Merge branch 'akpm' (patches from Andrew)

Merge more updates from Andrew Morton:
 "Various misc subsystems, before getting into the post-linux-next
  material.

  41 patches.

  Subsystems affected by this patch series: procfs, misc, core-kernel,
  lib, checkpatch, init, pipe, minix, fat, cgroups, kexec, kdump,
  taskstats, panic, kcov, resource, and ubsan"

* emailed patches from Andrew Morton <akpm@linux-foundation.org>: (41 commits)
  Revert "ubsan, kcsan: Don't combine sanitizer with kcov on clang"
  kernel/resource: fix kfree() of bootmem memory again
  kcov: properly handle subsequent mmap calls
  kcov: split ioctl handling into locked and unlocked parts
  panic: move panic_print before kmsg dumpers
  panic: add option to dump all CPUs backtraces in panic_print
  docs: sysctl/kernel: add missing bit to panic_print
  taskstats: remove unneeded dead assignment
  kasan: no need to unset panic_on_warn in end_report()
  ubsan: no need to unset panic_on_warn in ubsan_epilogue()
  panic: unset panic_on_warn inside panic()
  docs: kdump: add scp example to write out the dump file
  docs: kdump: update description about sysfs file system support
  arm64: mm: use IS_ENABLED(CONFIG_KEXEC_CORE) instead of #ifdef
  x86/setup: use IS_ENABLED(CONFIG_KEXEC_CORE) instead of #ifdef
  riscv: mm: init: use IS_ENABLED(CONFIG_KEXEC_CORE) instead of #ifdef
  kexec: make crashk_res, crashk_low_res and crash_notes symbols always visible
  cgroup: use irqsave in cgroup_rstat_flush_locked().
  fat: use pointer to simple type in put_user()
  minix: fix bug when opening a file with O_DIRECT
  ...

2 files changed, 27 insertions, 24 deletions

diff --git a/fs/proc/base.c b/fs/proc/base.c
index d654ce7150fd..76bf1aa3cfe8 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1764,25 +1764,25 @@ out:
 
 static int do_proc_readlink(struct path *path, char __user *buffer, int buflen)
 {
-	char *tmp = (char *)__get_free_page(GFP_KERNEL);
+	char *tmp = kmalloc(PATH_MAX, GFP_KERNEL);
 	char *pathname;
 	int len;
 
 	if (!tmp)
 		return -ENOMEM;
 
-	pathname = d_path(path, tmp, PAGE_SIZE);
+	pathname = d_path(path, tmp, PATH_MAX);
 	len = PTR_ERR(pathname);
 	if (IS_ERR(pathname))
 		goto out;
-	len = tmp + PAGE_SIZE - 1 - pathname;
+	len = tmp + PATH_MAX - 1 - pathname;
 
 	if (len > buflen)
 		len = buflen;
 	if (copy_to_user(buffer, pathname, len))
 		len = -EFAULT;
  out:
-	free_page((unsigned long)tmp);
+	kfree(tmp);
 	return len;
 }
 
diff --git a/fs/proc/vmcore.c b/fs/proc/vmcore.c
index 702754dd1daf..6f1b8ddc6f7a 100644
--- a/fs/proc/vmcore.c
+++ b/fs/proc/vmcore.c
@@ -62,7 +62,8 @@ core_param(novmcoredd, vmcoredd_disabled, bool, 0);
 /* Device Dump Size */
 static size_t vmcoredd_orig_sz;
 
-static DECLARE_RWSEM(vmcore_cb_rwsem);
+static DEFINE_SPINLOCK(vmcore_cb_lock);
+DEFINE_STATIC_SRCU(vmcore_cb_srcu);
 /* List of registered vmcore callbacks. */
 static LIST_HEAD(vmcore_cb_list);
 /* Whether the vmcore has been opened once. */
@@ -70,8 +71,8 @@ static bool vmcore_opened;
 
 void register_vmcore_cb(struct vmcore_cb *cb)
 {
-	down_write(&vmcore_cb_rwsem);
 	INIT_LIST_HEAD(&cb->next);
+	spin_lock(&vmcore_cb_lock);
 	list_add_tail(&cb->next, &vmcore_cb_list);
 	/*
 	 * Registering a vmcore callback after the vmcore was opened is
@@ -79,14 +80,14 @@ void register_vmcore_cb(struct vmcore_cb *cb)
 	 */
 	if (vmcore_opened)
 		pr_warn_once("Unexpected vmcore callback registration\n");
-	up_write(&vmcore_cb_rwsem);
+	spin_unlock(&vmcore_cb_lock);
 }
 EXPORT_SYMBOL_GPL(register_vmcore_cb);
 
