The existing SWP_SYNCHRONOUS_IO flag is not enough for certain swap
devices that support synchronous read operations but asynchronous write
operations, so we need to introduce a new flag SWP_READ_SYNCHRONOUS_IO.
Signed-off-by: Qun-Wei Lin <qun-wei.lin@xxxxxxxxxxxx>
---
include/linux/swap.h | 31 ++++++++++++++++---------------
mm/memory.c | 3 ++-
mm/page_io.c | 2 +-
mm/swapfile.c | 3 +++
4 files changed, 22 insertions(+), 17 deletions(-)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index ba7ea95d1c57..f595050f431b 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -205,21 +205,22 @@ struct swap_extent {
offsetof(union swap_header, info.badpages)) / sizeof(int))
enum {
- SWP_USED = (1 << 0), /* is slot in swap_info[] used? */
- SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */
- SWP_DISCARDABLE = (1 << 2), /* blkdev support discard */
- SWP_DISCARDING = (1 << 3), /* now discarding a free cluster */
- SWP_SOLIDSTATE = (1 << 4), /* blkdev seeks are cheap */
- SWP_CONTINUED = (1 << 5), /* swap_map has count continuation */
- SWP_BLKDEV = (1 << 6), /* its a block device */
- SWP_ACTIVATED = (1 << 7), /* set after swap_activate success */
- SWP_FS_OPS = (1 << 8), /* swapfile operations go through fs */
- SWP_AREA_DISCARD = (1 << 9), /* single-time swap area discards */
- SWP_PAGE_DISCARD = (1 << 10), /* freed swap page-cluster discards */
- SWP_STABLE_WRITES = (1 << 11), /* no overwrite PG_writeback pages */
- SWP_SYNCHRONOUS_IO = (1 << 12), /* synchronous IO is efficient */
- /* add others here before... */
- SWP_SCANNING = (1 << 14), /* refcount in scan_swap_map */
+ SWP_USED = (1 << 0), /* is slot in swap_info[] used? */
+ SWP_WRITEOK = (1 << 1), /* ok to write to this swap? */
+ SWP_DISCARDABLE = (1 << 2), /* blkdev support discard */
+ SWP_DISCARDING = (1 << 3), /* now discarding a free cluster */
+ SWP_SOLIDSTATE = (1 << 4), /* blkdev seeks are cheap */
+ SWP_CONTINUED = (1 << 5), /* swap_map has count continuation */
+ SWP_BLKDEV = (1 << 6), /* its a block device */
+ SWP_ACTIVATED = (1 << 7), /* set after swap_activate success */
+ SWP_FS_OPS = (1 << 8), /* swapfile operations go through fs */
+ SWP_AREA_DISCARD = (1 << 9), /* single-time swap area discards */
+ SWP_PAGE_DISCARD = (1 << 10), /* freed swap page-cluster discards */
+ SWP_STABLE_WRITES = (1 << 11), /* no overwrite PG_writeback pages */
+ SWP_SYNCHRONOUS_IO = (1 << 12), /* synchronous IO is efficient */
+ SWP_READ_SYNCHRONOUS_IO = (1 << 13), /* synchronous IO is efficient */
+ /* add others here before... */
+ SWP_SCANNING = (1 << 14), /* refcount in scan_swap_map */
};
#define SWAP_CLUSTER_MAX 32UL
diff --git a/mm/memory.c b/mm/memory.c
index ebfc9768f801..f531a6bfea5b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4089,7 +4089,8 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
swapcache = folio;
if (!folio) {
- if (data_race(si->flags & SWP_SYNCHRONOUS_IO) &&
+ if ((data_race(si->flags & (SWP_SYNCHRONOUS_IO |
+ SWP_READ_SYNCHRONOUS_IO))) &&
__swap_count(entry) == 1) {
/*
* Prevent parallel swapin from proceeding with
diff --git a/mm/page_io.c b/mm/page_io.c
index ff8c99ee3af7..98a00709e98c 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -499,7 +499,7 @@ static void swap_read_folio_bdev_async(struct folio *folio,
void swap_read_folio(struct folio *folio, struct swap_iocb **plug)
{
struct swap_info_struct *sis = swp_swap_info(folio->swap);
- bool synchronous = sis->flags & SWP_SYNCHRONOUS_IO;
+ bool synchronous = sis->flags & (SWP_SYNCHRONOUS_IO | SWP_READ_SYNCHRONOUS_IO);
bool workingset = folio_test_workingset(folio);
unsigned long pflags;
bool in_thrashing;
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 38bdc439651a..7b8feb235aab 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3177,6 +3177,9 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
if (p->bdev && bdev_synchronous(p->bdev))
p->flags |= SWP_SYNCHRONOUS_IO;
+ if (p->bdev && bdev_read_synchronous(p->bdev))
+ p->flags |= SWP_READ_SYNCHRONOUS_IO;
+
if (p->bdev && bdev_nonrot(p->bdev)) {
int cpu, i;
unsigned long ci, nr_cluster;
--
2.45.2
