xfs_trans_ail.c | Explore in Territory

// SPDX-License-Identifier: GPL-2.0
/*
 * Copyright (c) 2000-2002,2005 Silicon Graphics, Inc.
 * Copyright (c) 2008 Dave Chinner
 * All Rights Reserved.
 */
#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_mount.h"
#include "xfs_trans.h"
#include "xfs_trans_priv.h"
#include "xfs_trace.h"
#include "xfs_errortag.h"
#include "xfs_error.h"
#include "xfs_log.h"
#include "xfs_log_priv.h"

#ifdef DEBUG
/*
 * Check that the list is sorted as it should be.
 *
 * Called with the ail lock held, but we don't want to assert fail with it
 * held otherwise we'll lock everything up and won't be able to debug the
 * cause. Hence we sample and check the state under the AIL lock and return if
 * everything is fine, otherwise we drop the lock and run the ASSERT checks.
 * Asserts may not be fatal, so pick the lock back up and continue onwards.
 */
STATIC void
xfs_ail_check(
	struct xfs_ail		*ailp,
	struct xfs_log_item	*lip)
	__must_hold(&ailp->ail_lock)
{ … }
#else /* !DEBUG */
#define xfs_ail_check …
#endif /* DEBUG */

/*
 * Return a pointer to the last item in the AIL.  If the AIL is empty, then
 * return NULL.
 */
static struct xfs_log_item *
xfs_ail_max(
	struct xfs_ail  *ailp)
{ … }

/*
 * Return a pointer to the item which follows the given item in the AIL.  If
 * the given item is the last item in the list, then return NULL.
 */
static struct xfs_log_item *
xfs_ail_next(
	struct xfs_ail		*ailp,
	struct xfs_log_item	*lip)
{ … }

/*
 * This is called by the log manager code to determine the LSN of the tail of
 * the log.  This is exactly the LSN of the first item in the AIL.  If the AIL
 * is empty, then this function returns 0.
 *
 * We need the AIL lock in order to get a coherent read of the lsn of the last
 * item in the AIL.
 */
static xfs_lsn_t
__xfs_ail_min_lsn(
	struct xfs_ail		*ailp)
{ … }

xfs_lsn_t
xfs_ail_min_lsn(
	struct xfs_ail		*ailp)
{ … }

/*
 * The cursor keeps track of where our current traversal is up to by tracking
 * the next item in the list for us. However, for this to be safe, removing an
 * object from the AIL needs to invalidate any cursor that points to it. hence
 * the traversal cursor needs to be linked to the struct xfs_ail so that
 * deletion can search all the active cursors for invalidation.
 */
STATIC void
xfs_trans_ail_cursor_init(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur)
{ … }

/*
 * Get the next item in the traversal and advance the cursor.  If the cursor
 * was invalidated (indicated by a lip of 1), restart the traversal.
 */
struct xfs_log_item *
xfs_trans_ail_cursor_next(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur)
{ … }

/*
 * When the traversal is complete, we need to remove the cursor from the list
 * of traversing cursors.
 */
void
xfs_trans_ail_cursor_done(
	struct xfs_ail_cursor	*cur)
{ … }

/*
 * Invalidate any cursor that is pointing to this item. This is called when an
 * item is removed from the AIL. Any cursor pointing to this object is now
 * invalid and the traversal needs to be terminated so it doesn't reference a
 * freed object. We set the low bit of the cursor item pointer so we can
 * distinguish between an invalidation and the end of the list when getting the
 * next item from the cursor.
 */
STATIC void
xfs_trans_ail_cursor_clear(
	struct xfs_ail		*ailp,
	struct xfs_log_item	*lip)
{ … }

/*
 * Find the first item in the AIL with the given @lsn by searching in ascending
 * LSN order and initialise the cursor to point to the next item for a
 * ascending traversal.  Pass a @lsn of zero to initialise the cursor to the
 * first item in the AIL. Returns NULL if the list is empty.
 */
struct xfs_log_item *
xfs_trans_ail_cursor_first(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur,
	xfs_lsn_t		lsn)
{ … }

static struct xfs_log_item *
__xfs_trans_ail_cursor_last(
	struct xfs_ail		*ailp,
	xfs_lsn_t		lsn)
{ … }

/*
 * Find the last item in the AIL with the given @lsn by searching in descending
 * LSN order and initialise the cursor to point to that item.  If there is no
 * item with the value of @lsn, then it sets the cursor to the last item with an
 * LSN lower than @lsn.  Returns NULL if the list is empty.
 */
struct xfs_log_item *
xfs_trans_ail_cursor_last(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur,
	xfs_lsn_t		lsn)
{ … }

/*
 * Splice the log item list into the AIL at the given LSN. We splice to the
 * tail of the given LSN to maintain insert order for push traversals. The
 * cursor is optional, allowing repeated updates to the same LSN to avoid
 * repeated traversals.  This should not be called with an empty list.
 */
static void
xfs_ail_splice(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur,
	struct list_head	*list,
	xfs_lsn_t		lsn)
{ … }

