[libvirt] [PATCH v1 1/6] virlockspace: Introduce VIR_LOCK_SPACE_ACQUIRE_METADATA flag
This flag is going to be used to alter default behaviour of the
lock. Firstly, it means we will lock different offset in the file
(offset 1 instead of 0). Secondly, it means the lock acquiring
will actually wait for the lock to be set (compared to default
behaviour which is set or error out).
Signed-off-by: Michal Privoznik <mprivozn(a)redhat.com>
---
src/util/virlockspace.c | 40 +++++++++++++++++++++++++++++++++-------
src/util/virlockspace.h | 1 +
2 files changed, 34 insertions(+), 7 deletions(-)
diff --git a/src/util/virlockspace.c b/src/util/virlockspace.c
index 3364c843aa..a7ec0c05bf 100644
--- a/src/util/virlockspace.c
+++ b/src/util/virlockspace.c
@@ -111,6 +111,8 @@ static void virLockSpaceResourceFree(virLockSpaceResourcePtr res)
VIR_FREE(res);
}
+#define DEFAULT_OFFSET 0
+#define METADATA_OFFSET 1
static virLockSpaceResourcePtr
virLockSpaceResourceNew(virLockSpacePtr lockspace,
@@ -120,6 +122,18 @@ virLockSpaceResourceNew(virLockSpacePtr lockspace,
{
virLockSpaceResourcePtr res;
bool shared = !!(flags & VIR_LOCK_SPACE_ACQUIRE_SHARED);
+ bool metadata = !!(flags & VIR_LOCK_SPACE_ACQUIRE_METADATA);
+ off_t start = DEFAULT_OFFSET;
+ bool waitForLock = false;
+
+ if (metadata) {
+ /* We want the metadata lock to act like pthread mutex.
+ * This means waiting for the lock to be acquired. */
+ waitForLock = true;
+
+ /* Also, we are locking different offset. */
+ start = METADATA_OFFSET;
+ }
if (VIR_ALLOC(res) < 0)
return NULL;
@@ -157,7 +171,7 @@ virLockSpaceResourceNew(virLockSpacePtr lockspace,
goto error;
}
- if (virFileLock(res->fd, shared, 0, 1, false) < 0) {
+ if (virFileLock(res->fd, shared, start, 1, waitForLock) < 0) {
if (errno == EACCES || errno == EAGAIN) {
virReportError(VIR_ERR_RESOURCE_BUSY,
_("Lockspace resource '%s' is
locked"),
@@ -204,7 +218,7 @@ virLockSpaceResourceNew(virLockSpacePtr lockspace,
goto error;
}
- if (virFileLock(res->fd, shared, 0, 1, false) < 0) {
+ if (virFileLock(res->fd, shared, start, 1, waitForLock) < 0) {
if (errno == EACCES || errno == EAGAIN) {
virReportError(VIR_ERR_RESOURCE_BUSY,
_("Lockspace resource '%s' is locked"),
@@ -621,7 +635,15 @@ int virLockSpaceAcquireResource(virLockSpacePtr lockspace,
lockspace, resname, flags, (unsigned long long)owner);
virCheckFlags(VIR_LOCK_SPACE_ACQUIRE_SHARED |
- VIR_LOCK_SPACE_ACQUIRE_AUTOCREATE, -1);
+ VIR_LOCK_SPACE_ACQUIRE_AUTOCREATE |
+ VIR_LOCK_SPACE_ACQUIRE_METADATA, -1);
+
+ if (flags & VIR_LOCK_SPACE_ACQUIRE_METADATA &&
+ flags & VIR_LOCK_SPACE_ACQUIRE_SHARED) {
+ virReportInvalidArg(flags, "%s",
+ _("metadata and shared are mutually exclusive"));
+ return -1;
+ }
virMutexLock(&lockspace->lock);
@@ -635,10 +657,14 @@ int virLockSpaceAcquireResource(virLockSpacePtr lockspace,
goto done;
}
- virReportError(VIR_ERR_RESOURCE_BUSY,
- _("Lockspace resource '%s' is locked"),
- resname);
- goto cleanup;
+
+ if (!(res->flags & VIR_LOCK_SPACE_ACQUIRE_METADATA) ||
+ !(flags & VIR_LOCK_SPACE_ACQUIRE_METADATA)) {
+ virReportError(VIR_ERR_RESOURCE_BUSY,
+ _("Lockspace resource '%s' is locked"),
+ resname);
+ goto cleanup;
+ }
}
if (!(res = virLockSpaceResourceNew(lockspace, resname, flags, owner)))
diff --git a/src/util/virlockspace.h b/src/util/virlockspace.h
index 041cf20396..a9a3b2e73f 100644
--- a/src/util/virlockspace.h
+++ b/src/util/virlockspace.h
@@ -45,6 +45,7 @@ int virLockSpaceDeleteResource(virLockSpacePtr lockspace,
typedef enum {
VIR_LOCK_SPACE_ACQUIRE_SHARED = (1 << 0),
VIR_LOCK_SPACE_ACQUIRE_AUTOCREATE = (1 << 1),
+ VIR_LOCK_SPACE_ACQUIRE_METADATA = (1 << 2),
} virLockSpaceAcquireFlags;
int virLockSpaceAcquireResource(virLockSpacePtr lockspace,
--
2.16.4