEVEL);
> WARN_ON_ONCE(ret < 0);
> }
>
> diff --git a/drivers/md/dm-qcow2-target.c b/drivers/md/dm-qcow2-target.c
> index 3f65897ce9da2..0f1d3e3c5258e 100644
> --- a/drivers/md/dm-qcow2-target.c
> +++ b/drivers/md/dm-qcow2-target.c
> @@ -174,7 +174,7 @@ void qcow2_flush_deferred_activity(struct qcow2_target *tgt, struct qcow2 *qcow2
> int i;
>
> /*
> - * We need second iteration, since revert_clusters_alloc()
> + * We need second iteration, since revert_l_entries_update()
> * may start timer again after failed wb.
> */
> for (i = 0; i < 2; i++) {
> diff --git a/drivers/md/dm-qcow2.h b/drivers/md/dm-qcow2.h
> index 86f0688e7345a..aa3487007523f 100644
> --- a/drivers/md/dm-qcow2.h
> +++ b/drivers/md/dm-qcow2.h
> @@ -118,6 +118,7 @@ struct wb_desc {
> struct list_head dependent_list;
> int nr_submitted;
> bool completed;
> + u8 lx_level;
> int ret;
> };
>
--
Best regards, Pavel Tikhomirov
Senior Software Developer, Virtuozzo.
More information about the Devel
mailing list