fs/btrfs/transaction.h

/* SPDX-License-Identifier: GPL-2.0 */
/*
 * Copyright (C) 2007 Oracle.  All rights reserved.
 */

#ifndef BTRFS_TRANSACTION_H
#define BTRFS_TRANSACTION_H

#include <linux/atomic.h>
#include <linux/refcount.h>
#include <linux/list.h>
#include <linux/time64.h>
#include <linux/mutex.h>
#include <linux/wait.h>
#include <linux/xarray.h>
#include "btrfs_inode.h"
#include "delayed-ref.h"

struct dentry;
struct inode;
struct btrfs_pending_snapshot;
struct btrfs_fs_info;
struct btrfs_root_item;
struct btrfs_root;
struct btrfs_path;

/*
 * Signal that a direct IO write is in progress, to avoid deadlock for sync
 * direct IO writes when fsync is called during the direct IO write path.
 */
#define BTRFS_TRANS_DIO_WRITE_STUB	((void *) 1)

/* Radix-tree tag for roots that are part of the transaction. */
#define BTRFS_ROOT_TRANS_TAG			0

enum btrfs_trans_state {
	TRANS_STATE_RUNNING,
	TRANS_STATE_COMMIT_PREP,
	TRANS_STATE_COMMIT_START,
	TRANS_STATE_COMMIT_DOING,
	TRANS_STATE_UNBLOCKED,
	TRANS_STATE_SUPER_COMMITTED,
	TRANS_STATE_COMPLETED,
	TRANS_STATE_MAX,
};

#define BTRFS_TRANS_HAVE_FREE_BGS	0
#define BTRFS_TRANS_DIRTY_BG_RUN	1
#define BTRFS_TRANS_CACHE_ENOSPC	2

struct btrfs_transaction {
	u64 transid;
	/*
	 * total external writers(USERSPACE/START/ATTACH) in this
	 * transaction, it must be zero before the transaction is
	 * being committed
	 */
	atomic_t num_extwriters;
	/*
	 * total writers in this transaction, it must be zero before the
	 * transaction can end
	 */
	atomic_t num_writers;
	refcount_t use_count;

	unsigned long flags;

	/* Be protected by fs_info->trans_lock when we want to change it. */
	enum btrfs_trans_state state;
	int aborted;
	struct list_head list;
	struct extent_io_tree dirty_pages;
	time64_t start_time;
	wait_queue_head_t writer_wait;
	wait_queue_head_t commit_wait;
	struct list_head pending_snapshots;
	struct list_head dev_update_list;
	struct list_head switch_commits;
	struct list_head dirty_bgs;

	/*
	 * There is no explicit lock which protects io_bgs, rather its
	 * consistency is implied by the fact that all the sites which modify
	 * it do so under some form of transaction critical section, namely:
	 *
	 * - btrfs_start_dirty_block_groups - This function can only ever be
	 *   run by one of the transaction committers. Refer to
	 *   BTRFS_TRANS_DIRTY_BG_RUN usage in btrfs_commit_transaction
	 *
	 * - btrfs_write_dirty_blockgroups - this is called by
	 *   commit_cowonly_roots from transaction critical section
	 *   (TRANS_STATE_COMMIT_DOING)
	 *
	 * - btrfs_cleanup_dirty_bgs - called on transaction abort
	 */
	struct list_head io_bgs;
	struct list_head dropped_roots;
	struct extent_io_tree pinned_extents;

	/*
	 * we need to make sure block group deletion doesn't race with
	 * free space cache writeout.  This mutex keeps them from stomping
	 * on each other
	 */
	struct mutex cache_write_mutex;
	spinlock_t dirty_bgs_lock;
	/* Protected by spin lock fs_info->unused_bgs_lock. */
	struct list_head deleted_bgs;
	spinlock_t dropped_roots_lock;
	struct btrfs_delayed_ref_root delayed_refs;
	struct btrfs_fs_info *fs_info;

	/*
	 * Number of ordered extents the transaction must wait for before
	 * committing. These are ordered extents started by a fast fsync.
	 */
	atomic_t pending_ordered;
	wait_queue_head_t pending_wait;
};

enum {
	ENUM_BIT(__TRANS_FREEZABLE),
	ENUM_BIT(__TRANS_START),
	ENUM_BIT(__TRANS_ATTACH),
	ENUM_BIT(__TRANS_JOIN),
	ENUM_BIT(__TRANS_JOIN_NOLOCK),
	ENUM_BIT(__TRANS_DUMMY),
	ENUM_BIT(__TRANS_JOIN_NOSTART),
};

