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// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2022-2023 Oracle. All Rights Reserved.
* Author: Darrick J. Wong <djwong@kernel.org>
*/
#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)
{
static_branch_dec(&xfs_drain_waiter_gate);
}
void
xfs_drain_wait_enable(void)
{
static_branch_inc(&xfs_drain_waiter_gate);
}
void
xfs_defer_drain_init(
struct xfs_defer_drain *dr)
{
atomic_set(&dr->dr_count, 0);
init_waitqueue_head(&dr->dr_waiters);
}
void
xfs_defer_drain_free(struct xfs_defer_drain *dr)
{
ASSERT(atomic_read(&dr->dr_count) == 0);
}
/* Increase the pending intent count. */
static inline void xfs_defer_drain_grab(struct xfs_defer_drain *dr)
{
atomic_inc(&dr->dr_count);
}
static inline bool has_waiters(struct wait_queue_head *wq_head)
{
/*
* This memory barrier is paired with the one in set_current_state on
* the waiting side.
*/
smp_mb__after_atomic();
return waitqueue_active(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)
{
if (atomic_dec_and_test(&dr->dr_count) &&
static_branch_unlikely(&xfs_drain_waiter_gate) &&
has_waiters(&dr->dr_waiters))
wake_up(&dr->dr_waiters);
}
/* Are there intents pending? */
static inline bool xfs_defer_drain_busy(struct xfs_defer_drain *dr)
{
return atomic_read(&dr->dr_count) > 0;
}
/*
* 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)
{
return wait_event_killable(dr->dr_waiters, !xfs_defer_drain_busy(dr));
}
/*
* Get a passive reference to an AG and declare an intent to update its
* metadata.
*/
struct xfs_perag *
xfs_perag_intent_get(
struct xfs_mount *mp,
xfs_agnumber_t agno)
{
struct xfs_perag *pag;
pag = xfs_perag_get(mp, agno);
if (!pag)
return NULL;
xfs_perag_intent_hold(pag);
return pag;
}
/*
* 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)
{
xfs_perag_intent_rele(pag);
xfs_perag_put(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)
{
trace_xfs_perag_intent_hold(pag, __return_address);
xfs_defer_drain_grab(&pag->pag_intents_drain);
}
/* Release our intent to update this AG's metadata. */
void
xfs_perag_intent_rele(
struct xfs_perag *pag)
{
trace_xfs_perag_intent_rele(pag, __return_address);
xfs_defer_drain_rele(&pag->pag_intents_drain);
}
/*
* 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)
{
trace_xfs_perag_wait_intents(pag, __return_address);
return xfs_defer_drain_wait(&pag->pag_intents_drain);
}
/* Has anyone declared an intent to update this AG? */
bool
xfs_perag_intent_busy(
struct xfs_perag *pag)
{
return xfs_defer_drain_busy(&pag->pag_intents_drain);
}
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