xfs_log.c

/*
 * Copyright (c) 2000-2005 Silicon Graphics, Inc.
 * All Rights Reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it would be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write the Free Software Foundation,
 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */
#include "xfs.h"
#include "xfs_fs.h"
#include "xfs_types.h"
#include "xfs_bit.h"
#include "xfs_log.h"
#include "xfs_inum.h"
#include "xfs_trans.h"
#include "xfs_sb.h"
#include "xfs_ag.h"
#include "xfs_mount.h"
#include "xfs_error.h"
#include "xfs_log_priv.h"
#include "xfs_buf_item.h"
#include "xfs_bmap_btree.h"
#include "xfs_alloc_btree.h"
#include "xfs_ialloc_btree.h"
#include "xfs_log_recover.h"
#include "xfs_trans_priv.h"
#include "xfs_dinode.h"
#include "xfs_inode.h"
#include "xfs_rw.h"
#include "xfs_trace.h"

kmem_zone_t	*xfs_log_ticket_zone;

/* Local miscellaneous function prototypes */
STATIC int	 xlog_commit_record(struct log *log, struct xlog_ticket *ticket,
				    xlog_in_core_t **, xfs_lsn_t *);
STATIC xlog_t *  xlog_alloc_log(xfs_mount_t	*mp,
				xfs_buftarg_t	*log_target,
				xfs_daddr_t	blk_offset,
				int		num_bblks);
STATIC int	 xlog_space_left(struct log *log, atomic64_t *head);
STATIC int	 xlog_sync(xlog_t *log, xlog_in_core_t *iclog);
STATIC void	 xlog_dealloc_log(xlog_t *log);

/* local state machine functions */
STATIC void xlog_state_done_syncing(xlog_in_core_t *iclog, int);
STATIC void xlog_state_do_callback(xlog_t *log,int aborted, xlog_in_core_t *iclog);
STATIC int  xlog_state_get_iclog_space(xlog_t		*log,
				       int		len,
				       xlog_in_core_t	**iclog,
				       xlog_ticket_t	*ticket,
				       int		*continued_write,
				       int		*logoffsetp);
STATIC int  xlog_state_release_iclog(xlog_t		*log,
				     xlog_in_core_t	*iclog);
STATIC void xlog_state_switch_iclogs(xlog_t		*log,
				     xlog_in_core_t *iclog,
				     int		eventual_size);
STATIC void xlog_state_want_sync(xlog_t	*log, xlog_in_core_t *iclog);

/* local functions to manipulate grant head */
STATIC int  xlog_grant_log_space(xlog_t		*log,
				 xlog_ticket_t	*xtic);
STATIC void xlog_grant_push_ail(struct log	*log,
				int		need_bytes);
STATIC void xlog_regrant_reserve_log_space(xlog_t	 *log,
					   xlog_ticket_t *ticket);
STATIC int xlog_regrant_write_log_space(xlog_t		*log,
					 xlog_ticket_t  *ticket);
STATIC void xlog_ungrant_log_space(xlog_t	 *log,
				   xlog_ticket_t *ticket);

#if defined(DEBUG)
STATIC void	xlog_verify_dest_ptr(xlog_t *log, char *ptr);
STATIC void	xlog_verify_grant_tail(struct log *log);
STATIC void	xlog_verify_iclog(xlog_t *log, xlog_in_core_t *iclog,
				  int count, boolean_t syncing);
STATIC void	xlog_verify_tail_lsn(xlog_t *log, xlog_in_core_t *iclog,
				     xfs_lsn_t tail_lsn);
#else
#define xlog_verify_dest_ptr(a,b)
#define xlog_verify_grant_tail(a)
#define xlog_verify_iclog(a,b,c,d)
#define xlog_verify_tail_lsn(a,b,c)
#endif