 void unregister_vmcore_cb(struct vmcore_cb *cb)
 {
-	down_write(&vmcore_cb_rwsem);
-	list_del(&cb->next);
+	spin_lock(&vmcore_cb_lock);
+	list_del_rcu(&cb->next);
 	/*
 	 * Unregistering a vmcore callback after the vmcore was opened is
 	 * very unusual (e.g., forced driver removal), but we cannot stop
@@ -94,7 +95,9 @@ void unregister_vmcore_cb(struct vmcore_cb *cb)
 	 */
 	if (vmcore_opened)
 		pr_warn_once("Unexpected vmcore callback unregistration\n");
-	up_write(&vmcore_cb_rwsem);
+	spin_unlock(&vmcore_cb_lock);
+
+	synchronize_srcu(&vmcore_cb_srcu);
 }
 EXPORT_SYMBOL_GPL(unregister_vmcore_cb);
 
@@ -103,9 +106,8 @@ static bool pfn_is_ram(unsigned long pfn)
 	struct vmcore_cb *cb;
 	bool ret = true;
 
-	lockdep_assert_held_read(&vmcore_cb_rwsem);
-
-	list_for_each_entry(cb, &vmcore_cb_list, next) {
+	list_for_each_entry_srcu(cb, &vmcore_cb_list, next,
+				 srcu_read_lock_held(&vmcore_cb_srcu)) {
 		if (unlikely(!cb->pfn_is_ram))
 			continue;
 		ret = cb->pfn_is_ram(cb, pfn);
@@ -118,9 +120,9 @@ static bool pfn_is_ram(unsigned long pfn)
 
 static int open_vmcore(struct inode *inode, struct file *file)
 {
-	down_read(&vmcore_cb_rwsem);
+	spin_lock(&vmcore_cb_lock);
 	vmcore_opened = true;
-	up_read(&vmcore_cb_rwsem);
+	spin_unlock(&vmcore_cb_lock);
 
 	return 0;
 }
@@ -133,6 +135,7 @@ ssize_t read_from_oldmem(char *buf, size_t count,
 	unsigned long pfn, offset;
 	size_t nr_bytes;
 	ssize_t read = 0, tmp;
+	int idx;
 
 	if (!count)
 		return 0;
@@ -140,7 +143,7 @@ ssize_t read_from_oldmem(char *buf, size_t count,
 	offset = (unsigned long)(*ppos % PAGE_SIZE);
 	pfn = (unsigned long)(*ppos / PAGE_SIZE);
 
-	down_read(&vmcore_cb_rwsem);
+	idx = srcu_read_lock(&vmcore_cb_srcu);
 	do {
 		if (count > (PAGE_SIZE - offset))
 			nr_bytes = PAGE_SIZE - offset;
@@ -165,7 +168,7 @@ ssize_t read_from_oldmem(char *buf, size_t count,
 						       offset, userbuf);
 		}
 		if (tmp < 0) {
-			up_read(&vmcore_cb_rwsem);
+			srcu_read_unlock(&vmcore_cb_srcu, idx);
 			return tmp;
 		}
 
@@ -176,8 +179,8 @@ ssize_t read_from_oldmem(char *buf, size_t count,
 		++pfn;
 		offset = 0;
 	} while (count);
+	srcu_read_unlock(&vmcore_cb_srcu, idx);
 
-	up_read(&vmcore_cb_rwsem);
 	return read;
 }
 
@@ -477,7 +480,7 @@ static const struct vm_operations_struct vmcore_mmap_ops = {
 
 /**
  * vmcore_alloc_buf - allocate buffer in vmalloc memory
- * @sizez: size of buffer
+ * @size: size of buffer
  *
  * If CONFIG_MMU is defined, use vmalloc_user() to allow users to mmap
  * the buffer to user-space by means of remap_vmalloc_range().
@@ -568,18 +571,18 @@ static int vmcore_remap_oldmem_pfn(struct vm_area_struct *vma,
 			    unsigned long from, unsigned long pfn,
 			    unsigned long size, pgprot_t prot)
 {
-	int ret;
+	int ret, idx;
 
 	/*
-	 * Check if oldmem_pfn_is_ram was registered to avoid
-	 * looping over all pages without a reason.
+	 * Check if a callback was registered to avoid looping over all
+	 * pages without a reason.
 	 */
-	down_read(&vmcore_cb_rwsem);
+	idx = srcu_read_lock(&vmcore_cb_srcu);
 	if (!list_empty(&vmcore_cb_list))
 		ret = remap_oldmem_pfn_checked(vma, from, pfn, size, prot);
 	else
 		ret = remap_oldmem_pfn_range(vma, from, pfn, size, prot);
-	up_read(&vmcore_cb_rwsem);
+	srcu_read_unlock(&vmcore_cb_srcu, idx);
 	return ret;
 }