Re: [RFC V5] md/raid5: optimize Scattered Address Space and Thread-Level Parallelism to improve RAID5 performance

On Wed, 5 Jun 2024 10:03:27 -0700
Paul E Luse [off-list ref] wrote:

On Thu,  6 Jun 2024 00:53:42 +0800
Shushu Yi [off-list ref] wrote:

Awesome thanks!  FYi for everyone on V4 I ran both data integrity (no
issues) and perf tests and performance looked compelling.  I'm
re-running the baseline now (as I had to skip one patch because of the
conflict), once that's done tomrorow I will re-run V5 and publish
resutls for everyone.

-Paul

Performance results look very good.  Christoph I know you showed
interest in V1 of this patch, I'm think these numbers might peak your
interest again.

https://photos.app.goo.gl/5v2bWeYBsKWu6FHA8

quoted

Optimize scattered address space. Achieves significant improvements
in both throughput and latency.

Maximize thread-level parallelism and reduce CPU suspension time
caused by lock contention. Achieve increased overall storage
throughput by 89.4% and decrease the 99.99th percentile I/O latency
by 85.4% on a system with four PCIe 4.0 SSDs. (Set the iodepth to 32
and employ libaio. Configure the I/O size as 4 KB with sequential
write and 16 threads. In RAID5 consist of 2+1 1TB Samsung 980Pro
SSDs, throughput went from 5218MB/s to 9884MB/s.)

Note: Publish this work as a paper and provide the URL
(https://www.hotstorage.org/2022/camera-ready/hotstorage22-5/pdf/
hotstorage22-5.pdf).

Co-developed-by: Yiming Xu <redacted>
Signed-off-by: Yiming Xu <redacted>
Signed-off-by: Shushu Yi <redacted>
Tested-by: Paul Luse <redacted>
---
V1 -> V2: Cleaned up coding style and divided into 2 patches
(HemiRAID and ScalaRAID corresponding to the paper mentioned
above). ScalaRAID equipped every counter with a counter lock and
employ our D-Block. HemiRAID increased the number of stripe locks
to 128 V2 -> V3: Adjusted the language used in the subject and
changelog. Since patch 1/2 in V2 cannot be used independently and
does not encompass all of our work, it has been merged into a
single patch. V3 -> V4: Fixed incorrect sending address and
changelog format. V4 -> V5: Resolved a adress conflict on main
(commit f0e729af2eb6bee9eb58c4df1087f14ebaefe26b (HEAD -> md-6.10,
tag: md-6.10-20240502, origin/md-6.10)).

 drivers/md/md-bitmap.c | 197
++++++++++++++++++++++++++++++----------- drivers/md/md-bitmap.h |
12 ++- drivers/md/raid5.h     |   7 +-
 3 files changed, 155 insertions(+), 61 deletions(-)

diff --git a/drivers/md/md-bitmap.c b/drivers/md/md-bitmap.c
index 0a2d37eb38ef..f08d3228b305 100644
--- a/drivers/md/md-bitmap.c
+++ b/drivers/md/md-bitmap.c

@@ -47,10 +47,12 @@ static inline char *bmname(struct bitmap

*bitmap)
  * if we find our page, we increment the page's refcount so that it
stays
  * allocated while we're using it
  */
-static int md_bitmap_checkpage(struct bitmap_counts *bitmap,
-			       unsigned long page, int create, int
no_hijack) -__releases(bitmap->lock)
-__acquires(bitmap->lock)
+static int md_bitmap_checkpage(struct bitmap_counts *bitmap,
unsigned long page,
+			       int create, int no_hijack,
spinlock_t *bmclock, int locktype) +__releases(bmclock)
+__acquires(bmclock)
+__releases(bitmap->mlock)
+__acquires(bitmap->mlock)
 {
 	unsigned char *mappage;
 

@@ -65,8 +67,10 @@ __acquires(bitmap->lock)
 		return -ENOENT;
 
