erofs: avoid hardcoded blocksize for subpage block support

As the first step of converting hardcoded blocksize to that specified in
on-disk superblock, convert all call sites of hardcoded blocksize to
sb->s_blocksize except for:

1) use sbi->blkszbits instead of sb->s_blocksize in
erofs_superblock_csum_verify() since sb->s_blocksize has not been
updated with the on-disk blocksize yet when the function is called.

2) use inode->i_blkbits instead of sb->s_blocksize in erofs_bread(),
since the inode operated on may be an anonymous inode in fscache mode.
Currently the anonymous inode is allocated from an anonymous mount
maintained in erofs, while in the near future we may allocate anonymous
inodes from a generic API directly and thus have no access to the
anonymous inode's i_sb.  Thus we keep the block size in i_blkbits for
anonymous inodes in fscache mode.

Be noted that this patch only gets rid of the hardcoded blocksize, in
preparation for actually setting the on-disk block size in the following
patch.  The hard limit of constraining the block size to PAGE_SIZE still
exists until the next patch.

Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Yue Hu <huyue2@coolpad.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20230313135309.75269-2-jefflexu@linux.alibaba.com
[ Gao Xiang: fold a patch to fix incorrect truncated offsets. ]
Link: https://lore.kernel.org/r/20230413035734.15457-1-zhujia.zj@bytedance.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

1 files changed, 16 insertions, 11 deletions

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 19b1ae79cec4..4303b4e69e55 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -52,18 +52,21 @@ void _erofs_info(struct super_block *sb, const char *function,
 
 static int erofs_superblock_csum_verify(struct super_block *sb, void *sbdata)
 {
+	size_t len = 1 << EROFS_SB(sb)->blkszbits;
 	struct erofs_super_block *dsb;
 	u32 expected_crc, crc;
 
-	dsb = kmemdup(sbdata + EROFS_SUPER_OFFSET,
-		      EROFS_BLKSIZ - EROFS_SUPER_OFFSET, GFP_KERNEL);
+	if (len > EROFS_SUPER_OFFSET)
+		len -= EROFS_SUPER_OFFSET;
+
+	dsb = kmemdup(sbdata + EROFS_SUPER_OFFSET, len, GFP_KERNEL);
 	if (!dsb)
 		return -ENOMEM;
 
 	expected_crc = le32_to_cpu(dsb->checksum);
 	dsb->checksum = 0;
 	/* to allow for x86 boot sectors and other oddities. */
-	crc = crc32c(~0, dsb, EROFS_BLKSIZ - EROFS_SUPER_OFFSET);
+	crc = crc32c(~0, dsb, len);
 	kfree(dsb);
 
 	if (crc != expected_crc) {
@@ -132,11 +135,11 @@ static void *erofs_read_metadata(struct super_block *sb, struct erofs_buf *buf,
 	int len, i, cnt;
 
 	*offset = round_up(*offset, 4);
-	ptr = erofs_read_metabuf(buf, sb, erofs_blknr(*offset), EROFS_KMAP);
+	ptr = erofs_read_metabuf(buf, sb, erofs_blknr(sb, *offset), EROFS_KMAP);
 	if (IS_ERR(ptr))
 		return ptr;
 
-	len = le16_to_cpu(*(__le16 *)&ptr[erofs_blkoff(*offset)]);
+	len = le16_to_cpu(*(__le16 *)&ptr[erofs_blkoff(sb, *offset)]);
 	if (!len)
 		len = U16_MAX + 1;
 	buffer = kmalloc(len, GFP_KERNEL);
@@ -146,14 +149,15 @@ static void *erofs_read_metadata(struct super_block *sb, struct erofs_buf *buf,
 	*lengthp = len;
 
 	for (i = 0; i < len; i += cnt) {
-		cnt = min(EROFS_BLKSIZ - (int)erofs_blkoff(*offset), len - i);
-		ptr = erofs_read_metabuf(buf, sb, erofs_blknr(*offset),
+		cnt = min_t(int, sb->s_blocksize - erofs_blkoff(sb, *offset),
+			    len - i);
+		ptr = erofs_read_metabuf(buf, sb, erofs_blknr(sb, *offset),
 					 EROFS_KMAP);
 		if (IS_ERR(ptr)) {
 			kfree(buffer);
 			return ptr;
 		}
-		memcpy(buffer + i, ptr + erofs_blkoff(*offset), cnt);
+		memcpy(buffer + i, ptr + erofs_blkoff(sb, *offset), cnt);
 		*offset += cnt;
 	}
 	return buffer;
@@ -228,10 +232,10 @@ static int erofs_init_device(struct erofs_buf *buf, struct super_block *sb,
 	struct block_device *bdev;
 	void *ptr;
 
-	ptr = erofs_read_metabuf(buf, sb, erofs_blknr(*pos), EROFS_KMAP);
+	ptr = erofs_read_metabuf(buf, sb, erofs_blknr(sb, *pos), EROFS_KMAP);
 	if (IS_ERR(ptr))
 		return PTR_ERR(ptr);
-	dis = ptr + erofs_blkoff(*pos);
+	dis = ptr + erofs_blkoff(sb, *pos);
 
 	if (!dif->path) {
 		if (!dis->tag[0]) {
@@ -733,6 +737,7 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 	sbi->domain_id = ctx->domain_id;
 	ctx->domain_id = NULL;
 
+	sbi->blkszbits = PAGE_SHIFT;
 	if (erofs_is_fscache_mode(sb)) {
 		sb->s_blocksize = EROFS_BLKSIZ;
 		sb->s_blocksize_bits = LOG_BLOCK_SIZE;
@@ -1060,7 +1065,7 @@ static int erofs_statfs(struct dentry *dentry, struct kstatfs *buf)
 		id = huge_encode_dev(sb->s_bdev->bd_dev);
 
 	buf->f_type = sb->s_magic;
-	buf->f_bsize = EROFS_BLKSIZ;
+	buf->f_bsize = sb->s_blocksize;
 	buf->f_blocks = sbi->total_blocks;
 	buf->f_bfree = buf->f_bavail = 0;