2022-04-12 20:25:34

by Jakob Koschel

Subject: [PATCH net-next v3 14/18] sfc: 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 pointing to the location
where the element should be inserted [1].

Before, the code implicitly used the head when no element was found
when using &new->list. The new 'pos' variable is set to the list head
by default and overwritten if the list exits early, marking the
insertion point for list_add().

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <[email protected]>
---
drivers/net/ethernet/sfc/rx_common.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/sfc/rx_common.c b/drivers/net/ethernet/sfc/rx_common.c
index 1b22c7be0088..80894a35ea79 100644
--- a/drivers/net/ethernet/sfc/rx_common.c
+++ b/drivers/net/ethernet/sfc/rx_common.c
@@ -555,7 +555,7 @@ efx_rx_packet_gro(struct efx_channel *channel, struct efx_rx_buffer *rx_buf,
*/
struct efx_rss_context *efx_alloc_rss_context_entry(struct efx_nic *efx)
{
- struct list_head *head = &efx->rss_context.list;
+ struct list_head *head = *pos = &efx->rss_context.list;
struct efx_rss_context *ctx, *new;
u32 id = 1; /* Don't use zero, that refers to the master RSS context */

@@ -563,8 +563,10 @@ struct efx_rss_context *efx_alloc_rss_context_entry(struct efx_nic *efx)

/* Search for first gap in the numbering */
list_for_each_entry(ctx, head, list) {
- if (ctx->user_id != id)
+ if (ctx->user_id != id) {
+ pos = &ctx->list;
break;
+ }
id++;
/* Check for wrap. If this happens, we have nearly 2^32
* allocated RSS contexts, which seems unlikely.
@@ -582,7 +584,7 @@ struct efx_rss_context *efx_alloc_rss_context_entry(struct efx_nic *efx)

/* Insert the new entry into the gap */
new->user_id = id;
- list_add_tail(&new->list, &ctx->list);
+ list_add_tail(&new->list, pos);
return new;
}

--
2.25.1

2022-04-12 23:46:01

by Jakub Kicinski

Subject: Re: [PATCH net-next v3 14/18] sfc: Remove usage of list iterator for list_add() after the loop body

On Tue, 12 Apr 2022 14:15:53 +0200 Jakob Koschel wrote:
> - struct list_head *head = &efx->rss_context.list;
> + struct list_head *head = *pos = &efx->rss_context.list;

ENOTBUILT, please wait with the reposting. Since you posted two
versions today I guess that's 2x 24h? :)

2022-04-13 09:36:31

by Jakob Koschel

Subject: Re: [PATCH net-next v3 14/18] sfc: Remove usage of list iterator for list_add() after the loop body

> On 12. Apr 2022, at 23:29, Jakub Kicinski <[email protected]> wrote:
>
> On Tue, 12 Apr 2022 14:15:53 +0200 Jakob Koschel wrote:
>> - struct list_head *head = &efx->rss_context.list;
>> + struct list_head *head = *pos = &efx->rss_context.list;
>
> ENOTBUILT, please wait with the reposting. Since you posted two
> versions today I guess that's 2x 24h? :)

oh gosh, seems like I indeed forgot to build this commit.
Sorry about all the mess :( Also I'll wait with reposting (not
going to make the same mistake twice ;)).

I messed up three times yesterday, was really not on a high.
I'll be more careful in the future to not the the same kind of
mistakes again :/