 	/* this page has not been allocated yet */
-
-	spin_unlock_irq(&bitmap->lock);
+	if (locktype)
+		spin_unlock_irq(bmclock);
+	else
+		write_unlock_irq(&bitmap->mlock);
 	/* It is possible that this is being called inside a
 	 * prepare_to_wait/finish_wait loop from

raid5c:make_request().
 	 * In general it is not permitted to sleep in that context
as it @@ -81,7 +85,11 @@ __acquires(bitmap->lock)
 	 */
 	sched_annotate_sleep();
 	mappage = kzalloc(PAGE_SIZE, GFP_NOIO);
-	spin_lock_irq(&bitmap->lock);
+
+	if (locktype)
+		spin_lock_irq(bmclock);
+	else
+		write_lock_irq(&bitmap->mlock);
 
 	if (mappage == NULL) {
 		pr_debug("md/bitmap: map page allocation failed,
hijacking\n"); @@ -399,7 +407,7 @@ static int read_file_page(struct
file *file, unsigned long index, }
 
 	wait_event(bitmap->write_wait,
-		   atomic_read(&bitmap->pending_writes)==0);
+		   atomic_read(&bitmap->pending_writes) == 0);
 	if (test_bit(BITMAP_WRITE_ERROR, &bitmap->flags))
 		ret = -EIO;
 out:

@@ -458,7 +466,7 @@ static void md_bitmap_wait_writes(struct bitmap

*bitmap) {
 	if (bitmap->storage.file)
 		wait_event(bitmap->write_wait,
-
atomic_read(&bitmap->pending_writes)==0);
+			   atomic_read(&bitmap->pending_writes) ==
0); else
 		/* Note that we ignore the return value.  The
writes
 		 * might have failed, but that would just mean that

@@ -1248,16 +1256,28 @@ void md_bitmap_write_all(struct bitmap

*bitmap) static void md_bitmap_count_page(struct bitmap_counts
*bitmap, sector_t offset, int inc)
 {
-	sector_t chunk = offset >> bitmap->chunkshift;
-	unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
+	sector_t blockno = offset >> (PAGE_SHIFT - SECTOR_SHIFT);
+	sector_t totblocks = bitmap->chunks << (bitmap->chunkshift
- (PAGE_SHIFT - SECTOR_SHIFT));
+	unsigned long bits = totblocks ? fls((totblocks - 1)) : 0;
+	unsigned long mask = ULONG_MAX << bits | ~(ULONG_MAX <<
+					(bits - (bitmap->chunkshift
+ SECTOR_SHIFT - PAGE_SHIFT)));
+	unsigned long cntid = blockno & mask;
+	unsigned long page = cntid >> PAGE_COUNTER_SHIFT;
+
 	bitmap->bp[page].count += inc;
 	md_bitmap_checkfree(bitmap, page);
 }
 
 static void md_bitmap_set_pending(struct bitmap_counts *bitmap,
sector_t offset) {
-	sector_t chunk = offset >> bitmap->chunkshift;
-	unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
+	sector_t blockno = offset >> (PAGE_SHIFT - SECTOR_SHIFT);
+	sector_t totblocks = bitmap->chunks << (bitmap->chunkshift
- (PAGE_SHIFT - SECTOR_SHIFT));
+	unsigned long bits = totblocks ? fls((totblocks - 1)) : 0;
+	unsigned long mask = ULONG_MAX << bits | ~(ULONG_MAX <<
+					(bits - (bitmap->chunkshift
+ SECTOR_SHIFT - PAGE_SHIFT)));
+	unsigned long cntid = blockno & mask;
+	unsigned long page = cntid >> PAGE_COUNTER_SHIFT;
+
 	struct bitmap_page *bp = &bitmap->bp[page];
 
 	if (!bp->pending)

@@ -1266,7 +1286,7 @@ static void md_bitmap_set_pending(struct

bitmap_counts *bitmap, sector_t offset) 
 static bitmap_counter_t *md_bitmap_get_counter(struct bitmap_counts
*bitmap, sector_t offset, sector_t *blocks,
-					       int create);
+					       int create,
spinlock_t *bmclock, int locktype); 
 static void mddev_set_timeout(struct mddev *mddev, unsigned long
timeout, bool force)

@@ -1349,7 +1369,7 @@ void md_bitmap_daemon_work(struct mddev

*mddev)
 	 * decrement and handle accordingly.
 	 */
 	counts = &bitmap->counts;
-	spin_lock_irq(&counts->lock);
+	write_lock_irq(&counts->mlock);
 	nextpage = 0;
 	for (j = 0; j < counts->chunks; j++) {
 		bitmap_counter_t *bmc;

