Btrfs: Initialize btrfs_root->highest_objectid when loading tree root and subvolume...

The following call trace is seen when btrfs/031 test is executed in a loop,

[  158.661848] ------------[ cut here ]------------
[  158.662634] WARNING: CPU: 2 PID: 890 at /home/chandan/repos/linux/fs/btrfs/ioctl.c:558 create_subvol+0x3d1/0x6ea()
[  158.664102] BTRFS: Transaction aborted (error -2)
[  158.664774] Modules linked in:
[  158.665266] CPU: 2 PID: 890 Comm: btrfs Not tainted 4.4.0-rc6-g511711a #2
[  158.666251] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
[  158.667392]  ffffffff81c0a6b0 ffff8806c7c4f8e8 ffffffff81431fc8 ffff8806c7c4f930
[  158.668515]  ffff8806c7c4f920 ffffffff81051aa1 ffff880c85aff000 ffff8800bb44d000
[  158.669647]  ffff8808863b5c98 0000000000000000 00000000fffffffe ffff8806c7c4f980
[  158.670769] Call Trace:
[  158.671153]  [<ffffffff81431fc8>] dump_stack+0x44/0x5c
[  158.671884]  [<ffffffff81051aa1>] warn_slowpath_common+0x81/0xc0
[  158.672769]  [<ffffffff81051b27>] warn_slowpath_fmt+0x47/0x50
[  158.673620]  [<ffffffff813bc98d>] create_subvol+0x3d1/0x6ea
[  158.674440]  [<ffffffff813777c9>] btrfs_mksubvol.isra.30+0x369/0x520
[  158.675376]  [<ffffffff8108a4aa>] ? percpu_down_read+0x1a/0x50
[  158.676235]  [<ffffffff81377a81>] btrfs_ioctl_snap_create_transid+0x101/0x180
[  158.677268]  [<ffffffff81377b52>] btrfs_ioctl_snap_create+0x52/0x70
[  158.678183]  [<ffffffff8137afb4>] btrfs_ioctl+0x474/0x2f90
[  158.678975]  [<ffffffff81144b8e>] ? vma_merge+0xee/0x300
[  158.679751]  [<ffffffff8115be31>] ? alloc_pages_vma+0x91/0x170
[  158.680599]  [<ffffffff81123f62>] ? lru_cache_add_active_or_unevictable+0x22/0x70
[  158.681686]  [<ffffffff813d99cf>] ? selinux_file_ioctl+0xff/0x1d0
[  158.682581]  [<ffffffff8117b791>] do_vfs_ioctl+0x2c1/0x490
[  158.683399]  [<ffffffff813d3cde>] ? security_file_ioctl+0x3e/0x60
[  158.684297]  [<ffffffff8117b9d4>] SyS_ioctl+0x74/0x80
[  158.685051]  [<ffffffff819b2bd7>] entry_SYSCALL_64_fastpath+0x12/0x6a
[  158.685958] ---[ end trace 4b63312de5a2cb76 ]---
[  158.686647] BTRFS: error (device loop0) in create_subvol:558: errno=-2 No such entry
[  158.709508] BTRFS info (device loop0): forced readonly
[  158.737113] BTRFS info (device loop0): disk space caching is enabled
[  158.738096] BTRFS error (device loop0): Remounting read-write after error is not allowed
[  158.851303] BTRFS error (device loop0): cleaner transaction attach returned -30

This occurs because,

Mount filesystem
Create subvol with ID 257
Unmount filesystem
Mount filesystem
Delete subvol with ID 257
  btrfs_drop_snapshot()
    Add root corresponding to subvol 257 into
    btrfs_transaction->dropped_roots list
Create new subvol (i.e. create_subvol())
  257 is returned as the next free objectid
  btrfs_read_fs_root_no_name()
    Finds the btrfs_root instance corresponding to the old subvol with ID 257
    in btrfs_fs_info->fs_roots_radix.
    Returns error since btrfs_root_item->refs has the value of 0.

To fix the issue the commit initializes tree root's and subvolume root's
highest_objectid when loading the roots from disk.

