proc, oom_adj: extract oom_score_adj setting into a helper

Currently we have two proc interfaces to set oom_score_adj.  The legacy
/proc/<pid>/oom_adj and /proc/<pid>/oom_score_adj which both have their
specific handlers.  Big part of the logic is duplicated so extract the
common code into __set_oom_adj helper.  Legacy knob still expects some
details slightly different so make sure those are handled same way - e.g.
the legacy mode ignores oom_score_adj_min and it warns about the usage.

This patch shouldn't introduce any functional changes.

Link: http://lkml.kernel.org/r/1466426628-15074-4-git-send-email-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Vladimir Davydov <vdavydov@virtuozzo.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/proc/base.c b/fs/proc/base.c
index f7dc105..13a3459 100644 (file)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1037,7 +1037,47 @@ static ssize_t oom_adj_read(struct file *file, char __user *buf, size_t count,
        return simple_read_from_buffer(buf, count, ppos, buffer, len);
 }
 
-static DEFINE_MUTEX(oom_adj_mutex);
+static int __set_oom_adj(struct file *file, int oom_adj, bool legacy)
+{
+       static DEFINE_MUTEX(oom_adj_mutex);
+       struct task_struct *task;
+       int err = 0;
+
+       task = get_proc_task(file_inode(file));
+       if (!task)
+               return -ESRCH;
+
+       mutex_lock(&oom_adj_mutex);
+       if (legacy) {
+               if (oom_adj < task->signal->oom_score_adj &&
+                               !capable(CAP_SYS_RESOURCE)) {
+                       err = -EACCES;
+                       goto err_unlock;
+               }
+               /*
+                * /proc/pid/oom_adj is provided for legacy purposes, ask users to use
+                * /proc/pid/oom_score_adj instead.
+                */
+               pr_warn_once("%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n",
+                         current->comm, task_pid_nr(current), task_pid_nr(task),
+                         task_pid_nr(task));
+       } else {
+               if ((short)oom_adj < task->signal->oom_score_adj_min &&
+                               !capable(CAP_SYS_RESOURCE)) {
+                       err = -EACCES;
+                       goto err_unlock;
+               }
+       }
+
+       task->signal->oom_score_adj = oom_adj;
+       if (!legacy && has_capability_noaudit(current, CAP_SYS_RESOURCE))
+               task->signal->oom_score_adj_min = (short)oom_adj;
+       trace_oom_score_adj_update(task);
+err_unlock:
+       mutex_unlock(&oom_adj_mutex);
+       put_task_struct(task);
+       return err;
+}
 
 /*
  * /proc/pid/oom_adj exists solely for backwards compatibility with previous
@@ -1052,7 +1092,6 @@ static DEFINE_MUTEX(oom_adj_mutex);
 static ssize_t oom_adj_write(struct file *file, const char __user *buf,
                             size_t count, loff_t *ppos)
 {
-       struct task_struct *task;
        char buffer[PROC_NUMBUF];
        int oom_adj;
        int err;
@@ -1074,12 +1113,6 @@ static ssize_t oom_adj_write(struct file *file, const char __user *buf,
                goto out;
        }
 
-       task = get_proc_task(file_inode(file));
-       if (!task) {
-               err = -ESRCH;
-               goto out;
-       }
-
        /*
         * Scale /proc/pid/oom_score_adj appropriately ensuring that a maximum
         * value is always attainable.
@@ -1089,26 +1122,7 @@ static ssize_t oom_adj_write(struct file *file, const char __user *buf,
        else
                oom_adj = (oom_adj * OOM_SCORE_ADJ_MAX) / -OOM_DISABLE;
 
-       mutex_lock(&oom_adj_mutex);
-       if (oom_adj < task->signal->oom_score_adj &&
-           !capable(CAP_SYS_RESOURCE)) {
-               err = -EACCES;
-               goto err_unlock;
-       }
-
-       /*
-        * /proc/pid/oom_adj is provided for legacy purposes, ask users to use
-        * /proc/pid/oom_score_adj instead.
-        */
-       pr_warn_once("%s (%d): /proc/%d/oom_adj is deprecated, please use /proc/%d/oom_score_adj instead.\n",
-                 current->comm, task_pid_nr(current), task_pid_nr(task),
-                 task_pid_nr(task));
-
-       task->signal->oom_score_adj = oom_adj;
-       trace_oom_score_adj_update(task);
-err_unlock:
-       mutex_unlock(&oom_adj_mutex);
-       put_task_struct(task);
+       err = __set_oom_adj(file, oom_adj, true);
 out:
        return err < 0 ? err : count;
 }
@@ -1138,7 +1152,6 @@ static ssize_t oom_score_adj_read(struct file *file, char __user *buf,
 static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
                                        size_t count, loff_t *ppos)
 {
-       struct task_struct *task;
        char buffer[PROC_NUMBUF];
        int oom_score_adj;
        int err;
@@ -1160,28 +1173,7 @@ static ssize_t oom_score_adj_write(struct file *file, const char __user *buf,
                goto out;
        }
 
-       task = get_proc_task(file_inode(file));
-       if (!task) {
-               err = -ESRCH;
-               goto out;
-       }
-
-       mutex_lock(&oom_adj_mutex);
-       if ((short)oom_score_adj < task->signal->oom_score_adj_min &&
-                       !capable(CAP_SYS_RESOURCE)) {
-               err = -EACCES;
-               goto err_unlock;
-       }
-
-       task->signal->oom_score_adj = (short)oom_score_adj;
-       if (has_capability_noaudit(current, CAP_SYS_RESOURCE))
-               task->signal->oom_score_adj_min = (short)oom_score_adj;
-
-       trace_oom_score_adj_update(task);
-
-err_unlock:
-       mutex_unlock(&oom_adj_mutex);
-       put_task_struct(task);
+       err = __set_oom_adj(file, oom_score_adj, false);
 out:
        return err < 0 ? err : count;
 }