[PATCH v6 16/18] pstore/blk: Support non-block storage devices

From: Kees Cook
Date: Sat May 09 2020 - 19:47:09 EST

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From: WeiXiong Liao <liaoweixiong@xxxxxxxxxxxxxxxxx>

Add support for non-block devices (e.g. MTD). A non-block driver calls
pstore_blk_register_device() to register iself.

In addition, pstore/zone is updated to handle non-block devices,
where an erase must be done before a write. Without this, there is no
way to remove records stored to an MTD.

Signed-off-by: WeiXiong Liao <liaoweixiong@xxxxxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/1585126506-18635-11-git-send-email-liaoweixiong@xxxxxxxxxxxxxxxxx
Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
---
Documentation/admin-guide/pstore-blk.rst | 17 ++++-
fs/pstore/blk.c | 96 +++++++++++++-----------
fs/pstore/zone.c | 8 +-
include/linux/pstore_blk.h | 37 +++++++++
include/linux/pstore_zone.h | 6 ++
5 files changed, 115 insertions(+), 49 deletions(-)

diff --git a/Documentation/admin-guide/pstore-blk.rst b/Documentation/admin-guide/pstore-blk.rst
index bef8c7436721..faf9991879aa 100644
--- a/Documentation/admin-guide/pstore-blk.rst
+++ b/Documentation/admin-guide/pstore-blk.rst
@@ -7,8 +7,8 @@ Introduction
------------

pstore block (pstore/blk) is an oops/panic logger that writes its logs to a
-block device before the system crashes. You can get these log files by
-mounting pstore filesystem like::
+block device and non-block device before the system crashes. You can get
+these log files by mounting pstore filesystem like::

mount -t pstore pstore /sys/fs/pstore

@@ -24,8 +24,8 @@ Configurations for user determine how pstore/blk works, such as pmsg_size,
kmsg_size and so on. All of them support both Kconfig and module parameters,
but module parameters have priority over Kconfig.

-Configurations for driver are all about block device, such as total_size
-of block device and read/write operations.
+Configurations for driver are all about block device and non-block device,
+such as total_size of block device and read/write operations.

Configurations for user
-----------------------
@@ -152,6 +152,15 @@ driver uses ``register_pstore_blk`` to register to pstore/blk.
.. kernel-doc:: fs/pstore/blk.c
:identifiers: register_pstore_blk

+A non-block device driver uses ``register_pstore_device`` with
+``struct psblk_device`` to register to pstore/blk.
+
+.. kernel-doc:: fs/pstore/blk.c
+ :identifiers: register_pstore_device
+
+.. kernel-doc:: include/linux/pstore_blk.h
+ :identifiers: psblk_device
+
Compression and header
----------------------

diff --git a/fs/pstore/blk.c b/fs/pstore/blk.c
index 134c5e0c67c1..3e67bd4557ea 100644
--- a/fs/pstore/blk.c
+++ b/fs/pstore/blk.c
@@ -104,55 +104,23 @@ static struct bdev_info {
_##name_; \
})

-/**
- * struct psblk_device - back-end pstore/blk driver structure.
- *
- * @total_size: The total size in bytes pstore/blk can use. It must be greater
- * than 4096 and be multiple of 4096.
- * @flags: Refer to macro starting with PSTORE_FLAGS defined in
- * linux/pstore.h. It means what front-ends this device support.
- * Zero means all backends for compatible.
- * @read: The general read operation. Both of the function parameters
- * @size and @offset are relative value to bock device (not the
- * whole disk).
- * On success, the number of bytes should be returned, others
- * means error.
- * @write: The same as @read, but the following error number:
- * -EBUSY means try to write again later.
- * -ENOMSG means to try next zone.
- * @panic_write:The write operation only used for panic case. It's optional
- * if you do not care panic log. The parameters are relative
- * value to storage.
- * On success, the number of bytes should be returned, others
- * excluding -ENOMSG mean error. -ENOMSG means to try next zone.
- */
-struct psblk_device {
- unsigned long total_size;
- unsigned int flags;
- psz_read_op read;
- psz_write_op write;
- psz_write_op panic_write;
-};
-
-static int psblk_register_do(struct psblk_device *dev)
+static int __register_pstore_device(struct psblk_device *dev)
{
int ret;

- if (!dev || !dev->total_size || !dev->read || !dev->write)
+ if (WARN_ON(!mutex_is_locked(&pstore_blk_lock)))
return -EINVAL;

- mutex_lock(&pstore_blk_lock);
+ if (!dev || !dev->total_size || !dev->read || !dev->write)
+ return -EINVAL;

