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SubjectRe: [PATCH v4 2nd 2/4] pstore: support multiple pmsg instances
On Mon, Jan 30, 2017 at 5:58 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: Anton Vorontsov <anton@enomsg.org>
> Cc: Colin Cross <ccross@android.com>
> Cc: Kees Cook <keescook@chromium.org>
> Cc: Mark Salyzyn <salyzyn@android.com>
> Cc: Seiji Aguchi <seiji.aguchi.tr@hitachi.com>
> Cc: Tony Luck <tony.luck@intel.com>
>
> V4:
> Rebase.
> V3:
> rebase.
> merged device_create().
> ---
> fs/pstore/pmsg.c | 23 ++++++++++++++++-------
> include/linux/pstore.h | 1 +
> 2 files changed, 17 insertions(+), 7 deletions(-)
>
> diff --git a/fs/pstore/pmsg.c b/fs/pstore/pmsg.c
> index 78f6176c020f..5da5cba4b387 100644
> --- a/fs/pstore/pmsg.c
> +++ b/fs/pstore/pmsg.c
> @@ -34,7 +34,8 @@ static ssize_t write_pmsg(struct file *file, const char __user *buf,
> return -EFAULT;
>
> mutex_lock(&pmsg_lock);
> - ret = psinfo->write_buf_user(PSTORE_TYPE_PMSG, 0, &id, 0, buf, 0, count,
> + ret = psinfo->write_buf_user(PSTORE_TYPE_PMSG, 0, &id,
> + iminor(file->f_inode), buf, 0, count,
> psinfo);
> mutex_unlock(&pmsg_lock);
> return ret ? ret : count;
> @@ -61,7 +62,7 @@ static char *pmsg_devnode(struct device *dev, umode_t *mode)
>
> void pstore_register_pmsg(void)
> {
> - struct device *pmsg_device;
> + int i;
>
> pmsg_major = register_chrdev(0, PMSG_NAME, &pmsg_fops);
> if (pmsg_major < 0) {
> @@ -76,15 +77,23 @@ void pstore_register_pmsg(void)
> }
> pmsg_class->devnode = pmsg_devnode;
>
> - pmsg_device = device_create(pmsg_class, NULL, MKDEV(pmsg_major, 0),
> - NULL, "%s%d", PMSG_NAME, 0);
> - if (IS_ERR(pmsg_device)) {
> - pr_err("failed to create device\n");
> - goto err_device;
> + /* allocate additional /dev/pmsg[ID] */

This isn't "additional" any more, but rather "Allocate each pmsg
device" or something.

> + for (i = 0; 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;
> + }
> }
> return;
>
> err_device:
> + for (i--; i >= 0; i--)
> + device_destroy(pmsg_class, MKDEV(pmsg_major, i));
> 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 0da29cae009b..7a5db4833b8a 100644
> --- a/include/linux/pstore.h
> +++ b/include/linux/pstore.h
> @@ -55,6 +55,7 @@ struct pstore_info {
> size_t bufsize;
> struct mutex read_mutex; /* serialize open/read/close */
> int flags;
> + unsigned int num_pmsg;

Something in this patch needs to set num_pmsg to 1 unconditionally, so
that bisectability is retained. I.e. after this patch, I should still
get a /dev/pmsg0 device. Right now, it will be skipped since num_pmsg
will always == 0.

> int (*open)(struct pstore_info *psi);
> int (*close)(struct pstore_info *psi);
> ssize_t (*read)(u64 *id, enum pstore_type_id *type,
> --
> 2.11.0
>

Thanks for the rebasing!

-Kees

--
Kees Cook
Pixel Security

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