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It can be accessed and reviewed at: https://github.com/lxc/lxd/pull/2982
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=== Description (from pull-request) ===
For loop-backed btrfs pools we actually mount the loop device and so it's fine
to use LO_FLAGS_AUTOCLEAR since the loop device is guaranteed to be kept around
for as long as the mount exists. When we implement lvm loop-backed pools
however, we do not mount the loop device so we need to make sure that it is not
deconfigured automatically when we close all handles to it.
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
From 79a63c21b2f28971d61e2ea51ddd434f8049ed9a Mon Sep 17 00:00:00 2001
From: Christian Brauner <christian.brau...@ubuntu.com>
Date: Wed, 1 Mar 2017 02:24:27 +0100
Subject: [PATCH] storage_cgo: make flag argument configurable
For loop-backed btrfs pools we actually mount the loop device and so it's fine
to use LO_FLAGS_AUTOCLEAR since the loop device is guaranteed to be kept around
for as long as the mount exists. When we implement lvm loop-backed pools
however, we do not mount the loop device so we need to make sure that it is not
deconfigured automatically when we close all handles to it.
Signed-off-by: Christian Brauner <christian.brau...@ubuntu.com>
---
lxd/storage_btrfs.go | 5 ++++-
lxd/storage_cgo.go | 10 ++++++----
2 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/lxd/storage_btrfs.go b/lxd/storage_btrfs.go
index 7d62ae3..a69aac9 100644
--- a/lxd/storage_btrfs.go
+++ b/lxd/storage_btrfs.go
@@ -338,7 +338,10 @@ func (s *storageBtrfs) StoragePoolMount() (bool, error) {
mountSource := source
if filepath.IsAbs(source) {
if !shared.IsBlockdevPath(source) && s.d.BackingFs != "btrfs" {
- loopF, err := prepareLoopDev(source)
+ // Since we mount the loop device LO_FLAGS_AUTOCLEAR is
+ // fine since the loop device will be kept around for as
+ // long as the mount exists.
+ loopF, err := prepareLoopDev(source, LO_FLAGS_AUTOCLEAR)
if err != nil {
return false, fmt.Errorf("Could not prepare
loop device.")
}
diff --git a/lxd/storage_cgo.go b/lxd/storage_cgo.go
index 95ede6f..d7a6ba3 100644
--- a/lxd/storage_cgo.go
+++ b/lxd/storage_cgo.go
@@ -197,7 +197,7 @@ on_error:
return fd_tmp;
}
-int prepare_loop_dev(const char *source, char *loop_dev)
+int prepare_loop_dev(const char *source, char *loop_dev, int flags)
{
int ret;
struct loop_info64 lo64;
@@ -220,7 +220,7 @@ int prepare_loop_dev(const char *source, char *loop_dev)
goto on_error;
memset(&lo64, 0, sizeof(lo64));
- lo64.lo_flags = LO_FLAGS_AUTOCLEAR;
+ lo64.lo_flags = flags;
ret = ioctl(fd_loop, LOOP_SET_STATUS64, &lo64);
if (ret < 0)
@@ -248,10 +248,12 @@ import (
"unsafe"
)
+const LO_FLAGS_AUTOCLEAR int = C.LO_FLAGS_AUTOCLEAR
+
// prepareLoopDev() detects and sets up a loop device for source. It returns an
// open file descriptor to the free loop device and the path of the free loop
// device. It's the callers responsibility to close the open file descriptor.
-func prepareLoopDev(source string) (*os.File, error) {
+func prepareLoopDev(source string, flags int) (*os.File, error) {
cLoopDev := C.malloc(C.size_t(C.LO_NAME_SIZE))
if cLoopDev == nil {
return nil, fmt.Errorf("Failed to allocate memory in C.")
@@ -265,7 +267,7 @@ func prepareLoopDev(source string) (*os.File, error) {
return os.NewFile(uintptr(loopFd),
C.GoString((*C.char)(cLoopDev))), nil
}
- loopFd, err := C.prepare_loop_dev(cSource, (*C.char)(cLoopDev))
+ loopFd, err := C.prepare_loop_dev(cSource, (*C.char)(cLoopDev),
C.int(flags))
if loopFd < 0 {
if err != nil {
return nil, fmt.Errorf("Failed to prepare loop device:
%s.", err)
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