STATIC int	xlog_iclogs_empty(xlog_t *log);

static void
xlog_grant_sub_space(
	struct log	*log,
	atomic64_t	*head,
	int		bytes)
{
	int64_t	head_val = atomic64_read(head);
	int64_t new, old;

	do {
		int	cycle, space;

		xlog_crack_grant_head_val(head_val, &cycle, &space);

		space -= bytes;
		if (space < 0) {
			space += log->l_logsize;
			cycle--;
		}

		old = head_val;
		new = xlog_assign_grant_head_val(cycle, space);
		head_val = atomic64_cmpxchg(head, old, new);
	} while (head_val != old);
}

static void
xlog_grant_add_space(
	struct log	*log,
	atomic64_t	*head,
	int		bytes)
{
	int64_t	head_val = atomic64_read(head);
	int64_t new, old;

	do {
		int		tmp;
		int		cycle, space;

		xlog_crack_grant_head_val(head_val, &cycle, &space);

		tmp = log->l_logsize - space;
		if (tmp > bytes)
			space += bytes;
		else {
			space = bytes - tmp;
			cycle++;
		}

		old = head_val;
		new = xlog_assign_grant_head_val(cycle, space);
		head_val = atomic64_cmpxchg(head, old, new);
	} while (head_val != old);
}

static void
xlog_tic_reset_res(xlog_ticket_t *tic)
{
	tic->t_res_num = 0;
	tic->t_res_arr_sum = 0;
	tic->t_res_num_ophdrs = 0;
}

static void
xlog_tic_add_region(xlog_ticket_t *tic, uint len, uint type)
{
	if (tic->t_res_num == XLOG_TIC_LEN_MAX) {
		/* add to overflow and start again */
		tic->t_res_o_flow += tic->t_res_arr_sum;
		tic->t_res_num = 0;
		tic->t_res_arr_sum = 0;
	}

	tic->t_res_arr[tic->t_res_num].r_len = len;
	tic->t_res_arr[tic->t_res_num].r_type = type;
	tic->t_res_arr_sum += len;
	tic->t_res_num++;
}

/*
 * NOTES:
 *
 *	1. currblock field gets updated at startup and after in-core logs
 *		marked as with WANT_SYNC.
 */

/*
 * This routine is called when a user of a log manager ticket is done with
 * the reservation.  If the ticket was ever used, then a commit record for
 * the associated transaction is written out as a log operation header with
 * no data.  The flag XLOG_TIC_INITED is set when the first write occurs with
 * a given ticket.  If the ticket was one with a permanent reservation, then
 * a few operations are done differently.  Permanent reservation tickets by
 * default don't release the reservation.  They just commit the current
 * transaction with the belief that the reservation is still needed.  A flag
 * must be passed in before permanent reservations are actually released.
 * When these type of tickets are not released, they need to be set into
 * the inited state again.  By doing this, a start record will be written
 * out when the next write occurs.
 */
xfs_lsn_t
xfs_log_done(
	struct xfs_mount	*mp,
	struct xlog_ticket	*ticket,
	struct xlog_in_core	**iclog,
	uint			flags)
{
	struct log		*log = mp->m_log;
	xfs_lsn_t		lsn = 0;

	if (XLOG_FORCED_SHUTDOWN(log) ||
	    /*
	     * If nothing was ever written, don't write out commit record.
	     * If we get an error, just continue and give back the log ticket.
	     */
	    (((ticket->t_flags & XLOG_TIC_INITED) == 0) &&
	     (xlog_commit_record(log, ticket, iclog, &lsn)))) {
		lsn = (xfs_lsn_t) -1;
		if (ticket->t_flags & XLOG_TIC_PERM_RESERV) {
			flags |= XFS_LOG_REL_PERM_RESERV;
		}
	}


	if ((ticket->t_flags & XLOG_TIC_PERM_RESERV) == 0 ||
	    (flags & XFS_LOG_REL_PERM_RESERV)) {
		trace_xfs_log_done_nonperm(log, ticket);

		/*
		 * Release ticket if not permanent reservation or a specific
		 * request has been made to release a permanent reservation.
		 */
		xlog_ungrant_log_space(log, ticket);
		xfs_log_ticket_put(ticket);
	} else {
		trace_xfs_log_done_perm(log, ticket);

		xlog_regrant_reserve_log_space(log, ticket);
		/* If this ticket was a permanent reservation and we aren't
		 * trying to release it, reset the inited flags; so next time
		 * we write, a start record will be written out.
		 */
		ticket->t_flags |= XLOG_TIC_INITED;
	}

	return lsn;
}

/*
 * Attaches a new iclog I/O completion callback routine during
 * transaction commit.  If the log is in error state, a non-zero
 * return code is handed back and the caller is responsible for
 * executing the callback at an appropriate time.
 */
int
xfs_log_notify(
	struct xfs_mount	*mp,
	struct xlog_in_core	*iclog,
	xfs_log_callback_t	*cb)
{
	int	abortflg;

