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cephfs: added support for snapshot-backed volumes

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This commit implements most of
docs/design/proposals/cephfs-snapshot-shallow-ro-vol.md design document;
specifically (de-)provisioning of snapshot-backed volumes, mounting such
volumes as well as mounting pre-provisioned snapshot-backed volumes.

Signed-off-by: Robert Vasek <robert.vasek@cern.ch>
This commit is contained in:
Robert Vasek
2022-04-06 15:26:07 +02:00
committed by mergify[bot]
parent 0807fd2e6c
commit fd7559a903
7 changed files with 710 additions and 107 deletions
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130
internal/cephfs/nodeserver.go
View File

@ -21,6 +21,7 @@ import (
"errors"
"fmt"
"os"
"path"
"strings"
cerrors "github.com/ceph/ceph-csi/internal/cephfs/errors"
@ -101,6 +102,20 @@ func (ns *NodeServer) getVolumeOptions(
return volOptions, nil
}
func validateSnapshotBackedVolCapability(volCap *csi.VolumeCapability) error {
// Snapshot-backed volumes may be used with read-only volume access modes only.
mode := volCap.AccessMode.Mode
if mode != csi.VolumeCapability_AccessMode_MULTI_NODE_READER_ONLY &&
mode != csi.VolumeCapability_AccessMode_SINGLE_NODE_READER_ONLY {
return status.Error(codes.InvalidArgument,
"snapshot-backed volume supports only read-only access mode")
}
return nil
}
// NodeStageVolume mounts the volume to a staging path on the node.
func (ns *NodeServer) NodeStageVolume(
ctx context.Context,
@ -140,6 +155,12 @@ func (ns *NodeServer) NodeStageVolume(
}
}
if volOptions.BackingSnapshot {
if err = validateSnapshotBackedVolCapability(req.GetVolumeCapability()); err != nil {
return nil, err
}
}
mnt, err := mounter.New(volOptions)
if err != nil {
log.ErrorLog(ctx, "failed to create mounter for volume %s: %v", volID, err)
@ -192,7 +213,7 @@ func (ns *NodeServer) NodeStageVolume(
log.ErrorLog(ctx, "cephfs: failed to write NodeStageMountinfo for volume %s: %v", volID, err)
// Try to clean node stage mount.
if unmountErr := mounter.UnmountVolume(ctx, stagingTargetPath); unmountErr != nil {
if unmountErr := mounter.UnmountAll(ctx, stagingTargetPath); unmountErr != nil {
log.ErrorLog(ctx, "cephfs: failed to unmount %s in WriteNodeStageMountinfo clean up: %v",
stagingTargetPath, unmountErr)
}
@ -223,7 +244,7 @@ func (*NodeServer) mount(
log.DebugLog(ctx, "cephfs: mounting volume %s with %s", volID, mnt.Name())
readOnly := "ro"
const readOnly = "ro"
if volCap.AccessMode.Mode == csi.VolumeCapability_AccessMode_MULTI_NODE_READER_ONLY ||
volCap.AccessMode.Mode == csi.VolumeCapability_AccessMode_SINGLE_NODE_READER_ONLY {
@ -248,9 +269,112 @@ func (*NodeServer) mount(
return status.Error(codes.Internal, err.Error())
}
defer func() {
if err == nil {
return
}
unmountErr := mounter.UnmountAll(ctx, stagingTargetPath)
if unmountErr != nil {
log.ErrorLog(ctx, "failed to clean up mounts in rollback procedure: %v", unmountErr)
}
}()
if volOptions.BackingSnapshot {
snapshotRoot, err := getBackingSnapshotRoot(ctx, volOptions, stagingTargetPath)
if err != nil {
return err
}
absoluteSnapshotRoot := path.Join(stagingTargetPath, snapshotRoot)
err = mounter.BindMount(
ctx,
absoluteSnapshotRoot,
stagingTargetPath,
true,
[]string{"bind", "_netdev"},
)
if err != nil {
log.ErrorLog(ctx,
"failed to bind mount snapshot root %s: %v", absoluteSnapshotRoot, err)
return status.Error(codes.Internal, err.Error())
}
}
return nil
}
func getBackingSnapshotRoot(
ctx context.Context,
volOptions *store.VolumeOptions,
stagingTargetPath string,
) (string, error) {
if volOptions.ProvisionVolume {
// Provisioned snapshot-backed volumes should have their BackingSnapshotRoot
// already populated.
return volOptions.BackingSnapshotRoot, nil
}
// Pre-provisioned snapshot-backed volumes are more involved:
//
// Snapshots created with `ceph fs subvolume snapshot create` have following
// snap directory name format inside <root path>/.snap:
//
// _<snapshot>_<snapshot inode number>
//
// We don't know what <snapshot inode number> is, and so <root path>/.snap
// needs to be traversed in order to determine the full snapshot directory name.
snapshotsBase := path.Join(stagingTargetPath, ".snap")
dir, err := os.Open(snapshotsBase)
if err != nil {
log.ErrorLog(ctx, "failed to open %s when searching for snapshot root: %v", snapshotsBase, err)
return "", status.Errorf(codes.Internal, err.Error())
}
// Read the contents of <root path>/.snap directory into a string slice.
contents, err := dir.Readdirnames(0)
if err != nil {
log.ErrorLog(ctx, "failed to read %s when searching for snapshot root: %v", snapshotsBase, err)
return "", status.Errorf(codes.Internal, err.Error())
}
var (
found bool
snapshotDirName string
)
// Look through the directory's contents and try to find the correct snapshot
// dir name. The search must be exhaustive to catch possible ambiguous results.
for i := range contents {
if !strings.Contains(contents[i], volOptions.BackingSnapshotID) {
continue
}
if !found {
found = true
snapshotDirName = contents[i]
} else {
return "", status.Errorf(codes.InvalidArgument, "ambiguous backingSnapshotID %s in %s",
volOptions.BackingSnapshotID, snapshotsBase)
}
}
if !found {
return "", status.Errorf(codes.InvalidArgument, "no snapshot with backingSnapshotID %s found in %s",
volOptions.BackingSnapshotID, snapshotsBase)
}
return path.Join(".snap", snapshotDirName), nil
}
// NodePublishVolume mounts the volume mounted to the staging path to the target
// path.
func (ns *NodeServer) NodePublishVolume(
@ -444,7 +568,7 @@ func (ns *NodeServer) NodeUnstageVolume(
return &csi.NodeUnstageVolumeResponse{}, nil
}
// Unmount the volume
if err = mounter.UnmountVolume(ctx, stagingTargetPath); err != nil {
if err = mounter.UnmountAll(ctx, stagingTargetPath); err != nil {
return nil, status.Error(codes.Internal, err.Error())
}