linux-kernel - [PATCH 24/25] ext4: add checks for large folio incompatibilities when BS

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Message-Id: <20251025032221.2905818-25-libaokun@huaweicloud.com>
Date: Sat, 25 Oct 2025 11:22:20 +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,
	linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org,
	yi.zhang@...wei.com,
	yangerkun@...wei.com,
	chengzhihao1@...wei.com,
	libaokun1@...wei.com,
	libaokun@...weicloud.com
Subject: [PATCH 24/25] ext4: add checks for large folio incompatibilities when BS > PS

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

Supporting a block size greater than the page size (BS > PS) requires
support for large folios. However, several features (e.g., verity, encrypt)
and mount options (e.g., data=journal) do not yet support large folios.

To prevent conflicts, this patch adds checks at mount time to prohibit
these features and options from being used when BS > PS. Since the data
mode cannot be changed on remount, there is no need to check on remount.

A new mount flag, EXT4_MF_LARGE_FOLIO, is introduced. This flag is set
after the checks pass, indicating that the filesystem has no features or
mount options incompatible with large folios. Subsequent checks can simply
test for this flag to avoid redundant verifications.

Signed-off-by: Baokun Li <libaokun1@...wei.com>
Reviewed-by: Zhang Yi <yi.zhang@...wei.com>
---
 fs/ext4/ext4.h  |  3 ++-
 fs/ext4/inode.c | 10 ++++------
 fs/ext4/super.c | 26 ++++++++++++++++++++++++++
 3 files changed, 32 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 8223ed29b343..f1163deb0812 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1859,7 +1859,8 @@ static inline int ext4_get_resgid(struct ext4_super_block *es)
 enum {
 	EXT4_MF_MNTDIR_SAMPLED,
 	EXT4_MF_FC_INELIGIBLE,	/* Fast commit ineligible */
-	EXT4_MF_JOURNAL_DESTROY	/* Journal is in process of destroying */
+	EXT4_MF_JOURNAL_DESTROY,/* Journal is in process of destroying */
+	EXT4_MF_LARGE_FOLIO,	/* large folio is support */
 };
 
 static inline void ext4_set_mount_flag(struct super_block *sb, int bit)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b3fa29923a1d..04f9380d4211 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5143,14 +5143,12 @@ static bool ext4_should_enable_large_folio(struct inode *inode)
 {
 	struct super_block *sb = inode->i_sb;
 
-	if (!S_ISREG(inode->i_mode))
-		return false;
-	if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA ||
-	    ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA))
+	if (!ext4_test_mount_flag(sb, EXT4_MF_LARGE_FOLIO))
 		return false;
-	if (ext4_has_feature_verity(sb))
+
+	if (!S_ISREG(inode->i_mode))
 		return false;
-	if (ext4_has_feature_encrypt(sb))
+	if (ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA))
 		return false;
 
 	return true;
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7338c708ea1d..fdc006a973aa 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5034,6 +5034,28 @@ static const char *ext4_has_journal_option(struct super_block *sb)
 	return NULL;
 }
 
+static int ext4_check_large_folio(struct super_block *sb)
+{
+	const char *err_str = NULL;
+
+	if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)
+		err_str = "data=journal";
+	else if (ext4_has_feature_verity(sb))
+		err_str = "verity";
+	else if (ext4_has_feature_encrypt(sb))
+		err_str = "encrypt";
+
+	if (!err_str) {
+		ext4_set_mount_flag(sb, EXT4_MF_LARGE_FOLIO);
+	} else if (sb->s_blocksize > PAGE_SIZE) {
+		ext4_msg(sb, KERN_ERR, "bs(%lu) > ps(%lu) unsupported for %s",
+			 sb->s_blocksize, PAGE_SIZE, err_str);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int ext4_load_super(struct super_block *sb, ext4_fsblk_t *lsb,
 			   int silent)
 {
@@ -5310,6 +5332,10 @@ static int __ext4_fill_super(struct fs_context *fc, struct super_block *sb)
 
 	ext4_apply_options(fc, sb);
 
+	err = ext4_check_large_folio(sb);
+	if (err < 0)
+		goto failed_mount;
+
 	err = ext4_encoding_init(sb, es);
 	if (err)
 		goto failed_mount;
-- 
2.46.1