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

From: Jeff Layton
Date: Wed Mar 08 2017 - 11:55:28 EST

- 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:


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

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(-)