2022-04-01 13:49:44

by Jakob Koschel

Subject: [PATCH 1/2] dm snapshot: remove usage of list iterator for list_add() after the loop body

In preparation to limit the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element
[1].

Before, the code implicitly used the head when no element was found
when using &pos->list. Since the new variable is only set if an
element was found, the list_add() is performed within the loop
and only done after the loop if it is done on the list head directly.

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <[email protected]>
---
drivers/md/dm-snap.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/md/dm-snap.c b/drivers/md/dm-snap.c
index 0d336b5ec571..23386a6e67e7 100644
--- a/drivers/md/dm-snap.c
+++ b/drivers/md/dm-snap.c
@@ -528,13 +528,17 @@ static int __validate_exception_handover(struct dm_snapshot *snap)

static void __insert_snapshot(struct origin *o, struct dm_snapshot *s)
{
- struct dm_snapshot *l;
+ struct dm_snapshot *l = NULL, *iter;

/* Sort the list according to chunk size, largest-first smallest-last */
- list_for_each_entry(l, &o->snapshots, list)
- if (l->store->chunk_size < s->store->chunk_size)
+ list_for_each_entry(iter, &o->snapshots, list)
+ if (iter->store->chunk_size < s->store->chunk_size) {
+ l = iter;
+ list_add_tail(&s->list, &iter->list);
break;
- list_add_tail(&s->list, &l->list);
+ }
+ if (!l)
+ list_add_tail(&s->list, &o->snapshots);
}

/*

base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275
--
2.25.1

2022-04-02 14:42:34

by Jakob Koschel

Subject: [PATCH 2/2] dm: replace usage of found with dedicated list iterator variable

To move the list iterator variable into the list_for_each_entry_*()
macro in the future it should be avoided to use the list iterator
variable after the loop body.

To *never* use the list iterator variable after the loop it was
concluded to use a separate iterator variable instead of a
found boolean [1].

This removes the need to use a found variable and simply checking if
the variable was set, can determine if the break/goto was hit.

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <[email protected]>
---
drivers/md/dm-table.c | 11 +++++------
1 file changed, 5 insertions(+), 6 deletions(-)

diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 03541cfc2317..9cf87954c05a 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -424,17 +424,16 @@ static int dm_set_device_limits(struct dm_target *ti, struct dm_dev *dev,
*/
void dm_put_device(struct dm_target *ti, struct dm_dev *d)
{
- int found = 0;
struct list_head *devices = &ti->table->devices;
- struct dm_dev_internal *dd;
+ struct dm_dev_internal *dd = NULL, *iter;

- list_for_each_entry(dd, devices, list) {
- if (dd->dm_dev == d) {
- found = 1;
+ list_for_each_entry(iter, devices, list) {
+ if (iter->dm_dev == d) {
+ dd = iter;
break;
}
}
- if (!found) {
+ if (!dd) {
DMWARN("%s: device %s not in table devices list",
dm_device_name(ti->table->md), d->name);
return;
--
2.25.1