/*
 * Delete the given item from the AIL.  Return a pointer to the item.
 */
static void
xfs_ail_delete(
	struct xfs_ail		*ailp,
	struct xfs_log_item	*lip)
{ … }

/*
 * Requeue a failed buffer for writeback.
 *
 * We clear the log item failed state here as well, but we have to be careful
 * about reference counts because the only active reference counts on the buffer
 * may be the failed log items. Hence if we clear the log item failed state
 * before queuing the buffer for IO we can release all active references to
 * the buffer and free it, leading to use after free problems in
 * xfs_buf_delwri_queue. It makes no difference to the buffer or log items which
 * order we process them in - the buffer is locked, and we own the buffer list
 * so nothing on them is going to change while we are performing this action.
 *
 * Hence we can safely queue the buffer for IO before we clear the failed log
 * item state, therefore  always having an active reference to the buffer and
 * avoiding the transient zero-reference state that leads to use-after-free.
 */
static inline int
xfsaild_resubmit_item(
	struct xfs_log_item	*lip,
	struct list_head	*buffer_list)
{ … }

static inline uint
xfsaild_push_item(
	struct xfs_ail		*ailp,
	struct xfs_log_item	*lip)
{ … }

/*
 * Compute the LSN that we'd need to push the log tail towards in order to have
 * at least 25% of the log space free.  If the log free space already meets this
 * threshold, this function returns the lowest LSN in the AIL to slowly keep
 * writeback ticking over and the tail of the log moving forward.
 */
static xfs_lsn_t
xfs_ail_calc_push_target(
	struct xfs_ail		*ailp)
{ … }

static long
xfsaild_push(
	struct xfs_ail		*ailp)
{ … }

static int
xfsaild(
	void		*data)
{ … }

/*
 * Push out all items in the AIL immediately and wait until the AIL is empty.
 */
void
xfs_ail_push_all_sync(
	struct xfs_ail  *ailp)
{ … }

void
__xfs_ail_assign_tail_lsn(
	struct xfs_ail		*ailp)
{ … }

/*
 * Callers should pass the original tail lsn so that we can detect if the tail
 * has moved as a result of the operation that was performed. If the caller
 * needs to force a tail space update, it should pass NULLCOMMITLSN to bypass
 * the "did the tail LSN change?" checks. If the caller wants to avoid a tail
 * update (e.g. it knows the tail did not change) it should pass an @old_lsn of
 * 0.
 */
void
xfs_ail_update_finish(
	struct xfs_ail		*ailp,
	xfs_lsn_t		old_lsn) __releases(ailp->ail_lock)
{ … }

/*
 * xfs_trans_ail_update - bulk AIL insertion operation.
 *
 * @xfs_trans_ail_update takes an array of log items that all need to be
 * positioned at the same LSN in the AIL. If an item is not in the AIL, it will
 * be added.  Otherwise, it will be repositioned  by removing it and re-adding
 * it to the AIL. If we move the first item in the AIL, update the log tail to
 * match the new minimum LSN in the AIL.
 *
 * This function takes the AIL lock once to execute the update operations on
 * all the items in the array, and as such should not be called with the AIL
 * lock held. As a result, once we have the AIL lock, we need to check each log
 * item LSN to confirm it needs to be moved forward in the AIL.
 *
 * To optimise the insert operation, we delete all the items from the AIL in
 * the first pass, moving them into a temporary list, then splice the temporary
 * list into the correct position in the AIL. This avoids needing to do an
 * insert operation on every item.
 *
 * This function must be called with the AIL lock held.  The lock is dropped
 * before returning.
 */
void
xfs_trans_ail_update_bulk(
	struct xfs_ail		*ailp,
	struct xfs_ail_cursor	*cur,
	struct xfs_log_item	**log_items,
	int			nr_items,
	xfs_lsn_t		lsn) __releases(ailp->ail_lock)
{ … }

/* Insert a log item into the AIL. */
void
xfs_trans_ail_insert(
	struct xfs_ail		*ailp,
	struct xfs_log_item	*lip,
	xfs_lsn_t		lsn)
{ … }

/*
 * Delete one log item from the AIL.
 *
 * If this item was at the tail of the AIL, return the LSN of the log item so
 * that we can use it to check if the LSN of the tail of the log has moved
 * when finishing up the AIL delete process in xfs_ail_update_finish().
 */
xfs_lsn_t
xfs_ail_delete_one(
	struct xfs_ail		*ailp,
	struct xfs_log_item	*lip)
{ … }

void
xfs_trans_ail_delete(
	struct xfs_log_item	*lip,
	int			shutdown_type)
{ … }

int
xfs_trans_ail_init(
	xfs_mount_t	*mp)
{ … }

void
xfs_trans_ail_destroy(
	xfs_mount_t	*mp)
{ … }
linux/fs/xfs/xfs_trans_ail.c
