pstore updates for v5.11-rc1

- Clean up unused but exposed API (Christoph Hellwig)
 - Provide KCONFIG for default size of kmsg buffer (Vasile-Laurentiu Stanimir)
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Merge tag 'pstore-v5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux

Pull pstore updates from Kees Cook:

 - Clean up unused but exposed API (Christoph Hellwig)

 - Provide KCONFIG for default size of kmsg buffer (Vasile-Laurentiu
   Stanimir)

* tag 'pstore-v5.11-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/kees/linux:
  pstore: Move kmsg_bytes default into Kconfig
  pstore/blk: remove {un,}register_pstore_blk
  pstore/blk: update the command line example
  pstore/zone: cap the maximum device size

Documentation/admin-guide/pstore-blk.rst

@@ -35,7 +35,7 @@ module parameters have priority over Kconfig.
 
 Here is an example for module parameters::
 
-        pstore_blk.blkdev=179:7 pstore_blk.kmsg_size=64
+        pstore_blk.blkdev=/dev/mmcblk0p7 pstore_blk.kmsg_size=64 best_effort=y
 
 The detail of each configurations may be of interest to you.
 
@@ -151,10 +151,7 @@ otherwise KMSG_DUMP_MAX.
 Configurations for driver
 -------------------------
 
-Only a block device driver cares about these configurations. A block device
+A device driver uses ``register_pstore_device`` with
-driver uses ``register_pstore_blk`` to register to pstore/blk.
-
-A non-block device driver uses ``register_pstore_device`` with
 ``struct pstore_device_info`` to register to pstore/blk.
 
 .. kernel-doc:: fs/pstore/blk.c

fs/pstore/Kconfig

@@ -14,6 +14,14 @@ config PSTORE
 	   If you don't have a platform persistent store driver,
 	   say N.
 
+config PSTORE_DEFAULT_KMSG_BYTES
+	int "Default kernel log storage space" if EXPERT
+	depends on PSTORE
+	default "10240"
+	help
+	  Defines default size of pstore kernel log storage.
+	  Can be enlarged if needed, not recommended to shrink it.
+
 config PSTORE_DEFLATE_COMPRESS
 	tristate "DEFLATE (ZLIB) compression"
 	default y

fs/pstore/blk.c

@@ -90,7 +90,6 @@ MODULE_PARM_DESC(blkdev, "block device for pstore storage");
 static DEFINE_MUTEX(pstore_blk_lock);
 static struct block_device *psblk_bdev;
 static struct pstore_zone_info *pstore_zone_info;
-static pstore_blk_panic_write_op blkdev_panic_write;
 
 struct bdev_info {
 	dev_t devt;
@@ -341,24 +340,11 @@ static ssize_t psblk_generic_blk_write(const char *buf, size_t bytes,
 	return ret;
 }
 
-static ssize_t psblk_blk_panic_write(const char *buf, size_t size,
+/*
-		loff_t off)
+ * This takes its configuration only from the module parameters now.
-{
+ * See psblk_get_bdev() and blkdev.
-	int ret;
+ */
-
+static int __register_pstore_blk(void)
-	if (!blkdev_panic_write)
-		return -EOPNOTSUPP;
-
-	/* size and off must align to SECTOR_SIZE for block device */
-	ret = blkdev_panic_write(buf, off >> SECTOR_SHIFT,
-			size >> SECTOR_SHIFT);
-	/* try next zone */
-	if (ret == -ENOMSG)
-		return ret;
-	return ret ? -EIO : size;
-}
-
-static int __register_pstore_blk(struct pstore_blk_info *info)
 {
 	char bdev_name[BDEVNAME_SIZE];
 	struct block_device *bdev;
@@ -378,68 +364,34 @@ static int __register_pstore_blk(struct pstore_blk_info *info)
 	}
 
 	/* only allow driver matching the @blkdev */
-	if (!binfo.devt || (!best_effort &&
+	if (!binfo.devt) {
-			    MAJOR(binfo.devt) != info->major)) {
+		pr_debug("no major\n");
-		pr_debug("invalid major %u (expect %u)\n",
-				info->major, MAJOR(binfo.devt));
 		ret = -ENODEV;
 		goto err_put_bdev;
 	}
 
 	/* psblk_bdev must be assigned before register to pstore/blk */
 	psblk_bdev = bdev;
-	blkdev_panic_write = info->panic_write;
-
-	/* Copy back block device details. */
-	info->devt = binfo.devt;
-	info->nr_sects = binfo.nr_sects;
-	info->start_sect = binfo.start_sect;
 
 	memset(&dev, 0, sizeof(dev));
-	dev.total_size = info->nr_sects << SECTOR_SHIFT;
+	dev.total_size = binfo.nr_sects << SECTOR_SHIFT;
-	dev.flags = info->flags;
 	dev.read = psblk_generic_blk_read;
 	dev.write = psblk_generic_blk_write;
-	dev.erase = NULL;
-	dev.panic_write = info->panic_write ? psblk_blk_panic_write : NULL;
 
 	ret = __register_pstore_device(&dev);
 	if (ret)
 		goto err_put_bdev;
 
 	bdevname(bdev, bdev_name);
-	pr_info("attached %s%s\n", bdev_name,
+	pr_info("attached %s (no dedicated panic_write!)\n", bdev_name);
-		info->panic_write ? "" : " (no dedicated panic_write!)");
 	return 0;
 
 err_put_bdev:
 	psblk_bdev = NULL;
-	blkdev_panic_write = NULL;
 	psblk_put_bdev(bdev, holder);
 	return ret;
 }
 
