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Subject[PATCH v3 0/2] fix quota subdir mounts
Date
Hi,

As recently reported in the ceph-users mailing-list[1], the kernel client
behaves differently from the fuse client regarding mounting subdirs where
quotas are in effect. I've also created a bug to track this issue[2].

The following patches are a possible way of fixing this issue. The
performance impact should be close to zero if the mount is done in the
CephFS root inode. When we're mounting subdirs, we may have extra
queries to the MDSs, depending on how many extra realms we'll need to
loop through.

Changes since v2:

- Replaced inodes list in mdsc by an rbtree. This is because we need to
able to keep track errors in lookupino so that we don't keep sending the
same useless request for inodes that have failed. This also resulted in
reworking the locking in lookup_quotarealm_inode, so that 2 threads can
lookup the same inode at the same time

- No need to set realm->inode in lookup_quotarealm_inode() as the
lookupino has set it already.

Changes since v1:

- Loop to free mdsc->quotarealms_inodes_list list was moved further down
where it's not possible to race with insertions. This way there's no need
to hold the spinlock anymore.

- Clarified comments regarding the get_quota_realm function 'retry'
parameter, both in the function itself and in function
ceph_quota_is_same_realm, where that param is set to 'false'

- Distinguish between 'realm->inode is NULL' and igrab failures, both in
get_quota_realm and check_quota_exceeded

Changes since RFC:

The 1st patch hasn't been changed since the initial RFC. The 2nd patch
has been refactored to include the following changes:

- Zheng Yan's suggestions, i.e, move inode references from the realms to
ceph_mds_client instance

- It now also handles other cases where an MDS lookup may need to be
performed:
* statfs when there are quotas
* renames, to forbid cross-quota renames

[1] http://lists.ceph.com/pipermail/ceph-users-ceph.com/2019-February/033357.html
[2] https://tracker.ceph.com/issues/38482

Cheers,
--
Luís

Luis Henriques (2):
ceph: factor out ceph_lookup_inode()
ceph: quota: fix quota subdir mounts

fs/ceph/export.c | 14 +++-
fs/ceph/mds_client.c | 19 ++++++
fs/ceph/mds_client.h | 18 +++++
fs/ceph/quota.c | 158 ++++++++++++++++++++++++++++++++++++++++---
fs/ceph/super.h | 1 +
5 files changed, 199 insertions(+), 11 deletions(-)

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