3 files changed, 47 insertions, 16 deletions

diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
index cee58a972cb2..1b530197d114 100644
--- a/arch/x86/mm/init.c
+++ b/arch/x86/mm/init.c
@@ -4,6 +4,8 @@
 #include <linux/swap.h>
 #include <linux/memblock.h>
 #include <linux/bootmem.h>      /* for max_low_pfn */
+#include <linux/swapfile.h>
+#include <linux/swapops.h>
 
 #include <asm/set_memory.h>
 #include <asm/e820/api.h>
@@ -880,3 +882,16 @@ void update_cache_mode_entry(unsigned entry, enum page_cache_mode cache)
         __cachemode2pte_tbl[cache] = __cm_idx2pte(entry);
         __pte2cachemode_tbl[entry] = cache;
 }
+
+unsigned long max_swapfile_size(void)
+{
+        unsigned long pages;
+
+        pages = generic_max_swapfile_size();
+
+        if (boot_cpu_has_bug(X86_BUG_L1TF)) {
+                /* Limit the swap file size to MAX_PA/2 for L1TF workaround */
+                pages = min_t(unsigned long, l1tf_pfn_limit() + 1, pages);
+        }
+        return pages;
+}
diff --git a/include/linux/swapfile.h b/include/linux/swapfile.h
index 06bd7b096167..e06febf62978 100644
--- a/include/linux/swapfile.h
+++ b/include/linux/swapfile.h
@@ -10,5 +10,7 @@ extern spinlock_t swap_lock;
 extern struct plist_head swap_active_head;
 extern struct swap_info_struct *swap_info[];
 extern int try_to_unuse(unsigned int, bool, unsigned long);
+extern unsigned long generic_max_swapfile_size(void);
+extern unsigned long max_swapfile_size(void);
 
 #endif /* _LINUX_SWAPFILE_H */
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 2cc2972eedaf..18185ae4f223 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -2909,6 +2909,35 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode)
         return 0;
 }
 
+
+/*
+ * Find out how many pages are allowed for a single swap device. There
+ * are two limiting factors:
+ * 1) the number of bits for the swap offset in the swp_entry_t type, and
+ * 2) the number of bits in the swap pte, as defined by the different
+ * architectures.
+ *
+ * In order to find the largest possible bit mask, a swap entry with
+ * swap type 0 and swap offset ~0UL is created, encoded to a swap pte,
+ * decoded to a swp_entry_t again, and finally the swap offset is
+ * extracted.
+ *
+ * This will mask all the bits from the initial ~0UL mask that can't
+ * be encoded in either the swp_entry_t or the architecture definition
+ * of a swap pte.
+ */
+unsigned long generic_max_swapfile_size(void)
+{
+        return swp_offset(pte_to_swp_entry(
+                        swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+}
+
+/* Can be overridden by an architecture for additional checks. */
+__weak unsigned long max_swapfile_size(void)
+{
+        return generic_max_swapfile_size();
+}
+
 static unsigned long read_swap_header(struct swap_info_struct *p,
                                         union swap_header *swap_header,
                                         struct inode *inode)
@@ -2944,22 +2973,7 @@ static unsigned long read_swap_header(struct swap_info_struct *p,
         p->cluster_next = 1;
         p->cluster_nr = 0;
 
-        /*
-         * Find out how many pages are allowed for a single swap
-         * device. There are two limiting factors: 1) the number
-         * of bits for the swap offset in the swp_entry_t type, and
-         * 2) the number of bits in the swap pte as defined by the
-         * different architectures. In order to find the
-         * largest possible bit mask, a swap entry with swap type 0
-         * and swap offset ~0UL is created, encoded to a swap pte,
-         * decoded to a swp_entry_t again, and finally the swap
-         * offset is extracted. This will mask all the bits from
-         * the initial ~0UL mask that can't be encoded in either
-         * the swp_entry_t or the architecture definition of a
-         * swap pte.
-         */
-        maxpages = swp_offset(pte_to_swp_entry(
-                        swp_entry_to_pte(swp_entry(0, ~0UL)))) + 1;
+        maxpages = max_swapfile_size();
         last_page = swap_header->info.last_page;
         if (!last_page) {
                 pr_warn("Empty swap-file\n");