1. We no longer ad-hoc to the function tracer "high level" infrastructure

and no longer use its debugfs knobs. The change slightly touches
    kernel/trace directory, but it got the needed ack from Steven Rostedt:
    http://lkml.org/lkml/2012/8/21/688
 2. Added maintainers entry;
 3. A bunch of fixes, nothing special.
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Merge tag 'for-v3.7' of git://git.infradead.org/users/cbou/linux-pstore

Pull pstore changes from Anton Vorontsov:

 1) We no longer ad-hoc to the function tracer "high level"
    infrastructure and no longer use its debugfs knobs.  The change
    slightly touches kernel/trace directory, but it got the needed ack
    from Steven Rostedt:

      http://lkml.org/lkml/2012/8/21/688

 2) Added maintainers entry;

 3) A bunch of fixes, nothing special.

* tag 'for-v3.7' of git://git.infradead.org/users/cbou/linux-pstore:
  pstore: Avoid recursive spinlocks in the oops_in_progress case
  pstore/ftrace: Convert to its own enable/disable debugfs knob
  pstore/ram: Add missing platform_device_unregister
  MAINTAINERS: Add pstore maintainers
  pstore/ram: Mark ramoops_pstore_write_buf() as notrace
  pstore/ram: Fix printk format warning
  pstore/ram: Fix possible NULL dereference

fs/pstore/Kconfig

@@ -23,6 +23,7 @@ config PSTORE_FTRACE
 	bool "Persistent function tracer"
 	depends on PSTORE
 	depends on FUNCTION_TRACER
+	depends on DEBUG_FS
 	help
 	  With this option kernel traces function calls into a persistent
 	  ram buffer that can be decoded and dumped after reboot through

fs/pstore/ftrace.c

@@ -17,19 +17,113 @@
 #include <linux/percpu.h>
 #include <linux/smp.h>
 #include <linux/atomic.h>
+#include <linux/types.h>
+#include <linux/mutex.h>
+#include <linux/ftrace.h>
+#include <linux/fs.h>
+#include <linux/debugfs.h>
+#include <linux/err.h>
+#include <linux/cache.h>
 #include <asm/barrier.h>
 #include "internal.h"
 
-void notrace pstore_ftrace_call(unsigned long ip, unsigned long parent_ip)
+static void notrace pstore_ftrace_call(unsigned long ip,
+				       unsigned long parent_ip)
 {
+	unsigned long flags;
 	struct pstore_ftrace_record rec = {};
 
 	if (unlikely(oops_in_progress))
 		return;
 
+	local_irq_save(flags);
+
 	rec.ip = ip;
 	rec.parent_ip = parent_ip;
 	pstore_ftrace_encode_cpu(&rec, raw_smp_processor_id());
 	psinfo->write_buf(PSTORE_TYPE_FTRACE, 0, NULL, 0, (void *)&rec,
 			  sizeof(rec), psinfo);
+
+	local_irq_restore(flags);
+}
+
+static struct ftrace_ops pstore_ftrace_ops __read_mostly = {
+	.func	= pstore_ftrace_call,
+};
+
+static DEFINE_MUTEX(pstore_ftrace_lock);
+static bool pstore_ftrace_enabled;
+
+static ssize_t pstore_ftrace_knob_write(struct file *f, const char __user *buf,
+					size_t count, loff_t *ppos)
+{
+	u8 on;
+	ssize_t ret;
+
+	ret = kstrtou8_from_user(buf, count, 2, &on);
+	if (ret)
+		return ret;
+
+	mutex_lock(&pstore_ftrace_lock);
+
+	if (!on ^ pstore_ftrace_enabled)
+		goto out;
+
+	if (on)
+		ret = register_ftrace_function(&pstore_ftrace_ops);
+	else
+		ret = unregister_ftrace_function(&pstore_ftrace_ops);
+	if (ret) {
+		pr_err("%s: unable to %sregister ftrace ops: %zd\n",
+		       __func__, on ? "" : "un", ret);
+		goto err;
+	}
+
+	pstore_ftrace_enabled = on;
+out:
+	ret = count;
+err:
+	mutex_unlock(&pstore_ftrace_lock);
+
+	return ret;
+}
+
+static ssize_t pstore_ftrace_knob_read(struct file *f, char __user *buf,
+				       size_t count, loff_t *ppos)
+{
+	char val[] = { '0' + pstore_ftrace_enabled, '\n' };
+
+	return simple_read_from_buffer(buf, count, ppos, val, sizeof(val));
+}
+
+static const struct file_operations pstore_knob_fops = {
+	.open	= simple_open,
+	.read	= pstore_ftrace_knob_read,
+	.write	= pstore_ftrace_knob_write,
+};
+
+void pstore_register_ftrace(void)
+{
+	struct dentry *dir;
+	struct dentry *file;
+
+	if (!psinfo->write_buf)
+		return;
+
+	dir = debugfs_create_dir("pstore", NULL);
+	if (!dir) {
+		pr_err("%s: unable to create pstore directory\n", __func__);
+		return;
+	}
+
+	file = debugfs_create_file("record_ftrace", 0600, dir, NULL,
+				   &pstore_knob_fops);
+	if (!file) {
+		pr_err("%s: unable to create record_ftrace file\n", __func__);
+		goto err_file;
+	}
+
+	return;
+err_file:
+	debugfs_remove(dir);
 }

fs/pstore/internal.h

@@ -39,6 +39,12 @@ pstore_ftrace_decode_cpu(struct pstore_ftrace_record *rec)
 #endif
 }
 
