CGroups _s64 files: add cgroups read_s64/write_s64 file methods

These patches add cgroups read_s64 and write_s64 control file methods (the
signed equivalent of read_u64/write_u64) and use them to implement the
cpu.rt_runtime_us control file in the CFS cgroup subsystem.

This patch:

These are the signed equivalents of the read_u64/write_u64 methods

Signed-off-by: Paul Menage <menage@google.com>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 28 insertions, 10 deletions

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b5ef0c4772f7..bd6122ccc0ba 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1299,14 +1299,13 @@ enum cgroup_filetype {
         FILE_RELEASE_AGENT,
 };
 
-static ssize_t cgroup_write_u64(struct cgroup *cgrp, struct cftype *cft,
+static ssize_t cgroup_write_X64(struct cgroup *cgrp, 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)
@@ -1318,12 +1317,17 @@ static ssize_t cgroup_write_u64(struct cgroup *cgrp, struct cftype *cft,
 
         buffer[nbytes] = 0;     /* nul-terminate */
         strstrip(buffer);
-        val = simple_strtoull(buffer, &end, 0);
-        if (*end)
-                return -EINVAL;
-
-        /* Pass to subsystem */
-        retval = cft->write_u64(cgrp, cft, val);
+        if (cft->write_u64) {
+                u64 val = simple_strtoull(buffer, &end, 0);
+                if (*end)
+                        return -EINVAL;
+                retval = cft->write_u64(cgrp, cft, val);
+        } else {
+                s64 val = simple_strtoll(buffer, &end, 0);
+                if (*end)
+                        return -EINVAL;
+                retval = cft->write_s64(cgrp, cft, val);
+        }
         if (!retval)
                 retval = nbytes;
         return retval;
@@ -1404,8 +1408,8 @@ static ssize_t cgroup_file_write(struct file *file, const char __user *buf,
                 return -ENODEV;
         if (cft->write)
                 return cft->write(cgrp, cft, file, buf, nbytes, ppos);
-        if (cft->write_u64)
-                return cgroup_write_u64(cgrp, cft, file, buf, nbytes, ppos);
+        if (cft->write_u64 || cft->write_s64)
+                return cgroup_write_X64(cgrp, cft, file, buf, nbytes, ppos);
         return -EINVAL;
 }
 
@@ -1421,6 +1425,18 @@ static ssize_t cgroup_read_u64(struct cgroup *cgrp, struct cftype *cft,
         return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
 }
 
+static ssize_t cgroup_read_s64(struct cgroup *cgrp, struct cftype *cft,
+                               struct file *file,
+                               char __user *buf, size_t nbytes,
+                               loff_t *ppos)
+{
+        char tmp[64];
+        s64 val = cft->read_s64(cgrp, cft);
+        int len = sprintf(tmp, "%lld\n", (long long) val);
+
+        return simple_read_from_buffer(buf, nbytes, ppos, tmp, len);
+}
+
 static ssize_t cgroup_common_file_read(struct cgroup *cgrp,
                                           struct cftype *cft,
                                           struct file *file,
@@ -1477,6 +1493,8 @@ static ssize_t cgroup_file_read(struct file *file, char __user *buf,
                 return cft->read(cgrp, cft, file, buf, nbytes, ppos);
         if (cft->read_u64)
                 return cgroup_read_u64(cgrp, cft, file, buf, nbytes, ppos);
+        if (cft->read_s64)
+                return cgroup_read_s64(cgrp, cft, file, buf, nbytes, ppos);
         return -EINVAL;
 }