@@ -1364,7 +1384,7 @@ void md_bitmap_daemon_work(struct mddev

*mddev) counts->bp[j >> PAGE_COUNTER_SHIFT].pending
= 0; }
 
-		bmc = md_bitmap_get_counter(counts, block, &blocks,
0);
+		bmc = md_bitmap_get_counter(counts, block, &blocks,
0, 0, 0); if (!bmc) {
 			j |= PAGE_COUNTER_MASK;
 			continue;

@@ -1380,7 +1400,7 @@ void md_bitmap_daemon_work(struct mddev

*mddev) bitmap->allclean = 0;
 		}
 	}
-	spin_unlock_irq(&counts->lock);
+	write_unlock_irq(&counts->mlock);
 
 	md_bitmap_wait_writes(bitmap);
 	/* Now start writeout on any page in NEEDWRITE that isn't
DIRTY. @@ -1413,17 +1433,25 @@ void md_bitmap_daemon_work(struct
mddev *mddev) 
 static bitmap_counter_t *md_bitmap_get_counter(struct bitmap_counts
*bitmap, sector_t offset, sector_t *blocks,
-					       int create)
-__releases(bitmap->lock)
-__acquires(bitmap->lock)
+					       int create,
spinlock_t *bmclock, int locktype) +__releases(bmclock)
+__acquires(bmclock)
+__releases(bitmap->mlock)
+__acquires(bitmap->mlock)
 {
 	/* If 'create', we might release the lock and reclaim it.
 	 * The lock must have been taken with interrupts enabled.
 	 * If !create, we don't release the lock.
 	 */
-	sector_t chunk = offset >> bitmap->chunkshift;
-	unsigned long page = chunk >> PAGE_COUNTER_SHIFT;
-	unsigned long pageoff = (chunk & PAGE_COUNTER_MASK) <<
COUNTER_BYTE_SHIFT;
+	sector_t blockno = offset >> (PAGE_SHIFT - SECTOR_SHIFT);
+	sector_t totblocks = bitmap->chunks << (bitmap->chunkshift
- (PAGE_SHIFT - SECTOR_SHIFT));
+	unsigned long bits = totblocks ? fls((totblocks - 1)) : 0;
+	unsigned long mask = ULONG_MAX << bits | ~(ULONG_MAX <<
+					(bits - (bitmap->chunkshift
+ SECTOR_SHIFT - PAGE_SHIFT)));
+	unsigned long cntid = blockno & mask;
+	unsigned long page = cntid >> PAGE_COUNTER_SHIFT;
+	unsigned long pageoff = (cntid & PAGE_COUNTER_MASK) <<
COUNTER_BYTE_SHIFT; +
 	sector_t csize = ((sector_t)1) << bitmap->chunkshift;
 	int err;
 

@@ -1436,7 +1464,7 @@ __acquires(bitmap->lock)
 		*blocks = csize - (offset & (csize - 1));
 		return NULL;
 	}
-	err = md_bitmap_checkpage(bitmap, page, create, 0);
+	err = md_bitmap_checkpage(bitmap, page, create, 0, bmclock,

1); 
 	if (bitmap->bp[page].hijacked ||
 	    bitmap->bp[page].map == NULL)

@@ -1461,6 +1489,28 @@ __acquires(bitmap->lock)
 			&(bitmap->bp[page].map[pageoff]);
 }
 
+/* set-association */
+static spinlock_t *md_bitmap_get_bmclock(struct bitmap_counts

