Merge branch 'v4l_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/mchehab...

[zen-stable.git] / fs / gfs2 / log.c

/*
 * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
 * Copyright (C) 2004-2007 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include <linux/completion.h>
#include <linux/buffer_head.h>
#include <linux/gfs2_ondisk.h>
#include <linux/crc32.h>
#include <linux/delay.h>
#include <linux/kthread.h>
#include <linux/freezer.h>
#include <linux/bio.h>
#include <linux/writeback.h>

#include "gfs2.h"
#include "incore.h"
#include "bmap.h"
#include "glock.h"
#include "log.h"
#include "lops.h"
#include "meta_io.h"
#include "util.h"
#include "dir.h"
#include "trace_gfs2.h"

#define PULL 1

/**
 * gfs2_struct2blk - compute stuff
 * @sdp: the filesystem
 * @nstruct: the number of structures
 * @ssize: the size of the structures
 *
 * Compute the number of log descriptor blocks needed to hold a certain number
 * of structures of a certain size.
 *
 * Returns: the number of blocks needed (minimum is always 1)
 */

unsigned int gfs2_struct2blk(struct gfs2_sbd *sdp, unsigned int nstruct,
                             unsigned int ssize)
{
        unsigned int blks;
        unsigned int first, second;

        blks = 1;
        first = (sdp->sd_sb.sb_bsize - sizeof(struct gfs2_log_descriptor)) / ssize;

        if (nstruct > first) {
                second = (sdp->sd_sb.sb_bsize -
                          sizeof(struct gfs2_meta_header)) / ssize;
                blks += DIV_ROUND_UP(nstruct - first, second);
        }

        return blks;
}

/**
 * gfs2_remove_from_ail - Remove an entry from the ail lists, updating counters
 * @mapping: The associated mapping (maybe NULL)
 * @bd: The gfs2_bufdata to remove
 *
 * The ail lock _must_ be held when calling this function
 *
 */

void gfs2_remove_from_ail(struct gfs2_bufdata *bd)
{
        bd->bd_ail = NULL;
        list_del_init(&bd->bd_ail_st_list);
        list_del_init(&bd->bd_ail_gl_list);
        atomic_dec(&bd->bd_gl->gl_ail_count);
        brelse(bd->bd_bh);
}

/**
 * gfs2_ail1_start_one - Start I/O on a part of the AIL
 * @sdp: the filesystem
 * @wbc: The writeback control structure
 * @ai: The ail structure
 *
 */

static int gfs2_ail1_start_one(struct gfs2_sbd *sdp,
                               struct writeback_control *wbc,
                               struct gfs2_ail *ai)
__releases(&sdp->sd_ail_lock)
__acquires(&sdp->sd_ail_lock)
{
        struct gfs2_glock *gl = NULL;
        struct address_space *mapping;
        struct gfs2_bufdata *bd, *s;
        struct buffer_head *bh;

        list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list, bd_ail_st_list) {
                bh = bd->bd_bh;

                gfs2_assert(sdp, bd->bd_ail == ai);

                if (!buffer_busy(bh)) {
                        if (!buffer_uptodate(bh))
                                gfs2_io_error_bh(sdp, bh);
                        list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
                        continue;
                }

                if (!buffer_dirty(bh))
                        continue;
                if (gl == bd->bd_gl)
                        continue;
                gl = bd->bd_gl;
                list_move(&bd->bd_ail_st_list, &ai->ai_ail1_list);
                mapping = bh->b_page->mapping;
                if (!mapping)
                        continue;
                spin_unlock(&sdp->sd_ail_lock);
                generic_writepages(mapping, wbc);
                spin_lock(&sdp->sd_ail_lock);
                if (wbc->nr_to_write <= 0)
                        break;
                return 1;
        }

        return 0;
}


/**
 * gfs2_ail1_flush - start writeback of some ail1 entries 
 * @sdp: The super block
 * @wbc: The writeback control structure
 *
 * Writes back some ail1 entries, according to the limits in the
 * writeback control structure
 */

void gfs2_ail1_flush(struct gfs2_sbd *sdp, struct writeback_control *wbc)
{
        struct list_head *head = &sdp->sd_ail1_list;
        struct gfs2_ail *ai;

        trace_gfs2_ail_flush(sdp, wbc, 1);
        spin_lock(&sdp->sd_ail_lock);
restart:
        list_for_each_entry_reverse(ai, head, ai_list) {
                if (wbc->nr_to_write <= 0)
                        break;
                if (gfs2_ail1_start_one(sdp, wbc, ai))
                        goto restart;
        }
        spin_unlock(&sdp->sd_ail_lock);
        trace_gfs2_ail_flush(sdp, wbc, 0);
}

