[v8,6/8] mm/util: Deduplicate code in {kstrdup,kstrndup,kmemdup_nul}

Commit Message

Yafang Shao Aug. 28, 2024, 3:03 a.m. UTC

These three functions follow the same pattern. To deduplicate the code,
let's introduce a common helper __kmemdup_nul().

Suggested-by: Andrew Morton <[e-mail]>
Signed-off-by: Yafang Shao <[e-mail]>
Cc: Simon Horman <[e-mail]>
Cc: Matthew Wilcox <[e-mail]>
Cc: Alejandro Colomar <[e-mail]>
---
 mm/util.c | 68 ++++++++++++++++++++++---------------------------------
 1 file changed, 27 insertions(+), 41 deletions(-)

Comments

Alejandro Colomar Aug. 28, 2024, 10:32 a.m. UTC | #1

On Wed, Aug 28, 2024 at 11:03:19AM GMT, Yafang Shao wrote:
> These three functions follow the same pattern. To deduplicate the code,
> let's introduce a common helper __kmemdup_nul().
> 
> Suggested-by: Andrew Morton <[e-mail]>
> Signed-off-by: Yafang Shao <[e-mail]>
> Cc: Simon Horman <[e-mail]>
> Cc: Matthew Wilcox <[e-mail]>
> Cc: Alejandro Colomar <[e-mail]>
> ---

Reviewed-by: Alejandro Colomar <[e-mail]>

Cheers,
Alex

>  mm/util.c | 68 ++++++++++++++++++++++---------------------------------
>  1 file changed, 27 insertions(+), 41 deletions(-)
> 
> diff --git a/mm/util.c b/mm/util.c
> index 9a77a347c385..42714fe13e24 100644
> --- a/mm/util.c
> +++ b/mm/util.c
> @@ -45,33 +45,41 @@ 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 might be unterminated.
> + * @s: The data to copy
> + * @len: The size of the data, not including the NUL terminator
>   * @gfp: the GFP mask used in the kmalloc() call when allocating memory
>   *
> - * 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)
> +	/* '+1' for the NUL terminator */
> +	buf = kmalloc_track_caller(len + 1, gfp);
> +	if (!buf)
>  		return NULL;
>  
> -	len = strlen(s) + 1;
> -	buf = 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 NUL termimator.
> -		 */
> -		buf[len - 1] = '\0';
> -	}
> +	memcpy(buf, s, len);
> +	/* Ensure the buf is always NUL-terminated, regardless of @s. */
> +	buf[len] = '\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 memory
> + *
> + * 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), gfp) : NULL;
> +}
>  EXPORT_SYMBOL(kstrdup);
>  
>  /**
> @@ -106,19 +114,7 @@ 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 = strnlen(s, max);
> -	buf = kmalloc_track_caller(len+1, gfp);
> -	if (buf) {
> -		memcpy(buf, s, len);
> -		buf[len] = '\0';
> -	}
> -	return buf;
> +	return s ? __kmemdup_nul(s, strnlen(s, max), gfp) : NULL;
>  }
>  EXPORT_SYMBOL(kstrndup);
>  
> @@ -192,17 +188,7 @@ EXPORT_SYMBOL(kvmemdup);
>   */
>  char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
>  {
> -	char *buf;
> -
> -	if (!s)
> -		return NULL;
> -
> -	buf = kmalloc_track_caller(len + 1, gfp);
> -	if (buf) {
> -		memcpy(buf, s, len);
> -		buf[len] = '\0';
> -	}
> -	return buf;
> +	return s ? __kmemdup_nul(s, len, gfp) : NULL;
>  }
>  EXPORT_SYMBOL(kmemdup_nul);
>  
> -- 
> 2.43.5
>

Alejandro Colomar Aug. 28, 2024, 10:33 a.m. UTC | #2

On Wed, Aug 28, 2024 at 12:32:53PM GMT, Alejandro Colomar wrote:
> On Wed, Aug 28, 2024 at 11:03:19AM GMT, Yafang Shao wrote:
> > These three functions follow the same pattern. To deduplicate the code,
> > let's introduce a common helper __kmemdup_nul().
> > 
> > Suggested-by: Andrew Morton <[e-mail]>
> > Signed-off-by: Yafang Shao <[e-mail]>
> > Cc: Simon Horman <[e-mail]>
> > Cc: Matthew Wilcox <[e-mail]>
> > Cc: Alejandro Colomar <[e-mail]>
> > ---
> 
> Reviewed-by: Alejandro Colomar <[e-mail]>

(Or maybe I should say

Co-developed-by: Alejandro Colomar <[e-mail]>
Signed-off-by: Alejandro Colomar <[e-mail]>

)


