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SubjectRE: [PATCH v4 03/10] fs: Introduce ->corrupted_range() for superblock
Date
> -----Original Message-----
> From: Dan Williams <dan.j.williams@intel.com>
> Subject: Re: [PATCH v4 03/10] fs: Introduce ->corrupted_range() for superblock
>
> [ drop old linux-nvdimm@lists.01.org, add nvdimm@lists.linux.dev ]
>
> On Thu, Jun 3, 2021 at 6:19 PM Shiyang Ruan <ruansy.fnst@fujitsu.com> wrote:
> >
> > Memory failure occurs in fsdax mode will finally be handled in
> > filesystem. We introduce this interface to find out files or metadata
> > affected by the corrupted range, and try to recover the corrupted data
> > if possiable.
> >
> > Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> > ---
> > include/linux/fs.h | 2 ++
> > 1 file changed, 2 insertions(+)
> >
> > diff --git a/include/linux/fs.h b/include/linux/fs.h index
> > c3c88fdb9b2a..92af36c4225f 100644
> > --- a/include/linux/fs.h
> > +++ b/include/linux/fs.h
> > @@ -2176,6 +2176,8 @@ struct super_operations {
> > struct shrink_control *);
> > long (*free_cached_objects)(struct super_block *,
> > struct shrink_control *);
> > + int (*corrupted_range)(struct super_block *sb, struct block_device
> *bdev,
> > + loff_t offset, size_t len, void *data);
>
> Why does the superblock need a new operation? Wouldn't whatever function is
> specified here just be specified to the dax_dev as the
> ->notify_failure() holder callback?

Because we need to find out which file is effected by the given poison page so that memory-failure code can do collect_procs() and kill_procs() jobs. And it needs filesystem to use its rmap feature to search the file from a given offset. So, we need this implemented by the specified filesystem and called by dax_device's holder.

This is the call trace I described in cover letter:
memory_failure()
* fsdax case
pgmap->ops->memory_failure() => pmem_pgmap_memory_failure()
dax_device->holder_ops->corrupted_range() =>
- fs_dax_corrupted_range()
- md_dax_corrupted_range()
sb->s_ops->currupted_range() => xfs_fs_corrupted_range() <== **HERE**
xfs_rmap_query_range()
xfs_currupt_helper()
* corrupted on metadata
try to recover data, call xfs_force_shutdown()
* corrupted on file data
try to recover data, call mf_dax_kill_procs()
* normal case
mf_generic_kill_procs()

As you can see, this new added operation is an important for the whole progress.


--
Thanks,
Ruan.
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