gfs2: Add quota_change type
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Summary of Changes
gfs2: Add quota_change type
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=2224067 Upstream: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/fs/gfs2?id=432928c9377959684c748a9bc6553ed2d3c2ea4f
Function do_qc has two main uses: (1) to re-sync the local quota changes (qd) to the master quotas, and (2) normal quota changes. In the case of normal quota changes, the change can be positive or negative, as the quota usage goes up and down.
Before this patch function do_qc was distinguishing one from another by whether the resulting value is or isn't zero: In the case of a re-sync (called do_sync) the quota value is moved from the temporary value to a master value, so the amount is added to one and subtracted from the other. The problem is that since the values can be positive or negative we can occasionally run into situations where we are not doing a re-sync but the quota change just happens to cancel out the previous value.
In the case of a re-sync extra references and locks are taken, and so do_qc needs to release them. In the case of a normal quota change, no extra references and locks are taken, so it must not try to release them.
The problem is: if the quota change is not a re-sync but the value just happens to cancel out the original quota change, the resulting zero value fools do_qc into thinking this is a re-sync and therefore it must release the extra references. This results in problems, mainly having to do with slot reference numbers going smaller than zero.
This patch introduces new constants, QC_SYNC and QC_CHANGE so do_qc can really tell the difference. For QC_SYNC calls it must release the extra references acquired by gfs2_quota_unlock's call to qd_check_sync. For QC_CHANGE calls it does not have extra references to put.
Note that this allows quota changes back to a value of zero, and so I removed an assert warning related to that. (cherry-picked from commit 432928c9377959684c748a9bc6553ed2d3c2ea4f)
Signed-off-by: Bob Peterson rpeterso@redhat.com Signed-off-by: Andreas Gruenbacher agruenba@redhat.com
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