[PATCH 3/3] pstore: add 'rmmod ramoops' support

[Geliang Tang]

ramoops doesn't support unregistering yet, it was marked as TODO.
This patch adds some code to fix it:
 1) Add functions to unregister kmsg/console/ftrace/pmsg.
 2) Add a function to free compression buffer.
 3) Remove try_module_get() to allow this module can be unloaded.
 4) Unmap the memory and free it.
 5) Set console flags, make sure it can be registered again after
be unregistered.

Signed-off-by: Geliang Tang <geliangtang@xxxxxxx>
---
 fs/pstore/ftrace.c     | 15 ++++++++++++++-
 fs/pstore/internal.h   |  4 ++++
 fs/pstore/platform.c   | 40 ++++++++++++++++++++++++++++++++--------
 fs/pstore/pmsg.c       |  7 +++++++
 fs/pstore/ram.c        | 19 ++++++++-----------
 include/linux/pstore.h |  5 +++++
 6 files changed, 70 insertions(+), 20 deletions(-)

diff --git a/fs/pstore/ftrace.c b/fs/pstore/ftrace.c
index 76a4eeb..554c1ce 100644
--- a/fs/pstore/ftrace.c
+++ b/fs/pstore/ftrace.c
@@ -104,9 +104,10 @@ static const struct file_operations pstore_knob_fops = {
 	.write	= pstore_ftrace_knob_write,
 };
 
+static struct dentry *dir;
+
 void pstore_register_ftrace(void)
 {
-	struct dentry *dir;
 	struct dentry *file;
 
 	if (!psinfo->write_buf)
@@ -129,3 +130,15 @@ void pstore_register_ftrace(void)
 err_file:
 	debugfs_remove(dir);
 }
+
+void pstore_unregister_ftrace(void)
+{
+	mutex_lock(&pstore_ftrace_lock);
+	if (pstore_ftrace_enabled) {
+		unregister_ftrace_function(&pstore_ftrace_ops);
+		pstore_ftrace_enabled = 0;
+	}
+	mutex_unlock(&pstore_ftrace_lock);
+
+	debugfs_remove_recursive(dir);
+}
diff --git a/fs/pstore/internal.h b/fs/pstore/internal.h
index c36ba2c..96253c4 100644
--- a/fs/pstore/internal.h
+++ b/fs/pstore/internal.h
@@ -41,14 +41,18 @@ pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
 
 #ifdef CONFIG_PSTORE_FTRACE
 extern void pstore_register_ftrace(void);
+extern void pstore_unregister_ftrace(void);
 #else
 static inline void pstore_register_ftrace(void) {}
+static inline void pstore_unregister_ftrace(void) {}
 #endif
 
 #ifdef CONFIG_PSTORE_PMSG
 extern void pstore_register_pmsg(void);
+extern void pstore_unregister_pmsg(void);
 #else
 static inline void pstore_register_pmsg(void) {}
+static inline void pstore_unregister_pmsg(void) {}
 #endif
 
 extern struct pstore_info *psinfo;
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index 1b11249..c474dc2 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -237,6 +237,12 @@ static void allocate_buf_for_compression(void)
 
 }
 
+static void free_buf_for_compression(void)
+{
+	kfree(stream.workspace);
+	kfree(big_oops_buf);
+}
+
 /*
  * Called when compression fails, since the printk buffer
  * would be fetched for compression calling it again when
@@ -358,6 +364,11 @@ static void pstore_register_kmsg(void)
 	kmsg_dump_register(&pstore_dumper);
 }
 
+static void pstore_unregister_kmsg(void)
+{
+	kmsg_dump_unregister(&pstore_dumper);
+}
+
 #ifdef CONFIG_PSTORE_CONSOLE
 static void pstore_console_write(struct console *con, const char *s, unsigned c)
 {
@@ -387,16 +398,22 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 static struct console pstore_console = {
 	.name	= "pstore",
 	.write	= pstore_console_write,
-	.flags	= CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME,
 	.index	= -1,
 };
 
 static void pstore_register_console(void)
 {
+	pstore_console.flags = CON_PRINTBUFFER | CON_ENABLED | CON_ANYTIME;
 	register_console(&pstore_console);
 }
+
+static void pstore_unregister_console(void)
+{
+	unregister_console(&pstore_console);
+}
 #else
 static void pstore_register_console(void) {}
+static void pstore_unregister_console(void) {}
 #endif
 
 static int pstore_write_compat(enum pstore_type_id type,
@@ -420,8 +437,6 @@ static int pstore_write_compat(enum pstore_type_id type,
  */
 int pstore_register(struct pstore_info *psi)
 {
-	struct module *owner = psi->owner;
-
 	if (backend && strcmp(backend, psi->name))
 		return -EPERM;
 
