[RFC][PATCH 1/4] Provide a new procfs interface to set next id
Oren Laadan
orenl at cs.columbia.edu
Fri Mar 28 12:12:51 PDT 2008
On Fri, 28 Mar 2008, Nadia.Derbey at bull.net wrote:
> [PATCH 01/04]
>
> This patch proposes the procfs facilities needed to feed the id for the
> next object to be allocated.
>
> if an
> echo "LONG XX" > /proc/self/next_id
> is issued, next object to be created will have XX as its id.
>
> This applies to objects that need a single id, such as ipc objects.
>
> Signed-off-by: Nadia Derbey <Nadia.Derbey at bull.net>
>
> ---
> fs/proc/base.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++
> include/linux/sched.h | 3 ++
> include/linux/sysids.h | 18 ++++++++++++
> kernel/Makefile | 2 -
> kernel/fork.c | 2 +
> kernel/nextid.c | 69 ++++++++++++++++++++++++++++++++++++++++++++++
> 6 files changed, 166 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.25-rc3-mm1/include/linux/sysids.h
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6.25-rc3-mm1/include/linux/sysids.h 2008-03-27 18:02:08.000000000 +0100
> @@ -0,0 +1,18 @@
> +/*
> + * include/linux/sysids.h
> + *
> + * Definitions to support object creation with predefined id.
> + *
> + */
> +
> +#ifndef _LINUX_SYSIDS_H
> +#define _LINUX_SYSIDS_H
> +
> +struct sys_id {
> + long id;
> +};
> +
> +extern ssize_t get_nextid(struct task_struct *, char *);
> +extern int set_nextid(struct task_struct *, char *);
> +
> +#endif /* _LINUX_SYSIDS_H */
> Index: linux-2.6.25-rc3-mm1/include/linux/sched.h
> ===================================================================
> --- linux-2.6.25-rc3-mm1.orig/include/linux/sched.h 2008-03-10 09:18:46.000000000 +0100
> +++ linux-2.6.25-rc3-mm1/include/linux/sched.h 2008-03-10 09:28:30.000000000 +0100
> @@ -87,6 +87,7 @@ struct sched_param {
> #include <linux/task_io_accounting.h>
> #include <linux/kobject.h>
> #include <linux/latencytop.h>
> +#include <linux/sysids.h>
>
> #include <asm/processor.h>
>
> @@ -1261,6 +1262,8 @@ struct task_struct {
> int latency_record_count;
> struct latency_record latency_record[LT_SAVECOUNT];
> #endif
> + /* Id to assign to the next resource to be created */
> + struct sys_id *next_id;
> };
>
> /*
> Index: linux-2.6.25-rc3-mm1/fs/proc/base.c
> ===================================================================
> --- linux-2.6.25-rc3-mm1.orig/fs/proc/base.c 2008-03-10 09:19:39.000000000 +0100
> +++ linux-2.6.25-rc3-mm1/fs/proc/base.c 2008-03-21 12:03:09.000000000 +0100
> @@ -1080,6 +1080,77 @@ static const struct file_operations proc
> #endif
>
>
> +static ssize_t next_id_read(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct task_struct *task;
> + char *page;
> + ssize_t length;
> +
> + task = get_proc_task(file->f_path.dentry->d_inode);
> + if (!task)
> + return -ESRCH;
> +
> + if (count > PROC_BLOCK_SIZE)
> + count = PROC_BLOCK_SIZE;
> +
> + length = -ENOMEM;
> + page = (char *) __get_free_page(GFP_TEMPORARY);
> + if (!page)
> + goto out;
> +
> + length = get_nextid(task, (char *) page);
> + if (length >= 0)
> + length = simple_read_from_buffer(buf, count, ppos,
> + (char *)page, length);
> + free_page((unsigned long) page);
> +
> +out:
> + put_task_struct(task);
> + return length;
> +}
> +
> +static ssize_t next_id_write(struct file *file, const char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + struct inode *inode = file->f_path.dentry->d_inode;
> + char *page;
> + ssize_t length;
> +
> + if (pid_task(proc_pid(inode), PIDTYPE_PID) != current)
> + return -EPERM;
> +
> + if (count >= PAGE_SIZE)
> + count = PAGE_SIZE - 1;
> +
> + if (*ppos != 0) {
> + /* No partial writes. */
> + return -EINVAL;
> + }
> + page = (char *)__get_free_page(GFP_TEMPORARY);
> + if (!page)
> + return -ENOMEM;
> + length = -EFAULT;
> + if (copy_from_user(page, buf, count))
> + goto out_free_page;
> +
> + page[count] = '\0';
> +
> + length = set_nextid(current, page);
> + if (!length)
> + length = count;
> +
> +out_free_page:
> + free_page((unsigned long) page);
> + return length;
> +}
> +
> +static const struct file_operations proc_next_id_operations = {
> + .read = next_id_read,