#define TRANS_START		(__TRANS_START | __TRANS_FREEZABLE)
#define TRANS_ATTACH		(__TRANS_ATTACH)
#define TRANS_JOIN		(__TRANS_JOIN | __TRANS_FREEZABLE)
#define TRANS_JOIN_NOLOCK	(__TRANS_JOIN_NOLOCK)
#define TRANS_JOIN_NOSTART	(__TRANS_JOIN_NOSTART)

#define TRANS_EXTWRITERS	(__TRANS_START | __TRANS_ATTACH)

struct btrfs_trans_handle {
	u64 transid;
	u64 bytes_reserved;
	u64 delayed_refs_bytes_reserved;
	u64 chunk_bytes_reserved;
	unsigned long delayed_ref_updates;
	unsigned long delayed_ref_csum_deletions;
	struct btrfs_transaction *transaction;
	struct btrfs_block_rsv *block_rsv;
	struct btrfs_block_rsv *orig_rsv;
	/* Set by a task that wants to create a snapshot. */
	struct btrfs_pending_snapshot *pending_snapshot;
	refcount_t use_count;
	unsigned int type;
	/*
	 * Error code of transaction abort, set outside of locks and must use
	 * the READ_ONCE/WRITE_ONCE access
	 */
	short aborted;
	bool adding_csums;
	bool allocating_chunk;
	bool removing_chunk;
	bool reloc_reserved;
	bool in_fsync;
	struct btrfs_fs_info *fs_info;
	struct list_head new_bgs;
	struct btrfs_block_rsv delayed_rsv;
	/* Extent buffers with writeback inhibited by this handle. */
	struct xarray writeback_inhibited_ebs;
};

/*
 * The abort status can be changed between calls and is not protected by locks.
 * This accepts btrfs_transaction and btrfs_trans_handle as types. Once it's
 * set to a non-zero value it does not change, so the macro should be in checks
 * but is not necessary for further reads of the value.
 */
#define TRANS_ABORTED(trans)		(unlikely(READ_ONCE((trans)->aborted)))

struct btrfs_pending_snapshot {
	struct dentry *dentry;
	struct btrfs_inode *dir;
	struct btrfs_root *root;
	struct btrfs_root_item *root_item;
	struct btrfs_root *snap;
	struct btrfs_qgroup_inherit *inherit;
	struct btrfs_path *path;
	/* block reservation for the operation */
	struct btrfs_block_rsv block_rsv;
	/* extra metadata reservation for relocation */
	int error;
	/* Preallocated anonymous block device number */
	dev_t anon_dev;
	bool readonly;
	struct list_head list;
};

static inline void btrfs_set_inode_last_trans(struct btrfs_trans_handle *trans,
					      struct btrfs_inode *inode)
{
	spin_lock(&inode->lock);
	inode->last_trans = trans->transaction->transid;
	inode->last_sub_trans = btrfs_get_root_log_transid(inode->root);
	inode->last_log_commit = inode->last_sub_trans - 1;
	spin_unlock(&inode->lock);
}

/*
 * Make qgroup codes to skip given qgroupid, means the old/new_roots for
 * qgroup won't contain the qgroupid in it.
 */
static inline void btrfs_set_skip_qgroup(struct btrfs_trans_handle *trans,
					 u64 qgroupid)
{
	struct btrfs_delayed_ref_root *delayed_refs;

	delayed_refs = &trans->transaction->delayed_refs;
	WARN_ON(delayed_refs->qgroup_to_skip);
	delayed_refs->qgroup_to_skip = qgroupid;
}

static inline void btrfs_clear_skip_qgroup(struct btrfs_trans_handle *trans)
{
	struct btrfs_delayed_ref_root *delayed_refs;

	delayed_refs = &trans->transaction->delayed_refs;
	WARN_ON(!delayed_refs->qgroup_to_skip);
	delayed_refs->qgroup_to_skip = 0;
}

/*
 * We want the transaction abort to print stack trace only for errors where the
 * cause could be a bug, eg. due to ENOSPC, and not for common errors that are
 * caused by external factors.
 */
static inline bool btrfs_abort_should_print_stack(int error)
{
	switch (error) {
	case -EIO:
	case -EROFS:
	case -ENOMEM:
		return false;
	}
	return true;
}

