pstore/blk: Include zone in pstore_device_info

Information was redundant between struct pstore_zone_info and struct
pstore_device_info. Use struct pstore_zone_info, with member name "zone".

Additionally untangle the logic for the "best effort" block device
instance.

Signed-off-by: Kees Cook <keescook@chromium.org>
Fixed-by: Pu Lehui <pulehui@huawei.com>
Link: https://lore.kernel.org/lkml/20210617005424.182305-1-pulehui@huawei.com

Author: kees

drivers/mtd/mtdpstore.c

@@ -423,13 +423,13 @@ static void mtdpstore_notify_add(struct mtd_info *mtd)
 	longcnt = BITS_TO_LONGS(div_u64(mtd->size, mtd->erasesize));
 	cxt->badmap = kcalloc(longcnt, sizeof(long), GFP_KERNEL);
 
-	cxt->dev.total_size = mtd->size;
 	/* just support dmesg right now */
 	cxt->dev.flags = PSTORE_FLAGS_DMESG;
-	cxt->dev.read = mtdpstore_read;
-	cxt->dev.write = mtdpstore_write;
-	cxt->dev.erase = mtdpstore_erase;
-	cxt->dev.panic_write = mtdpstore_panic_write;
+	cxt->dev.zone.read = mtdpstore_read;
+	cxt->dev.zone.write = mtdpstore_write;
+	cxt->dev.zone.erase = mtdpstore_erase;
+	cxt->dev.zone.panic_write = mtdpstore_panic_write;
+	cxt->dev.zone.total_size = mtd->size;
 
 	ret = register_pstore_device(&cxt->dev);
 	if (ret) {

fs/pstore/blk.c

@@ -70,7 +70,7 @@ MODULE_PARM_DESC(blkdev, "block device for pstore storage");
  */
 static DEFINE_MUTEX(pstore_blk_lock);
 static struct file *psblk_file;
-static struct pstore_zone_info *pstore_zone_info;
+static struct pstore_device_info *pstore_device_info;
 
 #define check_size(name, alignsize) ({				\
 	long _##name_ = (name);					\
@@ -91,7 +91,7 @@ static struct pstore_zone_info *pstore_zone_info;
 		_##name_ = 0;					\
 	/* Synchronize module parameters with resuls. */	\
 	name = _##name_ / 1024;					\
-	pstore_zone_info->name = _##name_;			\
+	dev->zone.name = _##name_;				\
 }
 
 static int __register_pstore_device(struct pstore_device_info *dev)
@@ -104,50 +104,42 @@ static int __register_pstore_device(struct pstore_device_info *dev)
 		pr_err("NULL device info\n");
 		return -EINVAL;
 	}
-	if (!dev->total_size) {
+	if (!dev->zone.total_size) {
 		pr_err("zero sized device\n");
 		return -EINVAL;
 	}
-	if (!dev->read) {
+	if (!dev->zone.read) {
 		pr_err("no read handler for device\n");
 		return -EINVAL;
 	}
-	if (!dev->write) {
+	if (!dev->zone.write) {
 		pr_err("no write handler for device\n");
 		return -EINVAL;
 	}
 
 	/* someone already registered before */
-	if (pstore_zone_info)
+	if (pstore_device_info)
 		return -EBUSY;
 
-	pstore_zone_info = kzalloc(sizeof(struct pstore_zone_info), GFP_KERNEL);
-	if (!pstore_zone_info)
-		return -ENOMEM;
-
 	/* zero means not limit on which backends to attempt to store. */
 	if (!dev->flags)
 		dev->flags = UINT_MAX;
 
+	/* Copy in module parameters. */
 	verify_size(kmsg_size, 4096, dev->flags & PSTORE_FLAGS_DMESG);
 	verify_size(pmsg_size, 4096, dev->flags & PSTORE_FLAGS_PMSG);
 	verify_size(console_size, 4096, dev->flags & PSTORE_FLAGS_CONSOLE);
 	verify_size(ftrace_size, 4096, dev->flags & PSTORE_FLAGS_FTRACE);
+	dev->zone.max_reason = max_reason;
+
+	/* Initialize required zone ownership details. */
+	dev->zone.name = KBUILD_MODNAME;
+	dev->zone.owner = THIS_MODULE;
+
+	ret = register_pstore_zone(&dev->zone);
+	if (ret == 0)
+		pstore_device_info = dev;
 
-	pstore_zone_info->total_size = dev->total_size;
-	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;
-
-	ret = register_pstore_zone(pstore_zone_info);
-	if (ret) {
-		kfree(pstore_zone_info);
-		pstore_zone_info = NULL;
-	}
 	return ret;
 }
 /**
@@ -174,10 +166,9 @@ EXPORT_SYMBOL_GPL(register_pstore_device);
 static void __unregister_pstore_device(struct pstore_device_info *dev)
 {
 	lockdep_assert_held(&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;
+	if (pstore_device_info && pstore_device_info == dev) {
+		unregister_pstore_zone(&dev->zone);
+		pstore_device_info = NULL;
 	}
 }
 
