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From: Josef Bacik <josef@toxicpanda.com>
To: linux-btrfs@vger.kernel.org, kernel-team@fb.com
Subject: [PATCH 6/8] btrfs: don't take an extra root ref at allocation time
Date: Fri, 14 Feb 2020 16:11:45 -0500
Message-ID: <20200214211147.24610-7-josef@toxicpanda.com> (raw)
In-Reply-To: <20200214211147.24610-1-josef@toxicpanda.com>

Now that all the users of roots take references for them we can drop the
extra root ref we've been taking.  Before we had roots at 2 refs for the
life of the file system, one for the radix tree, and one simply for
existing.  Now that we have proper ref accounting in all places that use
roots we can drop this extra ref simply for existing as we no longer
need it.

Signed-off-by: Josef Bacik <josef@toxicpanda.com>
---
 fs/btrfs/disk-io.c            | 20 ++++++--------------
 fs/btrfs/tests/qgroup-tests.c |  2 ++
 2 files changed, 8 insertions(+), 14 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index ffbc4c6c17fe..052690799d64 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1645,22 +1645,11 @@ struct btrfs_root *btrfs_get_fs_root(struct btrfs_fs_info *fs_info,
 	if (ret == 0)
 		set_bit(BTRFS_ROOT_ORPHAN_ITEM_INSERTED, &root->state);
 
-	/*
-	 * All roots have two refs on them at all times, one for the mounted fs,
-	 * and one for being in the radix tree.  This way we only free the root
-	 * when we are unmounting or deleting the subvolume.  We get one ref
-	 * from __setup_root, one for inserting it into the radix tree, and then
-	 * we have the third for returning it, and the caller will put it when
-	 * it's done with the root.
-	 */
-	btrfs_grab_root(root);
 	ret = btrfs_insert_fs_root(fs_info, root);
 	if (ret) {
 		btrfs_put_root(root);
-		if (ret == -EEXIST) {
-			btrfs_put_root(root);
+		if (ret == -EEXIST)
 			goto again;
-		}
 		goto fail;
 	}
 	return root;
@@ -3896,11 +3885,13 @@ int write_all_supers(struct btrfs_fs_info *fs_info, int max_mirrors)
 void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
 				  struct btrfs_root *root)
 {
+	bool drop_ref = false;
+
 	spin_lock(&fs_info->fs_roots_radix_lock);
 	radix_tree_delete(&fs_info->fs_roots_radix,
 			  (unsigned long)root->root_key.objectid);
 	if (test_and_clear_bit(BTRFS_ROOT_IN_RADIX, &root->state))
-		btrfs_put_root(root);
+		drop_ref = true;
 	spin_unlock(&fs_info->fs_roots_radix_lock);
 
 	if (btrfs_root_refs(&root->root_item) == 0)
@@ -3922,7 +3913,8 @@ void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
 		iput(root->ino_cache_inode);
 		root->ino_cache_inode = NULL;
 	}
-	btrfs_put_root(root);
+	if (drop_ref)
+		btrfs_put_root(root);
 }
 
 int btrfs_cleanup_fs_roots(struct btrfs_fs_info *fs_info)
diff --git a/fs/btrfs/tests/qgroup-tests.c b/fs/btrfs/tests/qgroup-tests.c
index ac035a6fa003..ce1ca8e73c2d 100644
--- a/fs/btrfs/tests/qgroup-tests.c
+++ b/fs/btrfs/tests/qgroup-tests.c
@@ -507,6 +507,7 @@ int btrfs_test_qgroups(u32 sectorsize, u32 nodesize)
 		test_err("couldn't insert fs root %d", ret);
 		goto out;
 	}
+	btrfs_put_root(tmp_root);
 
 	tmp_root = btrfs_alloc_dummy_root(fs_info);
 	if (IS_ERR(tmp_root)) {
@@ -521,6 +522,7 @@ int btrfs_test_qgroups(u32 sectorsize, u32 nodesize)
 		test_err("couldn't insert fs root %d", ret);
 		goto out;
 	}
+	btrfs_put_root(tmp_root);
 
 	test_msg("running qgroup tests");
 	ret = test_no_shared_qgroup(root, sectorsize, nodesize);
-- 
2.24.1


  parent reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-14 21:11 [PATCH 0/8][v4] Cleanup how we handle root refs, part 2 Josef Bacik
2020-02-14 21:11 ` [PATCH 1/8] btrfs: make the extent buffer leak check per fs info Josef Bacik
2020-02-19 13:59   ` Nikolay Borisov
2020-02-20 15:49     ` Josef Bacik
2020-02-14 21:11 ` [PATCH 2/8] btrfs: move ino_cache_inode dropping Josef Bacik
2020-02-14 21:11 ` [PATCH 3/8] btrfs: move the root freeing stuff into btrfs_put_root Josef Bacik
2020-02-19 15:10   ` Nikolay Borisov
2020-02-20 15:48     ` Josef Bacik
2020-02-14 21:11 ` [PATCH 4/8] btrfs: make inodes hold a ref on their roots Josef Bacik
2020-02-14 21:11 ` [PATCH 5/8] btrfs: hold a ref on the root on the dead roots list Josef Bacik
2020-02-14 21:11 ` Josef Bacik [this message]
2020-02-14 21:11 ` [PATCH 7/8] btrfs: make btrfs_cleanup_fs_roots use the fs_roots_radix_lock Josef Bacik
2020-02-14 21:11 ` [PATCH 8/8] btrfs: kill the subvol_srcu Josef Bacik
  -- strict thread matches above, loose matches on Subject: below --
2020-01-17 13:52 [PATCH 0/8][v2] Cleanup how we handle root refs, part 2 Josef Bacik
2020-01-17 13:52 ` [PATCH 6/8] btrfs: don't take an extra root ref at allocation time Josef Bacik

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