-/**
- * register_pstore_blk() - register block device to pstore/blk
- *
- * @info: details on the desired block device interface
- *
- * Return:
- * * 0		- OK
- * * Others	- something error.
- */
-int register_pstore_blk(struct pstore_blk_info *info)
-{
-	int ret;
-
-	mutex_lock(&pstore_blk_lock);
-	ret = __register_pstore_blk(info);
-	mutex_unlock(&pstore_blk_lock);
-
-	return ret;
-}
-EXPORT_SYMBOL_GPL(register_pstore_blk);
-
 static void __unregister_pstore_blk(unsigned int major)
 {
 	struct pstore_device_info dev = { .read = psblk_generic_blk_read };
@@ -449,24 +401,10 @@ static void __unregister_pstore_blk(unsigned int major)
 	if (psblk_bdev && MAJOR(psblk_bdev->bd_dev) == major) {
 		__unregister_pstore_device(&dev);
 		psblk_put_bdev(psblk_bdev, holder);
-		blkdev_panic_write = NULL;
 		psblk_bdev = NULL;
 	}
 }
 
-/**
- * unregister_pstore_blk() - unregister block device from pstore/blk
- *
- * @major: the major device number of device
- */
-void unregister_pstore_blk(unsigned int major)
-{
-	mutex_lock(&pstore_blk_lock);
-	__unregister_pstore_blk(major);
-	mutex_unlock(&pstore_blk_lock);
-}
-EXPORT_SYMBOL_GPL(unregister_pstore_blk);
-
 /* get information of pstore/blk */
 int pstore_blk_get_config(struct pstore_blk_config *info)
 {
@@ -483,12 +421,11 @@ EXPORT_SYMBOL_GPL(pstore_blk_get_config);
 
 static int __init pstore_blk_init(void)
 {
-	struct pstore_blk_info info = { };
 	int ret = 0;
 
 	mutex_lock(&pstore_blk_lock);
 	if (!pstore_zone_info && best_effort && blkdev[0])
-		ret = __register_pstore_blk(&info);
+		ret = __register_pstore_blk();
 	mutex_unlock(&pstore_blk_lock);
 
 	return ret;

fs/pstore/inode.c

@@ -266,7 +266,7 @@ static void parse_options(char *options)
  */
 static int pstore_show_options(struct seq_file *m, struct dentry *root)
 {
-	if (kmsg_bytes != PSTORE_DEFAULT_KMSG_BYTES)
+	if (kmsg_bytes != CONFIG_PSTORE_DEFAULT_KMSG_BYTES)
 		seq_printf(m, ",kmsg_bytes=%lu", kmsg_bytes);
 	return 0;
 }

fs/pstore/internal.h

@@ -6,7 +6,6 @@
 #include <linux/time.h>
 #include <linux/pstore.h>
 
-#define PSTORE_DEFAULT_KMSG_BYTES 10240
 extern unsigned long kmsg_bytes;
 
 #ifdef CONFIG_PSTORE_FTRACE

fs/pstore/platform.c

@@ -101,7 +101,7 @@ static char *big_oops_buf;
 static size_t big_oops_buf_sz;
 
 /* How much of the console log to snapshot */
-unsigned long kmsg_bytes = PSTORE_DEFAULT_KMSG_BYTES;
+unsigned long kmsg_bytes = CONFIG_PSTORE_DEFAULT_KMSG_BYTES;
 
 void pstore_set_kmsg_bytes(int bytes)
 {

fs/pstore/zone.c

@@ -1299,6 +1299,10 @@ int register_pstore_zone(struct pstore_zone_info *info)
 		pr_warn("total_size must be >= 4096\n");
 		return -EINVAL;
 	}
+	if (info->total_size > SZ_128M) {
+		pr_warn("capping size to 128MiB\n");
+		info->total_size = SZ_128M;
+	}
 
 	if (!info->kmsg_size && !info->pmsg_size && !info->console_size &&
 	    !info->ftrace_size) {

include/linux/pstore_blk.h

@@ -7,48 +7,6 @@
 #include <linux/pstore.h>
 #include <linux/pstore_zone.h>
 
-/**
- * typedef pstore_blk_panic_write_op - panic write operation to block device
- *
- * @buf: the data to write
- * @start_sect: start sector to block device
- * @sects: sectors count on buf
- *
- * Return: On success, zero should be returned. Others excluding -ENOMSG
- * mean error. -ENOMSG means to try next zone.
- *
- * Panic write to block device must be aligned to SECTOR_SIZE.
- */
-typedef int (*pstore_blk_panic_write_op)(const char *buf, sector_t start_sect,
-		sector_t sects);
-
-/**
- * struct pstore_blk_info - pstore/blk registration details
- *
- * @major:	Which major device number to support with pstore/blk
- * @flags:	The supported PSTORE_FLAGS_* from linux/pstore.h.
- * @panic_write:The write operation only used for the panic case.
- *		This can be NULL, but is recommended to avoid losing
- *		crash data if the kernel's IO path or work queues are
- *		broken during a panic.
- * @devt:	The dev_t that pstore/blk has attached to.
- * @nr_sects:	Number of sectors on @devt.
- * @start_sect:	Starting sector on @devt.
- */
-struct pstore_blk_info {
-	unsigned int major;
-	unsigned int flags;
-	pstore_blk_panic_write_op panic_write;
-
-	/* Filled in by pstore/blk after registration. */
-	dev_t devt;
-	sector_t nr_sects;
-	sector_t start_sect;
-};
-
-int  register_pstore_blk(struct pstore_blk_info *info);
-void unregister_pstore_blk(unsigned int major);
-
 /**
  * struct pstore_device_info - back-end pstore/blk driver structure.
  *