> 
> Cheers,
> Alex
> 
> >  mm/util.c | 68 ++++++++++++++++++++++---------------------------------
> >  1 file changed, 27 insertions(+), 41 deletions(-)
> > 
> > diff --git a/mm/util.c b/mm/util.c
> > index 9a77a347c385..42714fe13e24 100644
> > --- a/mm/util.c
> > +++ b/mm/util.c
> > @@ -45,33 +45,41 @@ 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 might be unterminated.
> > + * @s: The data to copy
> > + * @len: The size of the data, not including the NUL terminator
> >   * @gfp: the GFP mask used in the kmalloc() call when allocating memory
> >   *
> > - * 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)
> > +	/* '+1' for the NUL terminator */
> > +	buf = kmalloc_track_caller(len + 1, gfp);
> > +	if (!buf)
> >  		return NULL;
> >  
> > -	len = strlen(s) + 1;
> > -	buf = 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 NUL termimator.
> > -		 */
> > -		buf[len - 1] = '\0';
> > -	}
> > +	memcpy(buf, s, len);
> > +	/* Ensure the buf is always NUL-terminated, regardless of @s. */
> > +	buf[len] = '\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 memory
> > + *
> > + * 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), gfp) : NULL;
> > +}
> >  EXPORT_SYMBOL(kstrdup);
> >  
> >  /**
> > @@ -106,19 +114,7 @@ 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 = strnlen(s, max);
> > -	buf = kmalloc_track_caller(len+1, gfp);
> > -	if (buf) {
> > -		memcpy(buf, s, len);
> > -		buf[len] = '\0';
> > -	}
> > -	return buf;
> > +	return s ? __kmemdup_nul(s, strnlen(s, max), gfp) : NULL;
> >  }
> >  EXPORT_SYMBOL(kstrndup);
> >  
> > @@ -192,17 +188,7 @@ EXPORT_SYMBOL(kvmemdup);
> >   */
> >  char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
> >  {
> > -	char *buf;
> > -
> > -	if (!s)
> > -		return NULL;
> > -
> > -	buf = kmalloc_track_caller(len + 1, gfp);
> > -	if (buf) {
> > -		memcpy(buf, s, len);
> > -		buf[len] = '\0';
> > -	}
> > -	return buf;
> > +	return s ? __kmemdup_nul(s, len, gfp) : NULL;
> >  }
> >  EXPORT_SYMBOL(kmemdup_nul);
> >  
> > -- 
> > 2.43.5
> > 
> 
> -- 
> <https://www.alejandro-colomar.es/>

Yafang Shao Aug. 28, 2024, 12:58 p.m. UTC | #3

On Wed, Aug 28, 2024 at 6:33 PM Alejandro Colomar <[e-mail]> wrote:
>
> On Wed, Aug 28, 2024 at 12:32:53PM GMT, Alejandro Colomar wrote:
> > On Wed, Aug 28, 2024 at 11:03:19AM GMT, Yafang Shao wrote:
> > > These three functions follow the same pattern. To deduplicate the code,
> > > let's introduce a common helper __kmemdup_nul().
> > >
> > > Suggested-by: Andrew Morton <[e-mail]>
> > > Signed-off-by: Yafang Shao <[e-mail]>
> > > Cc: Simon Horman <[e-mail]>
> > > Cc: Matthew Wilcox <[e-mail]>
> > > Cc: Alejandro Colomar <[e-mail]>
> > > ---
> >
> > Reviewed-by: Alejandro Colomar <[e-mail]>
>
> (Or maybe I should say
>
> Co-developed-by: Alejandro Colomar <[e-mail]>
> Signed-off-by: Alejandro Colomar <[e-mail]>

I will add it.
Thanks for your help.

Patch

diff --git a/mm/util.c b/mm/util.c
index 9a77a347c385..42714fe13e24 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -45,33 +45,41 @@  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 might be unterminated.
+ * @s: The data to copy
+ * @len: The size of the data, not including the NUL terminator
  * @gfp: the GFP mask used in the kmalloc() call when allocating memory
  *
- * 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)
+	/* '+1' for the NUL terminator */
+	buf = kmalloc_track_caller(len + 1, gfp);
+	if (!buf)
 		return NULL;
 
-	len = strlen(s) + 1;
-	buf = 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 NUL termimator.
-		 */
-		buf[len - 1] = '\0';
-	}
+	memcpy(buf, s, len);
+	/* Ensure the buf is always NUL-terminated, regardless of @s. */
+	buf[len] = '\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 memory
+ *
+ * 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), gfp) : NULL;
+}
 EXPORT_SYMBOL(kstrdup);
 
 /**
@@ -106,19 +114,7 @@  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 = strnlen(s, max);
-	buf = kmalloc_track_caller(len+1, gfp);
-	if (buf) {
-		memcpy(buf, s, len);
-		buf[len] = '\0';
-	}
-	return buf;
+	return s ? __kmemdup_nul(s, strnlen(s, max), gfp) : NULL;
 }
 EXPORT_SYMBOL(kstrndup);
 
@@ -192,17 +188,7 @@  EXPORT_SYMBOL(kvmemdup);
  */
 char *kmemdup_nul(const char *s, size_t len, gfp_t gfp)
 {
-	char *buf;
-
-	if (!s)
-		return NULL;
-
-	buf = kmalloc_track_caller(len + 1, gfp);
-	if (buf) {
-		memcpy(buf, s, len);
-		buf[len] = '\0';
-	}
-	return buf;
+	return s ? __kmemdup_nul(s, len, gfp) : NULL;
 }
 EXPORT_SYMBOL(kmemdup_nul);