+ mpage-clean-up-do_mpage_readpage.patch added to mm-new branch

+ mpage-clean-up-do_mpage_readpage.patch added to mm-new branch

[Andrew Morton]

The patch titled
     Subject: mpage: clean up do_mpage_readpage()
has been added to the -mm mm-new branch.  Its filename is
     mpage-clean-up-do_mpage_readpage.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mpage-clean-up-do_mpage_readpage.patch

This patch will later appear in the mm-new branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
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fixup patches in mm-new.

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------------------------------------------------------
From: Chi Zhiling <chizhiling@kylinos.cn>
Subject: mpage: clean up do_mpage_readpage()
Date: Tue, 12 Aug 2025 15:22:24 +0800

Replace two loop iterations with direct calculations.  The variable
nblocks now represents the number of avalid blocks we can obtain from
map_bh.  no functional change.

Link: https://lkml.kernel.org/r/20250812072225.181798-2-chizhiling@163.com
Signed-off-by: Chi Zhiling <chizhiling@kylinos.cn>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Namjae Jeon <linkinjeon@kernel.org>
Cc: Sungjong Seo <sj1557.seo@samsung.com>
Cc: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 fs/mpage.c |   42 +++++++++++++++++-------------------------
 1 file changed, 17 insertions(+), 25 deletions(-)

--- a/fs/mpage.c~mpage-clean-up-do_mpage_readpage
+++ a/fs/mpage.c
@@ -158,7 +158,6 @@ static struct bio *do_mpage_readpage(str
 	struct buffer_head *map_bh = &args->map_bh;
 	sector_t block_in_file;
 	sector_t last_block;
-	sector_t last_block_in_file;
 	sector_t first_block;
 	unsigned page_block;
 	unsigned first_hole = blocks_per_folio;
@@ -180,9 +179,8 @@ static struct bio *do_mpage_readpage(str
 
 	block_in_file = folio_pos(folio) >> blkbits;
 	last_block = block_in_file + ((args->nr_pages * PAGE_SIZE) >> blkbits);
-	last_block_in_file = (i_size_read(inode) + blocksize - 1) >> blkbits;
-	if (last_block > last_block_in_file)
-		last_block = last_block_in_file;
+	last_block = min_t(sector_t, last_block,
+			   (i_size_read(inode) + blocksize - 1) >> blkbits);
 	page_block = 0;
 
 	/*
@@ -193,19 +191,15 @@ static struct bio *do_mpage_readpage(str
 			block_in_file > args->first_logical_block &&
 			block_in_file < (args->first_logical_block + nblocks)) {
 		unsigned map_offset = block_in_file - args->first_logical_block;
-		unsigned last = nblocks - map_offset;
 
 		first_block = map_bh->b_blocknr + map_offset;
-		for (relative_block = 0; ; relative_block++) {
-			if (relative_block == last) {
-				clear_buffer_mapped(map_bh);
-				break;
-			}
-			if (page_block == blocks_per_folio)
-				break;
-			page_block++;
-			block_in_file++;
-		}
+		nblocks -= map_offset;
+		if (nblocks > blocks_per_folio - page_block)
+			nblocks = blocks_per_folio - page_block;
+		else
+			clear_buffer_mapped(map_bh);
+		page_block += nblocks;
+		block_in_file += nblocks;
 		bdev = map_bh->b_bdev;
 	}
 
@@ -243,7 +237,7 @@ static struct bio *do_mpage_readpage(str
 			map_buffer_to_folio(folio, map_bh, page_block);
 			goto confused;
 		}
-	
+
 		if (first_hole != blocks_per_folio)
 			goto confused;		/* hole -> non-hole */
 
@@ -252,16 +246,14 @@ static struct bio *do_mpage_readpage(str
 			first_block = map_bh->b_blocknr;
 		else if (first_block + page_block != map_bh->b_blocknr)
 			goto confused;
+
 		nblocks = map_bh->b_size >> blkbits;
-		for (relative_block = 0; ; relative_block++) {
-			if (relative_block == nblocks) {
-				clear_buffer_mapped(map_bh);
-				break;
-			} else if (page_block == blocks_per_folio)
-				break;
-			page_block++;
-			block_in_file++;
-		}
+		if (nblocks > blocks_per_folio - page_block)
+			nblocks = blocks_per_folio - page_block;
+		else
+			clear_buffer_mapped(map_bh);
+		page_block += nblocks;
+		block_in_file += nblocks;
 		bdev = map_bh->b_bdev;
 	}
 
_

Patches currently in -mm which might be from chizhiling@kylinos.cn are

mm-filemap-do-not-use-is_partially_uptodate-for-entire-folio.patch
mm-filemap-skip-non-uptodate-folio-if-there-are-available-folios.patch
mpage-terminate-read-ahead-on-read-error.patch
mpage-clean-up-do_mpage_readpage.patch
mpage-convert-do_mpage_readpage-to-return-int-type.patch