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 216f97765b565a157634cd78ec396a45db9408a8..868736dbe6ee04bcd422b151df8de7dee30d9b83 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1582,8 +1582,23 @@ int btrfs_init_fs_root(struct btrfs_root *root)
        ret = get_anon_bdev(&root->anon_dev);
        if (ret)
                goto free_writers;
+
+       mutex_lock(&root->objectid_mutex);
+       ret = btrfs_find_highest_objectid(root,
+                                       &root->highest_objectid);
+       if (ret) {
+               mutex_unlock(&root->objectid_mutex);
+               goto free_root_dev;
+       }
+
+       ASSERT(root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);
+
+       mutex_unlock(&root->objectid_mutex);
+
        return 0;
 
+free_root_dev:
+       free_anon_bdev(root->anon_dev);
 free_writers:
        btrfs_free_subvolume_writers(root->subv_writers);
 fail:
@@ -2901,6 +2916,18 @@ retry_root_backup:
        tree_root->commit_root = btrfs_root_node(tree_root);
        btrfs_set_root_refs(&tree_root->root_item, 1);
 
+       mutex_lock(&tree_root->objectid_mutex);
+       ret = btrfs_find_highest_objectid(tree_root,
+                                       &tree_root->highest_objectid);
+       if (ret) {
+               mutex_unlock(&tree_root->objectid_mutex);
+               goto recovery_tree_root;
+       }
+
+       ASSERT(tree_root->highest_objectid <= BTRFS_LAST_FREE_OBJECTID);
+
+       mutex_unlock(&tree_root->objectid_mutex);
+
        ret = btrfs_read_roots(fs_info, tree_root);
        if (ret)
                goto recovery_tree_root;

diff --git a/fs/btrfs/inode-map.c b/fs/btrfs/inode-map.c
index 1951ad69382fbe7d488d0ceb4be18e6b839d3a7d..29e23a57d6f36db06725d9dc6f3a8daab8c4fe4c 100644 (file)
--- a/fs/btrfs/inode-map.c
+++ b/fs/btrfs/inode-map.c
@@ -515,7 +515,7 @@ out:
        return ret;
 }
 
-static int btrfs_find_highest_objectid(struct btrfs_root *root, u64 *objectid)
+int btrfs_find_highest_objectid(struct btrfs_root *root, u64 *objectid)
 {
        struct btrfs_path *path;
        int ret;
@@ -555,13 +555,6 @@ int btrfs_find_free_objectid(struct btrfs_root *root, u64 *objectid)
        int ret;
        mutex_lock(&root->objectid_mutex);
 
-       if (unlikely(root->highest_objectid < BTRFS_FIRST_FREE_OBJECTID)) {
-               ret = btrfs_find_highest_objectid(root,
-                                                 &root->highest_objectid);
-               if (ret)
-                       goto out;
-       }
-
        if (unlikely(root->highest_objectid >= BTRFS_LAST_FREE_OBJECTID)) {
                ret = -ENOSPC;
                goto out;

diff --git a/fs/btrfs/inode-map.h b/fs/btrfs/inode-map.h
index ddb347bfee232ec26543055fbf408bfb92f8028f..c8e864b2d530f88c7e65350ca557e36e6061700e 100644 (file)
--- a/fs/btrfs/inode-map.h
+++ b/fs/btrfs/inode-map.h
@@ -9,5 +9,6 @@ int btrfs_save_ino_cache(struct btrfs_root *root,
                         struct btrfs_trans_handle *trans);
 
 int btrfs_find_free_objectid(struct btrfs_root *root, u64 *objectid);
+int btrfs_find_highest_objectid(struct btrfs_root *root, u64 *objectid);
 
 #endif

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 3d9b27d2176e7d075c0eb1384a772a434592c7e7..b20463b993a65cb660dfa4546f510bac85fb3917 100644 (file)
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -568,6 +568,10 @@ static noinline int create_subvol(struct inode *dir,
                goto fail;
        }
 
+       mutex_lock(&new_root->objectid_mutex);
+       new_root->highest_objectid = new_dirid;
+       mutex_unlock(&new_root->objectid_mutex);
+
        /*
         * insert the directory item
         */