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Tue, 6 Feb 2024 05:51:27 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap1.dmz-prg2.suse.org with ESMTPSA id cFk3Kt/IwWXiOAAAD6G6ig (envelope-from ); Tue, 06 Feb 2024 05:51:27 +0000 Message-ID: Date: Tue, 6 Feb 2024 14:51:24 +0900 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 12/12] nvmet-fc: use RCU list iterator for assoc_list Content-Language: en-US To: Daniel Wagner , James Smart Cc: Keith Busch , Christoph Hellwig , linux-nvme@lists.infradead.org, linux-kernel@vger.kernel.org References: <20240131085112.21668-1-dwagner@suse.de> <20240131085112.21668-13-dwagner@suse.de> From: Hannes Reinecke In-Reply-To: <20240131085112.21668-13-dwagner@suse.de> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Level: Authentication-Results: smtp-out2.suse.de; dkim=pass header.d=suse.de header.s=susede2_rsa header.b=FigCCNTf; dkim=pass header.d=suse.de header.s=susede2_ed25519 header.b=9lMbQusC X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spamd-Result: default: False [-4.46 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_DKIM_ALLOW(-0.20)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; XM_UA_NO_VERSION(0.01)[]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; BAYES_HAM(-3.00)[100.00%]; MIME_GOOD(-0.10)[text/plain]; SPAMHAUS_XBL(0.00)[2a07:de40:b281:104:10:150:64:97:from]; NEURAL_HAM_LONG(-1.00)[-1.000]; RCPT_COUNT_FIVE(0.00)[6]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; DKIM_TRACE(0.00)[suse.de:+]; MX_GOOD(-0.01)[]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,suse.de:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; NEURAL_HAM_SHORT(-0.16)[-0.789]; RCVD_TLS_ALL(0.00)[]; MID_RHS_MATCH_FROM(0.00)[] X-Spam-Score: -4.46 X-Rspamd-Queue-Id: AA8281F896 X-Spam-Flag: NO On 1/31/24 16:51, Daniel Wagner wrote: > The assoc_list is a RCU protected list, thus use the RCU flavor of list > functions. > > Let's use this opportunity and refactor this code and move the lookup > into a helper and give it a descriptive name. > > Signed-off-by: Daniel Wagner > --- > drivers/nvme/target/fc.c | 34 ++++++++++++++++++++++------------ > 1 file changed, 22 insertions(+), 12 deletions(-) > > diff --git a/drivers/nvme/target/fc.c b/drivers/nvme/target/fc.c > index 671d096745a5..fd229f310c93 100644 > --- a/drivers/nvme/target/fc.c > +++ b/drivers/nvme/target/fc.c > @@ -1114,14 +1114,27 @@ nvmet_fc_schedule_delete_assoc(struct nvmet_fc_tgt_assoc *assoc) > queue_work(nvmet_wq, &assoc->del_work); > } > > +static bool > +nvmet_fc_assoc_exits(struct nvmet_fc_tgtport *tgtport, u64 association_id) > +{ > + struct nvmet_fc_tgt_assoc *a; > + > + list_for_each_entry_rcu(a, &tgtport->assoc_list, a_list) { > + if (association_id == a->association_id) > + return true; > + } > + > + return false; > +} > + > static struct nvmet_fc_tgt_assoc * > nvmet_fc_alloc_target_assoc(struct nvmet_fc_tgtport *tgtport, void *hosthandle) > { > - struct nvmet_fc_tgt_assoc *assoc, *tmpassoc; > + struct nvmet_fc_tgt_assoc *assoc; > unsigned long flags; > + bool done; > u64 ran; > int idx; > - bool needrandom = true; > > if (!tgtport->pe) > return NULL; > @@ -1145,24 +1158,21 @@ nvmet_fc_alloc_target_assoc(struct nvmet_fc_tgtport *tgtport, void *hosthandle) > INIT_WORK(&assoc->del_work, nvmet_fc_delete_assoc_work); > atomic_set(&assoc->terminating, 0); > > - while (needrandom) { > + done = false; > + do { > get_random_bytes(&ran, sizeof(ran) - BYTES_FOR_QID); > ran = ran << BYTES_FOR_QID_SHIFT; > > spin_lock_irqsave(&tgtport->lock, flags); > - needrandom = false; > - list_for_each_entry(tmpassoc, &tgtport->assoc_list, a_list) { > - if (ran == tmpassoc->association_id) { > - needrandom = true; > - break; > - } > - } > - if (!needrandom) { > + rcu_read_lock(); > + if (!nvmet_fc_assoc_exits(tgtport, ran)) { > assoc->association_id = ran; > list_add_tail_rcu(&assoc->a_list, &tgtport->assoc_list); > + done = true; > } > + rcu_read_unlock(); > spin_unlock_irqrestore(&tgtport->lock, flags); Odd. You already take the tgtport lock, so there really is no point in using rcu_read_lock() here. Or does the tgtport lock not protect the assoc_list? Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg HRB 36809 (AG Nürnberg), GF: Ivo Totev, Andrew McDonald, Werner Knoblich