aboutsummaryrefslogtreecommitdiffstats
path: root/fs
diff options
context:
space:
mode:
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/ctree.h14
-rw-r--r--fs/btrfs/disk-io.c1
-rw-r--r--fs/btrfs/relocation.c30
-rw-r--r--fs/btrfs/transaction.c73
4 files changed, 105 insertions, 13 deletions
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 8490ee06370..a2c91a102b7 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -967,6 +967,12 @@ struct btrfs_fs_info {
struct srcu_struct subvol_srcu;
spinlock_t trans_lock;
+ /*
+ * the reloc mutex goes with the trans lock, it is taken
+ * during commit to protect us from the relocation code
+ */
+ struct mutex reloc_mutex;
+
struct list_head trans_list;
struct list_head hashers;
struct list_head dead_roots;
@@ -1172,6 +1178,14 @@ struct btrfs_root {
u32 type;
u64 highest_objectid;
+
+ /* btrfs_record_root_in_trans is a multi-step process,
+ * and it can race with the balancing code. But the
+ * race is very small, and only the first time the root
+ * is added to each transaction. So in_trans_setup
+ * is used to tell us when more checks are required
+ */
+ unsigned long in_trans_setup;
int ref_cows;
int track_dirty;
int in_radix;
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 20c111b3fa0..0b2b4b75913 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1620,6 +1620,7 @@ struct btrfs_root *open_ctree(struct super_block *sb,
spin_lock_init(&fs_info->fs_roots_radix_lock);
spin_lock_init(&fs_info->delayed_iput_lock);
spin_lock_init(&fs_info->defrag_inodes_lock);
+ mutex_init(&fs_info->reloc_mutex);
init_completion(&fs_info->kobj_unregister);
fs_info->tree_root = tree_root;
diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index f25b10a22a0..086b1e6b861 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -1368,7 +1368,7 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
int ret;
if (!root->reloc_root)
- return 0;
+ goto out;
reloc_root = root->reloc_root;
root_item = &reloc_root->root_item;
@@ -1390,6 +1390,8 @@ int btrfs_update_reloc_root(struct btrfs_trans_handle *trans,
ret = btrfs_update_root(trans, root->fs_info->tree_root,
&reloc_root->root_key, root_item);
BUG_ON(ret);
+
+out:
return 0;
}
@@ -2142,10 +2144,11 @@ int prepare_to_merge(struct reloc_control *rc, int err)
u64 num_bytes = 0;
int ret;
- spin_lock(&root->fs_info->trans_lock);
+ mutex_lock(&root->fs_info->reloc_mutex);
rc->merging_rsv_size += root->nodesize * (BTRFS_MAX_LEVEL - 1) * 2;
rc->merging_rsv_size += rc->nodes_relocated * 2;
- spin_unlock(&root->fs_info->trans_lock);
+ mutex_unlock(&root->fs_info->reloc_mutex);
+
again:
if (!err) {
num_bytes = rc->merging_rsv_size;
@@ -2214,9 +2217,16 @@ int merge_reloc_roots(struct reloc_control *rc)
int ret;
again:
root = rc->extent_root;
- spin_lock(&root->fs_info->trans_lock);
+
+ /*
+ * this serializes us with btrfs_record_root_in_transaction,
+ * we have to make sure nobody is in the middle of
+ * adding their roots to the list while we are
+ * doing this splice
+ */
+ mutex_lock(&root->fs_info->reloc_mutex);
list_splice_init(&rc->reloc_roots, &reloc_roots);
- spin_unlock(&root->fs_info->trans_lock);
+ mutex_unlock(&root->fs_info->reloc_mutex);
while (!list_empty(&reloc_roots)) {
found = 1;
@@ -3590,17 +3600,19 @@ next:
static void set_reloc_control(struct reloc_control *rc)
{
struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
- spin_lock(&fs_info->trans_lock);
+
+ mutex_lock(&fs_info->reloc_mutex);
fs_info->reloc_ctl = rc;
- spin_unlock(&fs_info->trans_lock);
+ mutex_unlock(&fs_info->reloc_mutex);
}
static void unset_reloc_control(struct reloc_control *rc)
{
struct btrfs_fs_info *fs_info = rc->extent_root->fs_info;
- spin_lock(&fs_info->trans_lock);
+
+ mutex_lock(&fs_info->reloc_mutex);
fs_info->reloc_ctl = NULL;
- spin_unlock(&fs_info->trans_lock);
+ mutex_unlock(&fs_info->reloc_mutex);
}
static int check_extent_flags(u64 flags)
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index 2b3590b9fe9..833996a0c62 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -126,28 +126,85 @@ static noinline int join_transaction(struct btrfs_root *root, int nofail)