@@ -211,12 +202,9 @@ static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
 /*
  * This takes its configuration only from the module parameters now.
  */
-static int __register_pstore_blk(const char *devpath)
+static int __register_pstore_blk(struct pstore_device_info *dev,
+				 const char *devpath)
 {
-	struct pstore_device_info dev = {
-		.read = psblk_generic_blk_read,
-		.write = psblk_generic_blk_write,
-	};
 	struct inode *inode;
 	int ret = -ENODEV;
 
@@ -236,9 +224,9 @@ static int __register_pstore_blk(const char *devpath)
 	}
 
 	inode = I_BDEV(psblk_file->f_mapping->host)->bd_inode;
-	dev.total_size = i_size_read(inode);
+	dev->zone.total_size = i_size_read(inode);
 
-	ret = __register_pstore_device(&dev);
+	ret = __register_pstore_device(dev);
 	if (ret)
 		goto err_fput;
 
@@ -252,18 +240,6 @@ static int __register_pstore_blk(const char *devpath)
 	return ret;
 }
 
-static void __unregister_pstore_blk(struct file *device)
-{
-	struct pstore_device_info dev = { .read = psblk_generic_blk_read };
-
-	lockdep_assert_held(&pstore_blk_lock);
-	if (psblk_file && psblk_file == device) {
-		__unregister_pstore_device(&dev);
-		fput(psblk_file);
-		psblk_file = NULL;
-	}
-}
-
 /* get information of pstore/blk */
 int pstore_blk_get_config(struct pstore_blk_config *info)
 {
@@ -308,18 +284,63 @@ static inline const char *early_boot_devpath(const char *initial_devname)
 }
 #endif
 
+static int __init __best_effort_init(void)
+{
+	struct pstore_device_info *best_effort_dev;
+	int ret;
+
+	/* No best-effort mode requested. */
+	if (!best_effort)
+		return 0;
+
+	/* Reject an empty blkdev. */
+	if (!blkdev[0]) {
+		pr_err("blkdev empty with best_effort=Y\n");
+		return -EINVAL;
+	}
+
+	best_effort_dev = kzalloc(sizeof(*best_effort_dev), GFP_KERNEL);
+	if (!best_effort_dev)
+		return -ENOMEM;
+
+	best_effort_dev->zone.read = psblk_generic_blk_read;
+	best_effort_dev->zone.write = psblk_generic_blk_write;
+
+	ret = __register_pstore_blk(best_effort_dev,
+				    early_boot_devpath(blkdev));
+	if (ret)
+		kfree(best_effort_dev);
+	else
+		pr_info("attached %s (%zu) (no dedicated panic_write!)\n",
+			blkdev, best_effort_dev->zone.total_size);
+
+	return ret;
+}
+
+static void __exit __best_effort_exit(void)
+{
+	/*
+	 * Currently, the only user of psblk_file is best_effort, so
+	 * we can assume that pstore_device_info is associated with it.
+	 * Once there are "real" blk devices, there will need to be a
+	 * dedicated pstore_blk_info, etc.
+	 */
+	if (psblk_file) {
+		struct pstore_device_info *dev = pstore_device_info;
+
+		__unregister_pstore_device(dev);
+		kfree(dev);
+		fput(psblk_file);
+		psblk_file = NULL;
+	}
+}
+
 static int __init pstore_blk_init(void)
 {
-	int ret = 0;
+	int ret;
 
 	mutex_lock(&pstore_blk_lock);
-	if (!pstore_zone_info && best_effort && blkdev[0]) {
-		ret = __register_pstore_blk(early_boot_devpath(blkdev));
-		if (ret == 0 && pstore_zone_info)
-			pr_info("attached %s:%s (%zu) (no dedicated panic_write!)\n",
-				pstore_zone_info->name, blkdev,
-				pstore_zone_info->total_size);
-	}
+	ret = __best_effort_init();
 	mutex_unlock(&pstore_blk_lock);
 
 	return ret;
@@ -329,15 +350,9 @@ late_initcall(pstore_blk_init);
 static void __exit pstore_blk_exit(void)
 {
 	mutex_lock(&pstore_blk_lock);
-	if (psblk_file)
-		__unregister_pstore_blk(psblk_file);
-	else {
-		struct pstore_device_info dev = { };
-
-		if (pstore_zone_info)
-			dev.read = pstore_zone_info->read;
-		__unregister_pstore_device(&dev);
-	}
+	__best_effort_exit();
+	/* If we've been asked to unload, unregister any remaining device. */
+	__unregister_pstore_device(pstore_device_info);
 	mutex_unlock(&pstore_blk_lock);
 }
 module_exit(pstore_blk_exit);

include/linux/pstore_blk.h

@@ -10,36 +10,15 @@
 /**
  * struct pstore_device_info - 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.
+ * @zone:	The struct pstore_zone_info details.
+ *
  */
 struct pstore_device_info {
-	unsigned long total_size;
 	unsigned int flags;
-	pstore_zone_read_op read;
-	pstore_zone_write_op write;
-	pstore_zone_erase_op erase;
-	pstore_zone_write_op panic_write;
+	struct pstore_zone_info zone;
 };
 
 int  register_pstore_device(struct pstore_device_info *dev);