	spin_lock(&iclog->ic_callback_lock);
	abortflg = (iclog->ic_state & XLOG_STATE_IOERROR);
	if (!abortflg) {
		ASSERT_ALWAYS((iclog->ic_state == XLOG_STATE_ACTIVE) ||
			      (iclog->ic_state == XLOG_STATE_WANT_SYNC));
		cb->cb_next = NULL;
		*(iclog->ic_callback_tail) = cb;
		iclog->ic_callback_tail = &(cb->cb_next);
	}
	spin_unlock(&iclog->ic_callback_lock);
	return abortflg;
}

int
xfs_log_release_iclog(
	struct xfs_mount	*mp,
	struct xlog_in_core	*iclog)
{
	if (xlog_state_release_iclog(mp->m_log, iclog)) {
		xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
		return EIO;
	}

	return 0;
}

/*
 *  1. Reserve an amount of on-disk log space and return a ticket corresponding
 *	to the reservation.
 *  2. Potentially, push buffers at tail of log to disk.
 *
 * Each reservation is going to reserve extra space for a log record header.
 * When writes happen to the on-disk log, we don't subtract the length of the
 * log record header from any reservation.  By wasting space in each
 * reservation, we prevent over allocation problems.
 */
int
xfs_log_reserve(
	struct xfs_mount	*mp,
	int		 	unit_bytes,
	int		 	cnt,
	struct xlog_ticket	**ticket,
	__uint8_t	 	client,
	uint		 	flags,
	uint		 	t_type)
{
	struct log		*log = mp->m_log;
	struct xlog_ticket	*internal_ticket;
	int			retval = 0;

	ASSERT(client == XFS_TRANSACTION || client == XFS_LOG);

	if (XLOG_FORCED_SHUTDOWN(log))
		return XFS_ERROR(EIO);

	XFS_STATS_INC(xs_try_logspace);


	if (*ticket != NULL) {
		ASSERT(flags & XFS_LOG_PERM_RESERV);
		internal_ticket = *ticket;

		/*
		 * this is a new transaction on the ticket, so we need to
		 * change the transaction ID so that the next transaction has a
		 * different TID in the log. Just add one to the existing tid
		 * so that we can see chains of rolling transactions in the log
		 * easily.
		 */
		internal_ticket->t_tid++;

		trace_xfs_log_reserve(log, internal_ticket);

		xlog_grant_push_ail(log, internal_ticket->t_unit_res);
		retval = xlog_regrant_write_log_space(log, internal_ticket);
	} else {
		/* may sleep if need to allocate more tickets */
		internal_ticket = xlog_ticket_alloc(log, unit_bytes, cnt,
						  client, flags,
						  KM_SLEEP|KM_MAYFAIL);
		if (!internal_ticket)
			return XFS_ERROR(ENOMEM);
		internal_ticket->t_trans_type = t_type;
		*ticket = internal_ticket;

		trace_xfs_log_reserve(log, internal_ticket);

		xlog_grant_push_ail(log,
				    (internal_ticket->t_unit_res *
				     internal_ticket->t_cnt));
		retval = xlog_grant_log_space(log, internal_ticket);
	}

	return retval;
}	/* xfs_log_reserve */


/*
 * Mount a log filesystem
 *
 * mp		- ubiquitous xfs mount point structure
 * log_target	- buftarg of on-disk log device
 * blk_offset	- Start block # where block size is 512 bytes (BBSIZE)
 * num_bblocks	- Number of BBSIZE blocks in on-disk log
 *
 * Return error or zero.
 */
int
xfs_log_mount(
	xfs_mount_t	*mp,
	xfs_buftarg_t	*log_target,
	xfs_daddr_t	blk_offset,
	int		num_bblks)
{
	int		error;

	if (!(mp->m_flags & XFS_MOUNT_NORECOVERY))
		xfs_notice(mp, "Mounting Filesystem");
	else {
		xfs_notice(mp,
"Mounting filesystem in no-recovery mode.  Filesystem will be inconsistent.");
		ASSERT(mp->m_flags & XFS_MOUNT_RDONLY);
	}

	mp->m_log = xlog_alloc_log(mp, log_target, blk_offset, num_bblks);
	if (IS_ERR(mp->m_log)) {
		error = -PTR_ERR(mp->m_log);
		goto out;
	}

