Re: [libvirt] [PATCH] Add support for shared sanlock leases

From: "Eric Blake" <eblake(a)redhat.com&gt; To: "Federico Simoncelli" <fsimonce(a)redhat.com&gt; Cc: "Daniel P. Berrange" <berrange(a)redhat.com&gt;, libvir-list(a)redhat.com Sent: Friday, June 22, 2012 6:19:34 AM Subject: Re: [libvirt] [PATCH] Add support for shared sanlock leases On 06/21/2012 11:00 AM, Federico Simoncelli wrote: > On Thu, Jun 21, 2012 at 03:37:10PM +0100, Daniel P. Berrange wrote: >> From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; >> >> A sanlock lease can be marked as shared (rather >> than exclusive) using SANLK_RES_SHARED flag. This >> adds support for that flag and ensures that in auto >> disk mode, any shared disks use shared leases. This >> also makes any read-only disks be completely >> ignored. >> >> case VIR_LOCK_MANAGER_RESOURCE_TYPE_DISK: >> if (driver->autoDiskLease) { >> - if (virLockManagerSanlockAddDisk(lock, name, nparams, >> params) < 0) >> + if (virLockManagerSanlockAddDisk(lock, name, nparams, >> params, >> + !!(flags & >> VIR_LOCK_MANAGER_RESOURCE_SHARED)) < 0) > > Just out of curiosity, you are using "!!" (both here and below) > because > the compiler is complaining about the type? Rather, it is a way of forcing a value to be 0 or 1 with the fewest characters possible (since the line is already long); shorter than constructs such as: (bool)(flags & VIR_LOCK_MANAGER_RESOURCE_SHARED) (flags & VIR_LOCK_MANAGER_RESOURCE_SHARED) != 0

But since virLockManagerSanlockAddDisk() declared its argument as bool, and we already require a C99 compiler, the !! trick is strictly unnecessary; C99 compilers already guarantee to implicitly convert any non-zero value to true when doing argument conversion.