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Commit 355e0c48 authored by Paul Menage's avatar Paul Menage Committed by Linus Torvalds
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Add cgroup write_uint() helper method 



Add write_uint() helper method for cgroup subsystems

This helper is analagous to the read_uint() helper method for
reporting u64 values to userspace. It's designed to reduce the amount
of boilerplate requierd for creating new cgroup subsystems.

Signed-off-by: default avatarPaul Menage <menage@google.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bbcb81d0

include/linux/cgroup.h

+8 −0
Original line number Diff line number Diff line
@@ -125,6 +125,14 @@ struct cftype { 
	ssize_t (*write) (struct cgroup *cont, struct cftype *cft,

			  struct file *file,

			  const char __user *buf, size_t nbytes, loff_t *ppos);



	/*

	 * write_uint() is a shortcut for the common case of accepting

	 * a single integer (as parsed by simple_strtoull) from

	 * userspace. Use in place of write(); return 0 or error.

	 */

	int (*write_uint) (struct cgroup *cont, struct cftype *cft, u64 val);



	int (*release) (struct inode *inode, struct file *file);

};

kernel/cgroup.c

+38 −4
Original line number Diff line number Diff line
@@ -829,6 +829,39 @@ enum cgroup_filetype { 
	FILE_TASKLIST,

};



static ssize_t cgroup_write_uint(struct cgroup *cont, struct cftype *cft,

				 struct file *file,

				 const char __user *userbuf,

				 size_t nbytes, loff_t *unused_ppos)

{

	char buffer[64];

	int retval = 0;

	u64 val;

	char *end;



	if (!nbytes)

		return -EINVAL;

	if (nbytes >= sizeof(buffer))

		return -E2BIG;

	if (copy_from_user(buffer, userbuf, nbytes))

		return -EFAULT;



	buffer[nbytes] = 0;     /* nul-terminate */



	/* strip newline if necessary */

	if (nbytes && (buffer[nbytes-1] == '\n'))

		buffer[nbytes-1] = 0;

	val = simple_strtoull(buffer, &end, 0);

	if (*end)

		return -EINVAL;



	/* Pass to subsystem */

	retval = cft->write_uint(cont, cft, val);

	if (!retval)

		retval = nbytes;

	return retval;

}



static ssize_t cgroup_common_file_write(struct cgroup *cont,

					   struct cftype *cft,

					   struct file *file,
@@ -886,10 +919,11 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf, 


	if (!cft)

		return -ENODEV;

	if (!cft->write)

		return -EINVAL;



	if (cft->write)

		return cft->write(cont, cft, file, buf, nbytes, ppos);

	if (cft->write_uint)

		return cgroup_write_uint(cont, cft, file, buf, nbytes, ppos);

	return -EINVAL;

}



static ssize_t cgroup_read_uint(struct cgroup *cont, struct cftype *cft,