Sheng Yong reported [1] that Android APEX images didn't work with
[PATCH v2] of upstream commit 072a7c7cdbea ("erofs: don't bother
with s_stack_depth increasing for now") because "EROFS-formatted APEX
file images can be stored within an EROFS-formatted Android system
partition."
In response, I sent a quick fat-fingered [PATCH v3] to address the
report. Unfortunately, the updated condition was incorrect:
if (erofs_is_fileio_mode(sbi)) {
- sb->s_stack_depth =
- file_inode(sbi->dif0.file)->i_sb->s_stack_depth + 1;
- if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
- erofs_err(sb, "maximum fs stacking depth exceeded");
+ inode = file_inode(sbi->dif0.file);
+ if ((inode->i_sb->s_op == &erofs_sops && !sb->s_bdev) ||
+ inode->i_sb->s_stack_depth) {
The condition `!sb->s_bdev` is always true for all file-backed EROFS
mounts, making the check effectively a no-op.
The real fix tested and confirmed by Sheng Yong [2] at that time was
[PATCH v3 RESEND], which correctly ensures the following EROFS^2 setup
works:
EROFS (on a block device) + EROFS (file-backed mount)
But sadly I screwed it up again by upstreaming the outdated [PATCH v3]
and I should be blamed.
This patch applies the same logic as the delta between the upstream
[PATCH v3] and the real fix [PATCH v3 RESEND].
Reported-by: Sheng Yong <[email protected]>
Closes:
https://lore.kernel.org/r/[email protected] [1]
Fixes: 072a7c7cdbea ("erofs: don't bother with s_stack_depth increasing for
now")
Link: https://lore.kernel.org/r/[email protected]
[2]
Signed-off-by: Gao Xiang <[email protected]>
---
Hi Linus,
As suggested by Amir, I send out the patch to fix the broken fix.
If possible, could you help apply this patch directly?
If you perfer another pull request I will do later too after a sleep,
but I guess I will just repeat my stupid mistake again in the pull
request and the tag message.
Thanks,
Gao Xiang
fs/erofs/super.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index e93264034b5d..5136cda5972a 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -655,7 +655,8 @@ static int erofs_fc_fill_super(struct super_block *sb,
struct fs_context *fc)
*/
if (erofs_is_fileio_mode(sbi)) {
inode = file_inode(sbi->dif0.file);
- if ((inode->i_sb->s_op == &erofs_sops && !sb->s_bdev) ||
+ if ((inode->i_sb->s_op == &erofs_sops &&
+ !inode->i_sb->s_bdev) ||
inode->i_sb->s_stack_depth) {
erofs_err(sb, "file-backed mounts cannot be
applied to stacked fses");
return -ENOTBLK;
--
2.43.5
