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Although they run as rpciod background tasks, under normal operation (i.e. no SIGKILL), functions like nfs_sillyrename(), nfs4_proc_unlck() and nfs4_do_close() want to be fully synchronous. This means that when we exit, we want all references to the rpc_task to be gone, and we want any dentry references etc. held by that task to be released. For this reason these functions call __rpc_wait_for_completion_task(), followed by rpc_put_task() in the expectation that the latter will be releasing the last reference to the rpc_task, and thus ensuring that the callback_ops->rpc_release() has been called synchronously. This patch fixes a race which exists due to the fact that rpciod calls rpc_complete_task() (in order to wake up the callers of __rpc_wait_for_completion_task()) and then subsequently calls rpc_put_task() without ensuring that these two steps are done atomically. In order to avoid adding new spin locks, the patch uses the existing waitqueue spin lock to order the rpc_task reference count releases between the waiting process and rpciod. The common case where nobody is waiting for completion is optimised for by checking if the RPC_TASK_ASYNC flag is cleared and/or if the rpc_task reference count is 1: in those cases we drop trying to grab the spin lock, and immediately free up the rpc_task. Those few processes that need to put the rpc_task from inside an asynchronous context and that do not care about ordering are given a new helper: rpc_put_task_async(). Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com> |
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| .. | ||
| cache_lib.c | ||
| cache_lib.h | ||
| callback_proc.c | ||
| callback_xdr.c | ||
| callback.c | ||
| callback.h | ||
| client.c | ||
| delegation.c | ||
| delegation.h | ||
| dir.c | ||
| direct.c | ||
| dns_resolve.c | ||
| dns_resolve.h | ||
| file.c | ||
| fscache-index.c | ||
| fscache.c | ||
| fscache.h | ||
| getroot.c | ||
| idmap.c | ||
| inode.c | ||
| internal.h | ||
| iostat.h | ||
| Kconfig | ||
| Makefile | ||
| mount_clnt.c | ||
| namespace.c | ||
| nfs2xdr.c | ||
| nfs3acl.c | ||
| nfs3proc.c | ||
| nfs3xdr.c | ||
| nfs4_fs.h | ||
| nfs4filelayout.c | ||
| nfs4filelayout.h | ||
| nfs4filelayoutdev.c | ||
| nfs4namespace.c | ||
| nfs4proc.c | ||
| nfs4renewd.c | ||
| nfs4state.c | ||
| nfs4xdr.c | ||
| nfsroot.c | ||
| pagelist.c | ||
| pnfs.c | ||
| pnfs.h | ||
| proc.c | ||
| read.c | ||
| super.c | ||
| symlink.c | ||
| sysctl.c | ||
| unlink.c | ||
| write.c | ||