/**
 * gfs2_ail1_start - start writeback of all ail1 entries
 * @sdp: The superblock
 */

static void gfs2_ail1_start(struct gfs2_sbd *sdp)
{
        struct writeback_control wbc = {
                .sync_mode = WB_SYNC_NONE,
                .nr_to_write = LONG_MAX,
                .range_start = 0,
                .range_end = LLONG_MAX,
        };

        return gfs2_ail1_flush(sdp, &wbc);
}

/**
 * gfs2_ail1_empty_one - Check whether or not a trans in the AIL has been synced
 * @sdp: the filesystem
 * @ai: the AIL entry
 *
 */

static void gfs2_ail1_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
{
        struct gfs2_bufdata *bd, *s;
        struct buffer_head *bh;

        list_for_each_entry_safe_reverse(bd, s, &ai->ai_ail1_list,
                                         bd_ail_st_list) {
                bh = bd->bd_bh;
                gfs2_assert(sdp, bd->bd_ail == ai);
                if (buffer_busy(bh))
                        continue;
                if (!buffer_uptodate(bh))
                        gfs2_io_error_bh(sdp, bh);
                list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
        }

}

/**
 * gfs2_ail1_empty - Try to empty the ail1 lists
 * @sdp: The superblock
 *
 * Tries to empty the ail1 lists, starting with the oldest first
 */

static int gfs2_ail1_empty(struct gfs2_sbd *sdp)
{
        struct gfs2_ail *ai, *s;
        int ret;

        spin_lock(&sdp->sd_ail_lock);
        list_for_each_entry_safe_reverse(ai, s, &sdp->sd_ail1_list, ai_list) {
                gfs2_ail1_empty_one(sdp, ai);
                if (list_empty(&ai->ai_ail1_list))
                        list_move(&ai->ai_list, &sdp->sd_ail2_list);
                else
                        break;
        }
        ret = list_empty(&sdp->sd_ail1_list);
        spin_unlock(&sdp->sd_ail_lock);

        return ret;
}

static void gfs2_ail1_wait(struct gfs2_sbd *sdp)
{
        struct gfs2_ail *ai;
        struct gfs2_bufdata *bd;
        struct buffer_head *bh;

        spin_lock(&sdp->sd_ail_lock);
        list_for_each_entry_reverse(ai, &sdp->sd_ail1_list, ai_list) {
                list_for_each_entry(bd, &ai->ai_ail1_list, bd_ail_st_list) {
                        bh = bd->bd_bh;
                        if (!buffer_locked(bh))
                                continue;
                        get_bh(bh);
                        spin_unlock(&sdp->sd_ail_lock);
                        wait_on_buffer(bh);
                        brelse(bh);
                        return;
                }
        }
        spin_unlock(&sdp->sd_ail_lock);
}

/**
 * gfs2_ail2_empty_one - Check whether or not a trans in the AIL has been synced
 * @sdp: the filesystem
 * @ai: the AIL entry
 *
 */

static void gfs2_ail2_empty_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
{
        struct list_head *head = &ai->ai_ail2_list;
        struct gfs2_bufdata *bd;

        while (!list_empty(head)) {
                bd = list_entry(head->prev, struct gfs2_bufdata,
                                bd_ail_st_list);
                gfs2_assert(sdp, bd->bd_ail == ai);
                gfs2_remove_from_ail(bd);
        }
}

