vfs: allow syncfs to return an error when inode writeback fails

From: Jeff Layton <[email protected]>

v2: don't modify sync_fs op prototype, handle errors at vfs layer

The syncfs system call returns an int error code, but in general it does not return errors when an inode fails writeback. It will return an error if __sync_blockdev fails, but that's not useful on non-block based filesystems and is generally not useful on more modern filesystems that don't rely on that call.

This patchset aims to remedy that by adding some infrastructure to allow syncfs to return an error when an inode fails writeback. The basic idea is to add a new errseq_t to the super_block to record writeback errors.

Because we don't want to grow struct file for this purpose, this new behavior is only activated when the fd passed to syncfs is opened with O_PATH.

One of the items on the wishlist from the PostgreSQL developers at this year's LSF/MM was a way to tell whether there has been any writeback failure on a filesystem without forcing everything to be synced out.

The final patch in this series adds a new generic vfs ioctl that presents the new sb->s_wb_err field to userland applications that wish to see it.

Comments and suggestions welcome.

Jeff Layton (5):
vfs: push __sync_blockdev calls down into sync_fs routines
vfs: add an errseq_t pointer arg to sync_filesystem and
__sync_filesystem
vfs: track per-sb writeback errors and report them to syncfs
buffer: record blockdev write errors in super_block that backs them
vfs: add a new ioctl for fetching the superblock's errseq_t

 drivers/staging/ncpfs/inode.c |  2 +-
 fs/adfs/super.c               |  2 +-
 fs/affs/super.c               |  4 +--
 fs/befs/linuxvfs.c            |  2 +-
 fs/block_dev.c                |  3 ++-
 fs/btrfs/super.c              |  4 +--
 fs/buffer.c                   |  2 ++
 fs/cachefiles/interface.c     |  2 +-
 fs/cifs/cifsfs.c              |  2 +-
 fs/coda/inode.c               |  2 +-
 fs/cramfs/inode.c             |  2 +-
 fs/debugfs/inode.c            |  2 +-
 fs/efs/super.c                |  2 +-
 fs/ext2/super.c               |  4 +--
 fs/ext4/super.c               | 13 +++++-----
 fs/f2fs/super.c               | 15 ++++++-----
 fs/fat/inode.c                |  2 +-
 fs/freevxfs/vxfs_super.c      |  2 +-
 fs/fuse/inode.c               |  2 +-
 fs/gfs2/super.c               |  6 +++--
 fs/hfs/super.c                |  4 +--
 fs/hfsplus/super.c            |  2 +-
 fs/hpfs/super.c               |  2 +-
 fs/internal.h                 |  7 ------
 fs/ioctl.c                    |  3 +++
 fs/isofs/inode.c              |  2 +-
 fs/jffs2/super.c              |  2 +-
 fs/jfs/super.c                |  5 ++--
 fs/minix/inode.c              |  2 +-
 fs/nfs/super.c                |  2 +-
 fs/nilfs2/super.c             |  7 +++---
 fs/ntfs/super.c               |  2 +-
 fs/ocfs2/super.c              |  4 +--
 fs/open.c                     |  6 ++---
 fs/openpromfs/inode.c         |  2 +-
 fs/overlayfs/super.c          |  2 +-
 fs/proc/root.c                |  2 +-
 fs/pstore/inode.c             |  2 +-
 fs/qnx4/inode.c               |  2 +-
 fs/qnx6/inode.c               |  2 +-
 fs/quota/dquot.c              | 11 +++-----
 fs/reiserfs/super.c           |  4 +--
 fs/romfs/super.c              |  2 +-
 fs/squashfs/super.c           |  2 +-
 fs/super.c                    |  4 +--
 fs/sync.c                     | 47 +++++++++++++++++++++++++++--------
 fs/sysv/inode.c               |  5 ++--
 fs/tracefs/inode.c            |  2 +-
 fs/ubifs/super.c              |  2 +-
 fs/udf/super.c                |  2 +-
 fs/ufs/super.c                |  2 +-
 fs/xfs/xfs_super.c            |  2 +-
 include/linux/errseq.h        |  1 +
 include/linux/fs.h            | 13 +++++++++-
 include/linux/pagemap.h       |  5 +++-
 include/uapi/linux/fs.h       |  1 +
 lib/errseq.c                  | 33 ++++++++++++++++++++++--
 57 files changed, 173 insertions(+), 102 deletions(-)

2.17.0