linux-kernel - [PATCH v2 0/9] mm/fs: get PG_error out of the writeback reporting business

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Date:   Wed,  8 Mar 2017 11:29:25 -0500
From:   Jeff Layton <jlayton@...hat.com>
To:     viro@...iv.linux.org.uk, akpm@...ux-foundation.org
Cc:     konishi.ryusuke@....ntt.co.jp, linux-fsdevel@...r.kernel.org,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        linux-nilfs@...r.kernel.org, ross.zwisler@...ux.intel.com,
        jack@...e.cz, neilb@...e.com, openosd@...il.com, adilger@...ger.ca,
        James.Bottomley@...senPartnership.com
Subject: [PATCH v2 0/9] mm/fs: get PG_error out of the writeback reporting business

v2:
- still ClearPageError during __filemap_fdatawait_range
- clear AS_* errors when reporting errors during write initiation
- set mapping errors when launder_page fails
- set mapping errors when writeback fails during migration
- set mapping errors when DAX writeback fails
- Documentation patch to give guidance about writeback errors

Here is v2 of this set. The main difference is some new patches to
ensure that mapping errors get set in a few rather obscure places when
writeback fails, and a patch (based on Jan's suggestion) to clear out
the address space errors when initiating writeback fails with -EIO. I
also left the code clearing PG_error in __filemap_fdatawait_range. We
may want to remove that eventually, but we need to ensure that it gets
cleared in some way when writeback fails.

I've done a bit of testing with this (mostly xfstests on xfs), and it
seems to work ok AFAICT.

Original cover letter follows:

------------------------------8<-----------------------------

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.

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 (9):
  mm: fix mapping_set_error call in me_pagecache_dirty
  mm: drop "wait" parameter from write_one_page
  mm: clear any AS_* errors when returning error on any fsync or close
  nilfs2: set the mapping error when calling SetPageError on writeback
  dax: set error in mapping when writeback fails
  mm: set mapping error when launder_pages fails
  mm: ensure that we set mapping error if writeout() fails
  mm: don't TestClearPageError in __filemap_fdatawait_range
  Documentation: document what to do on a writeback error

 Documentation/filesystems/vfs.txt |  7 +++++++
 fs/dax.c                          |  4 +++-
 fs/exofs/dir.c                    |  2 +-
 fs/ext2/dir.c                     |  2 +-
 fs/jfs/jfs_metapage.c             |  4 ++--
 fs/minix/dir.c                    |  2 +-
 fs/nilfs2/segment.c               |  1 +
 fs/sysv/dir.c                     |  2 +-
 fs/ufs/dir.c                      |  2 +-
 include/linux/mm.h                |  2 +-
 mm/filemap.c                      | 40 ++++++++++++++++++++++-----------------
 mm/memory-failure.c               |  2 +-
 mm/migrate.c                      |  6 +++++-
 mm/page-writeback.c               | 14 +++++++-------
 mm/truncate.c                     |  6 +++++-
 15 files changed, 60 insertions(+), 36 deletions(-)

-- 
2.9.3