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AJvYcCVJ7xPFJVfz0Ep91P3bL5cyYGcIpl6ZOo3cF9P9Qn3Roj8Ml8uPmbyi1FvnvQc71gQZLNEhTjTBJg==@kvack.org X-Gm-Message-State: AOJu0YzBlSXgVdDb3ELZjRXufONPoP7BdIVKpOnEkTy+CF6ByBNiiLpi EvqPDxEyZdK00FPmr+Av/yqNP8Gz9re7dncc2M4LcSbOVIHZYCcP1TRD/WgH5tA2BZjYhSURfVg eb40MY2k4yluIZgX4H5GbsH2ywNY= X-Google-Smtp-Source: AGHT+IEMzX23pNCTwUB3oEFnjtXMwQslYwQseElwS5dsww3heTV7mBPQDdBjGem5UqseBxKdUwlhHXFriIKrdvm/EEk= X-Received: by 2002:a05:6214:2b82:b0:6bf:78e1:74e7 with SMTP id 6a1803df08f44-6c16deb3b70mr122308516d6.50.1724678032741; Mon, 26 Aug 2024 06:13:52 -0700 (PDT) MIME-Version: 1.0 References: <20240817025624.13157-1-laoar.shao@gmail.com> <20240817025624.13157-7-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Mon, 26 Aug 2024 21:13:16 +0800 Message-ID: Subject: Re: [PATCH v7 6/8] mm/util: Deduplicate code in {kstrdup,kstrndup,kmemdup_nul} To: Alejandro Colomar Cc: akpm@linux-foundation.org, torvalds@linux-foundation.org, justinstitt@google.com, ebiederm@xmission.com, alexei.starovoitov@gmail.com, rostedt@goodmis.org, catalin.marinas@arm.com, penguin-kernel@i-love.sakura.ne.jp, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, audit@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, bpf@vger.kernel.org, netdev@vger.kernel.org, dri-devel@lists.freedesktop.org, Simon Horman , Matthew Wilcox Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: oq1rqhiyiha9bn9r54qqpzkmsu6sj34z X-Rspamd-Queue-Id: DADB916002D X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1724678033-551457 X-HE-Meta: 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 8/biQOBr 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Aug 26, 2024 at 5:25=E2=80=AFPM Alejandro Colomar = wrote: > > Hi Yafang, > > On Sat, Aug 17, 2024 at 10:58:02AM GMT, Alejandro Colomar wrote: > > Hi Yafang, > > > > On Sat, Aug 17, 2024 at 10:56:22AM GMT, Yafang Shao wrote: > > > These three functions follow the same pattern. To deduplicate the cod= e, > > > let's introduce a common helper __kmemdup_nul(). > > > > > > Suggested-by: Andrew Morton > > > Signed-off-by: Yafang Shao > > > Cc: Simon Horman > > > Cc: Matthew Wilcox > > > --- > > > mm/util.c | 67 +++++++++++++++++++++--------------------------------= -- > > > 1 file changed, 26 insertions(+), 41 deletions(-) > > > > > > diff --git a/mm/util.c b/mm/util.c > > > index 4542d8a800d9..310c7735c617 100644 > > > --- a/mm/util.c > > > +++ b/mm/util.c > > > @@ -45,33 +45,40 @@ void kfree_const(const void *x) > > > EXPORT_SYMBOL(kfree_const); > > > > > > /** > > > - * kstrdup - allocate space for and copy an existing string > > > - * @s: the string to duplicate > > > + * __kmemdup_nul - Create a NUL-terminated string from @s, which mig= ht be unterminated. > > > + * @s: The data to copy > > > + * @len: The size of the data, including the null terminator > > > * @gfp: the GFP mask used in the kmalloc() call when allocating mem= ory > > > * > > > - * Return: newly allocated copy of @s or %NULL in case of error > > > + * Return: newly allocated copy of @s with NUL-termination or %NULL = in > > > + * case of error > > > */ > > > -noinline > > > -char *kstrdup(const char *s, gfp_t gfp) > > > +static __always_inline char *__kmemdup_nul(const char *s, size_t len= , gfp_t gfp) > > > { > > > - size_t len; > > > char *buf; > > > > > > - if (!s) > > > + buf =3D kmalloc_track_caller(len, gfp); > > > + if (!buf) > > > return NULL; > > > > > > - len =3D strlen(s) + 1; > > > - buf =3D kmalloc_track_caller(len, gfp); > > > - if (buf) { > > > - memcpy(buf, s, len); > > > - /* During memcpy(), the string might be updated to a new = value, > > > - * which could be longer than the string when strlen() is > > > - * called. Therefore, we need to add a null termimator. > > > - */ > > > - buf[len - 1] =3D '\0'; > > > - } > > > + memcpy(buf, s, len); > > > + /* Ensure the buf is always NUL-terminated, regardless of @s. */ > > > + buf[len - 1] =3D '\0'; > > > return buf; > > > } > > > + > > > +/** > > > + * kstrdup - allocate space for and copy an existing string > > > + * @s: the string to duplicate > > > + * @gfp: the GFP mask used in the kmalloc() call when allocating mem= ory > > > + * > > > + * Return: newly allocated copy of @s or %NULL in case of error > > > + */ > > > +noinline > > > +char *kstrdup(const char *s, gfp_t gfp) > > > +{ > > > + return s ? __kmemdup_nul(s, strlen(s) + 1, gfp) : NULL; > > > +} > > > EXPORT_SYMBOL(kstrdup); > > > > > > /** > > > @@ -106,19 +113,7 @@ EXPORT_SYMBOL(kstrdup_const); > > > */ > > > char *kstrndup(const char *s, size_t max, gfp_t gfp) > > > { > > > - size_t len; > > > - char *buf; > > > - > > > - if (!s) > > > - return NULL; > > > - > > > - len =3D strnlen(s, max); > > > - buf =3D kmalloc_track_caller(len+1, gfp); > > > - if (buf) { > > > - memcpy(buf, s, len); > > > - buf[len] =3D '\0'; > > > - } > > > - return buf; > > > + return s ? __kmemdup_nul(s, strnlen(s, max) + 1, gfp) : NULL; > > > } > > > EXPORT_SYMBOL(kstrndup); > > > > > > @@ -192,17 +187,7 @@ EXPORT_SYMBOL(kvmemdup); > > > */ > > > char *kmemdup_nul(const char *s, size_t len, gfp_t gfp) > > > { > > > - char *buf; > > > - > > > - if (!s) > > > - return NULL; > > > - > > > - buf =3D kmalloc_track_caller(len + 1, gfp); > > > - if (buf) { > > > - memcpy(buf, s, len); > > > - buf[len] =3D '\0'; > > > - } > > > - return buf; > > > + return s ? __kmemdup_nul(s, len + 1, gfp) : NULL; > > > } > > > EXPORT_SYMBOL(kmemdup_nul); > > > > I like the idea of the patch, but it's plagued with all those +1 and -1= . > > I think that's due to a bad choice of value being passed by. If you > > pass the actual length of the string (as suggested in my reply to the > > previous patch) you should end up with a cleaner set of APIs. > > > > The only remaining +1 is for kmalloc_track_caller(), which I ignore wha= t > > it does. > > > > char * > > __kmemdup_nul(const char *s, size_t len, gfp_t gfp) > > { > > char *buf; > > > > buf =3D kmalloc_track_caller(len + 1, gfp); > > if (!buf) > > return NULL; > > > > strcpy(mempcpy(buf, s, len), ""); > > Changing these strcpy(, "") to the usual; =3D'\0' or =3D0, but I'd still > recommend the rest of the changes, that is, changing the value passed in > len, to remove several +1 and -1s. > > What do you think? I will update it. Thanks for your suggestion. --=20 Regards Yafang