commit_metadata export operation replacing nfsd_sync_dir

- Add commit_metadata export_operation to allow the underlying filesystem to
decide how to commit an inode most efficiently.

- Usage of nfsd_sync_dir and write_inode_now has been replaced with the
commit_metadata function that takes a svc_fh.

- The commit_metadata function calls the commit_metadata export_op if it's
there, or else falls back to sync_inode instead of fsync and write_inode_now
because only metadata need be synced here.

- nfsd4_sync_rec_dir now uses vfs_fsync so that commit_metadata can be static

Signed-off-by: Ben Myers <bpm@sgi.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>

2 files changed, 53 insertions, 57 deletions

diff --git a/fs/nfsd/nfs4recover.c b/fs/nfsd/nfs4recover.c
index 5a754f7b71ed..98fb98e330b4 100644
--- a/fs/nfsd/nfs4recover.c
+++ b/fs/nfsd/nfs4recover.c
@@ -119,9 +119,7 @@ out_no_tfm:
 static void
 nfsd4_sync_rec_dir(void)
 {
-        mutex_lock(&rec_dir.dentry->d_inode->i_mutex);
-        nfsd_sync_dir(rec_dir.dentry);
-        mutex_unlock(&rec_dir.dentry->d_inode->i_mutex);
+        vfs_fsync(NULL, rec_dir.dentry, 0);
 }
 
 int
diff --git a/fs/nfsd/vfs.c b/fs/nfsd/vfs.c
index ed024d329056..8afdba5082e8 100644
--- a/fs/nfsd/vfs.c
+++ b/fs/nfsd/vfs.c
@@ -27,6 +27,8 @@
 #include <linux/jhash.h>
 #include <linux/ima.h>
 #include <asm/uaccess.h>
+#include <linux/exportfs.h>
+#include <linux/writeback.h>
 
 #ifdef CONFIG_NFSD_V3
 #include "xdr3.h"
@@ -271,6 +273,32 @@ out:
         return err;
 }
 
+/*
+ * Commit metadata changes to stable storage.
+ */
+static int
+commit_metadata(struct svc_fh *fhp)
+{
+        struct inode *inode = fhp->fh_dentry->d_inode;
+        const struct export_operations *export_ops = inode->i_sb->s_export_op;
+        int error = 0;
+
+        if (!EX_ISSYNC(fhp->fh_export))
+                return 0;
+
+        if (export_ops->commit_metadata) {
+                error = export_ops->commit_metadata(inode);
+        } else {
+                struct writeback_control wbc = {
+                        .sync_mode = WB_SYNC_ALL,
+                        .nr_to_write = 0, /* metadata only */
+                };
+
+                error = sync_inode(inode, &wbc);
+        }
+
+        return error;
+}
 
 /*
  * Set various file attributes.
@@ -769,28 +797,6 @@ nfsd_close(struct file *filp)
 }
 
 /*
- * Sync a directory to disk.
- *
- * We can't just call vfs_fsync because our requirements are slightly odd:
- *
- *  a) we do not have a file struct available
- *  b) we expect to have i_mutex already held by the caller
- */
-int
-nfsd_sync_dir(struct dentry *dentry)
-{
-        struct inode *inode = dentry->d_inode;
-        int error;
-
-        WARN_ON(!mutex_is_locked(&inode->i_mutex));
-
-        error = filemap_write_and_wait(inode->i_mapping);
-        if (!error && inode->i_fop->fsync)
-                error = inode->i_fop->fsync(NULL, dentry, 0);
-        return error;
-}
-
-/*
  * Obtain the readahead parameters for the file
  * specified by (dev, ino).
  */
@@ -1331,12 +1337,14 @@ nfsd_create(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 goto out_nfserr;
         }
 
-        if (EX_ISSYNC(fhp->fh_export)) {
-                err = nfserrno(nfsd_sync_dir(dentry));
-                write_inode_now(dchild->d_inode, 1);
-        }
+        err = nfsd_create_setattr(rqstp, resfhp, iap);
 
