[Intel-gfx] NPE in i915_gemfs_init

[Heiner Kallweit]

On 14.07.2019 14:46, Chris Wilson wrote:
> Quoting Heiner Kallweit (2019-07-14 13:39:15)
>> On 14.07.2019 14:34, Chris Wilson wrote:
>>> Quoting Heiner Kallweit (2019-07-13 12:12:56)
>>>> I debugged a little bit and remount_fs isn't set in sb->s_op.
>>>> The following at least avoids the NPE, not sure whether it's the correct fix.
>>>
>>> I take it you don't have CONFIG_TMPFS set?
>>>
>> This option is set:
>>
>> [root at zotac linux-next]# grep TMPFS .config
>> CONFIG_DEVTMPFS=y
>> CONFIG_DEVTMPFS_MOUNT=y
>> CONFIG_TMPFS=y
>> CONFIG_TMPFS_POSIX_ACL=y
>> CONFIG_TMPFS_XATTR=y
> 
> Now that's weird, as
> 
> static const struct super_operations shmem_ops = {
>         .alloc_inode    = shmem_alloc_inode,
>         .free_inode     = shmem_free_in_core_inode,
>         .destroy_inode  = shmem_destroy_inode,
> #ifdef CONFIG_TMPFS
>         .statfs         = shmem_statfs,
>         .remount_fs     = shmem_remount_fs,
>         .show_options   = shmem_show_options,
> #endif
>         .evict_inode    = shmem_evict_inode,
>         .drop_inode     = generic_delete_inode,
>         .put_super      = shmem_put_super,
> #ifdef CONFIG_TRANSPARENT_HUGE_PAGECACHE
>         .nr_cached_objects      = shmem_unused_huge_count,
>         .free_cached_objects    = shmem_unused_huge_scan,
> #endif
> };
> 
> the only way it should be unset was if !CONFIG_TMPFS.
> 
> Hmm, we even select TMPFS so it should never be absent.
> 
> So the question is what mount did we get if it was not a shmemfs one?
> -Chris
> 
I think that's the reason:
144df3b288c4 ("vfs: Convert ramfs, shmem, tmpfs, devtmpfs, rootfs to use the new mount API")

@@ -3736,7 +3849,6 @@ static const struct super_operations shmem_ops = {
 	.destroy_inode	= shmem_destroy_inode,
 #ifdef CONFIG_TMPFS
 	.statfs		= shmem_statfs,
-	.remount_fs	= shmem_remount_fs,
 	.show_options	= shmem_show_options,
 #endif
 	.evict_inode	= shmem_evict_inode,

Most likely this "new mount API" impacts your code.