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From: David Laight <David.Laight@ACULAB.COM>
To: 'Al Viro' <viro@zeniv.linux.org.uk>, Christophe JAILLET
	<christophe.jaillet@wanadoo.fr>
CC: Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"kernel-janitors@vger.kernel.org" <kernel-janitors@vger.kernel.org>,
	"linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>
Subject: RE: [PATCH] seq_file: Optimize seq_puts()
Thread-Topic: [PATCH] seq_file: Optimize seq_puts()
Thread-Index: AQHaj3fscOebCwNNKkWKivYclXgg7bFrX8Cg
Date: Tue, 16 Apr 2024 20:56:51 +0000
Message-ID: <ba306b2a1b5743bab79b3ebb04ece4df@AcuMS.aculab.com>
References: <5c4f7ad7b88f5026940efa9c8be36a58755ec1b3.1704374916.git.christophe.jaillet@wanadoo.fr>
 <4b1a4cc5-e057-4944-be69-d25f28645256@wanadoo.fr>
 <20240415210035.GW2118490@ZenIV>
In-Reply-To: <20240415210035.GW2118490@ZenIV>
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From: Al Viro
> Sent: 15 April 2024 22:01
..
> No need to make it a macro, actually.  And I would suggest going
> a bit further:
>=20
> static inline void seq_puts(struct seq_file *m, const char *s)

That probably needs to be 'always_inline'.

> {
>=09if (!__builtin_constant_p(*s))
> =09=09__seq_puts(m, s);
> =09else if (s[0] && !s[1])
> =09=09seq_putc(m, s[0]);
> =09else
> =09=09seq_write(m, s, __builtin_strlen(s));
> }

You missed seq_puts(m, "");

I did wonder about checking sizeof(s) <=3D 2 in the #define version.
That would pick up the cases where a separator is changed/added
in a loop.

Could you do:
=09size_t len =3D __builtin_strlen(s);
=09if (!__builtin_constant_p(len))
=09=09__seq_puts(m, s);
=09else switch (len){
=09case 0: break;
=09case 1: seq_putc(m, s[0]);
=09default: seq_write(m, s, len);
=09}

=09David

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