Re: [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&gt; --- 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,