-        err2 = nfsd_create_setattr(rqstp, resfhp, iap);
+        /*
+         * nfsd_setattr already committed the child.  Transactional filesystems
+         * had a chance to commit changes for both parent and child
+         * simultaneously making the following commit_metadata a noop.
+         */
+        err2 = nfserrno(commit_metadata(fhp));
         if (err2)
                 err = err2;
         mnt_drop_write(fhp->fh_export->ex_path.mnt);
@@ -1368,7 +1376,6 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
         struct dentry   *dentry, *dchild = NULL;
         struct inode    *dirp;
         __be32          err;
-        __be32          err2;
         int             host_err;
         __u32           v_mtime=0, v_atime=0;
 
@@ -1463,11 +1470,6 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
         if (created)
                 *created = 1;
 
-        if (EX_ISSYNC(fhp->fh_export)) {
-                err = nfserrno(nfsd_sync_dir(dentry));
-                /* setattr will sync the child (or not) */
-        }
-
         nfsd_check_ignore_resizing(iap);
 
         if (createmode == NFS3_CREATE_EXCLUSIVE) {
@@ -1482,9 +1484,13 @@ nfsd_create_v3(struct svc_rqst *rqstp, struct svc_fh *fhp,
         }
 
  set_attr:
-        err2 = nfsd_create_setattr(rqstp, resfhp, iap);
-        if (err2)
-                err = err2;
+        err = nfsd_create_setattr(rqstp, resfhp, iap);
+
+        /*
+         * nfsd_setattr already committed the child (and possibly also the parent).
+         */
+        if (!err)
+                err = nfserrno(commit_metadata(fhp));
 
         mnt_drop_write(fhp->fh_export->ex_path.mnt);
         /*
@@ -1599,12 +1605,9 @@ nfsd_symlink(struct svc_rqst *rqstp, struct svc_fh *fhp,
                 }
         } else
                 host_err = vfs_symlink(dentry->d_inode, dnew, path);
-
-        if (!host_err) {
-                if (EX_ISSYNC(fhp->fh_export))
-                        host_err = nfsd_sync_dir(dentry);
-        }
         err = nfserrno(host_err);
+        if (!err)
+                err = nfserrno(commit_metadata(fhp));
         fh_unlock(fhp);
 
         mnt_drop_write(fhp->fh_export->ex_path.mnt);
@@ -1666,11 +1669,9 @@ nfsd_link(struct svc_rqst *rqstp, struct svc_fh *ffhp,
         }
         host_err = vfs_link(dold, dirp, dnew);
         if (!host_err) {
-                if (EX_ISSYNC(ffhp->fh_export)) {
-                        err = nfserrno(nfsd_sync_dir(ddir));
-                        write_inode_now(dest, 1);
-                }
-                err = 0;
+                err = nfserrno(commit_metadata(ffhp));
+                if (!err)
+                        err = nfserrno(commit_metadata(tfhp));
         } else {
                 if (host_err == -EXDEV && rqstp->rq_vers == 2)
                         err = nfserr_acces;
@@ -1766,10 +1767,10 @@ nfsd_rename(struct svc_rqst *rqstp, struct svc_fh *ffhp, char *fname, int flen,
                 goto out_dput_new;
 
         host_err = vfs_rename(fdir, odentry, tdir, ndentry);
-        if (!host_err && EX_ISSYNC(tfhp->fh_export)) {
-                host_err = nfsd_sync_dir(tdentry);
+        if (!host_err) {
+                host_err = commit_metadata(tfhp);
                 if (!host_err)
-                        host_err = nfsd_sync_dir(fdentry);
+                        host_err = commit_metadata(ffhp);
         }
 
         mnt_drop_write(ffhp->fh_export->ex_path.mnt);
@@ -1850,12 +1851,9 @@ nfsd_unlink(struct svc_rqst *rqstp, struct svc_fh *fhp, int type,
 
         dput(rdentry);
 
-        if (host_err)
-                goto out_drop;
-        if (EX_ISSYNC(fhp->fh_export))
-                host_err = nfsd_sync_dir(dentry);
+        if (!host_err)
+                host_err = commit_metadata(fhp);
 
-out_drop:
         mnt_drop_write(fhp->fh_export->ex_path.mnt);
 out_nfserr:
         err = nfserrno(host_err);