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Groups > linux.kernel > #1592776
| From | Jeff Layton <jlayton@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business |
| Date | 2017-03-05 15:50 +0100 |
| Message-ID | <thFDX-1GV-1@gated-at.bofh.it> (permalink) |
| References | <thEHU-ZX-9@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Sun, 2017-03-05 at 08:35 -0500, Jeff Layton wrote:
> I recently did some work to wire up -ENOSPC handling in ceph, and found
> I could get back -EIO errors in some cases when I should have instead
> gotten -ENOSPC. The problem was that the ceph writeback code would set
> PG_error on a writeback error, and that error would clobber the mapping
> error.
>
I should also note that relying on PG_error to report writeback errors
is inherently unreliable as well. If someone calls sync() before your
fsync gets in there, then you'll likely lose it anyway.
filemap_fdatawait_keep_errors will preserve the error in the mapping,
but not the individual PG_error flags, so I think we do want to ensure
that the mapping error is set when there is a writeback error and not
rely on PG_error bit for that.
> While I fixed that problem by simply not setting that bit on errors,
> that led me down a rabbit hole of looking at how PG_error is being
> handled in the kernel.
>
> This patch series is a few fixes for things that I 100% noticed by
> inspection. I don't have a great way to test these since they involve
> error handling. I can certainly doctor up a kernel to inject errors
> in this code and test by hand however if these look plausible up front.
>
> Jeff Layton (3):
> nilfs2: set the mapping error when calling SetPageError on writeback
> mm: don't TestClearPageError in __filemap_fdatawait_range
> mm: set mapping error when launder_pages fails
>
> fs/nilfs2/segment.c | 1 +
> mm/filemap.c | 19 ++++---------------
> mm/truncate.c | 6 +++++-
> 3 files changed, 10 insertions(+), 16 deletions(-)
>
(cc'ing Ross...)
Just when I thought that only NILFS2 needed a little work here, I see
another spot...
I think that we should also need to fix dax_writeback_mapping_range to
set a mapping error on writeback as well. It looks like that's not
happening today. Something like the patch below (obviously untested).
I'll also plan to follow up with a patch to vfs.txt to outline how
writeback errors should be handled by filesystems, assuming that this
patchset isn't completely off base.
-------------------8<-----------------------
[PATCH] dax: set error in mapping when writeback fails
In order to get proper error codes from fsync, we must set an error in
the mapping range when writeback fails.
Signed-off-by: Jeff Layton <jlayton@redhat.com>
---
fs/dax.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/fs/dax.c b/fs/dax.c
index c45598b912e1..9005d90deeda 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -888,8 +888,10 @@ int dax_writeback_mapping_range(struct address_space *mapping,
ret = dax_writeback_one(bdev, mapping, indices[i],
pvec.pages[i]);
- if (ret < 0)
+ if (ret < 0) {
+ mapping_set_error(mapping, ret);
return ret;
+ }
}
}
return 0;
--
2.9.3
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[PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jeff Layton <jlayton@redhat.com> - 2017-03-05 14:50 +0100
[PATCH 3/3] mm: set mapping error when launder_pages fails Jeff Layton <jlayton@redhat.com> - 2017-03-05 14:50 +0100
[PATCH 1/3] nilfs2: set the mapping error when calling SetPageError on writeback Jeff Layton <jlayton@redhat.com> - 2017-03-05 15:00 +0100
Re: [PATCH 1/3] nilfs2: set the mapping error when calling SetPageError on writeback Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp> - 2017-03-07 17:50 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jeff Layton <jlayton@redhat.com> - 2017-03-05 15:50 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Ross Zwisler <ross.zwisler@linux.intel.com> - 2017-03-07 03:00 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jan Kara <jack@suse.cz> - 2017-03-07 11:40 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jeff Layton <jlayton@redhat.com> - 2017-03-07 15:40 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Ross Zwisler <ross.zwisler@linux.intel.com> - 2017-03-07 17:10 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jan Kara <jack@suse.cz> - 2017-03-07 17:50 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Theodore Ts'o <tytso@mit.edu> - 2017-03-09 04:00 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jan Kara <jack@suse.cz> - 2017-03-09 10:30 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jeff Layton <jlayton@redhat.com> - 2017-03-09 12:00 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jan Kara <jack@suse.cz> - 2017-03-09 12:10 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jeff Layton <jlayton@redhat.com> - 2017-03-09 13:50 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Brian Foster <bfoster@redhat.com> - 2017-03-09 14:30 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Theodore Ts'o <tytso@mit.edu> - 2017-03-09 16:10 +0100
[PATCH 2/3] mm: don't TestClearPageError in __filemap_fdatawait_range Jeff Layton <jlayton@redhat.com> - 2017-03-05 16:30 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business NeilBrown <neilb@suse.com> - 2017-03-06 04:10 +0100
Re: [PATCH 0/3] mm/fs: get PG_error out of the writeback reporting business Jeff Layton <jlayton@redhat.com> - 2017-03-06 12:50 +0100
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