> + .write = next_id_write,
> +};
> +
> +
> #ifdef CONFIG_SCHED_DEBUG
> /*
> * Print out various scheduling related per-task fields:
> @@ -2391,6 +2462,7 @@ static const struct pid_entry tgid_base_
> #ifdef CONFIG_TASK_IO_ACCOUNTING
> INF("io", S_IRUGO, pid_io_accounting),
> #endif
> + REG("next_id", S_IRUGO|S_IWUSR, next_id),
> };
>
> static int proc_tgid_base_readdir(struct file * filp,
> @@ -2716,6 +2788,7 @@ static const struct pid_entry tid_base_s
> #ifdef CONFIG_FAULT_INJECTION
> REG("make-it-fail", S_IRUGO|S_IWUSR, fault_inject),
> #endif
> + REG("next_id", S_IRUGO|S_IWUSR, next_id),
> };
>
> static int proc_tid_base_readdir(struct file * filp,
> Index: linux-2.6.25-rc3-mm1/kernel/Makefile
> ===================================================================
> --- linux-2.6.25-rc3-mm1.orig/kernel/Makefile 2008-03-10 09:19:01.000000000 +0100
> +++ linux-2.6.25-rc3-mm1/kernel/Makefile 2008-03-20 17:29:50.000000000 +0100
> @@ -9,7 +9,7 @@ obj-y = sched.o fork.o exec_domain.o
> rcupdate.o extable.o params.o posix-timers.o \
> kthread.o wait.o kfifo.o sys_ni.o posix-cpu-timers.o mutex.o \
> hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
> - notifier.o ksysfs.o pm_qos_params.o
> + notifier.o ksysfs.o pm_qos_params.o nextid.o
>
> obj-$(CONFIG_SYSCTL_SYSCALL_CHECK) += sysctl_check.o
> obj-$(CONFIG_STACKTRACE) += stacktrace.o
> Index: linux-2.6.25-rc3-mm1/kernel/nextid.c
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6.25-rc3-mm1/kernel/nextid.c 2008-03-27 18:02:08.000000000 +0100
> @@ -0,0 +1,69 @@
> +/*
> + * linux/kernel/nextid.c
> + *
> + *
> + * Provide the get_nextid() / set_nextid() routines
> + * (called from fs/proc/base.c).
> + * They allow to specify the id for the next resource to be allocated,
> + * instead of letting the allocator set it for us.
> + */
> +
> +#include <linux/sched.h>
> +#include <linux/ctype.h>
> +
> +
> +
> +ssize_t get_nextid(struct task_struct *task, char *buffer)
> +{
> + struct sys_id *sid;
> +
> + sid = task->next_id;
> + if (!sid)
> + return snprintf(buffer, sizeof(buffer), "-1\n");
> +
> + return snprintf(buffer, sizeof(buffer), "%ld\n", sid->id);
> +}
Since the input format is "LONG <id>", why not have the output format
be the same ? This way, if in the future there are other formats (eg
CHAR, IPv4 ...). Same comment for the next patch, for LONG<n> format.
(disclaimer: at this point I don't see why one would want to read this
file, or usage for other formats...)
> +
> +static int set_single_id(struct task_struct *task, char *buffer)
> +{
> + struct sys_id *sid;
> + long next_id;
> + char *end;
> +
> + next_id = simple_strtol(buffer, &end, 0);
> + if (end == buffer || (end && !isspace(*end)))
> + return -EINVAL;
> +
> + sid = task->next_id;
> + if (!sid) {
> + sid = kzalloc(sizeof(*sid), GFP_KERNEL);
> + if (!sid)
> + return -ENOMEM;
> + task->next_id = sid;
> + }
> +
> + sid->id = next_id;
> +
> + return 0;
> +}
> +
> +#define SINGLE_LONG "LONG"
> +
> +/*
> + * Parses a line written to /proc/self/next_id.
> + * this line has the following format:
> + * LONG id --> a single id is specified
> + */
> +int set_nextid(struct task_struct *task, char *buffer)
> +{
> + char *token, *out = buffer;
> +
> + token = strsep(&out, " ");
> + if (!token || !out)
> + return -EINVAL;
> +
> + if (!strcmp(token, SINGLE_LONG))
> + return set_single_id(task, out);
> + else
> + return -EINVAL;
> +}
> Index: linux-2.6.25-rc3-mm1/kernel/fork.c
> ===================================================================
> --- linux-2.6.25-rc3-mm1.orig/kernel/fork.c 2008-03-27 18:01:56.000000000 +0100
> +++ linux-2.6.25-rc3-mm1/kernel/fork.c 2008-03-27 18:02:42.000000000 +0100
> @@ -1166,6 +1166,8 @@ static struct task_struct *copy_process(
> p->blocked_on = NULL; /* not blocked yet */
> #endif
>
> + p->next_id = NULL;
> +
> /* Perform scheduler related setup. Assign this task to a CPU. */
> sched_fork(p, clone_flags);
Freeing this memory when the task terminates could be helpful, too.
Probably execve() is another good candidate to free this, just in case.
Oren.
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