[PATCH 6.1] erofs: reliably distinguish block based and fscache mode

[PATCH 6.1] erofs: reliably distinguish block based and fscache mode

[Xiangyu Chen]

From: Christian Brauner <brauner@kernel.org>

commit 7af2ae1b1531feab5d38ec9c8f472dc6cceb4606 upstream.

When erofs_kill_sb() is called in block dev based mode, s_bdev may not
have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled,
it will be mistaken for fscache mode, and then attempt to free an anon_dev
that has never been allocated, triggering the following warning:

============================================
ida_free called for id=0 which is not allocated.
WARNING: CPU: 14 PID: 926 at lib/idr.c:525 ida_free+0x134/0x140
Modules linked in:
CPU: 14 PID: 926 Comm: mount Not tainted 6.9.0-rc3-dirty #630
RIP: 0010:ida_free+0x134/0x140
Call Trace:
 <TASK>
 erofs_kill_sb+0x81/0x90
 deactivate_locked_super+0x35/0x80
 get_tree_bdev+0x136/0x1e0
 vfs_get_tree+0x2c/0xf0
 do_new_mount+0x190/0x2f0
 [...]
============================================

Now when erofs_kill_sb() is called, erofs_sb_info must have been
initialised, so use sbi->fsid to distinguish between the two modes.

Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Link: https://lore.kernel.org/r/20240419123611.947084-3-libaokun1@huawei.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com>
---
 fs/erofs/super.c | 8 ++------
 1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/fs/erofs/super.c b/fs/erofs/super.c
index 25cd66e487e8..5bb194558da5 100644
--- a/fs/erofs/super.c
+++ b/fs/erofs/super.c
@@ -892,7 +892,7 @@ static int erofs_init_fs_context(struct fs_context *fc)
  */
 static void erofs_kill_sb(struct super_block *sb)
 {
-	struct erofs_sb_info *sbi;
+	struct erofs_sb_info *sbi = EROFS_SB(sb);
 
 	WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
 
@@ -902,15 +902,11 @@ static void erofs_kill_sb(struct super_block *sb)
 		return;
 	}
 
-	if (erofs_is_fscache_mode(sb))
+	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
 		kill_anon_super(sb);
 	else
 		kill_block_super(sb);
 
-	sbi = EROFS_SB(sb);
-	if (!sbi)
-		return;
-
 	erofs_free_dev_context(sbi->devs);
 	fs_put_dax(sbi->dax_dev, NULL);
 	erofs_fscache_unregister_fs(sb);
-- 
2.25.1

Re: [PATCH 6.1] erofs: reliably distinguish block based and fscache mode

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

The upstream commit SHA1 provided is correct: 7af2ae1b1531feab5d38ec9c8f472dc6cceb4606

WARNING: Author mismatch between patch and upstream commit:
Backport author: Xiangyu Chen <xiangyu.chen@eng.windriver.com>
Commit author: Christian Brauner <brauner@kernel.org>


Status in newer kernel trees:
6.12.y | Present (exact SHA1)
6.11.y | Present (exact SHA1)
6.6.y | Present (different SHA1: f9b877a7ee31)
6.1.y | Not found

Note: The patch differs from the upstream commit:
---
1:  7af2ae1b1531f ! 1:  bc9478262d424 erofs: reliably distinguish block based and fscache mode
    @@ Metadata
      ## Commit message ##
         erofs: reliably distinguish block based and fscache mode
     
    +    commit 7af2ae1b1531feab5d38ec9c8f472dc6cceb4606 upstream.
    +
         When erofs_kill_sb() is called in block dev based mode, s_bdev may not
         have been initialised yet, and if CONFIG_EROFS_FS_ONDEMAND is enabled,
         it will be mistaken for fscache mode, and then attempt to free an anon_dev
    @@ Commit message
         Reviewed-by: Chao Yu <chao@kernel.org>
         Link: https://lore.kernel.org/r/20240419123611.947084-3-libaokun1@huawei.com
         Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
    +    Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
    +    Signed-off-by: Xiangyu Chen <xiangyu.chen@windriver.com>
     
      ## fs/erofs/super.c ##
     @@ fs/erofs/super.c: static int erofs_init_fs_context(struct fs_context *fc)
    - 
    +  */
      static void erofs_kill_sb(struct super_block *sb)
      {
     -	struct erofs_sb_info *sbi;
     +	struct erofs_sb_info *sbi = EROFS_SB(sb);
      
    + 	WARN_ON(sb->s_magic != EROFS_SUPER_MAGIC);
    + 
    +@@ fs/erofs/super.c: static void erofs_kill_sb(struct super_block *sb)
    + 		return;
    + 	}
    + 
     -	if (erofs_is_fscache_mode(sb))
     +	if (IS_ENABLED(CONFIG_EROFS_FS_ONDEMAND) && sbi->fsid)
      		kill_anon_super(sb);
Using kernel version 6.1 as base for comparison
Comparing backport with upstream commit using range-diff...
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.1.y        |  Success    |  Success   |