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rbd: do not execute rbd sparsify when volume is in use #3985

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Jul 11, 2023
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rbd: do not execute rbd sparsify when volume is in use #3985

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9 changes: 9 additions & 0 deletions internal/csi-addons/rbd/reclaimspace.go
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Original file line number Diff line number Diff line change
Expand Up @@ -18,11 +18,13 @@ package rbd

import (
"context"
"errors"
"fmt"

csicommon "github.com/ceph/ceph-csi/internal/csi-common"
rbdutil "github.com/ceph/ceph-csi/internal/rbd"
"github.com/ceph/ceph-csi/internal/util"
"github.com/ceph/ceph-csi/internal/util/log"

"github.com/container-storage-interface/spec/lib/go/csi"
rs "github.com/csi-addons/spec/lib/go/reclaimspace"
Expand Down Expand Up @@ -69,6 +71,13 @@ func (rscs *ReclaimSpaceControllerServer) ControllerReclaimSpace(
defer rbdVol.Destroy()

err = rbdVol.Sparsify()
if errors.Is(err, rbdutil.ErrImageInUse) {
// FIXME: https://github.com/csi-addons/kubernetes-csi-addons/issues/406.
// treat sparsify call as no-op if volume is in use.
log.DebugLog(ctx, fmt.Sprintf("volume with ID %q is in use, skipping sparsify operation", volumeID))

return &rs.ControllerReclaimSpaceResponse{}, nil
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}
if err != nil {
// TODO: check for different error codes?
return nil, status.Errorf(codes.Internal, "failed to sparsify volume %q: %s", rbdVol, err.Error())
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11 changes: 11 additions & 0 deletions internal/rbd/diskusage.go
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Expand Up @@ -23,7 +23,18 @@ import (
// Sparsify checks the size of the objects in the RBD image and calls
// rbd_sparify() to free zero-filled blocks and reduce the storage consumption
// of the image.
// This function will return ErrImageInUse if the image is in use, since
// sparsifying an image on which i/o is in progress is not optimal.
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I don't want to sound like a broken record, but I have to ask again: do you have any data that would support automating rbd sparsify runs at all? In particular:

  • Have you done any research into how likely they are to be encountered?
  • Do you have ceph df outputs captured before and after rbd sparsify is run for typical customer scenarios?

If the answer is no, I don't understand why rbd sparsify is being conditioned on isInUse() instead of just being dropped entirely (to be resurrected as an optional step when the relevant CSI addon spec allows taking options from the user). Sparsifying the image the way Ceph CSI does it is likely not optimal in general, not just when there is competing I/O.

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on one heavily used cluster, I suspect I've seen 33% to 100% extra usage without sparsify. Hadn't had the chance to run it offline and haven't had the guts to run it online. This makes it sound like it was good for me to be hesitent.

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Yeah -- I would suggest starting with fstrim (assuming you aren't using raw block PVs).

func (ri *rbdImage) Sparsify() error {
inUse, err := ri.isInUse()
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if err != nil {
return fmt.Errorf("failed to check if image is in use: %w", err)
}
if inUse {
// if the image is in use, we should not sparsify it, return ErrImageInUse.
return ErrImageInUse
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}

image, err := ri.open()
if err != nil {
return err
Expand Down
2 changes: 2 additions & 0 deletions internal/rbd/errors.go
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Expand Up @@ -63,4 +63,6 @@ var (
ErrFetchingMirroringInfo = errors.New("failed to get mirroring info of image")
// ErrResyncImageFailed is returned when the operation to resync the image fails.
ErrResyncImageFailed = errors.New("failed to resync image")
// ErrImageInUse is returned when the image is in use.
ErrImageInUse = errors.New("image is in use")
)