The following call trace is seen when btrfs/031 test is executed in a loop,
[ 120.577208] WARNING: CPU: 3 PID: 6202 at /home/chandan/repos/linux/fs/btrfs/ioctl.c:558 create_subvol+0x3e6/0x729()
[ 120.581521] BTRFS: Transaction aborted (error -2)
[ 120.585410] Modules linked in:
[ 120.587460] CPU: 3 PID: 6202 Comm: btrfs Not tainted 4.2.0-rc5+ #27
[ 120.591232] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
[ 120.596134] ffffffff81c009d0 ffff880c846ff918 ffffffff81988f34 0000000000000001
[ 120.600754] ffff880c846ff968 ffff880c846ff958 ffffffff81050315 ffff880c846ff938
[ 120.605166] ffff880c85ae6000 ffff8809b944e000 ffff880a96c5a448 0000000000000000
[ 120.609589] Call Trace:
[ 120.610936] [<ffffffff81988f34>] dump_stack+0x45/0x57
[ 120.613868] [<ffffffff81050315>] warn_slowpath_common+0x85/0xc0
[ 120.616812] [<ffffffff81050391>] warn_slowpath_fmt+0x41/0x50
[ 120.619681] [<ffffffff81985a84>] create_subvol+0x3e6/0x729
[ 120.622390] [<ffffffff8112d977>] ? zone_statistics+0x77/0x90
[ 120.625111] [<ffffffff8136577e>] btrfs_mksubvol.isra.30+0x37e/0x530
[ 120.628091] [<ffffffff8111a248>] ? __alloc_pages_nodemask+0x1b8/0x950
[ 120.631091] [<ffffffff81180f6a>] ? __mnt_want_write_file+0x1a/0x30
[ 120.635156] [<ffffffff81365a31>] btrfs_ioctl_snap_create_transid+0x101/0x180
[ 120.639936] [<ffffffff81365b02>] btrfs_ioctl_snap_create+0x52/0x70
[ 120.643942] [<ffffffff813684ae>] btrfs_ioctl+0x46e/0x2450
[ 120.647204] [<ffffffff8111f926>] ? lru_cache_add_active_or_unevictable+0x26/0x80
[ 120.651647] [<ffffffff81174dd1>] do_vfs_ioctl+0x2c1/0x4a0
[ 120.655111] [<ffffffff813be198>] ? selinux_file_ioctl+0x48/0xd0
[ 120.658500] [<ffffffff813b875e>] ? security_file_ioctl+0x3e/0x60
[ 120.661680] [<ffffffff81175024>] SyS_ioctl+0x74/0x80
[ 120.664464] [<ffffffff819932d7>] entry_SYSCALL_64_fastpath+0x12/0x6a
[ 120.667824] ---[ end trace 13f2ab1e5917a256 ]---
[ 120.670159] BTRFS: error (device loop0) in create_subvol:558: errno=-2 No such entry
[ 120.673872] BTRFS info (device loop0): forced readonly
[ 120.701265] BTRFS info (device loop0): disk space caching is enabled
[ 120.704934] BTRFS error (device loop0): Remounting read-write after error is not allowed
[ 120.904385] 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 we now check for the existance of stale btrfs_root entry in
the btrfs_fs_info->fs_roots_radix tree and if such an entry does exist we
commit the current transaction.
Signed-off-by: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx>
---
fs/btrfs/disk-io.c | 4 ++--
fs/btrfs/disk-io.h | 2 ++
fs/btrfs/ioctl.c | 26 ++++++++++++++++++++------
3 files changed, 24 insertions(+), 8 deletions(-)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index aa59871..0c9e9d2 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1583,8 +1583,8 @@ fail:
return ret;
}
-static struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
- u64 root_id)
+struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
+ u64 root_id)
{
struct btrfs_root *root;
diff --git a/fs/btrfs/disk-io.h b/fs/btrfs/disk-io.h
index bdfb479..7f06e1f 100644
--- a/fs/btrfs/disk-io.h
+++ b/fs/btrfs/disk-io.h
@@ -86,6 +86,8 @@ void btrfs_btree_balance_dirty_nodelay(struct btrfs_root *root);
void btrfs_drop_and_free_fs_root(struct btrfs_fs_info *fs_info,
struct btrfs_root *root);
void btrfs_free_fs_root(struct btrfs_root *root);
+struct btrfs_root *btrfs_lookup_fs_root(struct btrfs_fs_info *fs_info,
+ u64 root_id);
#ifdef CONFIG_BTRFS_FS_RUN_SANITY_TESTS
struct btrfs_root *btrfs_alloc_dummy_root(void);
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0adf542..7123e96 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -474,13 +474,27 @@ static noinline int create_subvol(struct inode *dir,
if (ret)
return ret;
- trans = btrfs_start_transaction(root, 0);
- if (IS_ERR(trans)) {
- ret = PTR_ERR(trans);
- btrfs_subvolume_release_metadata(root, &block_rsv,
- qgroup_reserved);
- return ret;
+ while (1) {
+ trans = btrfs_start_transaction(root, 0);
+ if (IS_ERR(trans)) {
+ ret = PTR_ERR(trans);
+ btrfs_subvolume_release_metadata(root, &block_rsv,
+ qgroup_reserved);
+ return ret;
+ }
+
+ new_root = btrfs_lookup_fs_root(root->fs_info, objectid);
+ if (!new_root)
+ break;
+
+ ret = btrfs_commit_transaction(trans, root);
+ if (ret) {
+ btrfs_subvolume_release_metadata(root, &block_rsv,
+ qgroup_reserved);
+ return ret;
+ }
}
+
trans->block_rsv = &block_rsv;
trans->bytes_reserved = block_rsv.size;
--
2.1.0
--
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