static void ail2_empty(struct gfs2_sbd *sdp, unsigned int new_tail)
{
        struct gfs2_ail *ai, *safe;
        unsigned int old_tail = sdp->sd_log_tail;
        int wrap = (new_tail < old_tail);
        int a, b, rm;

        spin_lock(&sdp->sd_ail_lock);

        list_for_each_entry_safe(ai, safe, &sdp->sd_ail2_list, ai_list) {
                a = (old_tail <= ai->ai_first);
                b = (ai->ai_first < new_tail);
                rm = (wrap) ? (a || b) : (a && b);
                if (!rm)
                        continue;

                gfs2_ail2_empty_one(sdp, ai);
                list_del(&ai->ai_list);
                gfs2_assert_warn(sdp, list_empty(&ai->ai_ail1_list));
                gfs2_assert_warn(sdp, list_empty(&ai->ai_ail2_list));
                kfree(ai);
        }

        spin_unlock(&sdp->sd_ail_lock);
}

/**
 * gfs2_log_reserve - Make a log reservation
 * @sdp: The GFS2 superblock
 * @blks: The number of blocks to reserve
 *
 * Note that we never give out the last few blocks of the journal. Thats
 * due to the fact that there is a small number of header blocks
 * associated with each log flush. The exact number can't be known until
 * flush time, so we ensure that we have just enough free blocks at all
 * times to avoid running out during a log flush.
 *
 * We no longer flush the log here, instead we wake up logd to do that
 * for us. To avoid the thundering herd and to ensure that we deal fairly
 * with queued waiters, we use an exclusive wait. This means that when we
 * get woken with enough journal space to get our reservation, we need to
 * wake the next waiter on the list.
 *
 * Returns: errno
 */

int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
{
        unsigned reserved_blks = 6 * (4096 / sdp->sd_vfs->s_blocksize);
        unsigned wanted = blks + reserved_blks;
        DEFINE_WAIT(wait);
        int did_wait = 0;
        unsigned int free_blocks;

        if (gfs2_assert_warn(sdp, blks) ||
            gfs2_assert_warn(sdp, blks <= sdp->sd_jdesc->jd_blocks))
                return -EINVAL;
retry:
        free_blocks = atomic_read(&sdp->sd_log_blks_free);
        if (unlikely(free_blocks <= wanted)) {
                do {
                        prepare_to_wait_exclusive(&sdp->sd_log_waitq, &wait,
                                        TASK_UNINTERRUPTIBLE);
                        wake_up(&sdp->sd_logd_waitq);
                        did_wait = 1;
                        if (atomic_read(&sdp->sd_log_blks_free) <= wanted)
                                io_schedule();
                        free_blocks = atomic_read(&sdp->sd_log_blks_free);
                } while(free_blocks <= wanted);
                finish_wait(&sdp->sd_log_waitq, &wait);
        }
        if (atomic_cmpxchg(&sdp->sd_log_blks_free, free_blocks,
                                free_blocks - blks) != free_blocks)
                goto retry;
        trace_gfs2_log_blocks(sdp, -blks);

        /*
         * If we waited, then so might others, wake them up _after_ we get
         * our share of the log.
         */
        if (unlikely(did_wait))
                wake_up(&sdp->sd_log_waitq);

        down_read(&sdp->sd_log_flush_lock);

        return 0;
}

static u64 log_bmap(struct gfs2_sbd *sdp, unsigned int lbn)
{
        struct gfs2_journal_extent *je;

        list_for_each_entry(je, &sdp->sd_jdesc->extent_list, extent_list) {
                if (lbn >= je->lblock && lbn < je->lblock + je->blocks)
                        return je->dblock + lbn - je->lblock;
        }

        return -1;
}

/**
 * log_distance - Compute distance between two journal blocks
 * @sdp: The GFS2 superblock
 * @newer: The most recent journal block of the pair
 * @older: The older journal block of the pair
 *
 *   Compute the distance (in the journal direction) between two
 *   blocks in the journal
 *
 * Returns: the distance in blocks
 */

static inline unsigned int log_distance(struct gfs2_sbd *sdp, unsigned int newer,
                                        unsigned int older)
{
        int dist;