/* someone already registered before */
- if (pstore_zone_info) {
- mutex_unlock(&pstore_blk_lock);
+ if (pstore_zone_info)
return -EBUSY;
- }
+
pstore_zone_info = kzalloc(sizeof(struct pstore_zone_info), GFP_KERNEL);
- if (!pstore_zone_info) {
- mutex_unlock(&pstore_blk_lock);
+ if (!pstore_zone_info)
return -ENOMEM;
- }

/* zero means not limit on which backends to attempt to store. */
if (!dev->flags)
@@ -178,6 +146,7 @@ static int psblk_register_do(struct psblk_device *dev)
pstore_zone_info->max_reason = max_reason;
pstore_zone_info->read = dev->read;
pstore_zone_info->write = dev->write;
+ pstore_zone_info->erase = dev->erase;
pstore_zone_info->panic_write = dev->panic_write;
pstore_zone_info->name = KBUILD_MODNAME;
pstore_zone_info->owner = THIS_MODULE;
@@ -187,20 +156,51 @@ static int psblk_register_do(struct psblk_device *dev)
kfree(pstore_zone_info);
pstore_zone_info = NULL;
}
+ return ret;
+}
+/**
+ * register_pstore_device() - register non-block device to pstore/blk
+ *
+ * @dev: non-block device information
+ *
+ * Return:
+ * * 0 - OK
+ * * Others - something error.
+ */
+int register_pstore_device(struct psblk_device *dev)
+{
+ int ret;
+
+ mutex_lock(&pstore_blk_lock);
+ ret = __register_pstore_device(dev);
mutex_unlock(&pstore_blk_lock);
+
return ret;
}
+EXPORT_SYMBOL_GPL(register_pstore_device);

-static void psblk_unregister_do(struct psblk_device *dev)
+void __unregister_pstore_device(struct psblk_device *dev)
{
- mutex_lock(&pstore_blk_lock);
+ WARN_ON(!mutex_is_locked(&pstore_blk_lock));
if (pstore_zone_info && pstore_zone_info->read == dev->read) {
unregister_pstore_zone(pstore_zone_info);
kfree(pstore_zone_info);
pstore_zone_info = NULL;
}
+}
+
+/**
+ * unregister_pstore_device() - unregister non-block device from pstore/blk
+ *
+ * @dev: non-block device information
+ */
+void unregister_pstore_device(struct psblk_device *dev)
+{
+ mutex_lock(&pstore_blk_lock);
+ __unregister_pstore_device(dev);
mutex_unlock(&pstore_blk_lock);
}
+EXPORT_SYMBOL_GPL(unregister_pstore_device);

/**
* psblk_get_bdev() - open block device
@@ -407,11 +407,12 @@ static int __register_pstore_blk(unsigned int major, unsigned int flags,

dev.total_size = psblk_bdev_size(bdev);
dev.flags = flags;
- dev.panic_write = panic_write ? psblk_blk_panic_write : NULL;
dev.read = psblk_generic_blk_read;
dev.write = psblk_generic_blk_write;
+ dev.erase = NULL;
+ dev.panic_write = panic_write ? psblk_blk_panic_write : NULL;

- ret = psblk_register_do(&dev);
+ ret = __register_pstore_device(&dev);
if (ret)
goto err_put_bdev;

@@ -462,7 +463,7 @@ void __unregister_pstore_blk(unsigned int major)

WARN_ON(!mutex_is_locked(&pstore_blk_lock));
if (psblk_bdev && MAJOR(psblk_bdev->bd_dev) == major) {
- psblk_unregister_do(&dev);
+ __unregister_pstore_device(&dev);
psblk_put_bdev(psblk_bdev, holder);
blkdev_panic_write = NULL;
psblk_bdev = NULL;
@@ -536,6 +537,13 @@ static void __exit pstore_blk_exit(void)
mutex_lock(&pstore_blk_lock);
if (psblk_bdev)
__unregister_pstore_blk(MAJOR(psblk_bdev->bd_dev));
+ else {
+ struct psblk_device dev = { };
+
+ if (pstore_zone_info)
+ dev.read = pstore_zone_info->read;
+ __unregister_pstore_device(&dev);
+ }
mutex_unlock(&pstore_blk_lock);
}
module_exit(pstore_blk_exit);
diff --git a/fs/pstore/zone.c b/fs/pstore/zone.c
index 17c9a0439d6e..b04257f8420f 100644
--- a/fs/pstore/zone.c
+++ b/fs/pstore/zone.c
@@ -661,15 +661,21 @@ static inline int psz_kmsg_erase(struct psz_context *cxt,
struct psz_buffer *buffer = zone->buffer;
struct psz_kmsg_header *hdr =
(struct psz_kmsg_header *)buffer->data;
+ size_t size;

if (unlikely(!psz_ok(zone)))
return 0;
+
/* this zone is already updated, no need to erase */
if (record->count != hdr->counter)
return 0;

