[RFC PATCH v2 7/7] mm, swap: widen swap_info_struct max/pages to unsigned long
From: Nhat Pham
Date: Fri Jun 12 2026 - 15:41:13 EST
Widen swap_info_struct->max and ->pages from unsigned int to
unsigned long so the vswap device can exceed the current 16 TB
cap (ALIGN_DOWN(UINT_MAX, SWAPFILE_CLUSTER) pages).
Physical swap is unaffected; backing files/bdevs continue to bound
it independently of the field width.
The new vswap cap is the cluster_info_pool xarray's allocator
limit. XA_FLAGS_ALLOC stores allocated IDs in u32, so
max_pages = UINT_MAX * SWAPFILE_CLUSTER (~8 PB at the typical
SWAPFILE_CLUSTER=512 layout).
Signed-off-by: Nhat Pham <nphamcs@xxxxxxxxx>
---
include/linux/swap.h | 4 +--
mm/swapfile.c | 62 +++++++++++++++++++++++---------------------
2 files changed, 34 insertions(+), 32 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 2d6bc4cb442f..b8fc2aa4539f 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -253,7 +253,7 @@ struct swap_info_struct {
signed short prio; /* swap priority of this type */
struct plist_node list; /* entry in swap_active_head */
signed char type; /* strange name for an index */
- unsigned int max; /* size of this swap device */
+ unsigned long max; /* size of this swap device */
struct swap_cluster_info *cluster_info; /* cluster info. Only for SSD */
struct list_head free_clusters; /* free clusters list */
struct list_head full_clusters; /* full clusters list */
@@ -261,7 +261,7 @@ struct swap_info_struct {
/* list of cluster that contains at least one free slot */
struct list_head frag_clusters[SWAP_NR_ORDERS];
/* list of cluster that are fragmented or contented */
- unsigned int pages; /* total of usable pages of swap */
+ unsigned long pages; /* total of usable pages of swap */
atomic_long_t inuse_pages; /* number of those currently in use */
struct swap_sequential_cluster *global_cluster; /* Use one global cluster for rotating device */
spinlock_t global_cluster_lock; /* Serialize usage of global cluster */
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 0d48240de345..b03a81993a04 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -451,10 +451,10 @@ static inline unsigned int cluster_index(struct swap_info_struct *si,
return ci - si->cluster_info;
}
-static inline unsigned int cluster_offset(struct swap_info_struct *si,
- struct swap_cluster_info *ci)
+static inline unsigned long cluster_offset(struct swap_info_struct *si,
+ struct swap_cluster_info *ci)
{
- return cluster_index(si, ci) * SWAPFILE_CLUSTER;
+ return (unsigned long)cluster_index(si, ci) * SWAPFILE_CLUSTER;
}
static void swap_cluster_free_table_folio_rcu_cb(struct rcu_head *head)
@@ -876,7 +876,7 @@ static int swap_cluster_setup_bad_slot(struct swap_info_struct *si,
/* si->max may got shrunk by swap swap_activate() */
if (offset >= si->max && !mask) {
- pr_debug("Ignoring bad slot %u (max: %u)\n", offset, si->max);
+ pr_debug("Ignoring bad slot %u (max: %lu)\n", offset, si->max);
return 0;
}
/*
@@ -1152,12 +1152,12 @@ static bool __swap_cluster_alloc_entries(struct swap_info_struct *si,
}
/* Try use a new cluster for current CPU and allocate from it. */
-static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si,
- struct swap_cluster_info *ci,
- struct folio *folio,
- unsigned long offset)
+static unsigned long alloc_swap_scan_cluster(struct swap_info_struct *si,
+ struct swap_cluster_info *ci,
+ struct folio *folio,
+ unsigned long offset)
{
- unsigned int next = SWAP_ENTRY_INVALID, found = SWAP_ENTRY_INVALID;
+ unsigned long next = SWAP_ENTRY_INVALID, found = SWAP_ENTRY_INVALID;
unsigned long start = ALIGN_DOWN(offset, SWAPFILE_CLUSTER);
unsigned int order = folio ? folio_order(folio) : 0;
unsigned long end = start + SWAPFILE_CLUSTER;
@@ -1235,12 +1235,12 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si,
