+ mm-utilc-add-kstrimdup.patch added to -mm tree

+ mm-utilc-add-kstrimdup.patch added to -mm tree

[akpm]

Subject: + mm-utilc-add-kstrimdup.patch added to -mm tree
To: sebastian.capella@linaro.org,joe@perches.com,rientjes@google.com
From: akpm@linux-foundation.org
Date: Fri, 31 Jan 2014 13:45:02 -0800


The patch titled
     Subject: mm/util.c: add kstrimdup()
has been added to the -mm tree.  Its filename is
     mm-utilc-add-kstrimdup.patch

This patch should soon appear at
    http://ozlabs.org/~akpm/mmots/broken-out/mm-utilc-add-kstrimdup.patch
and later at
    http://ozlabs.org/~akpm/mmotm/broken-out/mm-utilc-add-kstrimdup.patch

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------------------------------------------------------
From: Sebastian Capella <sebastian.capella@linaro.org>
Subject: mm/util.c: add kstrimdup()

kstrimdup() creates a whitespace-trimmed duplicate of the passed in
null-terminated string.  This is useful for strings coming from sysfs that
often include trailing whitespace due to user input.

Thanks to Joe Perches for this implementation.

Signed-off-by: Sebastian Capella <sebastian.capella@linaro.org>
Cc: Joe Perches <joe@perches.com>
Cc: David Rientjes <rientjes@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/string.h |    1 +
 mm/util.c              |   30 ++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+)

diff -puN include/linux/string.h~mm-utilc-add-kstrimdup include/linux/string.h
--- a/include/linux/string.h~mm-utilc-add-kstrimdup
+++ a/include/linux/string.h
@@ -114,6 +114,7 @@ void *memchr_inv(const void *s, int c, s
 
 extern char *kstrdup(const char *s, gfp_t gfp);
 extern char *kstrndup(const char *s, size_t len, gfp_t gfp);
+extern char *kstrimdup(const char *s, gfp_t gfp);
 extern void *kmemdup(const void *src, size_t len, gfp_t gfp);
 
 extern char **argv_split(gfp_t gfp, const char *str, int *argcp);
diff -puN mm/util.c~mm-utilc-add-kstrimdup mm/util.c
--- a/mm/util.c~mm-utilc-add-kstrimdup
+++ a/mm/util.c
@@ -1,6 +1,7 @@
 #include <linux/mm.h>
 #include <linux/slab.h>
 #include <linux/string.h>
+#include <linux/ctype.h>
 #include <linux/export.h>
 #include <linux/err.h>
 #include <linux/sched.h>
@@ -63,6 +64,35 @@ char *kstrndup(const char *s, size_t max
 EXPORT_SYMBOL(kstrndup);
 
 /**
+ * kstrimdup - Trim and copy a %NUL terminated string.
+ * @s: the string to trim and duplicate
+ * @gfp: the GFP mask used in the kmalloc() call when allocating memory
+ *
+ * Returns an address, which the caller must kfree, containing
+ * a duplicate of the passed string with leading and/or trailing
+ * whitespace (as defined by isspace) removed.
+ */
+char *kstrimdup(const char *s, gfp_t gfp)
+{
+	char *buf;
+	char *begin = skip_spaces(s);
+	size_t len = strlen(begin);
+
+	while (len && isspace(begin[len - 1]))
+		len--;
+
+	buf = kmalloc_track_caller(len + 1, gfp);
+	if (!buf)
+		return NULL;
+
+	memcpy(buf, begin, len);
+	buf[len] = '\0';
+
+	return buf;
+}
+EXPORT_SYMBOL(kstrimdup);
+
+/**
  * kmemdup - duplicate region of memory
  *
  * @src: memory region to duplicate
_

Patches currently in -mm which might be from sebastian.capella@linaro.org are

mm-utilc-add-kstrimdup.patch

Re: + mm-utilc-add-kstrimdup.patch added to -mm tree

[Alexey Dobriyan]

On Sat, Feb 1, 2014 at 12:45 AM,  <akpm@linux-foundation.org> wrote:
> kstrimdup() creates a whitespace-trimmed duplicate of the passed in
> null-terminated string.  This is useful for strings coming from sysfs that
> often include trailing whitespace due to user input.

I think kernel should be strict in what it accepts, otherwise
case-insensivity and
what not will be added some day.

Shell will trim whitespace for you.

Re: + mm-utilc-add-kstrimdup.patch added to -mm tree

[David Rientjes]

On Mon, 3 Feb 2014, Alexey Dobriyan wrote:

> > kstrimdup() creates a whitespace-trimmed duplicate of the passed in
> > null-terminated string.  This is useful for strings coming from sysfs that
> > often include trailing whitespace due to user input.
> 
> I think kernel should be strict in what it accepts, otherwise
> case-insensivity and
> what not will be added some day.
> 
> Shell will trim whitespace for you.
> 

The last we heard, I think Sebastian is looking to redo this series and 
this patch is no longer needed.  Sebastian?

Re: + mm-utilc-add-kstrimdup.patch added to -mm tree

[Sebastian Capella]

Quoting David Rientjes (2014-02-03 17:05:04)
> The last we heard, I think Sebastian is looking to redo this series and 
> this patch is no longer needed.  Sebastian?
Hi David, Alexey,

I am in the process of reworking the patches.  I'm not sure if Andrew
was just interested in having the kstrimdup utility function available.

Isn't it too late to impose userspace trimming of newlines for sysfs?
It seems already fairly common and expected for the kernel to eat the
trailing whitespace, or at least ignore it.  If we change this won't we
be breaking userspace / tools / instructions / etc?

I'll try to post the new patches soon.

Thanks,

Sebastian

Re: + mm-utilc-add-kstrimdup.patch added to -mm tree

[David Rientjes]

On Mon, 3 Feb 2014, Sebastian Capella wrote:

> I am in the process of reworking the patches.  I'm not sure if Andrew
> was just interested in having the kstrimdup utility function available.
> 

I think the point Alexey is making is that whitespace is already stripped 
by the shell unless quoted; it seemed that you may have had a usecase 
where the string to be written would not be stripped by the shell for 
whatever reason and there was no convenient way to do it specifically for 
the file you were modifying?

Re: + mm-utilc-add-kstrimdup.patch added to -mm tree

[Andrew Morton]

On Mon, 03 Feb 2014 17:28:16 -0800 Sebastian Capella <sebastian.capella@linaro.org> wrote:

> Quoting David Rientjes (2014-02-03 17:05:04)
> > The last we heard, I think Sebastian is looking to redo this series and 
> > this patch is no longer needed.  Sebastian?
> Hi David, Alexey,
> 
> I am in the process of reworking the patches.  I'm not sure if Andrew
> was just interested in having the kstrimdup utility function available.
> 
> Isn't it too late to impose userspace trimming of newlines for sysfs?
> It seems already fairly common and expected for the kernel to eat the
> trailing whitespace, or at least ignore it.  If we change this won't we
> be breaking userspace / tools / instructions / etc?
> 

We have quite a lot of codesites which open-code the newline trimming. 
Providing a library function to do this will result in goodness.

That being said, I don't plan to merge kstrimdup() until it has some users.