        dist = newer - older;
        if (dist < 0)
                dist += sdp->sd_jdesc->jd_blocks;

        return dist;
}

/**
 * calc_reserved - Calculate the number of blocks to reserve when
 *                 refunding a transaction's unused buffers.
 * @sdp: The GFS2 superblock
 *
 * This is complex.  We need to reserve room for all our currently used
 * metadata buffers (e.g. normal file I/O rewriting file time stamps) and 
 * all our journaled data buffers for journaled files (e.g. files in the 
 * meta_fs like rindex, or files for which chattr +j was done.)
 * If we don't reserve enough space, gfs2_log_refund and gfs2_log_flush
 * will count it as free space (sd_log_blks_free) and corruption will follow.
 *
 * We can have metadata bufs and jdata bufs in the same journal.  So each
 * type gets its own log header, for which we need to reserve a block.
 * In fact, each type has the potential for needing more than one header 
 * in cases where we have more buffers than will fit on a journal page.
 * Metadata journal entries take up half the space of journaled buffer entries.
 * Thus, metadata entries have buf_limit (502) and journaled buffers have
 * databuf_limit (251) before they cause a wrap around.
 *
 * Also, we need to reserve blocks for revoke journal entries and one for an
 * overall header for the lot.
 *
 * Returns: the number of blocks reserved
 */
static unsigned int calc_reserved(struct gfs2_sbd *sdp)
{
        unsigned int reserved = 0;
        unsigned int mbuf_limit, metabufhdrs_needed;
        unsigned int dbuf_limit, databufhdrs_needed;
        unsigned int revokes = 0;

        mbuf_limit = buf_limit(sdp);
        metabufhdrs_needed = (sdp->sd_log_commited_buf +
                              (mbuf_limit - 1)) / mbuf_limit;
        dbuf_limit = databuf_limit(sdp);
        databufhdrs_needed = (sdp->sd_log_commited_databuf +
                              (dbuf_limit - 1)) / dbuf_limit;

        if (sdp->sd_log_commited_revoke > 0)
                revokes = gfs2_struct2blk(sdp, sdp->sd_log_commited_revoke,
                                          sizeof(u64));

        reserved = sdp->sd_log_commited_buf + metabufhdrs_needed +
                sdp->sd_log_commited_databuf + databufhdrs_needed +
                revokes;
        /* One for the overall header */
        if (reserved)
                reserved++;
        return reserved;
}

static unsigned int current_tail(struct gfs2_sbd *sdp)
{
        struct gfs2_ail *ai;
        unsigned int tail;

        spin_lock(&sdp->sd_ail_lock);

        if (list_empty(&sdp->sd_ail1_list)) {
                tail = sdp->sd_log_head;
        } else {
                ai = list_entry(sdp->sd_ail1_list.prev, struct gfs2_ail, ai_list);
                tail = ai->ai_first;
        }

        spin_unlock(&sdp->sd_ail_lock);

        return tail;
}

void gfs2_log_incr_head(struct gfs2_sbd *sdp)
{
        if (sdp->sd_log_flush_head == sdp->sd_log_tail)
                BUG_ON(sdp->sd_log_flush_head != sdp->sd_log_head);

        if (++sdp->sd_log_flush_head == sdp->sd_jdesc->jd_blocks) {
                sdp->sd_log_flush_head = 0;
                sdp->sd_log_flush_wrapped = 1;
        }
}

/**
 * gfs2_log_write_endio - End of I/O for a log buffer
 * @bh: The buffer head
 * @uptodate: I/O Status
 *
 */

static void gfs2_log_write_endio(struct buffer_head *bh, int uptodate)
{
        struct gfs2_sbd *sdp = bh->b_private;
        bh->b_private = NULL;

        end_buffer_write_sync(bh, uptodate);
        if (atomic_dec_and_test(&sdp->sd_log_in_flight))
                wake_up(&sdp->sd_log_flush_wait);
}

