[PATCH v3] erofs: fix blksize < PAGE_SIZE for file-backed mounts

[Hongzhen Luo]

Adjust sb->s_blocksize{,_bits} directly for file-backed
mounts when the fs block size is smaller than PAGE_SIZE.

Previously, EROFS used sb_set_blocksize(), which caused
a panic if bdev-backed mounts is not used.

Fixes: fb176750266a ("erofs: add file-backed mount support")
Signed-off-by: Hongzhen Luo <hongzhen at linux.alibaba.com>
---
v3: Fix trivial typos.
v2: https://lore.kernel.org/linux-erofs/20241015064007.3449582-1-hongzhen@linux.alibaba.com/
v1: https://lore.kernel.org/linux-erofs/20241015033601.3206952-1-hongzhen@linux.alibaba.com/
---
 fs/erofs/super.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 320d586c3896..ca45dfb17d7c 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -631,7 +631,11 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
 			errorfc(fc, "unsupported blksize for fscache mode");
 			return -EINVAL;
 		}
-		if (!sb_set_blocksize(sb, 1 << sbi->blkszbits)) {
+
+		if (erofs_is_fileio_mode(sbi)) {
+			sb->s_blocksize = (1 << sbi->blkszbits);
+			sb->s_blocksize_bits = sbi->blkszbits;
+		} else if (!sb_set_blocksize(sb, 1 << sbi->blkszbits)) {
 			errorfc(fc, "failed to set erofs blksize");
 			return -EINVAL;
 		}
-- 
2.43.5