ext4: add checks for large folio incompatibilities when BS > PS

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

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

This patch adds s_max_folio_order, initialized during mount according to
filesystem features and mount options. If s_max_folio_order is 0, large
folios are disabled.

With this in place, ext4_set_inode_mapping_order() can be simplified by
checking s_max_folio_order, avoiding redundant checks.

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Ojaswin Mujoo <ojaswin@linux.ibm.com>
Message-ID: <20251121090654.631996-24-libaokun@huaweicloud.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

1 files changed, 10 insertions, 28 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a566469ae07a..7510fce3d0f0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5148,41 +5148,23 @@ error:
 	return -EFSCORRUPTED;
 }
 
-static bool ext4_should_enable_large_folio(struct inode *inode)
+void ext4_set_inode_mapping_order(struct inode *inode)
 {
 	struct super_block *sb = inode->i_sb;
+	u16 min_order, max_order;
 
-	if (!S_ISREG(inode->i_mode))
-		return false;
-	if (ext4_has_feature_encrypt(sb))
-		return false;
-
-	return true;
-}
-
-/*
- * Limit the maximum folio order to 2048 blocks to prevent overestimation
- * of reserve handle credits during the folio writeback in environments
- * where the PAGE_SIZE exceeds 4KB.
- */
-#define EXT4_MAX_PAGECACHE_ORDER(i)		\
-		umin(MAX_PAGECACHE_ORDER, (11 + (i)->i_blkbits - PAGE_SHIFT))
-void ext4_set_inode_mapping_order(struct inode *inode)
-{
-	u32 max_order;
+	max_order = EXT4_SB(sb)->s_max_folio_order;
+	if (!max_order)
+		return;
 
-	if (!ext4_should_enable_large_folio(inode))
+	min_order = EXT4_SB(sb)->s_min_folio_order;
+	if (!min_order && !S_ISREG(inode->i_mode))
 		return;
 
-	if (test_opt(inode->i_sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA ||
-	    ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA))
-		max_order = EXT4_SB(inode->i_sb)->s_min_folio_order;
-	else
-		max_order = EXT4_MAX_PAGECACHE_ORDER(inode);
+	if (ext4_test_inode_flag(inode, EXT4_INODE_JOURNAL_DATA))
+		max_order = min_order;
 
-	mapping_set_folio_order_range(inode->i_mapping,
-				      EXT4_SB(inode->i_sb)->s_min_folio_order,
-				      max_order);
+	mapping_set_folio_order_range(inode->i_mapping, min_order, max_order);
 }
 
 struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,