+ size = buffer_datalen(zone) + sizeof(*zone->buffer);
atomic_set(&zone->buffer->datalen, 0);
- return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
+ if (cxt->pstore_zone_info->erase)
+ return cxt->pstore_zone_info->erase(size, zone->off);
+ else
+ return psz_zone_write(zone, FLUSH_META, NULL, 0, 0);
}

static inline int psz_record_erase(struct psz_context *cxt,
diff --git a/include/linux/pstore_blk.h b/include/linux/pstore_blk.h
index 8aae922caa27..de87373da3ff 100644
--- a/include/linux/pstore_blk.h
+++ b/include/linux/pstore_blk.h
@@ -7,6 +7,41 @@
#include <linux/pstore.h>
#include <linux/pstore_zone.h>

+/**
+ * struct psblk_device - back-end pstore/blk driver structure.
+ *
+ * @total_size: The total size in bytes pstore/blk can use. It must be greater
+ * than 4096 and be multiple of 4096.
+ * @flags: Refer to macro starting with PSTORE_FLAGS defined in
+ * linux/pstore.h. It means what front-ends this device support.
+ * Zero means all backends for compatible.
+ * @read: The general read operation. Both of the function parameters
+ * @size and @offset are relative value to bock device (not the
+ * whole disk).
+ * On success, the number of bytes should be returned, others
+ * means error.
+ * @write: The same as @read, but the following error number:
+ * -EBUSY means try to write again later.
+ * -ENOMSG means to try next zone.
+ * @erase: The general erase operation for device with special removing
+ * job. Both of the function parameters @size and @offset are
+ * relative value to storage.
+ * Return 0 on success and others on failure.
+ * @panic_write:The write operation only used for panic case. It's optional
+ * if you do not care panic log. The parameters are relative
+ * value to storage.
+ * On success, the number of bytes should be returned, others
+ * excluding -ENOMSG mean error. -ENOMSG means to try next zone.
+ */
+struct psblk_device {
+ unsigned long total_size;
+ unsigned int flags;
+ psz_read_op read;
+ psz_write_op write;
+ psz_erase_op erase;
+ psz_write_op panic_write;
+};
+
/**
* typedef psblk_panic_write_op - panic write operation to block device
*
@@ -22,6 +57,8 @@
typedef int (*psblk_panic_write_op)(const char *buf, sector_t start_sect,
sector_t sects);

+int register_pstore_device(struct psblk_device *dev);
+void psblk_unregister_device(struct psblk_device *dev);
int register_pstore_blk(unsigned int major, unsigned int flags,
psblk_panic_write_op panic_write);
void unregister_pstore_blk(unsigned int major);
diff --git a/include/linux/pstore_zone.h b/include/linux/pstore_zone.h
index ddb3dfea4ea6..2c031a25ee5f 100644
--- a/include/linux/pstore_zone.h
+++ b/include/linux/pstore_zone.h
@@ -7,6 +7,7 @@

typedef ssize_t (*psz_read_op)(char *, size_t, loff_t);
typedef ssize_t (*psz_write_op)(const char *, size_t, loff_t);
+typedef ssize_t (*psz_erase_op)(size_t, loff_t);
/**
* struct pstore_zone_info - pstore/zone back-end driver structure
*
@@ -27,6 +28,10 @@ typedef ssize_t (*psz_write_op)(const char *, size_t, loff_t);
* @write: The same as @read, but the following error number:
* -EBUSY means try to write again later.
* -ENOMSG means to try next zone.
+ * @erase: The general erase operation for device with special removing
+ * job. Both of the function parameters @size and @offset are
+ * relative value to storage.
+ * Return 0 on success and others on failure.
* @panic_write:The write operation only used for panic case. It's optional
* if you do not care panic log. The parameters are relative
* value to storage.
@@ -45,6 +50,7 @@ struct pstore_zone_info {
unsigned long ftrace_size;
psz_read_op read;
psz_write_op write;
+ psz_erase_op erase;
psz_write_op panic_write;
};

--
2.20.1

Next message: Al Viro: "[PATCH 06/20] n_hdlc_tty_read(): remove pointless access_ok()"
Previous message: Kees Cook: "[PATCH v6 17/18] mtd: Support kmsg dumper based on pstore/blk"
In reply to: Kees Cook: "[PATCH v6 17/18] mtd: Support kmsg dumper based on pstore/blk"
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