[PATCH v3 03/14] mm, swap: refactor free_swap_cluster_info to take swap_info_struct

[Baoquan He]

Change free_swap_cluster_info() to take struct swap_info_struct* instead
of (cluster_info, maxpages). It now extracts the fields from si and
clears si->cluster_info after freeing to avoid a double free on the
swapon() error path.

The new parameter also lets the xswap path access si->flags in the
function.

Signed-off-by: Baoquan He <hebaoquan@xxxxxxxxxx>
---
 mm/swapfile.c | 26 ++++++++++++++------------
 1 file changed, 14 insertions(+), 12 deletions(-)

diff --git a/mm/swapfile.c b/mm/swapfile.c
index 13ae681acf07..4b260f9760ac 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3142,14 +3142,17 @@ static void wait_for_allocation(struct swap_info_struct *si)
 	}
 }
 
-static void free_swap_cluster_info(struct swap_cluster_info *cluster_info,
-				   unsigned long maxpages)
+static void free_swap_cluster_info(struct swap_info_struct *si)
 {
+	struct swap_cluster_info *cluster_info = si->cluster_info;
+	unsigned long maxpages = si->max;
 	struct swap_cluster_info *ci;
-	int i, nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
+	int i, nr_clusters;
 
 	if (!cluster_info)
 		return;
+
+	nr_clusters = DIV_ROUND_UP(maxpages, SWAPFILE_CLUSTER);
 	for (i = 0; i < nr_clusters; i++) {
 		ci = cluster_info + i;
 		/* Cluster with bad marks count will have a remaining table */
@@ -3161,6 +3164,7 @@ static void free_swap_cluster_info(struct swap_cluster_info *cluster_info,
 		spin_unlock(&ci->lock);
 	}
 	kvfree(cluster_info);
+	si->cluster_info = NULL;
 }
 
 /*
@@ -3188,11 +3192,9 @@ static void flush_percpu_swap_cluster(struct swap_info_struct *si)
 SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 {
 	struct swap_info_struct *p = NULL;
-	struct swap_cluster_info *cluster_info;
 	struct file *swap_file, *victim;
 	struct address_space *mapping;
 	struct inode *inode;
-	unsigned int maxpages;
 	int err, found = 0;
 
 	if (!capable(CAP_SYS_ADMIN))
@@ -3284,10 +3286,6 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 
 	swap_file = p->swap_file;
 	p->swap_file = NULL;
-	maxpages = p->max;
-	cluster_info = p->cluster_info;
-	p->max = 0;
-	p->cluster_info = NULL;
 	spin_unlock(&p->lock);
 	spin_unlock(&swap_lock);
 	arch_swap_invalidate_area(p->type);
@@ -3295,7 +3293,9 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
 	mutex_unlock(&swapon_mutex);
 	kfree(p->global_cluster);
 	p->global_cluster = NULL;
-	free_swap_cluster_info(cluster_info, maxpages);
+	free_swap_cluster_info(p);
+	p->max = 0;
+	p->cluster_info = NULL;
 
 	inode = mapping->host;
 
@@ -3662,6 +3662,8 @@ static int setup_swap_clusters_info(struct swap_info_struct *si,
 	if (!cluster_info)
 		goto err;
 
+	si->cluster_info = cluster_info;
+
 	for (i = 0; i < nr_clusters; i++)
 		spin_lock_init(&cluster_info[i].lock);
 
@@ -3725,7 +3727,7 @@ static int setup_swap_clusters_info(struct swap_info_struct *si,
 	si->cluster_info = cluster_info;
 	return 0;
 err:
-	free_swap_cluster_info(cluster_info, maxpages);
+	free_swap_cluster_info(si);
 	return err;
 }
 
@@ -3947,7 +3949,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	si->global_cluster = NULL;
 	inode = NULL;
 	destroy_swap_extents(si, swap_file);
-	free_swap_cluster_info(si->cluster_info, si->max);
+	free_swap_cluster_info(si);
 	si->cluster_info = NULL;
 	/*
 	 * Clear the SWP_USED flag after all resources are freed so
-- 
2.54.0