[PATCH 11/13] ext4: allow encryption with a block size larger than the page size

[Baokun Li <libaokun@linux.alibaba.com>]

ext4 refuses encryption when the block size is larger than the page
size, both at mount time and on a mounted filesystem, and refuses to
load an existing encrypted inode.  The checks exist because such a
block size needs folios that cover a whole block, while file contents
were encrypted page by page in the fs-layer path, which cannot handle a
folio that covers several data units.

Since commit 5acc6f649a68 ("fscrypt: Always use blk-crypto for contents
on block-based filesystems") file contents are always encrypted through
blk-crypto, and after the adaptations in the preceding patches, both
inline encryption hardware and blk-crypto-fallback support data units
larger than a page, so the checks can be removed.

Encrypted filesystems still keep their folio order at s_min_folio_order;
allowing large folios needs additional work and will be enabled later.

Performance:

Hardware: 96-core machine, 3.84T NVMe, 512G memory
Filesystem: ext4, encryption on the fallback path

Buffered sequential 1M writes and reads (1G, fsync) in MiB/s; medians
of 3 runs.

  job          4k plain      4k enc    32k plain    32k enc    4k->32k
  ---------    --------    --------    ---------    -------    -------
  seqwrite         1981        1044         2062       1399       +34%
  seqread          1139         931         1791       1793       +93%

Signed-off-by: Baokun Li <libaokun@linux.alibaba.com>
---
 fs/ext4/crypto.c |  9 ---------
 fs/ext4/inode.c  |  6 ------
 fs/ext4/super.c  | 25 +++----------------------
 3 files changed, 3 insertions(+), 37 deletions(-)

diff --git a/fs/ext4/crypto.c b/fs/ext4/crypto.c
index 318b2eaea741..1a0fccb084ef 100644
--- a/fs/ext4/crypto.c
+++ b/fs/ext4/crypto.c
@@ -156,15 +156,6 @@ static int ext4_set_context(struct inode *inode, const void *ctx, size_t len,
 	if (ext4_test_inode_flag(inode, EXT4_INODE_DAX))
 		return -EOPNOTSUPP;
 
-	/*
-	 * Encryption is not supported when the block size is larger
-	 * than the page size.  This is rejected at mount time by
-	 * ext4_check_large_folio(), and this check here is for the case
-	 * when the 'encrypt' feature is enabled on a mounted filesystem.
-	 */
-	if (inode->i_sb->s_blocksize > PAGE_SIZE)
-		return -EOPNOTSUPP;
-
 	res = ext4_convert_inline_data(inode);
 	if (res)
 		return res;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 31248fef8bce..26f0f9714f03 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -5671,12 +5671,6 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
 		ret = -EFSCORRUPTED;
 		goto bad_inode;
 	}
-	if (IS_ENCRYPTED(inode) && sb->s_blocksize > PAGE_SIZE) {
-		ext4_error_inode(inode, function, line, 0,
-				 "encrypted inode with block size larger than page size");
-		ret = -EFSCORRUPTED;
-		goto bad_inode;
-	}
 
 	ext4_set_inode_mapping_order(inode);
 
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index bca0dc87d0b7..9cd5b7445a27 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -5116,30 +5116,13 @@ static void ext4_set_max_mapping_order(struct super_block *sb)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 
-	if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA)
+	if (test_opt(sb, DATA_FLAGS) == EXT4_MOUNT_JOURNAL_DATA ||
+	    ext4_has_feature_encrypt(sb))
 		sbi->s_max_folio_order = sbi->s_min_folio_order;
 	else
 		sbi->s_max_folio_order = EXT4_MAX_PAGECACHE_ORDER(sb);
 }
 
-static int ext4_check_large_folio(struct super_block *sb)
-{
-	const char *err_str = NULL;
-
-	if (ext4_has_feature_encrypt(sb))
-		err_str = "encrypt";
-
-	if (!err_str) {
-		ext4_set_max_mapping_order(sb);
-	} 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)
 {
@@ -5418,9 +5401,7 @@ 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;
+	ext4_set_max_mapping_order(sb);
 
 	err = ext4_encoding_init(sb, es);
 	if (err)
-- 
2.43.7