NFS: add comments clarifying the use of nfs_post_op_update()

Comments-only change to clarify a detail of the NFS protocol and how it is
implemented in Linux.

Test plan:
None.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
This commit is contained in:
Chuck Lever 2006-09-20 14:33:04 -04:00 committed by Trond Myklebust
parent a53a3c58fd
commit f551e44ff1
2 changed files with 13 additions and 1 deletions

View File

@ -840,6 +840,12 @@ int nfs_refresh_inode(struct inode *inode, struct nfs_fattr *fattr)
*
* After an operation that has changed the inode metadata, mark the
* attribute cache as being invalid, then try to update it.
*
* NB: if the server didn't return any post op attributes, this
* function will force the retrieval of attributes before the next
* NFS request. Thus it should be used only for operations that
* are expected to change one or more attributes, to avoid
* unnecessary NFS requests and trips through nfs_update_inode().
*/
int nfs_post_op_update_inode(struct inode *inode, struct nfs_fattr *fattr)
{

View File

@ -1253,7 +1253,13 @@ int nfs_writeback_done(struct rpc_task *task, struct nfs_write_data *data)
dprintk("NFS: %4d nfs_writeback_done (status %d)\n",
task->tk_pid, task->tk_status);
/* Call the NFS version-specific code */
/*
* ->write_done will attempt to use post-op attributes to detect
* conflicting writes by other clients. A strict interpretation
* of close-to-open would allow us to continue caching even if
* another writer had changed the file, but some applications
* depend on tighter cache coherency when writing.
*/
status = NFS_PROTO(data->inode)->write_done(task, data);
if (status != 0)
return status;