NFS: Fix writeback performance issue on cache invalidation

If a cache invalidation is triggered, and we happen to have a lot of
writebacks cached at the time, then the call to invalidate_inode_pages2()
will end up calling ->launder_page() on each and every dirty page in order
to sync its contents to disk, thus defeating write coalescing.
The following patch ensures that we try to sync the inode to disk before
calling invalidate_inode_pages2() so that we do the writeback as efficiently
as possible.

Reported-by: William Dauchy <william@gandi.net>
Reported-by: Pascal Bouchareine <pascal@gandi.net>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Tested-by: William Dauchy <william@gandi.net>
Reviewed-by: Jeff Layton <jlayton@redhat.com>

diff --git a/fs/nfs/inode.c b/fs/nfs/inode.c
index af6e806044d7cee5d8047a56de6693388fc8d34f..3ea4f641effc4c548073cca8e3923e27afbcb234 100644 (file)
--- a/fs/nfs/inode.c
+++ b/fs/nfs/inode.c
@@ -963,9 +963,15 @@ EXPORT_SYMBOL_GPL(nfs_revalidate_inode);
 static int nfs_invalidate_mapping(struct inode *inode, struct address_space *mapping)
 {
        struct nfs_inode *nfsi = NFS_I(inode);
-       
+       int ret;
+
        if (mapping->nrpages != 0) {
-               int ret = invalidate_inode_pages2(mapping);
+               if (S_ISREG(inode->i_mode)) {
+                       ret = nfs_sync_mapping(mapping);
+                       if (ret < 0)
+                               return ret;
+               }
+               ret = invalidate_inode_pages2(mapping);
                if (ret < 0)
                        return ret;
        }