*bitmap, sector_t offset); +
+static spinlock_t *md_bitmap_get_bmclock(struct bitmap_counts
*bitmap, sector_t offset) +{
+	sector_t blockno = offset >> (PAGE_SHIFT - SECTOR_SHIFT);
+	sector_t totblocks = bitmap->chunks << (bitmap->chunkshift
- (PAGE_SHIFT - SECTOR_SHIFT));
+	unsigned long bitscnt = totblocks ? fls((totblocks - 1)) :
0;
+	unsigned long maskcnt = ULONG_MAX << bitscnt | ~(ULONG_MAX
<< (bitscnt -
+					(bitmap->chunkshift +
SECTOR_SHIFT - PAGE_SHIFT)));
+	unsigned long cntid = blockno & maskcnt;
+
+	unsigned long totcnts = bitmap->chunks;
+	unsigned long bitslock = totcnts ? fls((totcnts - 1)) : 0;
+	unsigned long masklock = ULONG_MAX << bitslock |
~(ULONG_MAX <<
+					(bitslock -
BITMAP_COUNTER_LOCK_RATIO_SHIFT));
+	unsigned long lockid = cntid & masklock;
+
+	spinlock_t *bmclock = &(bitmap->bmclocks[lockid]);
+	return bmclock;
+}
+
 int md_bitmap_startwrite(struct bitmap *bitmap, sector_t offset,
unsigned long sectors, int behind) {
 	if (!bitmap)

@@ -1480,11 +1530,15 @@ int md_bitmap_startwrite(struct bitmap

*bitmap, sector_t offset, unsigned long s while (sectors) {
 		sector_t blocks;
 		bitmap_counter_t *bmc;
+		spinlock_t *bmclock;
 
-		spin_lock_irq(&bitmap->counts.lock);
-		bmc = md_bitmap_get_counter(&bitmap->counts,
offset, &blocks, 1);
+		bmclock = md_bitmap_get_bmclock(&bitmap->counts,
offset);
+		read_lock(&bitmap->counts.mlock);
+		spin_lock_irq(bmclock);
+		bmc = md_bitmap_get_counter(&bitmap->counts,
offset, &blocks, 1, bmclock, 1); if (!bmc) {
-			spin_unlock_irq(&bitmap->counts.lock);
+			spin_unlock_irq(bmclock);
+			read_unlock(&bitmap->counts.mlock);
 			return 0;
 		}
 

@@ -1496,7 +1550,8 @@ int md_bitmap_startwrite(struct bitmap

*bitmap, sector_t offset, unsigned long s */
 			prepare_to_wait(&bitmap->overflow_wait,
&__wait, TASK_UNINTERRUPTIBLE);
-			spin_unlock_irq(&bitmap->counts.lock);
+			spin_unlock_irq(bmclock);
+			read_unlock(&bitmap->counts.mlock);
 			schedule();
 			finish_wait(&bitmap->overflow_wait,
&__wait); continue;

@@ -1513,7 +1568,8 @@ int md_bitmap_startwrite(struct bitmap

*bitmap, sector_t offset, unsigned long s 
 		(*bmc)++;
 
-		spin_unlock_irq(&bitmap->counts.lock);
+		spin_unlock_irq(bmclock);
+		read_unlock(&bitmap->counts.mlock);
 
 		offset += blocks;
 		if (sectors > blocks)

@@ -1542,11 +1598,15 @@ void md_bitmap_endwrite(struct bitmap

*bitmap, sector_t offset, sector_t blocks;
 		unsigned long flags;
 		bitmap_counter_t *bmc;
+		spinlock_t *bmclock;
 
-		spin_lock_irqsave(&bitmap->counts.lock, flags);
-		bmc = md_bitmap_get_counter(&bitmap->counts,
offset, &blocks, 0);
+		bmclock = md_bitmap_get_bmclock(&bitmap->counts,
offset);
+		read_lock(&bitmap->counts.mlock);
+		spin_lock_irqsave(bmclock, flags);
+		bmc = md_bitmap_get_counter(&bitmap->counts,
offset, &blocks, 0, bmclock, 1); if (!bmc) {
-
spin_unlock_irqrestore(&bitmap->counts.lock, flags);
+			spin_unlock_irqrestore(bmclock, flags);
+			read_unlock(&bitmap->counts.mlock);
 			return;
 		}
 

@@ -1568,7 +1628,8 @@ void md_bitmap_endwrite(struct bitmap *bitmap,

sector_t offset, md_bitmap_set_pending(&bitmap->counts, offset);
 			bitmap->allclean = 0;
 		}
-		spin_unlock_irqrestore(&bitmap->counts.lock,
flags);
+		spin_unlock_irqrestore(bmclock, flags);
+		read_unlock(&bitmap->counts.mlock);
 		offset += blocks;
 		if (sectors > blocks)
 			sectors -= blocks;