/**
 * gfs2_log_get_buf - Get and initialize a buffer to use for log control data
 * @sdp: The GFS2 superblock
 *
 * Returns: the buffer_head
 */

struct buffer_head *gfs2_log_get_buf(struct gfs2_sbd *sdp)
{
        u64 blkno = log_bmap(sdp, sdp->sd_log_flush_head);
        struct buffer_head *bh;

        bh = sb_getblk(sdp->sd_vfs, blkno);
        lock_buffer(bh);
        memset(bh->b_data, 0, bh->b_size);
        set_buffer_uptodate(bh);
        clear_buffer_dirty(bh);
        gfs2_log_incr_head(sdp);
        atomic_inc(&sdp->sd_log_in_flight);
        bh->b_private = sdp;
        bh->b_end_io = gfs2_log_write_endio;

        return bh;
}

/**
 * gfs2_fake_write_endio - 
 * @bh: The buffer head
 * @uptodate: The I/O Status
 *
 */

static void gfs2_fake_write_endio(struct buffer_head *bh, int uptodate)
{
        struct buffer_head *real_bh = bh->b_private;
        struct gfs2_bufdata *bd = real_bh->b_private;
        struct gfs2_sbd *sdp = bd->bd_gl->gl_sbd;

        end_buffer_write_sync(bh, uptodate);
        free_buffer_head(bh);
        unlock_buffer(real_bh);
        brelse(real_bh);
        if (atomic_dec_and_test(&sdp->sd_log_in_flight))
                wake_up(&sdp->sd_log_flush_wait);
}

/**
 * gfs2_log_fake_buf - Build a fake buffer head to write metadata buffer to log
 * @sdp: the filesystem
 * @data: the data the buffer_head should point to
 *
 * Returns: the log buffer descriptor
 */

struct buffer_head *gfs2_log_fake_buf(struct gfs2_sbd *sdp,
                                      struct buffer_head *real)
{
        u64 blkno = log_bmap(sdp, sdp->sd_log_flush_head);
        struct buffer_head *bh;

        bh = alloc_buffer_head(GFP_NOFS | __GFP_NOFAIL);
        atomic_set(&bh->b_count, 1);
        bh->b_state = (1 << BH_Mapped) | (1 << BH_Uptodate) | (1 << BH_Lock);
        set_bh_page(bh, real->b_page, bh_offset(real));
        bh->b_blocknr = blkno;
        bh->b_size = sdp->sd_sb.sb_bsize;
        bh->b_bdev = sdp->sd_vfs->s_bdev;
        bh->b_private = real;
        bh->b_end_io = gfs2_fake_write_endio;

        gfs2_log_incr_head(sdp);
        atomic_inc(&sdp->sd_log_in_flight);

        return bh;
}

static void log_pull_tail(struct gfs2_sbd *sdp, unsigned int new_tail)
{
        unsigned int dist = log_distance(sdp, new_tail, sdp->sd_log_tail);

        ail2_empty(sdp, new_tail);

        atomic_add(dist, &sdp->sd_log_blks_free);
        trace_gfs2_log_blocks(sdp, dist);
        gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
                             sdp->sd_jdesc->jd_blocks);

        sdp->sd_log_tail = new_tail;
}

/**
 * log_write_header - Get and initialize a journal header buffer
 * @sdp: The GFS2 superblock
 *
 * Returns: the initialized log buffer descriptor
 */

static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull)
{
        u64 blkno = log_bmap(sdp, sdp->sd_log_flush_head);
        struct buffer_head *bh;
        struct gfs2_log_header *lh;
        unsigned int tail;
        u32 hash;

        bh = sb_getblk(sdp->sd_vfs, blkno);
        lock_buffer(bh);
        memset(bh->b_data, 0, bh->b_size);
        set_buffer_uptodate(bh);
        clear_buffer_dirty(bh);

        gfs2_ail1_empty(sdp);
        tail = current_tail(sdp);

