diff options
Diffstat (limited to 'fs/btrfs/transaction.c')
| -rw-r--r-- | fs/btrfs/transaction.c | 67 |
1 files changed, 65 insertions, 2 deletions
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c index 444abe0796a..11266d68a6c 100644 --- a/fs/btrfs/transaction.c +++ b/fs/btrfs/transaction.c @@ -46,6 +46,9 @@ static noinline void put_transaction(struct btrfs_transaction *transaction) } } +/* + * either allocate a new transaction or hop into the existing one + */ static noinline int join_transaction(struct btrfs_root *root) { struct btrfs_transaction *cur_trans; @@ -85,6 +88,12 @@ static noinline int join_transaction(struct btrfs_root *root) return 0; } +/* + * this does all the record keeping required to make sure that a + * reference counted root is properly recorded in a given transaction. + * This is required to make sure the old root from before we joined the transaction + * is deleted when the transaction commits + */ noinline int btrfs_record_root_in_trans(struct btrfs_root *root) { struct btrfs_dirty_root *dirty; @@ -127,6 +136,10 @@ noinline int btrfs_record_root_in_trans(struct btrfs_root *root) 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. + */ static void wait_current_trans(struct btrfs_root *root) { struct btrfs_transaction *cur_trans; @@ -198,7 +211,7 @@ struct btrfs_trans_handle *btrfs_start_ioctl_transaction(struct btrfs_root *r, return start_transaction(r, num_blocks, 2); } - +/* wait for a transaction commit to be fully complete */ static noinline int wait_for_commit(struct btrfs_root *root, struct btrfs_transaction *commit) { @@ -218,6 +231,10 @@ static noinline int wait_for_commit(struct btrfs_root *root, return 0; } +/* + * rate limit against the drop_snapshot code. This helps to slow down new operations + * if the drop_snapshot code isn't able to keep up. + */ static void throttle_on_drops(struct btrfs_root *root) { struct btrfs_fs_info *info = root->fs_info; @@ -302,7 +319,11 @@ int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans, return __btrfs_end_transaction(trans, root, 1); } - +/* + * when btree blocks are allocated, they have some corresponding bits set for + * them in one of two extent_io trees. This is used to make sure all of + * those extents are on disk for transaction or log commit + */ int btrfs_write_and_wait_marked_extents(struct btrfs_root *root, struct extent_io_tree *dirty_pages) { @@ -393,6 +414,16 @@ int btrfs_write_and_wait_transaction(struct btrfs_trans_handle *trans, &trans->transaction->dirty_pages); } +/* + * this is used to update the root pointer in the tree of tree roots. + * + * But, in the case of the extent allocation tree, updating the root + * pointer may allocate blocks which may change the root of the extent + * allocation tree. + * + * So, this loops and repeats and makes sure the cowonly root didn't + * change while the root pointer was being updated in the metadata. + */ static int update_cowonly_root(struct btrfs_trans_handle *trans, struct btrfs_root *root) { @@ -418,6 +449,9 @@ static int update_cowonly_root(struct btrfs_trans_handle *trans, return 0; } +/* + * update all the cowonly tree roots on disk + */ int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans, struct btrfs_root *root) { @@ -433,6 +467,11 @@ int btrfs_commit_tree_roots(struct btrfs_trans_handle *trans, return 0; } +/* + * dead roots are old snapshots that need to be deleted. This allocates + * a dirty root struct and adds it into the list of dead roots that need to + * be deleted + */ int btrfs_add_dead_root(struct btrfs_root *root, struct btrfs_root *latest) { struct btrfs_dirty_root *dirty; @@ -449,6 +488,12 @@ int btrfs_add_dead_root(struct btrfs_root *root, struct btrfs_root *latest) return 0; } +/* + * at transaction commit time we need to schedule the old roots for + * deletion via btrfs_drop_snapshot. This runs through all the + * reference counted roots that were modified in the current + * transaction and puts them into the drop list + */ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans, struct radix_tree_root *radix, struct list_head *list) @@ -541,6 +586,10 @@ static noinline int add_dirty_roots(struct btrfs_trans_handle *trans, return err; } +/* + * defrag a given btree. If cacheonly == 1, this won't read from the disk, + * otherwise every leaf in the btree is read and defragged. + */ int btrfs_defrag_root(struct btrfs_root *root, int cacheonly) { struct btrfs_fs_info *info = root->fs_info; @@ -570,6 +619,10 @@ int btrfs_defrag_root(struct btrfs_root *root, int cacheonly) return 0; } +/* + * Given a list of roots that need to be deleted, call btrfs_drop_snapshot on + * all of them + */ static noinline int drop_dirty_roots(struct btrfs_root *tree_root, struct list_head *list) { @@ -664,6 +717,10 @@ static noinline int drop_dirty_roots(struct btrfs_root *tree_root, return ret; } +/* + * new snapshots need to be created at a very specific time in the + * transaction commit. This does the actual creation + */ static noinline int create_pending_snapshot(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info, struct btrfs_pending_snapshot *pending) @@ -734,6 +791,9 @@ fail: return ret; } +/* + * create all the snapshots we've scheduled for creation + */ static noinline int create_pending_snapshots(struct btrfs_trans_handle *trans, struct btrfs_fs_info *fs_info) { @@ -944,6 +1004,9 @@ int btrfs_commit_transaction(struct btrfs_trans_handle *trans, return ret; } +/* + * interface function to delete all the snapshots we have scheduled for deletion + */ int btrfs_clean_old_snapshots(struct btrfs_root *root) { struct list_head dirty_roots; |