	/*
	 * Initialize the AIL now we have a log.
	 */
	error = xfs_trans_ail_init(mp);
	if (error) {
		xfs_warn(mp, "AIL initialisation failed: error %d", error);
		goto out_free_log;
	}
	mp->m_log->l_ailp = mp->m_ail;

	/*
	 * skip log recovery on a norecovery mount.  pretend it all
	 * just worked.
	 */
	if (!(mp->m_flags & XFS_MOUNT_NORECOVERY)) {
		int	readonly = (mp->m_flags & XFS_MOUNT_RDONLY);

		if (readonly)
			mp->m_flags &= ~XFS_MOUNT_RDONLY;

		error = xlog_recover(mp->m_log);

		if (readonly)
			mp->m_flags |= XFS_MOUNT_RDONLY;
		if (error) {
			xfs_warn(mp, "log mount/recovery failed: error %d",
				error);
			goto out_destroy_ail;
		}
	}

	/* Normal transactions can now occur */
	mp->m_log->l_flags &= ~XLOG_ACTIVE_RECOVERY;

	/*
	 * Now the log has been fully initialised and we know were our
	 * space grant counters are, we can initialise the permanent ticket
	 * needed for delayed logging to work.
	 */
	xlog_cil_init_post_recovery(mp->m_log);

	return 0;

out_destroy_ail:
	xfs_trans_ail_destroy(mp);
out_free_log:
	xlog_dealloc_log(mp->m_log);
out:
	return error;
}

/*
 * Finish the recovery of the file system.  This is separate from
 * the xfs_log_mount() call, because it depends on the code in
 * xfs_mountfs() to read in the root and real-time bitmap inodes
 * between calling xfs_log_mount() and here.
 *
 * mp		- ubiquitous xfs mount point structure
 */
int
xfs_log_mount_finish(xfs_mount_t *mp)
{
	int	error;

	if (!(mp->m_flags & XFS_MOUNT_NORECOVERY))
		error = xlog_recover_finish(mp->m_log);
	else {
		error = 0;
		ASSERT(mp->m_flags & XFS_MOUNT_RDONLY);
	}

	return error;
}

/*
 * Final log writes as part of unmount.
 *
 * Mark the filesystem clean as unmount happens.  Note that during relocation
 * this routine needs to be executed as part of source-bag while the
 * deallocation must not be done until source-end.
 */

/*
 * Unmount record used to have a string "Unmount filesystem--" in the
 * data section where the "Un" was really a magic number (XLOG_UNMOUNT_TYPE).
 * We just write the magic number now since that particular field isn't
 * currently architecture converted and "nUmount" is a bit foo.
 * As far as I know, there weren't any dependencies on the old behaviour.
 */

int
xfs_log_unmount_write(xfs_mount_t *mp)
{
	xlog_t		 *log = mp->m_log;
	xlog_in_core_t	 *iclog;
#ifdef DEBUG
	xlog_in_core_t	 *first_iclog;
#endif
	xlog_ticket_t	*tic = NULL;
	xfs_lsn_t	 lsn;
	int		 error;

	/*
	 * Don't write out unmount record on read-only mounts.
	 * Or, if we are doing a forced umount (typically because of IO errors).
	 */
	if (mp->m_flags & XFS_MOUNT_RDONLY)
		return 0;

	error = _xfs_log_force(mp, XFS_LOG_SYNC, NULL);
	ASSERT(error || !(XLOG_FORCED_SHUTDOWN(log)));

#ifdef DEBUG
	first_iclog = iclog = log->l_iclog;
	do {
		if (!(iclog->ic_state & XLOG_STATE_IOERROR)) {
			ASSERT(iclog->ic_state & XLOG_STATE_ACTIVE);
			ASSERT(iclog->ic_offset == 0);
		}
		iclog = iclog->ic_next;
	} while (iclog != first_iclog);
#endif
	if (! (XLOG_FORCED_SHUTDOWN(log))) {
		error = xfs_log_reserve(mp, 600, 1, &tic,
					XFS_LOG, 0, XLOG_UNMOUNT_REC_TYPE);
		if (!error) {
			/* the data section must be 32 bit size aligned */
			struct {
			    __uint16_t magic;
			    __uint16_t pad1;
			    __uint32_t pad2; /* may as well make it 64 bits */
			} magic = {
				.magic = XLOG_UNMOUNT_TYPE,
			};
			struct xfs_log_iovec reg = {
				.i_addr = &magic,
				.i_len = sizeof(magic),
				.i_type = XLOG_REG_TYPE_UNMOUNT,
			};
			struct xfs_log_vec vec = {
				.lv_niovecs = 1,
				.lv_iovecp = &reg,
			};

