Hi all,

This patchset adds some generic helpers so that filesystems can report
errors to fsnotify in a standard way.  Then it adapts iomap to use the
generic helpers so that any iomap-enabled filesystem can report I/O
errors through this mechanism as well.  Finally, it makes XFS report
metadata errors through this mechanism in much the same way that ext4
does now.

These are a prerequisite for the XFS self-healing series which will
come at a later time.

v5: tidy comments, un-inline the unmount function
v4: drag out of RFC status, finalize the sign of errnos that we accept

If you're going to start using this code, I strongly recommend pulling
from my git trees, which are linked below.

This has been running on the djcloud for months with no problems.  Enjoy!
Comments and questions are, as always, welcome.

--D

kernel git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=filesystem-error-reporting

fstests git tree:
https://git.kernel.org/cgit/linux/kernel/git/djwong/xfstests-dev.git/log/?h=filesystem-error-reporting
---
Commits in this patchset:
 * uapi: promote EFSCORRUPTED and EUCLEAN to errno.h
 * fs: report filesystem and file I/O errors to fsnotify
 * iomap: report file I/O errors to the VFS
 * xfs: report fs metadata errors via fsnotify
 * xfs: translate fsdax media errors into file "data lost" errors when convenient
 * ext4: convert to new fserror helpers
---
 arch/alpha/include/uapi/asm/errno.h        |    2 
 arch/mips/include/uapi/asm/errno.h         |    2 
 arch/parisc/include/uapi/asm/errno.h       |    2 
 arch/sparc/include/uapi/asm/errno.h        |    2 
 fs/erofs/internal.h                        |    2 
 fs/ext2/ext2.h                             |    1 
 fs/ext4/ext4.h                             |    3 
 fs/f2fs/f2fs.h                             |    3 
 fs/minix/minix.h                           |    2 
 fs/udf/udf_sb.h                            |    2 
 fs/xfs/xfs_linux.h                         |    2 
 include/linux/fs/super_types.h             |    7 +
 include/linux/fserror.h                    |   75 +++++++++++
 include/linux/jbd2.h                       |    3 
 include/uapi/asm-generic/errno.h           |    2 
 tools/arch/alpha/include/uapi/asm/errno.h  |    2 
 tools/arch/mips/include/uapi/asm/errno.h   |    2 
 tools/arch/parisc/include/uapi/asm/errno.h |    2 
 tools/arch/sparc/include/uapi/asm/errno.h  |    2 
 tools/include/uapi/asm-generic/errno.h     |    2 
 fs/Makefile                                |    2 
 fs/ext4/ioctl.c                            |    2 
 fs/ext4/super.c                            |   13 +-
 fs/fserror.c                               |  194 ++++++++++++++++++++++++++++
 fs/iomap/buffered-io.c                     |   23 +++
 fs/iomap/direct-io.c                       |   12 ++
 fs/iomap/ioend.c                           |    6 +
 fs/super.c                                 |    3 
 fs/xfs/xfs_fsops.c                         |    4 +
 fs/xfs/xfs_health.c                        |   14 ++
 fs/xfs/xfs_notify_failure.c                |    4 +
 31 files changed, 373 insertions(+), 24 deletions(-)
 create mode 100644 include/linux/fserror.h
 create mode 100644 fs/fserror.c