The logic for determining when to demote a glock in glock_work_func(),
introduced in commit 7cf8dcd3b68a ("GFS2: Automatically adjust glock min
hold time"), doesn't make sense: inode glocks have a minimum hold time
that delays demotion, while all other glocks are expected to be demoted
immediately.  Instead of demoting non-inode glocks immediately,
glock_work_func() schedules glock work for them to be demoted, however.
Get rid of that unnecessary indirection.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Since the previous commit, function gfs2_quota_sync() will not cause the
sync generation to creep forward by one every time the function is
called; this helps keep things a but more tidy.  We also don't care that
this function allocates a page of memory every time it is called, so no
good reason for keeping qd_changed() anymore, which just duplicates
qd_grab_sync().

This reverts commit 06aa6fd31a5f402b055e12ea53bb7b086359d3c8.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

The quota sync generation is only ever updated under sd_quota_sync_mutex
by gfs2_quota_sync(), but its current value is fetched ouside of that
mutex, so use WRITE_ONCE() and READ_ONCE() when accessing it without
holding that mutex.

Pass the current sync generation to do_sync() from its callers to ensure
that we're not recording the wrong generation when the syncing is
done.  Also, make sure that qd->qd_sync_gen only ever moves forward.

In gfs2_quota_sync(), only write the new sync generation when we know
that there are changes.  This eliminates the need for function
sd_changed(), which we will remove in the next commit.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

With the locking the previous patch has introduced for each struct
gfs2_quota_data object, sd_quota_mutex has become largely irrelevant.
By waiting on the buffer head instead of waiting on the mutex in
get_bh(), it becomes completely irrelevant and can be removed.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

The quota code is missing some locking between local quota changes and
syncing those quota changes to the global quota file (gfs2_quota_sync);
in particular, qd->qd_change needs to be kept in sync with the
QDF_CHANGE change flag and the number of references held.  Use the
qd->qd_lockref.lock spinlock for that.

With the qd->qd_lockref.lock spinlock held, we can no longer call
lockref_get(), so turn qd_hold() into a variant that assumes that the
lock is held.  This function is really supposed to take an additional
reference when one or more references are already held, so check for
that instead of checking if the lockref is dead.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

The split between qd_fish() and gfs2_quota_sync() is rather unfortunate
as qd_fish() is repeatedly called to scan sdp->sd_quota_list only to
find the next object to that needs syncing; if there are multiple
objects on the list that need syncing, it makes more sense to grab them
all in one go.  This is relatively easy to do when qd_fish() is folded
into gfs2_quota_sync().

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Rename variable 'value' to 'change' as it stores a change in value.

Add new 'value' and 'limit' variables for the current value and limit.

Only fetch the tuning parameters when we need them.

Get rid of unnecessary nesting.

No change in functionality.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Function do_qc() is supposed to be conceptually simple: it alters the
current in-memory and on-disk quota change values for a given uid/gid by
a given delta.  If the on-disk record isn't defined yet, a new record is
created.  If the on-disk record exists and the resulting change value is
zero, there no longer is a need for that record and so the record is
deleted.  On top of that, some reference counting is involved when
creating and deleting records.

Currently, instead of doing the above, do_qc() alters the on-disk value
and then it sets the in-memory value to the on-disk value.  This is
incorrect when the on-disk value differs from the in-memory value.  The
two values are allowed to differ when quota changes are synced to the
global quota file.  Fix by changing both values by the same amount.

In addition, do_qc() currently gets confused when the delta value is 0.
It isn't supposed to be called that way, but that assumption isn't
mentioned and it makes the code harder to read.  Make the code more
explicit.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Commit 432928c93779 ("gfs2: Add quota_change type") makes the incorrect
assertion that function do_qc() should behave differently in the two
contexts it is used in, but that isn't actually true.  In all cases,
do_qc() grabs a "reference" when it starts using a slot in the per-node
quota changes file, and it releases that "reference" when no more
residual changes remain.  Revert that broken commit.

There are some remaining issues with function do_qc() which are
addressed in the next commit.

This reverts commit 432928c9377959684c748a9bc6553ed2d3c2ea4f.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

Commit 4c6a08125f22 ("gfs2: ignore negated quota changes") skips quota
changes with qd_change == 0 instead of writing them back, which leaves
behind non-zero qd_change values in the affected slots.  The kernel then
assumes that those slots are unused, while the qd_change values on disk
indicate that they are indeed still in use.  The next time the
filesystem is mounted, those invalid slots are read in from disk, which
will cause inconsistencies.

Revert that commit to avoid filesystem corruption.

This reverts commit 4c6a08125f2249531ec01783a5f4317d7342add5.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>