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Wed, 13 Sep 2023 13:53:26 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id DD8FA13582; Wed, 13 Sep 2023 13:53:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 2wJaNNW+AWVuUgAAMHmgww (envelope-from ); Wed, 13 Sep 2023 13:53:25 +0000 Message-ID: <592dd1bd954e2ccc33e1e0d837421d649fdafdf7.camel@suse.com> From: Martin Wilck To: Benjamin Marzinski Date: Wed, 13 Sep 2023 15:53:25 +0200 In-Reply-To: <20230912230048.GR7412@octiron.msp.redhat.com> References: <20230911163846.27197-1-mwilck@suse.com> <20230911163846.27197-23-mwilck@suse.com> <20230912230048.GR7412@octiron.msp.redhat.com> User-Agent: Evolution 3.48.4 MIME-Version: 1.0 X-Mimecast-Impersonation-Protect: Policy=CLT - Impersonation Protection Definition; Similar Internal Domain=false; Similar Monitored External Domain=false; Custom External Domain=false; Mimecast External Domain=false; Newly Observed Domain=false; Internal User Name=false; Custom Display Name List=false; Reply-to Address Mismatch=false; Targeted Threat Dictionary=false; Mimecast Threat Dictionary=false; Custom Threat Dictionary=false X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Subject: Re: [dm-devel] [PATCH v2 22/37] libmultipath: sort aliases by length and strcmp X-BeenThere: dm-devel@redhat.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: device-mapper development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: dm-devel@redhat.com Errors-To: dm-devel-bounces@redhat.com Sender: "dm-devel" X-Scanned-By: MIMEDefang 3.1 on 10.11.54.1 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: suse.com Content-Type: text/plain; charset="iso-8859-15" Content-Transfer-Encoding: quoted-printable On Tue, 2023-09-12 at 18:00 -0500, Benjamin Marzinski wrote: > On Mon, Sep 11, 2023 at 06:38:31PM +0200, mwilck@suse.com=A0wrote: > > From: Martin Wilck > >=20 > > The current sort order of aliases is alphabetical, which is does > > not match > > the actual order of aliases, where "mpathaa" > "mpathz". Change the > > ordering as > > follows: first sort by string length, then alphabetically. This > > will make > > sure that for aliases with the same prefix, alias order is correct > > ("mpathaaa" > > will be sorted after "mpathzz", etc). Even for mixed prefixes, the > > alias > > order will be correct for every individual prefix, even though > > aliases with > > different prefixes may alternate in the file. > >=20 > > Signed-off-by: Martin Wilck > > --- > > =A0libmultipath/alias.c | 45 +++++++++++++++++++++++++++++++++------- > > ---- > > =A01 file changed, 34 insertions(+), 11 deletions(-) > >=20 > > diff --git a/libmultipath/alias.c b/libmultipath/alias.c > > index 58436ec..af6565b 100644 > > --- a/libmultipath/alias.c > > +++ b/libmultipath/alias.c > > @@ -117,6 +117,35 @@ static const struct binding > > *get_binding_for_wwid(const Bindings *bindings, > > =A0=A0=A0=A0=A0=A0=A0=A0return NULL; > > =A0} > > =A0 > > +/* > > + * Sort order for aliases. > > + * > > + * The "numeric" ordering of aliases for a given prefix P is > > + * Pa, ..., Pz, Paa, ..., Paz, Pba, ... , Pzz, Paaa, ..., Pzzz, > > Paaaa, ... > > + * We use the fact that for equal prefix, longer strings are > > always > > + * higher than shorter ones. Strings of equal length are sorted > > alphabetically. > > + * This is achieved by sorting be length first, then using > > strcmp(). > > + * If multiple prefixes are in use, the aliases with a given > > prefix will > > + * not necessarily be in a contiguous range of the vector, but > > they will > > + * be ordered such that for a given prefix, numercally higher > > aliases will > > + * always be sorted after lower ones. > > + */ > > +static int alias_compar(const void *p1, const void *p2) > > +{ >=20 > I'm confused as to why we need to pass p1 and p2 and pointers to > pointers to chars, instead of simply as pointers to chars. We always > derefence them immediately, and only use the dereferenced pointers. > Am I > missing something? I wanted to make the relationship of alias_compar() and mp_alias_compar() as obvious as possible. mp_alias_compar() takes=20 (struct mpentry **) arguments, because it's used as an argument to vector_sort() aka msort(), which has the same calling convention as qsort()'s "compar" argument. Therefore I wrote alias_compar() such that it takes (char **) pointers. This way we could use alias_compar() as an argument to vector_sort() as well, even though we currently don't. Does this make sense? If not, I can change it, but I think the function should not be named alias_compar() if it can't be passed to vector_sort(). Martin -- dm-devel mailing list dm-devel@redhat.com https://listman.redhat.com/mailman/listinfo/dm-devel