xfs_inode_util.c | Explore in Territory

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
 * All Rights Reserved.
 */
#include <linux/iversion.h>
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_log_format.h"
#include "xfs_trans_resv.h"
#include "xfs_sb.h"
#include "xfs_mount.h"
#include "xfs_inode.h"
#include "xfs_inode_util.h"
#include "xfs_trans.h"
#include "xfs_ialloc.h"
#include "xfs_health.h"
#include "xfs_bmap.h"
#include "xfs_error.h"
#include "xfs_trace.h"
#include "xfs_ag.h"
#include "xfs_iunlink_item.h"
#include "xfs_inode_item.h"

uint16_t
xfs_flags2diflags(
	struct xfs_inode	*ip,
	unsigned int		xflags)
{ … }

uint64_t
xfs_flags2diflags2(
	struct xfs_inode	*ip,
	unsigned int		xflags)
{ … }

uint32_t
xfs_ip2xflags(
	struct xfs_inode	*ip)
{ … }

prid_t
xfs_get_initial_prid(struct xfs_inode *dp)
{ … }

/* Propagate di_flags from a parent inode to a child inode. */
static inline void
xfs_inode_inherit_flags(
	struct xfs_inode	*ip,
	const struct xfs_inode	*pip)
{ … }

/* Propagate di_flags2 from a parent inode to a child inode. */
static inline void
xfs_inode_inherit_flags2(
	struct xfs_inode	*ip,
	const struct xfs_inode	*pip)
{ … }

/*
 * If we need to create attributes immediately after allocating the inode,
 * initialise an empty attribute fork right now. We use the default fork offset
 * for attributes here as we don't know exactly what size or how many
 * attributes we might be adding. We can do this safely here because we know
 * the data fork is completely empty and this saves us from needing to run a
 * separate transaction to set the fork offset in the immediate future.
 *
 * If we have parent pointers and the caller hasn't told us that the file will
 * never be linked into a directory tree, we /must/ create the attr fork.
 */
static inline bool
xfs_icreate_want_attrfork(
	struct xfs_mount		*mp,
	const struct xfs_icreate_args	*args)
{ … }

/* Initialise an inode's attributes. */
void
xfs_inode_init(
	struct xfs_trans	*tp,
	const struct xfs_icreate_args *args,
	struct xfs_inode	*ip)
{ … }

/*
 * In-Core Unlinked List Lookups
 * =============================
 *
 * Every inode is supposed to be reachable from some other piece of metadata
 * with the exception of the root directory.  Inodes with a connection to a
 * file descriptor but not linked from anywhere in the on-disk directory tree
 * are collectively known as unlinked inodes, though the filesystem itself
 * maintains links to these inodes so that on-disk metadata are consistent.
 *
 * XFS implements a per-AG on-disk hash table of unlinked inodes.  The AGI
 * header contains a number of buckets that point to an inode, and each inode
 * record has a pointer to the next inode in the hash chain.  This
 * singly-linked list causes scaling problems in the iunlink remove function
 * because we must walk that list to find the inode that points to the inode
 * being removed from the unlinked hash bucket list.
 *
 * Hence we keep an in-memory double linked list to link each inode on an
 * unlinked list. Because there are 64 unlinked lists per AGI, keeping pointer
 * based lists would require having 64 list heads in the perag, one for each
 * list. This is expensive in terms of memory (think millions of AGs) and cache
 * misses on lookups. Instead, use the fact that inodes on the unlinked list
 * must be referenced at the VFS level to keep them on the list and hence we
 * have an existence guarantee for inodes on the unlinked list.
 *
 * Given we have an existence guarantee, we can use lockless inode cache lookups
 * to resolve aginos to xfs inodes. This means we only need 8 bytes per inode
 * for the double linked unlinked list, and we don't need any extra locking to
 * keep the list safe as all manipulations are done under the AGI buffer lock.
 * Keeping the list up to date does not require memory allocation, just finding
 * the XFS inode and updating the next/prev unlinked list aginos.
 */

/*
 * Update the prev pointer of the next agino.  Returns -ENOLINK if the inode
 * is not in cache.
 */
static int
xfs_iunlink_update_backref(
	struct xfs_perag	*pag,
	xfs_agino_t		prev_agino,
	xfs_agino_t		next_agino)
{ … }

/*
 * Point the AGI unlinked bucket at an inode and log the results.  The caller
 * is responsible for validating the old value.
 */
STATIC int
xfs_iunlink_update_bucket(
	struct xfs_trans	*tp,
	struct xfs_perag	*pag,
	struct xfs_buf		*agibp,
	unsigned int		bucket_index,
	xfs_agino_t		new_agino)
{ … }

static int
xfs_iunlink_insert_inode(
	struct xfs_trans	*tp,
	struct xfs_perag	*pag,
	struct xfs_buf		*agibp,
	struct xfs_inode	*ip)
{ … }

/*
 * This is called when the inode's link count has gone to 0 or we are creating
 * a tmpfile via O_TMPFILE.  The inode @ip must have nlink == 0.
 *
 * We place the on-disk inode on a list in the AGI.  It will be pulled from this
 * list when the inode is freed.
 */
int
xfs_iunlink(
	struct xfs_trans	*tp,
	struct xfs_inode	*ip)
{ … }

static int
xfs_iunlink_remove_inode(
	struct xfs_trans	*tp,
	struct xfs_perag	*pag,
	struct xfs_buf		*agibp,
	struct xfs_inode	*ip)
{ … }

/*
 * Pull the on-disk inode from the AGI unlinked list.
 */
int
xfs_iunlink_remove(
	struct xfs_trans	*tp,
	struct xfs_perag	*pag,
	struct xfs_inode	*ip)
{ … }

/*
 * Decrement the link count on an inode & log the change.  If this causes the
 * link count to go to zero, move the inode to AGI unlinked list so that it can
 * be freed when the last active reference goes away via xfs_inactive().
 */
int
xfs_droplink(
	struct xfs_trans	*tp,
	struct xfs_inode	*ip)
{ … }

/*
 * Increment the link count on an inode & log the change.
 */
void
xfs_bumplink(
	struct xfs_trans	*tp,
	struct xfs_inode	*ip)
{ … }

/* Free an inode in the ondisk index and zero it out. */
int
xfs_inode_uninit(
	struct xfs_trans	*tp,
	struct xfs_perag	*pag,
	struct xfs_inode	*ip,
	struct xfs_icluster	*xic)
{ … }
linux/fs/xfs/libxfs/xfs_inode_util.c
