Patch "dax: make sure inodes are flushed before destroy cache" has been added to the 5.17-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    dax: make sure inodes are flushed before destroy cache

to the 5.17-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     dax-make-sure-inodes-are-flushed-before-destroy-cach.patch
and it can be found in the queue-5.17 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 70f93eab8f1f74ea0306bc94cf7e096694eab706
Author: Tong Zhang <ztong0001@xxxxxxxxx>
Date:   Fri Feb 11 23:11:11 2022 -0800

    dax: make sure inodes are flushed before destroy cache
    
    [ Upstream commit a7e8de822e0b1979f08767c751f6c8a9c1d4ad86 ]
    
    A bug can be triggered by following command
    
    $ modprobe nd_pmem && modprobe -r nd_pmem
    
    [   10.060014] BUG dax_cache (Not tainted): Objects remaining in dax_cache on __kmem_cache_shutdown()
    [   10.060938] Slab 0x0000000085b729ac objects=9 used=1 fp=0x000000004f5ae469 flags=0x200000000010200(slab|head|node)
    [   10.062433] Call Trace:
    [   10.062673]  dump_stack_lvl+0x34/0x44
    [   10.062865]  slab_err+0x90/0xd0
    [   10.063619]  __kmem_cache_shutdown+0x13b/0x2f0
    [   10.063848]  kmem_cache_destroy+0x4a/0x110
    [   10.064058]  __x64_sys_delete_module+0x265/0x300
    
    This is caused by dax_fs_exit() not flushing inodes before destroy cache.
    To fix this issue, call rcu_barrier() before destroy cache.
    
    Signed-off-by: Tong Zhang <ztong0001@xxxxxxxxx>
    Reviewed-by: Ira Weiny <ira.weiny@xxxxxxxxx>
    Reviewed-by: Christoph Hellwig <hch@xxxxxx>
    Link: https://lore.kernel.org/r/20220212071111.148575-1-ztong0001@xxxxxxxxx
    Fixes: 7b6be8444e0f ("dax: refactor dax-fs into a generic provider of 'struct dax_device' instances")
    Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/dax/super.c b/drivers/dax/super.c
index e3029389d809..6bd565fe2e63 100644
--- a/drivers/dax/super.c
+++ b/drivers/dax/super.c
@@ -476,6 +476,7 @@ static int dax_fs_init(void)
 static void dax_fs_exit(void)
 {
 	kern_unmount(dax_mnt);
+	rcu_barrier();
 	kmem_cache_destroy(dax_cache);
 }