On Thu, Dec 03, 2015 at 06:34:56PM -0500, Ira Cooper wrote: > Kaleb KEITHLEY <kkeithle@xxxxxxxxxx> writes: > > > On 12/03/2015 03:10 PM, Ira Cooper wrote: > >> Poornima Gurusiddaiah <pgurusid@xxxxxxxxxx> writes: > >> > >>> Hi, > >>> > >>> Brief Background: > >>> ============ > >>> For the below two features, we need ligfapi to take 2 other parameters from the applications for most number of fops. > >>> http://review.gluster.org/#/c/12014/ > >>> http://review.gluster.org/#/c/11980/ > >>> > >>> For leases to work as explained in the above doc, every file data read/write fop needs to be associated with a lease ID. This is specially required for Samba and NFS-Ganesha as they inturn serve other clients who request for leases. For Gluster to identify the end client (which is not Samba/NFS Ganesha) we need lease ID to be filled by Samba/NFS Ganesha. > >>> > >>> For mandatory locks feature to work as explained, every file data read/write fop needs to be associated with a lk_owner. In linux Kernel VFS takes care of filling the lk_ownere for the file system. In libgfapi case, the applications calling into libgfapi should be providing lk_owner with every fop. This is again required mainly for Samba and NFS Ganesha, as they serve multiple clients. > >>> > >>> Possible solutions: > >>> ============= > >>> 1. Modify all the required APIs to take 2 other parameter, lease ID and lk_owner. But that would mean backward compatibility issues and is a programming overhead for applications not interested in Leases and mandatory lock feature. > >>> 2. Add an API called glfs_set_fop_attrs (lease ID, lk_owner) which works similar to glfs_set_uid(uid). The API sets a thread local storage (pthread_key) with the values provided, the further fops on that thread will pick the lease ID and lk_owner from the thread local storage (pthread_key). There are few minor details that needs to be worked out: > >>> - In case of async API will end up using lease ID and lk_owner from wrong thread. > >>> - unset lease ID and lk_owner after every fop to ensure there is no stale lease ID or lk_owner set? > >>> - For fd based fops we can store the lease ID and lk_owner in glfd, so that the application writed need not set it for every fop. But for handle based fops lease ID and lk_owner needs to be set explicitly every-time. > >>> > >>> Solution 2 is more preferable except for that it adds overhead of calling another API, for the libgfapi users who intends to use these features. > >>> A prototype of solution 2 can be found at http://review.gluster.org/#/c/12876/ > >>> > > > > why not use storage in the client_t instead of thread local? > > It comes down to the use case. For Samba, the right spot is almost > certainly the fd, because lease keys are a per-handle (which we map to > fd) property. > > client_t is a horror show, due to race conditions between threads, IMHO. If there are known races, should we not address that? Got a bug that explains it in more detail? Thanks, Niels
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