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SubjectRe: [PATCH v2 3/5] pstore: support multiple pmsg instances
On Sun, Jul 24, 2016 at 8:56 PM, Nobuhiro Iwamatsu
<nobuhiro.iwamatsu.kw@hitachi.com> wrote:
> From: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
>
> This enables pmsg to deal with multiple instances. One possible
> use is content priority control on limited persistent store space. By
> using different buffers, we can prevent important messages from being
> overwritten by less important messages.
>
> When pstore backend module specifies the number of instances (num_pmsg)
> in pstore_info, multiple /dev/pmsg[ID] appear. (ID is an integer
> starting at 0. It corresponds to minor number of the each char device.)
> Writes to each /dev/pmsg[ID] are isolated each other. After reboot, the
> contents are available in /sys/fs/pstore/pmsg-[backend]-[ID].
>
> Signed-off-by: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
> Signed-off-by: Nobuhiro Iwamatsu <nobuhiro.iwamatsu.kw@hitachi.com>
> Cc: Mark Salyzyn <salyzyn@android.com>
> Cc: Seiji Aguchi <seiji.aguchi.tr@hitachi.com>
> ---
> fs/pstore/pmsg.c | 20 ++++++++++++++++++--
> include/linux/pstore.h | 1 +
> 2 files changed, 19 insertions(+), 2 deletions(-)
>
> diff --git a/fs/pstore/pmsg.c b/fs/pstore/pmsg.c
> index 7de20cd..2e281ed 100644
> --- a/fs/pstore/pmsg.c
> +++ b/fs/pstore/pmsg.c
> @@ -52,8 +52,8 @@ static ssize_t write_pmsg(struct file *file, const char __user *buf,
> vfree(buffer);
> return -EFAULT;
> }
> - psinfo->write_buf(PSTORE_TYPE_PMSG, 0, &id, 0, buffer, 0, c,
> - psinfo);
> + psinfo->write_buf(PSTORE_TYPE_PMSG, 0, &id,
> + iminor(file->f_inode), buffer, 0, c, psinfo);
>
> i += c;
> }
> @@ -85,6 +85,7 @@ static char *pmsg_devnode(struct device *dev, umode_t *mode)
> void pstore_register_pmsg(void)
> {
> struct device *pmsg_device;
> + int i = 0;
>
> pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
> if (pmsg_major < 0) {
> @@ -105,9 +106,24 @@ void pstore_register_pmsg(void)
> pr_err("failed to create device\n");
> goto err_device;
> }
> +
> + /* allocate additional /dev/pmsg[ID] */
> + for (i = 1; i < psinfo->num_pmsg; i++) {
> + struct device *pmsg_device;
> +
> + pmsg_device = device_create(pmsg_class, NULL,
> + MKDEV(pmsg_major, i), NULL, "%s%d",
> + PMSG_NAME, i);
> + if (IS_ERR(pmsg_device)) {
> + pr_err("failed to create device\n");
> + goto err_device;
> + }
> + }

This should just be merged into the first device_create call (i.e.
drop the first one, keep your loop, but have "i" start at 0). There's
no reason that I can see to do it separately.

> return;
>
> err_device:
> + for (i--; i >= 0; i--)
> + device_destroy(pmsg_class, MKDEV(pmsg_major, i));

Was the device_destroy() for /dev/pmsg0 missing before? (i.e. does
class_destroy() or unregister_chrdev() already clean up the devices?)

> class_destroy(pmsg_class);
> err_class:
> unregister_chrdev(pmsg_major, PMSG_NAME);
> diff --git a/include/linux/pstore.h b/include/linux/pstore.h
> index 831479f..b0c24cc 100644
> --- a/include/linux/pstore.h
> +++ b/include/linux/pstore.h
> @@ -54,6 +54,7 @@ struct pstore_info {
> size_t bufsize;
> struct mutex read_mutex; /* serialize open/read/close */
> int flags;
> + unsigned int num_pmsg;
> int (*open)(struct pstore_info *psi);
> int (*close)(struct pstore_info *psi);
> ssize_t (*read)(u64 *id, enum pstore_type_id *type,
> --
> 2.8.1
>
>

-Kees


--
Kees Cook
Nexus Security

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