linux/fs/xfs/xfs_drain.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Copyright (C) 2022-2023 Oracle.  All Rights Reserved.
 * Author: Darrick J. Wong <[email protected]>
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_shared.h"
#include "xfs_format.h"
#include "xfs_trans_resv.h"
#include "xfs_mount.h"
#include "xfs_ag.h"
#include "xfs_trace.h"

/*
 * Use a static key here to reduce the overhead of xfs_drain_rele.  If the
 * compiler supports jump labels, the static branch will be replaced by a nop
 * sled when there are no xfs_drain_wait callers.  Online fsck is currently
 * the only caller, so this is a reasonable tradeoff.
 *
 * Note: Patching the kernel code requires taking the cpu hotplug lock.  Other
 * parts of the kernel allocate memory with that lock held, which means that
 * XFS callers cannot hold any locks that might be used by memory reclaim or
 * writeback when calling the static_branch_{inc,dec} functions.
 */
static DEFINE_STATIC_KEY_FALSE(xfs_drain_waiter_gate);

void
xfs_drain_wait_disable(void)
{ … }

void
xfs_drain_wait_enable(void)
{ … }

void
xfs_defer_drain_init(
	struct xfs_defer_drain	*dr)
{ … }

void
xfs_defer_drain_free(struct xfs_defer_drain	*dr)
{ … }

/* Increase the pending intent count. */
static inline void xfs_defer_drain_grab(struct xfs_defer_drain *dr)
{ … }

static inline bool has_waiters(struct wait_queue_head *wq_head)
{ … }

/* Decrease the pending intent count, and wake any waiters, if appropriate. */
static inline void xfs_defer_drain_rele(struct xfs_defer_drain *dr)
{ … }

/* Are there intents pending? */
static inline bool xfs_defer_drain_busy(struct xfs_defer_drain *dr)
{ … }

/*
 * Wait for the pending intent count for a drain to hit zero.
 *
 * Callers must not hold any locks that would prevent intents from being
 * finished.
 */
static inline int xfs_defer_drain_wait(struct xfs_defer_drain *dr)
{ … }

/*
 * Get a passive reference to the AG that contains a fsbno and declare an intent
 * to update its metadata.
 */
struct xfs_perag *
xfs_perag_intent_get(
	struct xfs_mount	*mp,
	xfs_fsblock_t		fsbno)
{ … }

/*
 * Release our intent to update this AG's metadata, and then release our
 * passive ref to the AG.
 */
void
xfs_perag_intent_put(
	struct xfs_perag	*pag)
{ … }

/*
 * Declare an intent to update AG metadata.  Other threads that need exclusive
 * access can decide to back off if they see declared intentions.
 */
void
xfs_perag_intent_hold(
	struct xfs_perag	*pag)
{ … }

/* Release our intent to update this AG's metadata. */
void
xfs_perag_intent_rele(
	struct xfs_perag	*pag)
{ … }

/*
 * Wait for the intent update count for this AG to hit zero.
 * Callers must not hold any AG header buffers.
 */
int
xfs_perag_intent_drain(
	struct xfs_perag	*pag)
{ … }

/* Has anyone declared an intent to update this AG? */
bool
xfs_perag_intent_busy(
	struct xfs_perag	*pag)
{ … }