@@ -1582,13 +1643,16 @@ static int __bitmap_start_sync(struct bitmap

*bitmap, sector_t offset, sector_t int degraded)
 {
 	bitmap_counter_t *bmc;
+	spinlock_t *bmclock;
 	int rv;
 	if (bitmap == NULL) {/* FIXME or bitmap set as 'failed' */
 		*blocks = 1024;
 		return 1; /* always resync if no bitmap */
 	}
-	spin_lock_irq(&bitmap->counts.lock);
-	bmc = md_bitmap_get_counter(&bitmap->counts, offset,
blocks, 0);
+	bmclock = md_bitmap_get_bmclock(&bitmap->counts, offset);
+	read_lock(&bitmap->counts.mlock);
+	spin_lock_irq(bmclock);
+	bmc = md_bitmap_get_counter(&bitmap->counts, offset,
blocks, 0, bmclock, 1); rv = 0;
 	if (bmc) {
 		/* locked */

@@ -1602,7 +1666,8 @@ static int __bitmap_start_sync(struct bitmap

*bitmap, sector_t offset, sector_t }
 		}
 	}
-	spin_unlock_irq(&bitmap->counts.lock);
+	spin_unlock_irq(bmclock);
+	read_unlock(&bitmap->counts.mlock);
 	return rv;
 }
 

@@ -1634,13 +1699,16 @@ void md_bitmap_end_sync(struct bitmap

*bitmap, sector_t offset, sector_t *blocks {
 	bitmap_counter_t *bmc;
 	unsigned long flags;
+	spinlock_t *bmclock;
 
 	if (bitmap == NULL) {
 		*blocks = 1024;
 		return;
 	}
-	spin_lock_irqsave(&bitmap->counts.lock, flags);
-	bmc = md_bitmap_get_counter(&bitmap->counts, offset,
blocks, 0);
+	bmclock = md_bitmap_get_bmclock(&bitmap->counts, offset);
+	read_lock(&bitmap->counts.mlock);
+	spin_lock_irqsave(bmclock, flags);
+	bmc = md_bitmap_get_counter(&bitmap->counts, offset,
blocks, 0, bmclock, 1); if (bmc == NULL)
 		goto unlock;
 	/* locked */

@@ -1657,7 +1725,8 @@ void md_bitmap_end_sync(struct bitmap *bitmap,

sector_t offset, sector_t *blocks }
 	}
  unlock:
-	spin_unlock_irqrestore(&bitmap->counts.lock, flags);
+	spin_unlock_irqrestore(bmclock, flags);
+	read_unlock(&bitmap->counts.mlock);
 }
 EXPORT_SYMBOL(md_bitmap_end_sync);
 

@@ -1738,10 +1807,15 @@ static void md_bitmap_set_memory_bits(struct

bitmap *bitmap, sector_t offset, in 
 	sector_t secs;
 	bitmap_counter_t *bmc;
-	spin_lock_irq(&bitmap->counts.lock);
-	bmc = md_bitmap_get_counter(&bitmap->counts, offset, &secs,
1);
+	spinlock_t *bmclock;
+
+	bmclock = md_bitmap_get_bmclock(&bitmap->counts, offset);
+	read_lock(&bitmap->counts.mlock);
+	spin_lock_irq(bmclock);
+	bmc = md_bitmap_get_counter(&bitmap->counts, offset, &secs,
1, bmclock, 1); if (!bmc) {
-		spin_unlock_irq(&bitmap->counts.lock);
+		spin_unlock_irq(bmclock);
+		read_unlock(&bitmap->counts.mlock);
 		return;
 	}
 	if (!*bmc) {

@@ -1752,7 +1826,8 @@ static void md_bitmap_set_memory_bits(struct

bitmap *bitmap, sector_t offset, in }
 	if (needed)
 		*bmc |= NEEDED_MASK;
-	spin_unlock_irq(&bitmap->counts.lock);
+	spin_unlock_irq(bmclock);
+	read_unlock(&bitmap->counts.mlock);
 }
 
 /* dirty the memory and file bits for bitmap chunks "s" to "e" */

@@ -1806,6 +1881,7 @@ void md_bitmap_free(struct bitmap *bitmap)
 {
 	unsigned long k, pages;
 	struct bitmap_page *bp;
+	spinlock_t *bmclocks;
 
 	if (!bitmap) /* there was no bitmap */
 		return;

