ext4: enable block size larger than page size

Since block device (See commit 3c20917 ("block/bdev: enable large
folio support for large logical block sizes")) and page cache (See commit
ab95d23 ("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 7ac6730 ("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, block sizes larger than the page size are currently supported
only when CONFIG_TRANSPARENT_HUGEPAGE is enabled. To make this explicit,
a blocksize_gt_pagesize entry has been added under /sys/fs/ext4/feature/,
indicating whether bs > ps is supported. This allows mke2fs to check the
interface and determine whether a warning should be issued when formatting
a filesystem with block size larger than the page size.

Suggested-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Pankaj Raghav <p.raghav@samsung.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Message-ID: <20251121090654.631996-25-libaokun@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: LiBaokun96

fs/ext4/super.c

@@ -7453,7 +7453,8 @@ 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");
 

fs/ext4/sysfs.c

@@ -332,6 +332,9 @@ EXT4_ATTR_FEATURE(fast_commit);
 #if IS_ENABLED(CONFIG_UNICODE) && defined(CONFIG_FS_ENCRYPTION)
 EXT4_ATTR_FEATURE(encrypted_casefold);
 #endif
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+EXT4_ATTR_FEATURE(blocksize_gt_pagesize);
+#endif
 
 static struct attribute *ext4_feat_attrs[] = {
 	ATTR_LIST(lazy_itable_init),
@@ -351,6 +354,9 @@ static struct attribute *ext4_feat_attrs[] = {
 	ATTR_LIST(fast_commit),
 #if IS_ENABLED(CONFIG_UNICODE) && defined(CONFIG_FS_ENCRYPTION)
 	ATTR_LIST(encrypted_casefold),
+#endif
+#ifdef CONFIG_TRANSPARENT_HUGEPAGE
+	ATTR_LIST(blocksize_gt_pagesize),
 #endif
 	NULL,
 };