			/* remove inited flag */
			tic->t_flags = 0;
			error = xlog_write(log, &vec, tic, &lsn,
					   NULL, XLOG_UNMOUNT_TRANS);
			/*
			 * At this point, we're umounting anyway,
			 * so there's no point in transitioning log state
			 * to IOERROR. Just continue...
			 */
		}

		if (error)
			xfs_alert(mp, "%s: unmount record failed", __func__);


		spin_lock(&log->l_icloglock);
		iclog = log->l_iclog;
		atomic_inc(&iclog->ic_refcnt);
		xlog_state_want_sync(log, iclog);
		spin_unlock(&log->l_icloglock);
		error = xlog_state_release_iclog(log, iclog);

		spin_lock(&log->l_icloglock);
		if (!(iclog->ic_state == XLOG_STATE_ACTIVE ||
		      iclog->ic_state == XLOG_STATE_DIRTY)) {
			if (!XLOG_FORCED_SHUTDOWN(log)) {
				xlog_wait(&iclog->ic_force_wait,
							&log->l_icloglock);
			} else {
				spin_unlock(&log->l_icloglock);
			}
		} else {
			spin_unlock(&log->l_icloglock);
		}
		if (tic) {
			trace_xfs_log_umount_write(log, tic);
			xlog_ungrant_log_space(log, tic);
			xfs_log_ticket_put(tic);
		}
	} else {
		/*
		 * We're already in forced_shutdown mode, couldn't
		 * even attempt to write out the unmount transaction.
		 *
		 * Go through the motions of sync'ing and releasing
		 * the iclog, even though no I/O will actually happen,
		 * we need to wait for other log I/Os that may already
		 * be in progress.  Do this as a separate section of
		 * code so we'll know if we ever get stuck here that
		 * we're in this odd situation of trying to unmount
		 * a file system that went into forced_shutdown as
		 * the result of an unmount..
		 */
		spin_lock(&log->l_icloglock);
		iclog = log->l_iclog;
		atomic_inc(&iclog->ic_refcnt);

		xlog_state_want_sync(log, iclog);
		spin_unlock(&log->l_icloglock);
		error =  xlog_state_release_iclog(log, iclog);

		spin_lock(&log->l_icloglock);

		if ( ! (   iclog->ic_state == XLOG_STATE_ACTIVE
			|| iclog->ic_state == XLOG_STATE_DIRTY
			|| iclog->ic_state == XLOG_STATE_IOERROR) ) {

				xlog_wait(&iclog->ic_force_wait,
							&log->l_icloglock);
		} else {
			spin_unlock(&log->l_icloglock);
		}
	}

	return error;
}	/* xfs_log_unmount_write */

/*
 * Deallocate log structures for unmount/relocation.
 *
 * We need to stop the aild from running before we destroy
 * and deallocate the log as the aild references the log.
 */
void
xfs_log_unmount(xfs_mount_t *mp)
{
	xfs_trans_ail_destroy(mp);
	xlog_dealloc_log(mp->m_log);
}

void
xfs_log_item_init(
	struct xfs_mount	*mp,
	struct xfs_log_item	*item,
	int			type,
	struct xfs_item_ops	*ops)
{
	item->li_mountp = mp;
	item->li_ailp = mp->m_ail;
	item->li_type = type;
	item->li_ops = ops;
	item->li_lv = NULL;

