1. Patchew
  2. linux
  3. View series

[PATCH] mm: Split BLK_FEAT_SYNCHRONOUS and SWP_SYNCHRONOUS_IO into separate read and write flags

Qun-Wei Lin posted 1 patch 1 month, 2 weeks ago 
drivers/block/brd.c           |  3 ++-
drivers/block/zram/zram_drv.c |  5 +++--
drivers/nvdimm/btt.c          |  3 ++-
drivers/nvdimm/pmem.c         |  5 +++--
include/linux/blkdev.h        | 24 ++++++++++++++++--------
include/linux/swap.h          | 31 ++++++++++++++++---------------
mm/memory.c                   |  4 ++--
mm/page_io.c                  |  6 +++---
mm/swapfile.c                 |  7 +++++--
9 files changed, 52 insertions(+), 36 deletions(-)
[PATCH] mm: Split BLK_FEAT_SYNCHRONOUS and SWP_SYNCHRONOUS_IO into separate read and write flags
Posted by Qun-Wei Lin 1 month, 2 weeks ago 
This patch splits the BLK_FEAT_SYNCHRONOUS feature flag into two
separate flags: BLK_FEAT_READ_SYNCHRONOUS and
BLK_FEAT_WRITE_SYNCHRONOUS. Similarly, the SWP_SYNCHRONOUS_IO flag is
split into SWP_READ_SYNCHRONOUS_IO and SWP_WRITE_SYNCHRONOUS_IO.

These changes are motivated by the need to better accommodate certain
swap devices that support synchronous read operations but asynchronous write
operations.

The existing BLK_FEAT_SYNCHRONOUS and SWP_SYNCHRONOUS_IO flags are not
sufficient for these devices, as they enforce synchronous behavior for
both read and write operations.

Signed-off-by: Qun-Wei Lin <qun-wei.lin@mediatek.com>
---
 drivers/block/brd.c           |  3 ++-
 drivers/block/zram/zram_drv.c |  5 +++--
 drivers/nvdimm/btt.c          |  3 ++-
 drivers/nvdimm/pmem.c         |  5 +++--
 include/linux/blkdev.h        | 24 ++++++++++++++++--------
 include/linux/swap.h          | 31 ++++++++++++++++---------------
 mm/memory.c                   |  4 ++--
 mm/page_io.c                  |  6 +++---
 mm/swapfile.c                 |  7 +++++--
 9 files changed, 52 insertions(+), 36 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 2fd1ed101748..619a56bf747e 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -336,7 +336,8 @@ static int brd_alloc(int i)
 		.max_hw_discard_sectors	= UINT_MAX,
 		.max_discard_segments	= 1,
 		.discard_granularity	= PAGE_SIZE,
-		.features		= BLK_FEAT_SYNCHRONOUS |
+		.features		= BLK_FEAT_READ_SYNCHRONOUS	|
+					  BLK_FEAT_WRITE_SYNCHRONOUS	|
 					  BLK_FEAT_NOWAIT,
 	};
 
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index ad9c9bc3ccfc..d2927ea76488 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -2345,8 +2345,9 @@ static int zram_add(void)
 #if ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE
 		.max_write_zeroes_sectors	= UINT_MAX,
 #endif
-		.features			= BLK_FEAT_STABLE_WRITES |
-						  BLK_FEAT_SYNCHRONOUS,
+		.features			= BLK_FEAT_STABLE_WRITES	|
+						  BLK_FEAT_READ_SYNCHRONOUS	|
+						  BLK_FEAT_WRITE_SYNCHRONOUS,
 	};
 	struct zram *zram;
 	int ret, device_id;
diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index 423dcd190906..1665d98f51af 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -1501,7 +1501,8 @@ static int btt_blk_init(struct btt *btt)
 		.logical_block_size	= btt->sector_size,
 		.max_hw_sectors		= UINT_MAX,
 		.max_integrity_segments	= 1,
-		.features		= BLK_FEAT_SYNCHRONOUS,
+		.features		= BLK_FEAT_READ_SYNCHRONOUS |
+					  BLK_FEAT_WRITE_SYNCHRONOUS,
 	};
 	int rc;
 