* to make sure the old root from before we joined the transaction is deleted
* when the transaction commits
*/
-int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
+static int record_root_in_trans(struct btrfs_trans_handle *trans,
struct btrfs_root *root)
{
if (root->ref_cows && root->last_trans < trans->transid) {
WARN_ON(root == root->fs_info->extent_root);
WARN_ON(root->commit_root != root->node);
+ /*
+ * see below for in_trans_setup usage rules
+ * we have the reloc mutex held now, so there
+ * is only one writer in this function
+ */
+ root->in_trans_setup = 1;
+
+ /* make sure readers find in_trans_setup before
+ * they find our root->last_trans update
+ */
+ smp_wmb();
+
spin_lock(&root->fs_info->fs_roots_radix_lock);
if (root->last_trans == trans->transid) {
spin_unlock(&root->fs_info->fs_roots_radix_lock);
return 0;
}
- root->last_trans = trans->transid;
radix_tree_tag_set(&root->fs_info->fs_roots_radix,
(unsigned long)root->root_key.objectid,
BTRFS_ROOT_TRANS_TAG);
spin_unlock(&root->fs_info->fs_roots_radix_lock);
+ root->last_trans = trans->transid;
+
+ /* this is pretty tricky. We don't want to
+ * take the relocation lock in btrfs_record_root_in_trans
+ * unless we're really doing the first setup for this root in
+ * this transaction.
+ *
+ * Normally we'd use root->last_trans as a flag to decide
+ * if we want to take the expensive mutex.
+ *
+ * But, we have to set root->last_trans before we
+ * init the relocation root, otherwise, we trip over warnings
+ * in ctree.c. The solution used here is to flag ourselves
+ * with root->in_trans_setup. When this is 1, we're still
+ * fixing up the reloc trees and everyone must wait.
+ *
+ * When this is zero, they can trust root->last_trans and fly
+ * through btrfs_record_root_in_trans without having to take the
+ * lock. smp_wmb() makes sure that all the writes above are
+ * done before we pop in the zero below
+ */
btrfs_init_reloc_root(trans, root);
+ smp_wmb();
+ root->in_trans_setup = 0;
}
return 0;
}
+
+int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
+ struct btrfs_root *root)
+{
+ if (!root->ref_cows)
+ return 0;
+
+ /*
+ * see record_root_in_trans for comments about in_trans_setup usage
+ * and barriers
+ */
+ smp_rmb();
+ if (root->last_trans == trans->transid &&
+ !root->in_trans_setup)
+ return 0;
+
+ mutex_lock(&root->fs_info->reloc_mutex);
+ record_root_in_trans(trans, root);
+ mutex_unlock(&root->fs_info->reloc_mutex);
+
+ return 0;
+}
+
/* wait for commit against the current transaction to become unblocked
* when this is done, it is safe to start a new transaction, but the current
* transaction might not be fully on disk.
@@ -882,7 +939,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
parent = dget_parent(dentry);
parent_inode = parent->d_inode;
parent_root = BTRFS_I(parent_inode)->root;
- btrfs_record_root_in_trans(trans, parent_root);
+ record_root_in_trans(trans, parent_root);
/*
* insert the directory item
@@ -900,7 +957,7 @@ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans,
ret = btrfs_update_inode(trans, parent_root, parent_inode);
BUG_ON(ret);
- btrfs_record_root_in_trans(trans, root);
+ record_root_in_trans(trans, root);
btrfs_set_root_last_snapshot(&root->root_item, trans->transid);
memcpy(new_root_item, &root->root_item, sizeof(*new_root_item));
btrfs_check_and_init_root_item(new_root_item);
@@ -1247,6 +1304,13 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
} while (atomic_read(&cur_trans->num_writers) > 1 ||
(should_grow && cur_trans->num_joined != joined));
+ /*
+ * the reloc mutex makes sure that we stop
+ * the balancing code from coming in and moving
+ * extents around in the middle of the commit
+ */
+ mutex_lock(&root->fs_info->reloc_mutex);
+
ret = create_pending_snapshots(trans, root->fs_info);
BUG_ON(ret);
@@ -1312,6 +1376,7 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans,
root->fs_info->running_transaction = NULL;
root->fs_info->trans_no_join = 0;
spin_unlock(&root->fs_info->trans_lock);
+ mutex_unlock(&root->fs_info->reloc_mutex);
wake_up(&root->fs_info->transaction_wait);