	INIT_LIST_HEAD(&item->li_ail);
	INIT_LIST_HEAD(&item->li_cil);
}

/*
 * Write region vectors to log.  The write happens using the space reservation
 * of the ticket (tic).  It is not a requirement that all writes for a given
 * transaction occur with one call to xfs_log_write(). However, it is important
 * to note that the transaction reservation code makes an assumption about the
 * number of log headers a transaction requires that may be violated if you
 * don't pass all the transaction vectors in one call....
 */
int
xfs_log_write(
	struct xfs_mount	*mp,
	struct xfs_log_iovec	reg[],
	int			nentries,
	struct xlog_ticket	*tic,
	xfs_lsn_t		*start_lsn)
{
	struct log		*log = mp->m_log;
	int			error;
	struct xfs_log_vec	vec = {
		.lv_niovecs = nentries,
		.lv_iovecp = reg,
	};

	if (XLOG_FORCED_SHUTDOWN(log))
		return XFS_ERROR(EIO);

	error = xlog_write(log, &vec, tic, start_lsn, NULL, 0);
	if (error)
		xfs_force_shutdown(mp, SHUTDOWN_LOG_IO_ERROR);
	return error;
}

void
xfs_log_move_tail(xfs_mount_t	*mp,
		  xfs_lsn_t	tail_lsn)
{
	xlog_ticket_t	*tic;
	xlog_t		*log = mp->m_log;
	int		need_bytes, free_bytes;

	if (XLOG_FORCED_SHUTDOWN(log))
		return;

	if (tail_lsn == 0)
		tail_lsn = atomic64_read(&log->l_last_sync_lsn);

	/* tail_lsn == 1 implies that we weren't passed a valid value.  */
	if (tail_lsn != 1)
		atomic64_set(&log->l_tail_lsn, tail_lsn);

	if (!list_empty_careful(&log->l_writeq)) {
#ifdef DEBUG
		if (log->l_flags & XLOG_ACTIVE_RECOVERY)
			panic("Recovery problem");
#endif
		spin_lock(&log->l_grant_write_lock);
		free_bytes = xlog_space_left(log, &log->l_grant_write_head);
		list_for_each_entry(tic, &log->l_writeq, t_queue) {
			ASSERT(tic->t_flags & XLOG_TIC_PERM_RESERV);

			if (free_bytes < tic->t_unit_res && tail_lsn != 1)
				break;
			tail_lsn = 0;
			free_bytes -= tic->t_unit_res;
			trace_xfs_log_regrant_write_wake_up(log, tic);
			wake_up(&tic->t_wait);
		}
		spin_unlock(&log->l_grant_write_lock);
	}

	if (!list_empty_careful(&log->l_reserveq)) {
#ifdef DEBUG
		if (log->l_flags & XLOG_ACTIVE_RECOVERY)
			panic("Recovery problem");
#endif
		spin_lock(&log->l_grant_reserve_lock);
		free_bytes = xlog_space_left(log, &log->l_grant_reserve_head);
		list_for_each_entry(tic, &log->l_reserveq, t_queue) {
			if (tic->t_flags & XLOG_TIC_PERM_RESERV)
				need_bytes = tic->t_unit_res*tic->t_cnt;
			else
				need_bytes = tic->t_unit_res;
			if (free_bytes < need_bytes && tail_lsn != 1)
				break;
			tail_lsn = 0;
			free_bytes -= need_bytes;
			trace_xfs_log_grant_wake_up(log, tic);
			wake_up(&tic->t_wait);
		}
		spin_unlock(&log->l_grant_reserve_lock);
	}
}

/*
 * Determine if we have a transaction that has gone to disk
 * that needs to be covered. To begin the transition to the idle state
 * firstly the log needs to be idle (no AIL and nothing in the iclogs).
 * If we are then in a state where covering is needed, the caller is informed
 * that dummy transactions are required to move the log into the idle state.
 *
 * Because this is called as part of the sync process, we should also indicate
 * that dummy transactions should be issued in anything but the covered or
 * idle states. This ensures that the log tail is accurately reflected in
 * the log at the end of the sync, hence if a crash occurrs avoids replay
 * of transactions where the metadata is already on disk.
 */
int
xfs_log_need_covered(xfs_mount_t *mp)
{
	int		needed = 0;
	xlog_t		*log = mp->m_log;

	if (!xfs_fs_writable(mp))
		return 0;

	spin_lock(&log->l_icloglock);
	switch (log->l_covered_state) {
	case XLOG_STATE_COVER_DONE:
	case XLOG_STATE_COVER_DONE2:
	case XLOG_STATE_COVER_IDLE:
		break;
	case XLOG_STATE_COVER_NEED:
	case XLOG_STATE_COVER_NEED2:
		if (!xfs_ail_min_lsn(log->l_ailp) &&
		    xlog_iclogs_empty(log)) {
			if (log->l_covered_state == XLOG_STATE_COVER_NEED)
				log->l_covered_state = XLOG_STATE_COVER_DONE;
			else
				log->l_covered_state = XLOG_STATE_COVER_DONE2;
		}
		/* FALLTHRU */
	default:
		needed = 1;
		break;
	}
	spin_unlock(&log->l_icloglock);
	return needed;
}

