linux-kernel - [PATCH v2 24/24] ext4: enable block size larger than page size

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Message-Id: <20251107144249.435029-25-libaokun@huaweicloud.com>
Date: Fri,  7 Nov 2025 22:42:49 +0800
From: libaokun@...weicloud.com
To: linux-ext4@...r.kernel.org
Cc: tytso@....edu,
	adilger.kernel@...ger.ca,
	jack@...e.cz,
	linux-kernel@...r.kernel.org,
	kernel@...kajraghav.com,
	mcgrof@...nel.org,
	ebiggers@...nel.org,
	willy@...radead.org,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	chengzhihao1@...wei.com,
	libaokun1@...wei.com,
	libaokun@...weicloud.com
Subject: [PATCH v2 24/24] ext4: enable block size larger than page size

From: Baokun Li <libaokun1@...wei.com>

Since block device (See commit 3c20917120ce ("block/bdev: enable large
folio support for large logical block sizes")) and page cache (See commit
ab95d23bab220ef8 ("filemap: allocate mapping_min_order folios in the page
cache")) has the ability to have a minimum order when allocating folio,
and ext4 has supported large folio in commit 7ac67301e82f ("ext4: enable
large folio for regular file"), now add support for block_size > PAGE_SIZE
in ext4.

set_blocksize() -> bdev_validate_blocksize() already validates the block
size, so ext4_load_super() does not need to perform additional checks.

Here we only need to add the FS_LBS bit to fs_flags.

In addition, allocation failures for large folios may trigger warn_alloc()
warnings. Therefore, as with XFS, mark this feature as experimental.

Signed-off-by: Baokun Li <libaokun1@...wei.com>
Reviewed-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/ext4/super.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 6735152dd219..1fbbae5a0426 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5074,6 +5074,9 @@ static int ext4_check_large_folio(struct super_block *sb)
 		return -EINVAL;
 	}

+	if (sb->s_blocksize > PAGE_SIZE)
+		ext4_msg(sb, KERN_NOTICE, "EXPERIMENTAL bs(%lu) > ps(%lu) enabled.",
+			 sb->s_blocksize, PAGE_SIZE);
 	return 0;
 }

@@ -7453,7 +7456,8 @@ static struct file_system_type ext4_fs_type = {
 	.init_fs_context	= ext4_init_fs_context,
 	.parameters		= ext4_param_specs,
 	.kill_sb		= ext4_kill_sb,
-	.fs_flags		= FS_REQUIRES_DEV | FS_ALLOW_IDMAP | FS_MGTIME,
+	.fs_flags		= FS_REQUIRES_DEV | FS_ALLOW_IDMAP | FS_MGTIME |
+				  FS_LBS,
 };
 MODULE_ALIAS_FS("ext4");

-- 
2.46.1