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SubjectRe: [Intel-gfx] [linux-next] mm/i915: i915_gemfs_init() NULL dereference
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Quoting Sergey Senozhatsky (2019-07-31 17:48:29)
> @@ -36,19 +38,35 @@ int i915_gemfs_init(struct drm_i915_private *i915)
> struct super_block *sb = gemfs->mnt_sb;
> /* FIXME: Disabled until we get W/A for read BW issue. */
> char options[] = "huge=never";
> - int flags = 0;
> int err;
>
> - err = sb->s_op->remount_fs(sb, &flags, options);
> - if (err) {
> - kern_unmount(gemfs);
> - return err;
> - }
> + fc = fs_context_for_reconfigure(sb->s_root, 0, 0);
> + if (IS_ERR(fc))
> + goto err;
> +
> + if (!fc->ops->parse_monolithic)
> + goto err;
> +
> + err = fc->ops->parse_monolithic(fc, options);
> + if (err)
> + goto err;
> +
> + if (!fc->ops->reconfigure)

It would be odd for fs_context_for_reconfigure() to allow creation of a
context if that context couldn't perform a reconfigre, nevertheless that
seems to be the case.

> + goto err;
> +
> + err = fc->ops->reconfigure(fc);
> + if (err)
> + goto err;

Only thing that stands out is that we should put_fs_context() here as
well. I guess it's better than poking at the SB_INFO directly ourselves.

I think though we shouldn't bail if we can't change the thp setting, and
just accept whatever with a warning.

Looks like the API is already available in dinq, so we can apply this
ahead of the next merge window.
-Chris

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