/******************************************************************************
 *
 *	local routines
 *
 ******************************************************************************
 */

/* xfs_trans_tail_ail returns 0 when there is nothing in the list.
 * The log manager must keep track of the last LR which was committed
 * to disk.  The lsn of this LR will become the new tail_lsn whenever
 * xfs_trans_tail_ail returns 0.  If we don't do this, we run into
 * the situation where stuff could be written into the log but nothing
 * was ever in the AIL when asked.  Eventually, we panic since the
 * tail hits the head.
 *
 * We may be holding the log iclog lock upon entering this routine.
 */
xfs_lsn_t
xlog_assign_tail_lsn(
	struct xfs_mount	*mp)
{
	xfs_lsn_t		tail_lsn;
	struct log		*log = mp->m_log;

	tail_lsn = xfs_ail_min_lsn(mp->m_ail);
	if (!tail_lsn)
		tail_lsn = atomic64_read(&log->l_last_sync_lsn);

	atomic64_set(&log->l_tail_lsn, tail_lsn);
	return tail_lsn;
}

/*
 * Return the space in the log between the tail and the head.  The head
 * is passed in the cycle/bytes formal parms.  In the special case where
 * the reserve head has wrapped passed the tail, this calculation is no
 * longer valid.  In this case, just return 0 which means there is no space
 * in the log.  This works for all places where this function is called
 * with the reserve head.  Of course, if the write head were to ever
 * wrap the tail, we should blow up.  Rather than catch this case here,
 * we depend on other ASSERTions in other parts of the code.   XXXmiken
 *
 * This code also handles the case where the reservation head is behind
 * the tail.  The details of this case are described below, but the end
 * result is that we return the size of the log as the amount of space left.
 */
STATIC int
xlog_space_left(
	struct log	*log,
	atomic64_t	*head)
{
	int		free_bytes;
	int		tail_bytes;
	int		tail_cycle;
	int		head_cycle;
	int		head_bytes;

	xlog_crack_grant_head(head, &head_cycle, &head_bytes);
	xlog_crack_atomic_lsn(&log->l_tail_lsn, &tail_cycle, &tail_bytes);
	tail_bytes = BBTOB(tail_bytes);
	if (tail_cycle == head_cycle && head_bytes >= tail_bytes)
		free_bytes = log->l_logsize - (head_bytes - tail_bytes);
	else if (tail_cycle + 1 < head_cycle)
		return 0;
	else if (tail_cycle < head_cycle) {
		ASSERT(tail_cycle == (head_cycle - 1));
		free_bytes = tail_bytes - head_bytes;
	} else {
		/*
		 * The reservation head is behind the tail.
		 * In this case we just want to return the size of the
		 * log as the amount of space left.
		 */
		xfs_alert(log->l_mp,
			"xlog_space_left: head behind tail\n"
			"  tail_cycle = %d, tail_bytes = %d\n"
			"  GH   cycle = %d, GH   bytes = %d",
			tail_cycle, tail_bytes, head_cycle, head_bytes);
		ASSERT(0);
		free_bytes = log->l_logsize;
	}
	return free_bytes;
}


/*
 * Log function which is called when an io completes.
 *
 * The log manager needs its own routine, in order to control what
 * happens with the buffer after the write completes.
 */
void
xlog_iodone(xfs_buf_t *bp)
{
	xlog_in_core_t	*iclog;
	xlog_t		*l;
	int		aborted;

	iclog = XFS_BUF_FSPRIVATE(bp, xlog_in_core_t *);
	ASSERT(XFS_BUF_FSPRIVATE2(bp, unsigned long) == (unsigned long) 2);
	XFS_BUF_SET_FSPRIVATE2(bp, (unsigned long)1);
	aborted = 0;
	l = iclog->ic_log;