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 210fb77f51ba..c22a6ee13769 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -455,8 +455,9 @@ static int pmem_attach_disk(struct device *dev,
 		.logical_block_size	= pmem_sector_size(ndns),
 		.physical_block_size	= PAGE_SIZE,
 		.max_hw_sectors		= UINT_MAX,
-		.features		= BLK_FEAT_WRITE_CACHE |
-					  BLK_FEAT_SYNCHRONOUS,
+		.features		= BLK_FEAT_WRITE_CACHE		|
+					  BLK_FEAT_READ_SYNCHRONOUS	|
+					  BLK_FEAT_WRITE_SYNCHRONOUS,
 	};
 	int nid = dev_to_node(dev), fua;
 	struct resource *res = &nsio->res;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 50c3b959da28..88e96d6cead2 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -304,20 +304,23 @@ typedef unsigned int __bitwise blk_features_t;
 /* don't modify data until writeback is done */
 #define BLK_FEAT_STABLE_WRITES		((__force blk_features_t)(1u << 5))
 
-/* always completes in submit context */
-#define BLK_FEAT_SYNCHRONOUS		((__force blk_features_t)(1u << 6))
+/* read operations always completes in submit context */
+#define BLK_FEAT_READ_SYNCHRONOUS	((__force blk_features_t)(1u << 6))
+
+/* write operations always completes in submit context */
+#define BLK_FEAT_WRITE_SYNCHRONOUS	((__force blk_features_t)(1u << 7))
 
 /* supports REQ_NOWAIT */
-#define BLK_FEAT_NOWAIT			((__force blk_features_t)(1u << 7))
+#define BLK_FEAT_NOWAIT			((__force blk_features_t)(1u << 8))
 
 /* supports DAX */
-#define BLK_FEAT_DAX			((__force blk_features_t)(1u << 8))
+#define BLK_FEAT_DAX			((__force blk_features_t)(1u << 9))
 
 /* supports I/O polling */
-#define BLK_FEAT_POLL			((__force blk_features_t)(1u << 9))
+#define BLK_FEAT_POLL			((__force blk_features_t)(1u << 10))
 
 /* is a zoned device */
-#define BLK_FEAT_ZONED			((__force blk_features_t)(1u << 10))
+#define BLK_FEAT_ZONED			((__force blk_features_t)(1u << 11))
 
 /* supports PCI(e) p2p requests */
 #define BLK_FEAT_PCI_P2PDMA		((__force blk_features_t)(1u << 12))
@@ -1303,9 +1306,14 @@ static inline bool bdev_nonrot(struct block_device *bdev)
 	return blk_queue_nonrot(bdev_get_queue(bdev));
 }
 
-static inline bool bdev_synchronous(struct block_device *bdev)
+static inline bool bdev_read_synchronous(struct block_device *bdev)
+{
+	return bdev->bd_disk->queue->limits.features & BLK_FEAT_READ_SYNCHRONOUS;
+}
+
+static inline bool bdev_write_synchronous(struct block_device *bdev)
 {
-	return bdev->bd_disk->queue->limits.features & BLK_FEAT_SYNCHRONOUS;
+	return bdev->bd_disk->queue->limits.features & BLK_FEAT_WRITE_SYNCHRONOUS;
 }
 
 static inline bool bdev_stable_writes(struct block_device *bdev)
diff --git a/include/linux/swap.h b/include/linux/swap.h
index ca533b478c21..6719c6006894 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_READ_SYNCHRONOUS_IO = (1 << 12),	/* synchronous read IO is efficient */
+	SWP_WRITE_SYNCHRONOUS_IO = (1 << 13),	/* synchronous write 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 2366578015ad..93eb6c29e52c 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4278,7 +4278,7 @@ 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_READ_SYNCHRONOUS_IO) &&
 		    __swap_count(entry) == 1) {
 			/* skip swapcache */
 			folio = alloc_swap_folio(vmf);
@@ -4413,7 +4413,7 @@ vm_fault_t do_swap_page(struct vm_fault *vmf)
 		goto out_nomap;
 	}
 
