Simplify BDI integration

Update the code to use the bdi_setup_and_register() helper to
simplify the bdi integration code.  The updated code now just
registers the bdi during mount and destroys it during unmount.

The only complication is that for 2.6.32 - 2.6.33 kernels the
helper wasn't available so in these cases the zfs code must
provide it.  Luckily the bdi_setup_and_register() function
is trivial.

Signed-off-by: Brian Behlendorf <[email protected]>
Closes #367

1 files changed, 23 insertions, 25 deletions

diff --git a/module/zfs/zfs_vfsops.c b/module/zfs/zfs_vfsops.c
index ed847f130..920d87e4f 100644
--- a/module/zfs/zfs_vfsops.c
+++ b/module/zfs/zfs_vfsops.c
@@ -600,12 +600,6 @@ zfs_sb_create(const char *osname, zfs_sb_t **zsbp)
 	zsb->z_show_ctldir = ZFS_SNAPDIR_VISIBLE;
 	zsb->z_os = os;
 
-	error = -bdi_init(&zsb->z_bdi);
-	if (error) {
-		kmem_free(zsb, sizeof (zfs_sb_t));
-		return (error);
-	}
-
 	error = zfs_get_zplprop(os, ZFS_PROP_VERSION, &zsb->z_version);
 	if (error) {
 		goto out;
@@ -807,7 +801,6 @@ zfs_sb_free(zfs_sb_t *zsb)
 
 	zfs_fuid_destroy(zsb);
 
-	bdi_destroy(&zsb->z_bdi);
 	mutex_destroy(&zsb->z_znodes_lock);
 	mutex_destroy(&zsb->z_lock);
 	list_destroy(&zsb->z_all_znodes);
@@ -1089,9 +1082,9 @@ zfs_sb_teardown(zfs_sb_t *zsb, boolean_t unmounting)
 }
 EXPORT_SYMBOL(zfs_sb_teardown);
 
-#ifdef HAVE_BDI
-static atomic_long_t bdi_seq = ATOMIC_LONG_INIT(0);
-#endif /* HAVE_BDI */
+#if defined(HAVE_BDI) && !defined(HAVE_BDI_SETUP_AND_REGISTER)
+atomic_long_t zfs_bdi_seq = ATOMIC_LONG_INIT(0);
+#endif /* HAVE_BDI && !HAVE_BDI_SETUP_AND_REGISTER */
 
 int
 zfs_domount(struct super_block *sb, void *data, int silent)
@@ -1118,7 +1111,23 @@ zfs_domount(struct super_block *sb, void *data, int silent)
 	sb->s_time_gran = 1;
 	sb->s_blocksize = recordsize;
 	sb->s_blocksize_bits = ilog2(recordsize);
-	bdi_put_sb(sb, NULL);
+
+#ifdef HAVE_BDI
+	/*
+	 * 2.6.32 API change,
+	 * Added backing_device_info (BDI) per super block interfaces.  A BDI
+	 * must be configured when using a non-device backed filesystem for
+	 * proper writeback.  This is not required for older pdflush kernels.
+	 *
+	 * NOTE: Linux read-ahead is disabled in favor of zfs read-ahead.
+	 */
+	zsb->z_bdi.ra_pages = 0;
+	sb->s_bdi = &zsb->z_bdi;
+
+	error = -bdi_setup_and_register(&zsb->z_bdi, "zfs", BDI_CAP_MAP_COPY);
+	if (error)
+		goto out;
+#endif /* HAVE_BDI */
 
 	/* Set callback operations for the file system. */
 	sb->s_op = &zpl_super_operations;
@@ -1143,16 +1152,6 @@ zfs_domount(struct super_block *sb, void *data, int silent)
 		dmu_objset_set_user(zsb->z_os, zsb);
 		mutex_exit(&zsb->z_os->os_user_ptr_lock);
 	} else {
-		/* Disable Linux read-ahead handled by lower layers */
-		zsb->z_bdi.ra_pages = 0;
-
-		error = -bdi_register(&zsb->z_bdi, NULL, "zfs-%d",
-		    atomic_long_inc_return(&bdi_seq));
-		if (error)
-			goto out;
-
-		bdi_put_sb(sb, &zsb->z_bdi);
-
 		error = zfs_sb_setup(zsb, B_TRUE);
 #ifdef HAVE_SNAPSHOT
 		(void) zfs_snap_create(zsb);
@@ -1193,10 +1192,9 @@ zfs_umount(struct super_block *sb)
 	VERIFY(zfs_sb_teardown(zsb, B_TRUE) == 0);
 	os = zsb->z_os;
 
-	if (bdi_get_sb(sb)) {
-		bdi_unregister(bdi_get_sb(sb));
-		bdi_put_sb(sb, NULL);
-	}
+#ifdef HAVE_BDI
+	bdi_destroy(sb->s_bdi);
+#endif /* HAVE_BDI */
 
 	/*
 	 * z_os will be NULL if there was an error in