	/*
	 * Race to shutdown the filesystem if we see an error.
	 */
	if (XFS_TEST_ERROR((XFS_BUF_GETERROR(bp)), l->l_mp,
			XFS_ERRTAG_IODONE_IOERR, XFS_RANDOM_IODONE_IOERR)) {
		xfs_ioerror_alert("xlog_iodone", l->l_mp, bp, XFS_BUF_ADDR(bp));
		XFS_BUF_STALE(bp);
		xfs_force_shutdown(l->l_mp, SHUTDOWN_LOG_IO_ERROR);
		/*
		 * This flag will be propagated to the trans-committed
		 * callback routines to let them know that the log-commit
		 * didn't succeed.
		 */
		aborted = XFS_LI_ABORTED;
	} else if (iclog->ic_state & XLOG_STATE_IOERROR) {
		aborted = XFS_LI_ABORTED;
	}

	/* log I/O is always issued ASYNC */
	ASSERT(XFS_BUF_ISASYNC(bp));
	xlog_state_done_syncing(iclog, aborted);
	/*
	 * do not reference the buffer (bp) here as we could race
	 * with it being freed after writing the unmount record to the
	 * log.
	 */

}	/* xlog_iodone */

/*
 * Return size of each in-core log record buffer.
 *
 * All machines get 8 x 32kB buffers by default, unless tuned otherwise.
 *
 * If the filesystem blocksize is too large, we may need to choose a
 * larger size since the directory code currently logs entire blocks.
 */

STATIC void
xlog_get_iclog_buffer_size(xfs_mount_t	*mp,
			   xlog_t	*log)
{
	int size;
	int xhdrs;

	if (mp->m_logbufs <= 0)
		log->l_iclog_bufs = XLOG_MAX_ICLOGS;
	else
		log->l_iclog_bufs = mp->m_logbufs;

	/*
	 * Buffer size passed in from mount system call.
	 */
	if (mp->m_logbsize > 0) {
		size = log->l_iclog_size = mp->m_logbsize;
		log->l_iclog_size_log = 0;
		while (size != 1) {
			log->l_iclog_size_log++;
			size >>= 1;
		}

		if (xfs_sb_version_haslogv2(&mp->m_sb)) {
			/* # headers = size / 32k
			 * one header holds cycles from 32k of data
			 */

			xhdrs = mp->m_logbsize / XLOG_HEADER_CYCLE_SIZE;
			if (mp->m_logbsize % XLOG_HEADER_CYCLE_SIZE)
				xhdrs++;
			log->l_iclog_hsize = xhdrs << BBSHIFT;
			log->l_iclog_heads = xhdrs;
		} else {
			ASSERT(mp->m_logbsize <= XLOG_BIG_RECORD_BSIZE);
			log->l_iclog_hsize = BBSIZE;
			log->l_iclog_heads = 1;
		}
		goto done;
	}

	/* All machines use 32kB buffers by default. */
	log->l_iclog_size = XLOG_BIG_RECORD_BSIZE;
	log->l_iclog_size_log = XLOG_BIG_RECORD_BSHIFT;

	/* the default log size is 16k or 32k which is one header sector */
	log->l_iclog_hsize = BBSIZE;
	log->l_iclog_heads = 1;

done:
	/* are we being asked to make the sizes selected above visible? */
	if (mp->m_logbufs == 0)
		mp->m_logbufs = log->l_iclog_bufs;
	if (mp->m_logbsize == 0)
		mp->m_logbsize = log->l_iclog_size;
}	/* xlog_get_iclog_buffer_size */


/*
 * This routine initializes some of the log structure for a given mount point.
 * Its primary purpose is to fill in enough, so recovery can occur.  However,
 * some other stuff may be filled in too.
 */
STATIC xlog_t *
xlog_alloc_log(xfs_mount_t	*mp,
	       xfs_buftarg_t	*log_target,
	       xfs_daddr_t	blk_offset,
	       int		num_bblks)
{
	xlog_t			*log;
	xlog_rec_header_t	*head;
	xlog_in_core_t		**iclogp;
	xlog_in_core_t		*iclog, *prev_iclog=NULL;
	xfs_buf_t		*bp;
	int			i;
	int			error = ENOMEM;
	uint			log2_size = 0;

	log = kmem_zalloc(sizeof(xlog_t), KM_MAYFAIL);