/*
 * Compile-time and run-time verification of error passed to transaction abort.
 * Direct constants will be caught at compile time, errors read from variables
 * can be caught only at run-time and will warn under debugging config.
 *
 * How verification works:
 * - accepted builtin constants are all -EIO and such
 * - for compile-time check, invalid condition produces a negative-sized array
 *   type, valid zero-sized
 * - when a variable is passed as error the first check is a no-op
 * - with enabled debugging, the second array type size is constructed from the
 *   real variable value, valid condition produces array of size 1
 * - sizeof(type) does not generate any code
 */
#define VERIFY_NEGATIVE_ERROR(error)						\
do {										\
	(void)sizeof(char[-!(__builtin_constant_p(error) ? (error) < 0 : 1)]);	\
	if (IS_ENABLED(CONFIG_BTRFS_DEBUG)) {					\
		if (sizeof(char[(error) < 0]) != 1)				\
			DEBUG_WARN("error >= 0 passed to btrfs_abort_transaction()"); \
	}									\
} while(0)

/*
 * Call btrfs_abort_transaction() as early as possible when an error condition
 * is detected, that way the exact stack trace is reported for some errors.
 *
 * Error number must be negative as it encodes wheather it's the first abort.
 */
#define btrfs_abort_transaction(trans, error)		\
do {								\
	int __error = (error);					\
								\
	VERIFY_NEGATIVE_ERROR(error);				\
	/* Report first abort since mount */			\
	if (!test_and_set_bit(BTRFS_FS_STATE_TRANS_ABORTED,	\
			&((trans)->fs_info->fs_state))) {	\
		WARN_ON(btrfs_abort_should_print_stack(__error)); \
		__error = -__error;				\
	}							\
	__btrfs_abort_transaction((trans), __func__,		\
				  __LINE__, __error);		\
} while (0)

int btrfs_end_transaction(struct btrfs_trans_handle *trans);
struct btrfs_trans_handle *btrfs_start_transaction(struct btrfs_root *root,
						   unsigned int num_items);
struct btrfs_trans_handle *btrfs_start_transaction_fallback_global_rsv(
					struct btrfs_root *root,
					unsigned int num_items);
struct btrfs_trans_handle *btrfs_join_transaction(struct btrfs_root *root);
struct btrfs_trans_handle *btrfs_join_transaction_spacecache(struct btrfs_root *root);
struct btrfs_trans_handle *btrfs_join_transaction_nostart(struct btrfs_root *root);
struct btrfs_trans_handle *btrfs_attach_transaction(struct btrfs_root *root);
struct btrfs_trans_handle *btrfs_attach_transaction_barrier(
					struct btrfs_root *root);
int btrfs_wait_for_commit(struct btrfs_fs_info *fs_info, u64 transid);

void btrfs_add_dead_root(struct btrfs_root *root);
void btrfs_maybe_wake_unfinished_drop(struct btrfs_fs_info *fs_info);
int btrfs_clean_one_deleted_snapshot(struct btrfs_fs_info *fs_info);
int btrfs_commit_transaction(struct btrfs_trans_handle *trans);
void btrfs_commit_transaction_async(struct btrfs_trans_handle *trans);
int btrfs_commit_current_transaction(struct btrfs_root *root);
int btrfs_end_transaction_throttle(struct btrfs_trans_handle *trans);
bool btrfs_should_end_transaction(struct btrfs_trans_handle *trans);
void btrfs_throttle(struct btrfs_fs_info *fs_info);
int btrfs_record_root_in_trans(struct btrfs_trans_handle *trans,
				struct btrfs_root *root);
int btrfs_write_marked_extents(struct btrfs_fs_info *fs_info,
				struct extent_io_tree *dirty_pages, int mark);
int btrfs_wait_tree_log_extents(struct btrfs_root *root, int mark);
int btrfs_transaction_blocked(struct btrfs_fs_info *info);
void btrfs_put_transaction(struct btrfs_transaction *transaction);
void btrfs_add_dropped_root(struct btrfs_trans_handle *trans,
			    struct btrfs_root *root);
void btrfs_trans_release_chunk_metadata(struct btrfs_trans_handle *trans);
void __cold __btrfs_abort_transaction(struct btrfs_trans_handle *trans,
				      const char *function,
				      unsigned int line, int error);

int __init btrfs_transaction_init(void);
void __cold btrfs_transaction_exit(void);

#endif