+#ifdef CONFIG_PSTORE_FTRACE
+extern void pstore_register_ftrace(void);
+#else
+static inline void pstore_register_ftrace(void) {}
+#endif
+
 extern struct pstore_info *psinfo;
 
 extern void	pstore_set_kmsg_bytes(int);

fs/pstore/platform.c

@@ -164,7 +164,13 @@ static void pstore_console_write(struct console *con, const char *s, unsigned c)
 
 		if (c > psinfo->bufsize)
 			c = psinfo->bufsize;
-		spin_lock_irqsave(&psinfo->buf_lock, flags);
+
+		if (oops_in_progress) {
+			if (!spin_trylock_irqsave(&psinfo->buf_lock, flags))
+				break;
+		} else {
+			spin_lock_irqsave(&psinfo->buf_lock, flags);
+		}
 		memcpy(psinfo->buf, s, c);
 		psinfo->write(PSTORE_TYPE_CONSOLE, 0, NULL, 0, c, psinfo);
 		spin_unlock_irqrestore(&psinfo->buf_lock, flags);
@@ -236,6 +242,7 @@ int pstore_register(struct pstore_info *psi)
 
 	kmsg_dump_register(&pstore_dumper);
 	pstore_register_console();
+	pstore_register_ftrace();
 
 	if (pstore_update_ms >= 0) {
 		pstore_timer.expires = jiffies +

fs/pstore/ram.c

@@ -32,6 +32,7 @@
 #include <linux/ioport.h>
 #include <linux/platform_device.h>
 #include <linux/slab.h>
+#include <linux/compiler.h>
 #include <linux/pstore_ram.h>
 
 #define RAMOOPS_KERNMSG_HDR "===="
@@ -181,12 +182,11 @@ static size_t ramoops_write_kmsg_hdr(struct persistent_ram_zone *prz)
 	return len;
 }
 
-
-static int ramoops_pstore_write_buf(enum pstore_type_id type,
-				    enum kmsg_dump_reason reason,
-				    u64 *id, unsigned int part,
-				    const char *buf, size_t size,
-				    struct pstore_info *psi)
+static int notrace ramoops_pstore_write_buf(enum pstore_type_id type,
+					    enum kmsg_dump_reason reason,
+					    u64 *id, unsigned int part,
+					    const char *buf, size_t size,
+					    struct pstore_info *psi)
 {
 	struct ramoops_context *cxt = psi->data;
 	struct persistent_ram_zone *prz = cxt->przs[cxt->dump_write_cnt];
@@ -406,7 +406,7 @@ static int __devinit ramoops_probe(struct platform_device *pdev)
 		goto fail_init_fprz;
 
 	if (!cxt->przs && !cxt->cprz && !cxt->fprz) {
-		pr_err("memory size too small, minimum is %lu\n",
+		pr_err("memory size too small, minimum is %zu\n",
 			cxt->console_size + cxt->record_size +
 			cxt->ftrace_size);
 		goto fail_cnt;
@@ -414,13 +414,14 @@ static int __devinit ramoops_probe(struct platform_device *pdev)
 
 	cxt->pstore.data = cxt;
 	/*
-	 * Console can handle any buffer size, so prefer dumps buffer
-	 * size since usually it is smaller.
+	 * Console can handle any buffer size, so prefer LOG_LINE_MAX. If we
+	 * have to handle dumps, we must have at least record_size buffer. And
+	 * for ftrace, bufsize is irrelevant (if bufsize is 0, buf will be
+	 * ZERO_SIZE_PTR).
 	 */
-	if (cxt->przs)
-		cxt->pstore.bufsize = cxt->przs[0]->buffer_size;
-	else
-		cxt->pstore.bufsize = cxt->cprz->buffer_size;
+	if (cxt->console_size)
+		cxt->pstore.bufsize = 1024; /* LOG_LINE_MAX */
+	cxt->pstore.bufsize = max(cxt->record_size, cxt->pstore.bufsize);
 	cxt->pstore.buf = kmalloc(cxt->pstore.bufsize, GFP_KERNEL);
 	spin_lock_init(&cxt->pstore.buf_lock);
 	if (!cxt->pstore.buf) {
@@ -537,6 +538,7 @@ postcore_initcall(ramoops_init);
 static void __exit ramoops_exit(void)
 {
 	platform_driver_unregister(&ramoops_driver);
+	platform_device_unregister(dummy);
 	kfree(dummy_data);
 }
 module_exit(ramoops_exit);