-	/* allocated large folios for SWP_SYNCHRONOUS_IO */
+	/* allocated large folios for SWP_READ_SYNCHRONOUS_IO */
 	if (folio_test_large(folio) && !folio_test_swapcache(folio)) {
 		unsigned long nr = folio_nr_pages(folio);
 		unsigned long folio_start = ALIGN_DOWN(vmf->address, nr * PAGE_SIZE);
diff --git a/mm/page_io.c b/mm/page_io.c
index 78bc88acee79..ffcc9dbbe61e 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -455,10 +455,10 @@ void __swap_writepage(struct folio *folio, struct writeback_control *wbc)
 		swap_writepage_fs(folio, wbc);
 	/*
 	 * ->flags can be updated non-atomicially (scan_swap_map_slots),
-	 * but that will never affect SWP_SYNCHRONOUS_IO, so the data_race
+	 * but that will never affect SWP_WRITE_SYNCHRONOUS_IO, so the data_race
 	 * is safe.
 	 */
-	else if (data_race(sis->flags & SWP_SYNCHRONOUS_IO))
+	else if (data_race(sis->flags & SWP_WRITE_SYNCHRONOUS_IO))
 		swap_writepage_bdev_sync(folio, wbc, sis);
 	else
 		swap_writepage_bdev_async(folio, wbc, sis);
@@ -592,7 +592,7 @@ 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_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 0cded32414a1..84f6fc86be2b 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3460,8 +3460,11 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
 	if (si->bdev && bdev_stable_writes(si->bdev))
 		si->flags |= SWP_STABLE_WRITES;
 
-	if (si->bdev && bdev_synchronous(si->bdev))
-		si->flags |= SWP_SYNCHRONOUS_IO;
+	if (si->bdev && bdev_read_synchronous(si->bdev))
+		si->flags |= SWP_READ_SYNCHRONOUS_IO;
+
+	if (si->bdev && bdev_write_synchronous(si->bdev))
+		si->flags |= SWP_WRITE_SYNCHRONOUS_IO;
 
 	if (si->bdev && bdev_nonrot(si->bdev)) {
 		si->flags |= SWP_SOLIDSTATE;
-- 
2.45.2
Re: [PATCH] mm: Split BLK_FEAT_SYNCHRONOUS and SWP_SYNCHRONOUS_IO into separate read and write flags
Posted by Christoph Hellwig 1 month, 2 weeks ago 
On Fri, Oct 11, 2024 at 05:11:33PM +0800, Qun-Wei Lin wrote:
> This patch splits the BLK_FEAT_SYNCHRONOUS feature flag into two
> separate flags: BLK_FEAT_READ_SYNCHRONOUS and
> BLK_FEAT_WRITE_SYNCHRONOUS. Similarly, the SWP_SYNCHRONOUS_IO flag is
> split into SWP_READ_SYNCHRONOUS_IO and SWP_WRITE_SYNCHRONOUS_IO.
> 
> These changes are motivated by the need to better accommodate certain
> swap devices that support synchronous read operations but asynchronous write
> operations.
> 
> The existing BLK_FEAT_SYNCHRONOUS and SWP_SYNCHRONOUS_IO flags are not
> sufficient for these devices, as they enforce synchronous behavior for
> both read and write operations.

You're still failing to provide a user.  Without that it is dead in
the water from the very beginning.

Patchew 2.1-devel-b67e4c2

© 2016 - 2024 Red Hat, Inc.