nfsd: Only set PF_LESS_THROTTLE when really needed.

PF_LESS_THROTTLE has a very specific use case: to avoid deadlocks
and live-locks while writing to the page cache in a loop-back
NFS mount situation.

It therefore makes sense to *only* set PF_LESS_THROTTLE in this
situation.
We now know when a request came from the local-host so it could be a
loop-back mount.  We already know when we are handling write requests,
and when we are doing anything else.

So combine those two to allow nfsd to still be throttled (like any
other process) in every situation except when it is known to be
problematic.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: J. Bruce Fields <bfields@redhat.com>

2 files changed, 12 insertions, 6 deletions

diff --git a/fs/nfsd/nfssvc.c b/fs/nfsd/nfssvc.c
index 9a4a5f9e7468..1879e43f2868 100644
--- a/fs/nfsd/nfssvc.c
+++ b/fs/nfsd/nfssvc.c
@@ -591,12 +591,6 @@ nfsd(void *vrqstp)
         nfsdstats.th_cnt++;
         mutex_unlock(&nfsd_mutex);
 
-        /*
-         * We want less throttling in balance_dirty_pages() so that nfs to
-         * localhost doesn't cause nfsd to lock up due to all the client's
-         * dirty pages.
-         */
-        current->flags |= PF_LESS_THROTTLE;
         set_freezable();
 
         /*
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index 6aaa3057683a..3aa38523b6d7 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -908,6 +908,16 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
         int                     stable = *stablep;
         int                     use_wgather;
         loff_t                  pos = offset;
+        unsigned int            pflags = current->flags;
+
+        if (rqstp->rq_local)
+                /*
+                 * We want less throttling in balance_dirty_pages()
+                 * and shrink_inactive_list() so that nfs to
+                 * localhost doesn't cause nfsd to lock up due to all
+                 * the client's dirty pages or its congested queue.
+                 */
+                current->flags |= PF_LESS_THROTTLE;
 
         dentry = file->f_path.dentry;
         inode = dentry->d_inode;
@@ -941,6 +951,8 @@ out_nfserr:
                 err = 0;
         else
                 err = nfserrno(host_err);
+        if (rqstp->rq_local)
+                tsk_restore_flags(current, pflags, PF_LESS_THROTTLE);
         return err;
 }