@@ -1826,6 +1902,7 @@ void md_bitmap_free(struct bitmap *bitmap)
 
 	bp = bitmap->counts.bp;
 	pages = bitmap->counts.pages;
+	bmclocks = bitmap->counts.bmclocks;
 
 	/* free all allocated memory */
 

@@ -1834,6 +1911,7 @@ void md_bitmap_free(struct bitmap *bitmap)
 			if (bp[k].map && !bp[k].hijacked)
 				kfree(bp[k].map);
 	kfree(bp);
+	kfree(bmclocks);
 	kfree(bitmap);
 }
 EXPORT_SYMBOL(md_bitmap_free);

@@ -1900,7 +1978,9 @@ struct bitmap *md_bitmap_create(struct mddev

*mddev, int slot) if (!bitmap)
 		return ERR_PTR(-ENOMEM);
 
-	spin_lock_init(&bitmap->counts.lock);
+	/* initialize metadata lock */
+	rwlock_init(&bitmap->counts.mlock);
+
 	atomic_set(&bitmap->pending_writes, 0);
 	init_waitqueue_head(&bitmap->write_wait);
 	init_waitqueue_head(&bitmap->overflow_wait);

@@ -2143,6 +2223,8 @@ int md_bitmap_resize(struct bitmap *bitmap,

sector_t blocks, int ret = 0;
 	long pages;
 	struct bitmap_page *new_bp;
+	spinlock_t *new_bmclocks;
+	int num_bmclocks, i;
 
 	if (bitmap->storage.file && !init) {
 		pr_info("md: cannot resize file-based bitmap\n");

@@ -2211,7 +2293,7 @@ int md_bitmap_resize(struct bitmap *bitmap,

sector_t blocks, memcpy(page_address(store.sb_page),
 		       page_address(bitmap->storage.sb_page),
 		       sizeof(bitmap_super_t));
-	spin_lock_irq(&bitmap->counts.lock);
+	write_lock_irq(&bitmap->counts.mlock);
 	md_bitmap_file_unmap(&bitmap->storage);
 	bitmap->storage = store;
 

@@ -2227,18 +2309,28 @@ int md_bitmap_resize(struct bitmap *bitmap,

sector_t blocks, blocks = min(old_counts.chunks <<
old_counts.chunkshift, chunks << chunkshift);
 
+	/* initialize bmc locks */
+	num_bmclocks = DIV_ROUND_UP(chunks,
BITMAP_COUNTER_LOCK_RATIO); +
+	new_bmclocks = kvcalloc(num_bmclocks,
sizeof(*new_bmclocks), GFP_KERNEL);
+	bitmap->counts.bmclocks = new_bmclocks;
+	for (i = 0; i < num_bmclocks; ++i) {
+		spinlock_t *bmclock =
&(bitmap->counts.bmclocks)[i]; +
+		spin_lock_init(bmclock);
+	}
+
 	/* For cluster raid, need to pre-allocate bitmap */
 	if (mddev_is_clustered(bitmap->mddev)) {
 		unsigned long page;
 		for (page = 0; page < pages; page++) {
-			ret = md_bitmap_checkpage(&bitmap->counts,
page, 1, 1);
+			ret = md_bitmap_checkpage(&bitmap->counts,
page, 1, 1, 0, 0); if (ret) {
 				unsigned long k;
 
 				/* deallocate the page memory */
-				for (k = 0; k < page; k++) {
+				for (k = 0; k < page; k++)
 					kfree(new_bp[k].map);
-				}
 				kfree(new_bp);
 
 				/* restore some fields from
old_counts */ @@ -2261,11 +2353,12 @@ int md_bitmap_resize(struct
bitmap *bitmap, sector_t blocks, bitmap_counter_t *bmc_old,
*bmc_new; int set;
 
