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authorPaul Menage <menage@google.com>2008-07-25 04:46:58 -0400
committerLinus Torvalds <torvalds@linux-foundation.org>2008-07-25 13:53:35 -0400
commitdb3b14978abc02041046ed8353f0899cb58ffffc (patch)
tree355ba027c6354bd13bcbb5318e8478b3de4599e9 /kernel/cgroup.c
parentce16b49d37e748574f7fabc2726268d542d0aa1a (diff)
cgroup files: add write_string cgroup control file method
This patch adds a write_string() method for cgroups control files. The semantics are that a buffer is copied from userspace to kernelspace and the handler function invoked on that buffer. The buffer is guaranteed to be nul-terminated, and no longer than max_write_len (defaulting to 64 bytes if unspecified). Later patches will convert existing raw file write handlers in control group subsystems to use this method. Signed-off-by: Paul Menage <menage@google.com> Cc: Paul Jackson <pj@sgi.com> Cc: Pavel Emelyanov <xemul@openvz.org> Acked-by: Balbir Singh <balbir@in.ibm.com> Acked-by: Serge Hallyn <serue@us.ibm.com> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'kernel/cgroup.c')
-rw-r--r--kernel/cgroup.c35
1 files changed, 35 insertions, 0 deletions
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 70d083c6fb6b..3a99cc2df860 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1363,6 +1363,39 @@ static ssize_t cgroup_write_X64(struct cgroup *cgrp, struct cftype *cft,
1363 return retval; 1363 return retval;
1364} 1364}
1365 1365
1366static ssize_t cgroup_write_string(struct cgroup *cgrp, struct cftype *cft,
1367 struct file *file,
1368 const char __user *userbuf,
1369 size_t nbytes, loff_t *unused_ppos)
1370{
1371 char local_buffer[64];
1372 int retval = 0;
1373 size_t max_bytes = cft->max_write_len;
1374 char *buffer = local_buffer;
1375
1376 if (!max_bytes)
1377 max_bytes = sizeof(local_buffer) - 1;
1378 if (nbytes >= max_bytes)
1379 return -E2BIG;
1380 /* Allocate a dynamic buffer if we need one */
1381 if (nbytes >= sizeof(local_buffer)) {
1382 buffer = kmalloc(nbytes + 1, GFP_KERNEL);
1383 if (buffer == NULL)
1384 return -ENOMEM;
1385 }
1386 if (nbytes && copy_from_user(buffer, userbuf, nbytes))
1387 return -EFAULT;
1388
1389 buffer[nbytes] = 0; /* nul-terminate */
1390 strstrip(buffer);
1391 retval = cft->write_string(cgrp, cft, buffer);
1392 if (!retval)
1393 retval = nbytes;
1394 if (buffer != local_buffer)
1395 kfree(buffer);
1396 return retval;
1397}
1398
1366static ssize_t cgroup_common_file_write(struct cgroup *cgrp, 1399static ssize_t cgroup_common_file_write(struct cgroup *cgrp,
1367 struct cftype *cft, 1400 struct cftype *cft,
1368 struct file *file, 1401 struct file *file,
@@ -1440,6 +1473,8 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
1440 return cft->write(cgrp, cft, file, buf, nbytes, ppos); 1473 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
1441 if (cft->write_u64 || cft->write_s64) 1474 if (cft->write_u64 || cft->write_s64)
1442 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos); 1475 return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
1476 if (cft->write_string)
1477 return cgroup_write_string(cgrp, cft, file, buf, nbytes, ppos);
1443 if (cft->trigger) { 1478 if (cft->trigger) {
1444 int ret = cft->trigger(cgrp, (unsigned int)cft->private); 1479 int ret = cft->trigger(cgrp, (unsigned int)cft->private);
1445 return ret ? ret : nbytes; 1480 return ret ? ret : nbytes;