From: Jeff Layton <jlayton@xxxxxxxxxx>
Currently, syncfs does not return errors when one of the inodes fails
to be written back. It will return errors based on the legacy AS_EIO
and AS_ENOSPC flags when syncing out the block device fails, but that's
not particularly helpful for filesystems that aren't backed by a
blockdev and more granular errors are often not caught.
At LSF/MM this year, we had a discussion about tracking writeback
errors on a per-sb basis to help remedy this. This patchset is an inital
foray into doing that:
The basic idea is to add a new errseq_t to struct super_block, and use
that to track writeback errors for the filesystem as a whole.
Because syncfs is not a common operation, it's not desirable to grow
struct file in order to house an errseq_t cursor for it. Willy's
suggestion was to reuse file->f_wb_err, but only when the file is opened
with O_PATH. fsync always returns an error on an O_PATH fd, so this
should be safe, and seems semantically sane, given that syncfs operates
on the whole filesystem.
The patchset starts by pushing the __sync_blockdev calls down into the
various sync_fs operations. It then plumbs in an extra errseq_t pointer
into the sync_fs ops, and the relevant callers. It then adds the new
errseq_t field to struct super_block, and adds the machinery to handle
syncfs on an O_PATH open correctly. Lastly, it has some filesystems
return stored writeback errors in sync_fs ops when they are passed a
non-NULL errseq_t pointer.
This is just a start (more filesystems will need similar patches to the
later ones in the pile). This all works vs. the fstests testcase I have.
I haven't submitted that testcase yet, as I want to get consensus about
the interface. Does it make sense to treat O_PATH opens specially like
this?
Another thing on the wishlist for this is to expose the per-sb errseq_t
via another interface so that applications could periodically check to
see whether there has been a writeback error without syncing out the
whole fs. This patch doesn't add that yet, but once sb->s_wb_err is in
place and tracking errors it should be simple to do (possibly via a new
generic filesystem ioctl).
Jeff Layton (11):
vfs: push __sync_blockdev calls down into sync_fs routines
vfs: add a new errseq_t pointer to sync_fs prototype
vfs: add an errseq_t pointer to sync_filesystem
vfs: add errseq_t pointer to __sync_filesystem
fs: track per-sb writeback errors and report them to syncfs
buffer: record blockdev write errors in super_block that backs them
ext4: have sync_fs op report writeback errors when passed a since
pointer
xfs: have sync_fs op report writeback errors when passed a since
pointer
btrfs: have sync_fs op report writeback errors when passed a since
pointer
ext2: have sync_fs op report writeback errors when passed a since
pointer
vfs: have call_sync_fs op report writeback errors when passed a since
pointer
drivers/staging/ncpfs/inode.c | 2 +-
fs/adfs/super.c | 2 +-
fs/affs/super.c | 6 +++---
fs/befs/linuxvfs.c | 2 +-
fs/block_dev.c | 3 ++-
fs/btrfs/ctree.h | 2 +-
fs/btrfs/ioctl.c | 2 +-
fs/btrfs/super.c | 28 +++++++++++++++++++---------
fs/buffer.c | 2 ++
fs/cachefiles/interface.c | 2 +-
fs/ceph/super.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/exofs/super.c | 2 +-
fs/ext2/super.c | 19 +++++++++++++------
fs/ext4/super.c | 19 +++++++++++--------
fs/f2fs/f2fs.h | 2 +-
fs/f2fs/file.c | 6 +++---
fs/f2fs/namei.c | 16 ++++++++--------
fs/f2fs/segment.c | 2 +-
fs/f2fs/super.c | 19 +++++++++++--------
fs/fat/inode.c | 2 +-
fs/freevxfs/vxfs_super.c | 2 +-
fs/fuse/inode.c | 2 +-
fs/gfs2/super.c | 8 +++++---
fs/hfs/super.c | 6 +++---
fs/hfsplus/super.c | 10 +++++-----
fs/hpfs/super.c | 2 +-
fs/internal.h | 7 -------
fs/isofs/inode.c | 2 +-
fs/jffs2/super.c | 4 ++--
fs/jfs/super.c | 7 +++----
fs/minix/inode.c | 2 +-
fs/nfs/super.c | 2 +-
fs/nilfs2/super.c | 9 +++++----
fs/ntfs/super.c | 2 +-
fs/ocfs2/super.c | 8 ++++----
fs/open.c | 6 +++---
fs/openpromfs/inode.c | 2 +-
fs/overlayfs/super.c | 4 ++--
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 | 8 ++++----
fs/romfs/super.c | 2 +-
fs/squashfs/super.c | 2 +-
fs/super.c | 4 ++--
fs/sync.c | 28 +++++++++++++++++-----------
fs/sysv/inode.c | 7 +++----
fs/tracefs/inode.c | 2 +-
fs/ubifs/super.c | 4 ++--
fs/udf/super.c | 6 +++---
fs/ufs/super.c | 6 +++---
fs/xfs/xfs_super.c | 18 +++++++++++++-----
include/linux/fs.h | 35 +++++++++++++++++++++++++++++++++--
include/linux/pagemap.h | 5 ++++-
61 files changed, 223 insertions(+), 158 deletions(-)
--
2.17.0
