linux-kernel - [PATCH] md/md-llbitmap: Use DIV_ROUND_UP_SECTOR

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Message-Id: <20250910-llbitmap-fix-64-div-for-32-bit-v1-1-453a5c8e3e00@kernel.org>
Date: Wed, 10 Sep 2025 13:47:26 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Jens Axboe <axboe@...nel.dk>, Song Liu <song@...nel.org>, 
 Yu Kuai <yukuai3@...wei.com>, Li Nan <linan122@...wei.com>
Cc: linux-raid@...r.kernel.org, linux-block@...r.kernel.org, 
 linux-kernel@...r.kernel.org, Nathan Chancellor <nathan@...nel.org>
Subject: [PATCH] md/md-llbitmap: Use DIV_ROUND_UP_SECTOR_T

When building for 32-bit platforms, there are several link (if builtin)
or modpost (if a module) errors due to dividends of type 'sector_t' in
DIV_ROUND_UP:

  arm-linux-gnueabi-ld: drivers/md/md-llbitmap.o: in function `llbitmap_resize':
  drivers/md/md-llbitmap.c:1017:(.text+0xae8): undefined reference to `__aeabi_uldivmod'
  arm-linux-gnueabi-ld: drivers/md/md-llbitmap.c:1020:(.text+0xb10): undefined reference to `__aeabi_uldivmod'
  arm-linux-gnueabi-ld: drivers/md/md-llbitmap.o: in function `llbitmap_end_discard':
  drivers/md/md-llbitmap.c:1114:(.text+0xf14): undefined reference to `__aeabi_uldivmod'
  arm-linux-gnueabi-ld: drivers/md/md-llbitmap.o: in function `llbitmap_start_discard':
  drivers/md/md-llbitmap.c:1097:(.text+0x1808): undefined reference to `__aeabi_uldivmod'
  arm-linux-gnueabi-ld: drivers/md/md-llbitmap.o: in function `llbitmap_read_sb':
  drivers/md/md-llbitmap.c:867:(.text+0x2080): undefined reference to `__aeabi_uldivmod'
  arm-linux-gnueabi-ld: drivers/md/md-llbitmap.o:drivers/md/md-llbitmap.c:895: more undefined references to `__aeabi_uldivmod' follow

Use DIV_ROUND_UP_SECTOR_T instead of DIV_ROUND_UP, which exists to
handle this exact situation.

Fixes: 5ab829f1971d ("md/md-llbitmap: introduce new lockless bitmap")
Signed-off-by: Nathan Chancellor <nathan@...nel.org>
---
 drivers/md/md-llbitmap.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/md/md-llbitmap.c b/drivers/md/md-llbitmap.c
index 3337d5c7e7e5..1eb434306162 100644
--- a/drivers/md/md-llbitmap.c
+++ b/drivers/md/md-llbitmap.c
@@ -781,7 +781,7 @@ static int llbitmap_init(struct llbitmap *llbitmap)
 
 	while (chunks > space) {
 		chunksize = chunksize << 1;
-		chunks = DIV_ROUND_UP(blocks, chunksize);
+		chunks = DIV_ROUND_UP_SECTOR_T(blocks, chunksize);
 	}
 
 	llbitmap->barrier_idle = DEFAULT_BARRIER_IDLE;
@@ -864,8 +864,8 @@ static int llbitmap_read_sb(struct llbitmap *llbitmap)
 		goto out_put_page;
 	}
 
-	if (chunksize < DIV_ROUND_UP(mddev->resync_max_sectors,
-				     mddev->bitmap_info.space << SECTOR_SHIFT)) {
+	if (chunksize < DIV_ROUND_UP_SECTOR_T(mddev->resync_max_sectors,
+					      mddev->bitmap_info.space << SECTOR_SHIFT)) {
 		pr_err("md/llbitmap: %s: chunksize too small %lu < %llu / %lu",
 		       mdname(mddev), chunksize, mddev->resync_max_sectors,
 		       mddev->bitmap_info.space);
@@ -892,7 +892,7 @@ static int llbitmap_read_sb(struct llbitmap *llbitmap)
 
 	llbitmap->barrier_idle = DEFAULT_BARRIER_IDLE;
 	llbitmap->chunksize = chunksize;
-	llbitmap->chunks = DIV_ROUND_UP(mddev->resync_max_sectors, chunksize);
+	llbitmap->chunks = DIV_ROUND_UP_SECTOR_T(mddev->resync_max_sectors, chunksize);
 	llbitmap->chunkshift = ffz(~chunksize);
 	ret = llbitmap_cache_pages(llbitmap);
 
@@ -1014,10 +1014,10 @@ static int llbitmap_resize(struct mddev *mddev, sector_t blocks, int chunksize)
 		chunksize = llbitmap->chunksize;
 
 	/* If there is enough space, leave the chunksize unchanged. */
-	chunks = DIV_ROUND_UP(blocks, chunksize);
+	chunks = DIV_ROUND_UP_SECTOR_T(blocks, chunksize);
 	while (chunks > mddev->bitmap_info.space << SECTOR_SHIFT) {
 		chunksize = chunksize << 1;
-		chunks = DIV_ROUND_UP(blocks, chunksize);
+		chunks = DIV_ROUND_UP_SECTOR_T(blocks, chunksize);
 	}
 
 	llbitmap->chunkshift = ffz(~chunksize);
@@ -1094,7 +1094,7 @@ static void llbitmap_start_discard(struct mddev *mddev, sector_t offset,
 				   unsigned long sectors)
 {
 	struct llbitmap *llbitmap = mddev->bitmap;
-	unsigned long start = DIV_ROUND_UP(offset, llbitmap->chunksize);
+	unsigned long start = DIV_ROUND_UP_SECTOR_T(offset, llbitmap->chunksize);
 	unsigned long end = (offset + sectors - 1) >> llbitmap->chunkshift;
 	int page_start = (start + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
 	int page_end = (end + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
@@ -1111,7 +1111,7 @@ static void llbitmap_end_discard(struct mddev *mddev, sector_t offset,
 				 unsigned long sectors)
 {
 	struct llbitmap *llbitmap = mddev->bitmap;
-	unsigned long start = DIV_ROUND_UP(offset, llbitmap->chunksize);
+	unsigned long start = DIV_ROUND_UP_SECTOR_T(offset, llbitmap->chunksize);
 	unsigned long end = (offset + sectors - 1) >> llbitmap->chunkshift;
 	int page_start = (start + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;
 	int page_end = (end + BITMAP_DATA_OFFSET) >> PAGE_SHIFT;

---
base-commit: 5ab829f1971dc99f2aac10846c378e67fc875abc
change-id: 20250910-llbitmap-fix-64-div-for-32-bit-9885a1d28834

Best regards,
--  
Nathan Chancellor <nathan@...nel.org>