fs/ext4/ext4_jbd2.h

Source file repositories/reference/linux-study-clean/fs/ext4/ext4_jbd2.h

File Facts

System
Linux kernel
Corpus path
fs/ext4/ext4_jbd2.h
Extension
.h
Size
15372 bytes
Lines
462
Domain
Core OS
Bucket
VFS And Filesystem Core
Inferred role
Core OS: implementation source
Status
source implementation candidate

Why This File Exists

Core operating-system implementation surface: boot, tasks, memory, VFS, syscall-facing interfaces, synchronization, credentials, and isolation.

Dependency Surface

Detected Declarations

Annotated Snippet

// SPDX-License-Identifier: GPL-2.0+
/*
 * ext4_jbd2.h
 *
 * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
 *
 * Copyright 1998--1999 Red Hat corp --- All Rights Reserved
 *
 * Ext4-specific journaling extensions.
 */

#ifndef _EXT4_JBD2_H
#define _EXT4_JBD2_H

#include <linux/fs.h>
#include <linux/jbd2.h>
#include "ext4.h"

#define EXT4_JOURNAL(inode)	(EXT4_SB((inode)->i_sb)->s_journal)

/* Define the number of blocks we need to account to a transaction to
 * modify one block of data.
 *
 * We may have to touch one inode, one bitmap buffer, up to three
 * indirection blocks, the group and superblock summaries, and the data
 * block to complete the transaction.
 *
 * For extents-enabled fs we may have to allocate and modify up to
 * 5 levels of tree, data block (for each of these we need bitmap + group
 * summaries), root which is stored in the inode, sb
 */

#define EXT4_SINGLEDATA_TRANS_BLOCKS(sb)				\
	(ext4_has_feature_extents(sb) ? 20U : 8U)

/* Extended attribute operations touch at most two data buffers,
 * two bitmap buffers, and two group summaries, in addition to the inode
 * and the superblock, which are already accounted for. */

#define EXT4_XATTR_TRANS_BLOCKS		6U

/* Define the minimum size for a transaction which modifies data.  This
 * needs to take into account the fact that we may end up modifying two
 * quota files too (one for the group, one for the user quota).  The
 * superblock only gets updated once, of course, so don't bother
 * counting that again for the quota updates. */

#define EXT4_DATA_TRANS_BLOCKS(sb)	(EXT4_SINGLEDATA_TRANS_BLOCKS(sb) + \
					 EXT4_XATTR_TRANS_BLOCKS - 2 + \
					 EXT4_MAXQUOTAS_TRANS_BLOCKS(sb))

/*
 * Define the number of metadata blocks we need to account to modify data.
 *
 * This include super block, inode block, quota blocks and xattr blocks
 */
#define EXT4_META_TRANS_BLOCKS(sb)	(EXT4_XATTR_TRANS_BLOCKS + \
					EXT4_MAXQUOTAS_TRANS_BLOCKS(sb))

/* Define an arbitrary limit for the amount of data we will anticipate
 * writing to any given transaction.  For unbounded transactions such as
 * write(2) and truncate(2) we can write more than this, but we always
 * start off at the maximum transaction size and grow the transaction
 * optimistically as we go. */

#define EXT4_MAX_TRANS_DATA		64U

/* We break up a large truncate or write transaction once the handle's
 * buffer credits gets this low, we need either to extend the
 * transaction or to start a new one.  Reserve enough space here for
 * inode, bitmap, superblock, group and indirection updates for at least
 * one block, plus two quota updates.  Quota allocations are not
 * needed. */

#define EXT4_RESERVE_TRANS_BLOCKS	12U

/*
 * Number of credits needed if we need to insert an entry into a
 * directory.  For each new index block, we need 4 blocks (old index
 * block, new index block, bitmap block, bg summary).  For normal
 * htree directories there are 2 levels; if the largedir feature
 * enabled it's 3 levels.
 */
#define EXT4_INDEX_EXTRA_TRANS_BLOCKS	12U

#ifdef CONFIG_QUOTA
/* Amount of blocks needed for quota update - we know that the structure was
 * allocated so we need to update only data block */
#define EXT4_QUOTA_TRANS_BLOCKS(sb) ((ext4_quota_capable(sb)) ? 1 : 0)
/* Amount of blocks needed for quota insert/delete - we do some block writes

Annotation

Implementation Notes