piaojun wrote on Tue, Jul 17, 2018:
> In p9_read_work(), we use spin_lock for client->lock, but misuse
> spin_lock_irqsave for it in p9_fid_create(). As p9_client lock won't be
> locked in irq context, so spin_lock is enough. And that will improve the
> performance.
(I didn't say in v1, but the commit message sounds a bit odd to me, if
there is any other change to the patch could you please rephrase it a
bit?)
> Rebased on 9p-next.
(Likewise, this should probably go below the '---' mark to not be in the
final commit message, 9p-next does not make sense to linux as a whole)
>
> Signed-off-by: Jun Piao <piao...@huawei.com>
Nitpicks aside this still looks good to me, I'm not expert in locking
but I believe the conn_cancel stuff in trans_fd is called either from
user context or workqueue which also is process context, while the rest
comes from user context only.
There *are* common functions called from interrupt context (I see:
p9_tag_lookup, p9_client_cb, p9_parse_header) but luckily enough
none of these take the lock.
I'll give this one a little bit of time for others to review before
picking it up, just in case, but will do if no-one complains.
> ---
> net/9p/client.c | 18 ++++++++----------
> net/9p/trans_fd.c | 7 +++----
> 2 files changed, 11 insertions(+), 14 deletions(-)
>
> diff --git a/net/9p/client.c b/net/9p/client.c
> index 30f9aee..f6897ee 100644
> --- a/net/9p/client.c
> +++ b/net/9p/client.c
> @@ -275,14 +275,14 @@ static struct p9_fcall *p9_fcall_alloc(int alloc_msize)
> INIT_LIST_HEAD(&req->req_list);
>
> idr_preload(GFP_NOFS);
> - spin_lock_irq(&c->lock);
> + spin_lock(&c->lock);
> if (type == P9_TVERSION)
> tag = idr_alloc(&c->reqs, req, P9_NOTAG, P9_NOTAG + 1,
> GFP_NOWAIT);
> else
> tag = idr_alloc(&c->reqs, req, 0, P9_NOTAG, GFP_NOWAIT);
> req->tc->tag = tag;
> - spin_unlock_irq(&c->lock);
> + spin_unlock(&c->lock);
> idr_preload_end();
> if (tag < 0)
> goto free;
> @@ -328,13 +328,12 @@ struct p9_req_t *p9_tag_lookup(struct p9_client *c, u16
> tag)
> */
> static void p9_free_req(struct p9_client *c, struct p9_req_t *r)
> {
> - unsigned long flags;
> u16 tag = r->tc->tag;
>
> p9_debug(P9_DEBUG_MUX, "clnt %p req %p tag: %d\n", c, r, tag);
> - spin_lock_irqsave(&c->lock, flags);
> + spin_lock(&c->lock);
> idr_remove(&c->reqs, tag);
> - spin_unlock_irqrestore(&c->lock, flags);
> + spin_unlock(&c->lock);
> kfree(r->tc);
> kfree(r->rc);
> kmem_cache_free(p9_req_cache, r);
> @@ -846,10 +845,10 @@ static struct p9_fid *p9_fid_create(struct p9_client
> *clnt)
> fid->fid = 0;
>
> idr_preload(GFP_KERNEL);
> - spin_lock_irq(&clnt->lock);
> + spin_lock(&clnt->lock);
> ret = idr_alloc_u32(&clnt->fids, fid, &fid->fid, P9_NOFID - 1,
> GFP_NOWAIT);
> - spin_unlock_irq(&clnt->lock);
> + spin_unlock(&clnt->lock);
> idr_preload_end();
>
> if (!ret)
> @@ -862,13 +861,12 @@ static struct p9_fid *p9_fid_create(struct p9_client
> *clnt)
> static void p9_fid_destroy(struct p9_fid *fid)
> {
> struct p9_client *clnt;
> - unsigned long flags;
>
> p9_debug(P9_DEBUG_FID, "fid %d\n", fid->fid);
> clnt = fid->clnt;
> - spin_lock_irqsave(&clnt->lock, flags);
> + spin_lock(&clnt->lock);
> idr_remove(&clnt->fids, fid->fid);
> - spin_unlock_irqrestore(&clnt->lock, flags);
> + spin_unlock(&clnt->lock);
> kfree(fid->rdir);
> kfree(fid);
> }
> diff --git a/net/9p/trans_fd.c b/net/9p/trans_fd.c
> index bf459ee..94ef685 100644
> --- a/net/9p/trans_fd.c
> +++ b/net/9p/trans_fd.c
> @@ -197,15 +197,14 @@ static void p9_mux_poll_stop(struct p9_conn *m)
> static void p9_conn_cancel(struct p9_conn *m, int err)
> {
> struct p9_req_t *req, *rtmp;
> - unsigned long flags;
> LIST_HEAD(cancel_list);
>
> p9_debug(P9_DEBUG_ERROR, "mux %p err %d\n", m, err);
>
> - spin_lock_irqsave(&m->client->lock, flags);
> + spin_lock(&m->client->lock);
>
> if (m->err) {
> - spin_unlock_irqrestore(&m->client->lock, flags);
> + spin_unlock(&m->client->lock);
> return;
> }
>
> @@ -217,7 +216,7 @@ static void p9_conn_cancel(struct p9_conn *m, int err)
> list_for_each_entry_safe(req, rtmp, &m->unsent_req_list, req_list) {
> list_move(&req->req_list, &cancel_list);
> }
> - spin_unlock_irqrestore(&m->client->lock, flags);
> + spin_unlock(&m->client->lock);
>
> list_for_each_entry_safe(req, rtmp, &cancel_list, req_list) {
> p9_debug(P9_DEBUG_ERROR, "call back req %p\n", req);
> --
--
Dominique Martinet
