nfsd: Pull write-gathering code out of nfsd_vfs_write

This is a relatively self-contained piece of code that handles a special
case--move it to its own function.

Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ebf56c6..6ad76a4 100644 (file)
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -963,6 +963,43 @@ static void kill_suid(struct dentry *dentry)
        mutex_unlock(&dentry->d_inode->i_mutex);
 }
 
+/*
+ * Gathered writes: If another process is currently writing to the file,
+ * there's a high chance this is another nfsd (triggered by a bulk write
+ * from a client's biod). Rather than syncing the file with each write
+ * request, we sleep for 10 msec.
+ *
+ * I don't know if this roughly approximates C. Juszak's idea of
+ * gathered writes, but it's a nice and simple solution (IMHO), and it
+ * seems to work:-)
+ *
+ * Note: we do this only in the NFSv2 case, since v3 and higher have a
+ * better tool (separate unstable writes and commits) for solving this
+ * problem.
+ */
+static int wait_for_concurrent_writes(struct file *file)
+{
+       struct inode *inode = file->f_path.dentry->d_inode;
+       static ino_t last_ino;
+       static dev_t last_dev;
+       int err = 0;
+
+       if (atomic_read(&inode->i_writecount) > 1
+           || (last_ino == inode->i_ino && last_dev == inode->i_sb->s_dev)) {
+               dprintk("nfsd: write defer %d\n", task_pid_nr(current));
+               msleep(10);
+               dprintk("nfsd: write resume %d\n", task_pid_nr(current));
+       }
+
+       if (inode->i_state & I_DIRTY) {
+               dprintk("nfsd: write sync %d\n", task_pid_nr(current));
+               err = nfsd_sync(file);
+       }
+       last_ino = inode->i_ino;
+       last_dev = inode->i_sb->s_dev;
+       return err;
+}
+
 static __be32
 nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
                                loff_t offset, struct kvec *vec, int vlen,
@@ -1026,36 +1063,8 @@ nfsd_vfs_write(struct svc_rqst *rqstp, struct svc_fh *fhp, struct file *file,
        if (host_err >= 0 && (inode->i_mode & (S_ISUID | S_ISGID)))
                kill_suid(dentry);
 
-       if (host_err >= 0 && stable && use_wgather) {
-               static ino_t    last_ino;
-               static dev_t    last_dev;
-
-               /*
-                * Gathered writes: If another process is currently
-                * writing to the file, there's a high chance
-                * this is another nfsd (triggered by a bulk write
-                * from a client's biod). Rather than syncing the
-                * file with each write request, we sleep for 10 msec.
-                *
-                * I don't know if this roughly approximates
-                * C. Juszak's idea of gathered writes, but it's a
-                * nice and simple solution (IMHO), and it seems to
-                * work:-)
-                */
-               if (atomic_read(&inode->i_writecount) > 1
-                   || (last_ino == inode->i_ino && last_dev == inode->i_sb->s_dev)) {
-                       dprintk("nfsd: write defer %d\n", task_pid_nr(current));
-                       msleep(10);
-                       dprintk("nfsd: write resume %d\n", task_pid_nr(current));
-               }
-
-               if (inode->i_state & I_DIRTY) {
-                       dprintk("nfsd: write sync %d\n", task_pid_nr(current));
-                       host_err=nfsd_sync(file);
-               }
-               last_ino = inode->i_ino;
-               last_dev = inode->i_sb->s_dev;
-       }
+       if (host_err >= 0 && stable && use_wgather)
+               host_err = wait_for_concurrent_writes(file);
 
        dprintk("nfsd: write complete host_err=%d\n", host_err);
        if (host_err >= 0)