return found;
}
-static unsigned int alloc_swap_scan_list(struct swap_info_struct *si,
- struct list_head *list,
- struct folio *folio,
- bool scan_all)
+static unsigned long alloc_swap_scan_list(struct swap_info_struct *si,
+ struct list_head *list,
+ struct folio *folio,
+ bool scan_all)
{
- unsigned int found = SWAP_ENTRY_INVALID;
+ unsigned long found = SWAP_ENTRY_INVALID;
do {
struct swap_cluster_info *ci = isolate_lock_cluster(si, list);
@@ -1257,8 +1257,8 @@ static unsigned int alloc_swap_scan_list(struct swap_info_struct *si,
return found;
}
-static unsigned int alloc_swap_scan_dynamic(struct swap_info_struct *si,
- struct folio *folio)
+static unsigned long alloc_swap_scan_dynamic(struct swap_info_struct *si,
+ struct folio *folio)
{
struct swap_cluster_info_dynamic *ci_dyn;
struct swap_cluster_info *ci;
@@ -1373,7 +1373,7 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si,
{
unsigned int order = folio ? folio_order(folio) : 0;
struct swap_cluster_info *ci;
- unsigned int offset = SWAP_ENTRY_INVALID, found = SWAP_ENTRY_INVALID;
+ unsigned long offset = SWAP_ENTRY_INVALID, found = SWAP_ENTRY_INVALID;
/*
* File-based swap can't do large contiguous IO. vswap has no IO
@@ -3492,10 +3492,10 @@ static int unuse_mm(struct mm_struct *mm, unsigned int type)
* Return 0 if there are no inuse entries after prev till end of
* the map.
*/
-static unsigned int find_next_to_unuse(struct swap_info_struct *si,
- unsigned int prev)
+static unsigned long find_next_to_unuse(struct swap_info_struct *si,
+ unsigned long prev)
{
- unsigned int i;
+ unsigned long i;
unsigned long swp_tb;
/*
@@ -3533,7 +3533,8 @@ static int try_to_unuse(unsigned int type)
struct folio *folio;
swp_entry_t entry, vswap_entry;
unsigned long swp_tb;
- unsigned int i, j, ci_off;
+ unsigned long i;
+ unsigned int j, ci_off;
if (!swap_usage_in_pages(si))
goto success;
@@ -3970,7 +3971,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
struct file *swap_file, *victim;
struct address_space *mapping;
struct inode *inode;
- unsigned int maxpages;
+ unsigned long maxpages;
int err, found = 0;
if (!capable(CAP_SYS_ADMIN))
@@ -4404,12 +4405,8 @@ static unsigned long read_swap_header(struct swap_info_struct *si,
pr_warn("Truncating oversized swap area, only using %luk out of %luk\n",
K(maxpages), K(last_page));
}
- if (maxpages > last_page) {
+ if (maxpages > last_page)
maxpages = last_page + 1;
- /* p->max is an unsigned int: don't overflow it */
- if ((unsigned int)maxpages == 0)
- maxpages = UINT_MAX;
- }
if (!maxpages)
return 0;
@@ -4640,7 +4637,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
goto bad_swap_unlock_inode;
}
if (si->pages != si->max - 1) {
- pr_err("swap:%u != (max:%u - 1)\n", si->pages, si->max);
+ pr_err("swap:%lu != (max:%lu - 1)\n", si->pages, si->max);
error = -EINVAL;
goto bad_swap_unlock_inode;
}
@@ -4728,7 +4725,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
/* Sets SWP_WRITEOK, resurrect the percpu ref, expose the swap device */
enable_swap_info(si);
- pr_info("Adding %uk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s\n",
+ pr_info("Adding %luk swap on %s. Priority:%d extents:%d across:%lluk %s%s%s%s\n",
K(si->pages), name->name, si->prio, nr_extents,
K((unsigned long long)span),
(si->flags & SWP_SOLIDSTATE) ? "SS" : "",
@@ -4900,8 +4897,13 @@ static int __init vswap_init(void)
return 0;
}
+ /*
+ * Cap at the cluster_info_pool xarray's allocator limit
+ * (XA_FLAGS_ALLOC stores IDs in u32, tops out at UINT_MAX).
+ */
maxpages = min(swapfile_maximum_size,
- ALIGN_DOWN((unsigned long)UINT_MAX, SWAPFILE_CLUSTER));
+ ALIGN_DOWN((unsigned long)UINT_MAX * SWAPFILE_CLUSTER,
+ SWAPFILE_CLUSTER));
si->flags |= SWP_VSWAP | SWP_SOLIDSTATE | SWP_WRITEOK;
si->bdev = NULL;
si->max = maxpages;
--
2.53.0-Meta