@@ -437,11 +452,6 @@ int pstore_register(struct pstore_info *psi)
 	mutex_init(&psinfo->read_mutex);
 	spin_unlock(&pstore_lock);
 
-	if (owner && !try_module_get(owner)) {
-		psinfo = NULL;
-		return -EINVAL;
-	}
-
 	allocate_buf_for_compression();
 
 	if (pstore_is_mounted())
@@ -473,6 +483,20 @@ int pstore_register(struct pstore_info *psi)
 }
 EXPORT_SYMBOL_GPL(pstore_register);
 
+void pstore_unregister(void)
+{
+	pstore_unregister_pmsg();
+	pstore_unregister_ftrace();
+	pstore_unregister_console();
+	pstore_unregister_kmsg();
+
+	free_buf_for_compression();
+
+	psinfo = NULL;
+	backend = NULL;
+}
+EXPORT_SYMBOL_GPL(pstore_unregister);
+
 /*
  * Read all the records from the persistent store. Create
  * files in our filesystem.  Don't warn about -EEXIST errors
diff --git a/fs/pstore/pmsg.c b/fs/pstore/pmsg.c
index 5a2f05a..7de20cd 100644
--- a/fs/pstore/pmsg.c
+++ b/fs/pstore/pmsg.c
@@ -114,3 +114,10 @@ err_class:
 err:
 	return;
 }
+
+void pstore_unregister_pmsg(void)
+{
+	device_destroy(pmsg_class, MKDEV(pmsg_major, 0));
+	class_destroy(pmsg_class);
+	unregister_chrdev(pmsg_major, PMSG_NAME);
+}
diff --git a/fs/pstore/ram.c b/fs/pstore/ram.c
index 6c26c4d..d938bc1 100644
--- a/fs/pstore/ram.c
+++ b/fs/pstore/ram.c
@@ -580,28 +580,25 @@ fail_out:
 
 static int __exit ramoops_remove(struct platform_device *pdev)
 {
-#if 0
-	/* TODO(kees): We cannot unload ramoops since pstore doesn't support
-	 * unregistering yet.
-	 */
 	struct ramoops_context *cxt = &oops_cxt;
 
-	iounmap(cxt->virt_addr);
-	release_mem_region(cxt->phys_addr, cxt->size);
-	cxt->max_dump_cnt = 0;
+	pstore_unregister();
 
-	/* TODO(kees): When pstore supports unregistering, call it here. */
+	cxt->max_dump_cnt = 0;
 	kfree(cxt->pstore.buf);
 	cxt->pstore.bufsize = 0;
 
+	persistent_ram_free(cxt->mprz);
+	persistent_ram_free(cxt->fprz);
+	persistent_ram_free(cxt->cprz);
+	ramoops_free_przs(cxt);
+
 	return 0;
-#endif
-	return -EBUSY;
 }
 
 static struct platform_driver ramoops_driver = {
 	.probe		= ramoops_probe,
-	.remove		= __exit_p(ramoops_remove),
+	.remove		= ramoops_remove,
 	.driver		= {
 		.name	= "ramoops",
 	},
diff --git a/include/linux/pstore.h b/include/linux/pstore.h
index 8e7a25b..34e4a6d 100644
--- a/include/linux/pstore.h
+++ b/include/linux/pstore.h
@@ -77,6 +77,7 @@ struct pstore_info {
 
 #ifdef CONFIG_PSTORE
 extern int pstore_register(struct pstore_info *);
+extern void pstore_unregister(void);
 extern bool pstore_cannot_block_path(enum kmsg_dump_reason reason);
 #else
 static inline int
@@ -84,6 +85,10 @@ pstore_register(struct pstore_info *psi)
 {
 	return -ENODEV;
 }
+static inline void
+pstore_unregister(void)
+{
+}
 static inline bool
 pstore_cannot_block_path(enum kmsg_dump_reason reason)
 {
-- 
2.5.0


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