Messages in this thread | | | From | Miklos Szeredi <> | Date | Mon, 18 May 2020 13:12:47 +0200 | Subject | Re: kernel BUG at mm/hugetlb.c:LINE! |
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On Sat, May 16, 2020 at 12:15 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
> I started going down the path of creating a get_unmapped_area f_op for > overlayfs. That is pretty straight forward and works well. But that > did not take care of the is_file_hugepages() routine. Recall that > is_file_hugepages simply does if (file->f_op == &hugetlbfs_file_operations). > > I suppose I could add a specific overlayfs check like real_file here. But, > that does not seem like a clean solution. > > I also discovered other routines doing comparisons like > if (file->f_op == <expected_fops>), they are: > is_dma_buf_file() > is_file_shm_hugepages() > get_pipe_info() > is_file_epoll() > > So, it seems that these routines are also impacted if operating on files > in an overlayfs?
Those are non-filesystems, with the exception of is_file_shm_hugepages(), the only caller of which is is_file_hugepages().
> Any suggestions on how to move forward? It seems like there may be the > need for a real_file() routine? I see a d_real dentry_op was added to > deal with this issue for dentries. Might we need something similiar for > files (f_real)? > > Looking for suggestions as I do not normally work with this code.
And I'm not so familiar with hugepages code. I'd suggest moving length alignment into f_op->get_unmapped_area() and cleaning up other special casing of hugetlb mappings, but it's probably far from trivial...
So yeah, that leaves a real_file() helper or something similar. Unlike the example I gave first it actually needs to be recursive:
static inline struct file *real_file(struct file *file) { whole (unlikely(file->f_op == ovl_file_operations)) file = file->private_data; return file; }
Thanks, Miklos
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