-		bmc_old = md_bitmap_get_counter(&old_counts, block,
&old_blocks, 0);
+		bmc_old = md_bitmap_get_counter(&old_counts, block,
&old_blocks, 0, 0, 0); set = bmc_old && NEEDED(*bmc_old);
 
 		if (set) {
-			bmc_new =
md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1);
+			bmc_new =
md_bitmap_get_counter(&bitmap->counts, block, &new_blocks,
+
		1, 0, 0); if (bmc_new) {
 				if (*bmc_new == 0) {
 					/* need to set on-disk bits
too. */ @@ -2301,7 +2394,7 @@ int md_bitmap_resize(struct bitmap
*bitmap, sector_t blocks, int i;
 		while (block < (chunks << chunkshift)) {
 			bitmap_counter_t *bmc;
-			bmc =
md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1);
+			bmc =
md_bitmap_get_counter(&bitmap->counts, block, &new_blocks, 1, 0,
0); if (bmc) { /* new space.  It needs to be
resynced, so
 				 * we set NEEDED_MASK.

@@ -2317,7 +2410,7 @@ int md_bitmap_resize(struct bitmap *bitmap,

sector_t blocks, for (i = 0; i < bitmap->storage.file_pages; i++)
 			set_page_attr(bitmap, i,
BITMAP_PAGE_DIRTY); }
-	spin_unlock_irq(&bitmap->counts.lock);
+	write_unlock_irq(&bitmap->counts.mlock);
 
 	if (!init) {
 		md_bitmap_unplug(bitmap);

diff --git a/drivers/md/md-bitmap.h b/drivers/md/md-bitmap.h
index bb9eb418780a..1b9c36bb73ed 100644
--- a/drivers/md/md-bitmap.h
+++ b/drivers/md/md-bitmap.h

@@ -2,7 +2,9 @@
 /*
  * bitmap.h: Copyright (C) Peter T. Breuer (ptb@ot.uc3m.es) 2003
  *
- * additions: Copyright (C) 2003-2004, Paul Clements, SteelEye

Technology, Inc.
+ * additions:
+ *		Copyright (C) 2003-2004, Paul Clements, SteelEye
Technology, Inc.
+ *		Copyright (C) 2022-2023, Shushu Yi
(firnyee@gmail.com) */
 #ifndef BITMAP_H
 #define BITMAP_H 1

@@ -103,6 +105,9 @@ typedef __u16 bitmap_counter_t;
 #define PAGE_COUNTER_MASK  (PAGE_COUNTER_RATIO - 1)
 
 #define BITMAP_BLOCK_SHIFT 9
+/* how many counters share the same bmclock? */
+#define BITMAP_COUNTER_LOCK_RATIO_SHIFT 0
+#define BITMAP_COUNTER_LOCK_RATIO (1 <<

BITMAP_COUNTER_LOCK_RATIO_SHIFT) 
 #endif
 

@@ -116,7 +121,7 @@ typedef __u16 bitmap_counter_t;
 enum bitmap_state {
 	BITMAP_STALE	   = 1,  /* the bitmap file is out of

date or had -EIO */ BITMAP_WRITE_ERROR = 2, /* A write error has
occurred */
-	BITMAP_HOSTENDIAN  =15,
+	BITMAP_HOSTENDIAN  = 15,
 };
 
 /* the superblock at the front of the bitmap file -- little endian
*/ @@ -180,7 +185,8 @@ struct bitmap_page {
 struct bitmap {
 
 	struct bitmap_counts {
-		spinlock_t lock;
+		rwlock_t mlock;				/*
lock for metadata */
+		spinlock_t *bmclocks;		/* locks for
bmc */ struct bitmap_page *bp;
 		unsigned long pages;		/* total number
of pages
 						 * in the bitmap */

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index 9b5a7dc3f2a0..818ce86f4b2c 100644
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h

@@ -496,12 +496,7 @@ struct disk_info {
 #define HASH_MASK		(NR_HASH - 1)
 #define MAX_STRIPE_BATCH	8
 
-/* NOTE NR_STRIPE_HASH_LOCKS must remain below 64.
- * This is because we sometimes take all the spinlocks
- * and creating that much locking depth can cause
- * problems.
- */

I'm no expert in this code but I assume it is the case that the reduced
lock contention is the reason this is no longer a concern? How did you
come up with the number 128?

quoted

-#define NR_STRIPE_HASH_LOCKS 8
+#define NR_STRIPE_HASH_LOCKS 128
 #define STRIPE_HASH_LOCKS_MASK (NR_STRIPE_HASH_LOCKS - 1)
 
 struct r5worker {