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>

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index b40fd5e..785a01c 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -215,6 +215,10 @@ struct cftype {
         * single integer. Use it in place of read()
         */
        u64 (*read_u64) (struct cgroup *cgrp, struct cftype *cft);
+       /*
+        * read_s64() is a signed version of read_u64()
+        */
+       s64 (*read_s64) (struct cgroup *cgrp, struct cftype *cft);
        /*
         * read_map() is used for defining a map of key/value
         * pairs. It should call cb->fill(cb, key, value) for each
@@ -234,6 +238,10 @@ struct cftype {
         * userspace. Use in place of write(); return 0 or error.
         */
        int (*write_u64) (struct cgroup *cgrp, struct cftype *cft, u64 val);
+       /*
+        * write_s64() is a signed version of write_u64()
+        */
+       int (*write_s64) (struct cgroup *cgrp, struct cftype *cft, s64 val);
 
        int (*release) (struct inode *inode, struct file *file);
 };

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b5ef0c4..bd6122c 100644 (file)
--- 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;
 }