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Subject[PATCH v4 1/3] mm/shmem: add __rcu annotations and properly deref radix entry
Date
In preparation for memfd code restucture, clean up sparse warnings.
Most changes required adding __rcu annotations. The routine
find_swap_entry was modified to properly deference radix tree
entries.

Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
---
mm/shmem.c | 20 +++++++++++++-------
1 file changed, 13 insertions(+), 7 deletions(-)

diff --git a/mm/shmem.c b/mm/shmem.c
index b85919243399..c7bad16fe884 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -327,7 +327,7 @@ static int shmem_radix_tree_replace(struct address_space *mapping,
pgoff_t index, void *expected, void *replacement)
{
struct radix_tree_node *node;
- void **pslot;
+ void __rcu **pslot;
void *item;

VM_BUG_ON(!expected);
@@ -395,7 +395,7 @@ static bool shmem_confirm_swap(struct address_space *mapping,
#ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
/* ifdef here to avoid bloating shmem.o when not necessary */

-int shmem_huge __read_mostly;
+static int shmem_huge __read_mostly;

#if defined(CONFIG_SYSFS) || defined(CONFIG_TMPFS)
static int shmem_parse_huge(const char *str)
@@ -682,7 +682,7 @@ unsigned long shmem_partial_swap_usage(struct address_space *mapping,
pgoff_t start, pgoff_t end)
{
struct radix_tree_iter iter;
- void **slot;
+ void __rcu **slot;
struct page *page;
unsigned long swapped = 0;

@@ -1098,13 +1098,19 @@ static void shmem_evict_inode(struct inode *inode)
static unsigned long find_swap_entry(struct radix_tree_root *root, void *item)
{
struct radix_tree_iter iter;
- void **slot;
+ void __rcu **slot;
unsigned long found = -1;
unsigned int checked = 0;

rcu_read_lock();
radix_tree_for_each_slot(slot, root, &iter, 0) {
- if (*slot == item) {
+ void *entry = radix_tree_deref_slot(slot);
+
+ if (radix_tree_deref_retry(entry)) {
+ slot = radix_tree_iter_retry(&iter);
+ continue;
+ }
+ if (entry == item) {
found = iter.index;
break;
}
@@ -2623,7 +2629,7 @@ static loff_t shmem_file_llseek(struct file *file, loff_t offset, int whence)
static void shmem_tag_pins(struct address_space *mapping)
{
struct radix_tree_iter iter;
- void **slot;
+ void __rcu **slot;
pgoff_t start;
struct page *page;

@@ -2665,7 +2671,7 @@ static void shmem_tag_pins(struct address_space *mapping)
static int shmem_wait_for_pins(struct address_space *mapping)
{
struct radix_tree_iter iter;
- void **slot;
+ void __rcu **slot;
pgoff_t start;
struct page *page;
int error, scan;
--
2.13.6
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