[PATCH v6 00/12] xfs: mount API patch series

Ian Kent
2019-10-16T00:41:20Z

This patch series add support to xfs for the new kernel mount API
as described in the LWN article at https://lwn.net/Articles/780267/.

In the article there's a lengthy description of the reasons for
adopting the API and problems expected to be resolved by using it.

The series has been applied to the repository located at
git://git.kernel.org/pub/scm/fs/xfs/xfs-linux.git, and built and
some simple tests run on it along with the generic xfstests.

Other things that continue to cause me concern:

- Message logging.
There is error logging done in the VFS by the mount-api code, some
is VFS specific while some is file system specific. This can lead
to duplicated and sometimes inconsistent logging.

The mount-api feature of saving error message text to the mount
context for later retrieval by fsopen()/fsconfig()/fsmount() users
is the reason the mount-api log macros are present. But, at the
moment (last time I looked), these macros will either log the
error message or save it to the mount context. There's not yet
a way to modify this behaviour so it which can lead to messages,
possibly needed for debug purposes, not being sent to the kernel
log. There's also the pr_xxx() log functions (not a problem for
xfs AFAICS) that aren't aware of the mount context at all.

In the xfs patches I've used the same method that is used in
gfs2 and was suggested by Al Viro (essentially return the error
if fs_parse() returns one) except that I've also not used the
mount api log macros to minimise the possibility of lost log
messages.

This isn't the best so follow up patches for RFC (with a
slightly wider audience) will be needed to try and improve
this aspect of the mount api.

The first patch in the series is needed only for testing. It is now
present in the current upstream rc kernel so it will need to be dropped
before merging.

Changes for v6:
- drop get_tree_bdev() patch since it's now present in the xfs-linux repo.
- eliminate unused mount info. field m_fsname_len.
- eliminate mount info field m_fsname, use super block field s_id instead.
- dont use XFS_IS_QUOTA_RUNNING() when checking if quota options have been
specified.
- combine mount-api specific patches into a single patch to help with
bi-sectability.

hanges for v5:
- give error exit label in xfs_fill_super() a sensible name.
- use original comment about options handling in xfs_fs_remount() for
comment above xfs_reconfigure().
- use a much simpler comment in xfs_fc_free(), thanks to Brian Foster.
- move cover letter comment about the first two patches above the
revision comentary so it isn't missed.

Changes for v4:
- changed xfs_fill_super() cleanup back to what it was in v2, until
I can work out what's causing the problem had previously seen (I can't
reproduce it myself), since it looks like it was right from the start.
- use get_tree_bdev() instead of vfs_get_block_super() in xfs_get_tree()
as requested by Al Viro.
- removed redundant initialisation in xfs_fs_fill_super().
- fix long line in xfs_validate_params().
- no need to validate if parameter parsing fails, just return the error.
- summarise reconfigure comment about option handling, transfer bulk
of comment to commit log message.
- use minimal change in xfs_parse_param(), deffer discussion of mount
api logging improvements until later and with a wider audience.

Changes for v3:
- fix struct xfs_fs_context initialisation in xfs_parseargs().
- move call to xfs_validate_params() below label "done".
- if allocation of xfs_mount fails return ENOMEM immediately.
- remove erroneous kfree(mp) in xfs_fill_super().
- move the removal of xfs_fs_remount() and xfs_test_remount_options()
to the switch to mount api patch.
- retain original usage of distinct , no usage.
- fix line length and a white space problem in xfs_parseargs().
- defer introduction of struct fs_context_operations until mount
api implementation.
- don't use a new line for the void parameter of xfs_mount_alloc().
- check for -ENOPARAM in xfs_parse_param() to report invalid options
using the options switch (to avoid double entry log messages).
- remove obsolete mount option biosize.
- try and make comment in xfs_fc_free() more understandable.

Changes for v2:
- changed .name to uppercase in fs_parameter_description to ensure
consistent error log messages between the vfs parser and the xfs
parameter parser.
- clarify comment above xfs_parse_param() about when possibly
allocated mp->m_logname or mp->m_rtname are freed.
- factor out xfs_remount_rw() and xfs_remount_ro() from xfs_remount().
- changed xfs_mount_alloc() to not set super block in xfs_mount so it
can be re-used when switching to the mount-api.
- fixed don't check for NULL when calling kfree() in xfs_fc_free().
- refactored xfs_parseargs() in an attempt to highlight the code
that actually changes in converting to use the new mount api.
- dropped xfs-mount-api-rename-xfs_fill_super.patch, it didn't seem
necessary.
- move comment about remount difficulties above xfs_reconfigure()
and increase line length to try and make the comment manageable.
---

Ian Kent (12):
vfs: add missing blkdev_put() in get_tree_bdev()
xfs: remove very old mount option
xfs: remove unused mount info field m_fsname_len
xfs: use super s_id instead of mount info m_fsname
xfs: dont use XFS_IS_QUOTA_RUNNING() for option check
xfs: add xfs_remount_rw() helper
xfs: add xfs_remount_ro() helper
xfs: refactor suffix_kstrtoint()
xfs: refactor xfs_parseags()
xfs: move xfs_parseargs() validation to a helper
xfs: dont set sb in xfs_mount_alloc()
xfs: switch to use the new mount-api

fs/super.c | 5
fs/xfs/xfs_error.c | 2
fs/xfs/xfs_log.c | 2
fs/xfs/xfs_message.c | 4
fs/xfs/xfs_mount.c | 5
fs/xfs/xfs_mount.h | 2
fs/xfs/xfs_pnfs.c | 2
fs/xfs/xfs_super.c | 903 ++++++++++++++++++++++++------------------------
fs/xfs/xfs_trans_ail.c | 2
9 files changed, 469 insertions(+), 458 deletions(-)

--
Ian