On Mon, May 24, 2010 at 12:02 PM, Tao Guo <glorioustao@xxxxxxxxx> wrote: > On Mon, May 24, 2010 at 9:43 PM, William A. (Andy) Adamson > <androsadamson@xxxxxxxxx> wrote: >> On Mon, May 24, 2010 at 2:37 AM, Tao Guo <glorioustao@xxxxxxxxx> wrote: >>> I see... But what if sync == 1? At that time, data must have already >>> been freed, so you should not use data->cred anymore. >> >> Agreed. >> >> Since LAYOUTCOMMIT is not called after close, we can get rid of taking >> the reference all together since a reference is taken on OPEN and >> dropped on CLOSE. I forgot memory mapped files where writes can occur after the close, and so layoutcommit can also occur after the close. So, I will keep the get_rpccred in pnfs_need_layout commit and resend this patch with the put_rpccred in the layoutcommit done routine. >> >> -->Andy > I agree. However that will change several functions' interface I guess. > > I still have a question: why some procedures need to set rpc_cred > whereas some needn't ? what is the connection between ctx's rpc_cred > and nfs4_state_owner's so_cred? Any guidance will be appreciated... Here's my take on an answer... If an rpc_cred is not specified in the rpc_msg then the fsuid, fsgid, and group info toe the current_cred is used to lookup an rpc_cred. RPC's can be sent from several tasks - rpciod vrs the application task for example. OPEN, CLOSE, LOCK, UNLOCK, READ, WRITE (and memmapped I/O) should all be sent with the credential that opened the file. So, in order to ensure this the nfs4_state_owner->so_cred is used for these compounds even if the task is rpciod with root fsuid/fsgid. The nfs_open_context rpc_cred is the nfs4_state_owner so_cred. The nfs_open_context can exist longer than the nfs4_state_owner. I think LAYOUTCOMMIT also wants to use the credential that did the I/O - not for the file layout driver which doesn't care, but for the object and block layout drivers that use the layout as a lock and where a permissions check (?) is done on LAYOUTCOMMIT. Currently, LAYOUTGET and LAYOUTRETURN don't set the rpc_cred. This is because the layout can last past opens and closes. If we ever want to support EXCHGID4_FLAG_BIND_PRINC_STATEID we will need to remember the cred and set it for these calls. -->Andy > >>> >>> -- >>> tao. >>> >> > > > > -- > tao. > -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