        lh = (struct gfs2_log_header *)bh->b_data;
        memset(lh, 0, sizeof(struct gfs2_log_header));
        lh->lh_header.mh_magic = cpu_to_be32(GFS2_MAGIC);
        lh->lh_header.mh_type = cpu_to_be32(GFS2_METATYPE_LH);
        lh->lh_header.__pad0 = cpu_to_be64(0);
        lh->lh_header.mh_format = cpu_to_be32(GFS2_FORMAT_LH);
        lh->lh_header.mh_jid = cpu_to_be32(sdp->sd_jdesc->jd_jid);
        lh->lh_sequence = cpu_to_be64(sdp->sd_log_sequence++);
        lh->lh_flags = cpu_to_be32(flags);
        lh->lh_tail = cpu_to_be32(tail);
        lh->lh_blkno = cpu_to_be32(sdp->sd_log_flush_head);
        hash = gfs2_disk_hash(bh->b_data, sizeof(struct gfs2_log_header));
        lh->lh_hash = cpu_to_be32(hash);

        bh->b_end_io = end_buffer_write_sync;
        get_bh(bh);
        if (test_bit(SDF_NOBARRIERS, &sdp->sd_flags))
                submit_bh(WRITE_SYNC | REQ_META | REQ_PRIO, bh);
        else
                submit_bh(WRITE_FLUSH_FUA | REQ_META | REQ_PRIO, bh);
        wait_on_buffer(bh);

        if (!buffer_uptodate(bh))
                gfs2_io_error_bh(sdp, bh);
        brelse(bh);

        if (sdp->sd_log_tail != tail)
                log_pull_tail(sdp, tail);
        else
                gfs2_assert_withdraw(sdp, !pull);

        sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
        gfs2_log_incr_head(sdp);
}

static void log_flush_commit(struct gfs2_sbd *sdp)
{
        DEFINE_WAIT(wait);

        if (atomic_read(&sdp->sd_log_in_flight)) {
                do {
                        prepare_to_wait(&sdp->sd_log_flush_wait, &wait,
                                        TASK_UNINTERRUPTIBLE);
                        if (atomic_read(&sdp->sd_log_in_flight))
                                io_schedule();
                } while(atomic_read(&sdp->sd_log_in_flight));
                finish_wait(&sdp->sd_log_flush_wait, &wait);
        }

        log_write_header(sdp, 0, 0);
}

static void gfs2_ordered_write(struct gfs2_sbd *sdp)
{
        struct gfs2_bufdata *bd;
        struct buffer_head *bh;
        LIST_HEAD(written);

        gfs2_log_lock(sdp);
        while (!list_empty(&sdp->sd_log_le_ordered)) {
                bd = list_entry(sdp->sd_log_le_ordered.next, struct gfs2_bufdata, bd_le.le_list);
                list_move(&bd->bd_le.le_list, &written);
                bh = bd->bd_bh;
                if (!buffer_dirty(bh))
                        continue;
                get_bh(bh);
                gfs2_log_unlock(sdp);
                lock_buffer(bh);
                if (buffer_mapped(bh) && test_clear_buffer_dirty(bh)) {
                        bh->b_end_io = end_buffer_write_sync;
                        submit_bh(WRITE_SYNC, bh);
                } else {
                        unlock_buffer(bh);
                        brelse(bh);
                }
                gfs2_log_lock(sdp);
        }
        list_splice(&written, &sdp->sd_log_le_ordered);
        gfs2_log_unlock(sdp);
}

static void gfs2_ordered_wait(struct gfs2_sbd *sdp)
{
        struct gfs2_bufdata *bd;
        struct buffer_head *bh;

        gfs2_log_lock(sdp);
        while (!list_empty(&sdp->sd_log_le_ordered)) {
                bd = list_entry(sdp->sd_log_le_ordered.prev, struct gfs2_bufdata, bd_le.le_list);
                bh = bd->bd_bh;
                if (buffer_locked(bh)) {
                        get_bh(bh);
                        gfs2_log_unlock(sdp);
                        wait_on_buffer(bh);
                        brelse(bh);
                        gfs2_log_lock(sdp);
                        continue;
                }
                list_del_init(&bd->bd_le.le_list);
        }
        gfs2_log_unlock(sdp);
}

/**
 * gfs2_log_flush - flush incore transaction(s)
 * @sdp: the filesystem
 * @gl: The glock structure to flush.  If NULL, flush the whole incore log
 *
 */

void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl)
{
        struct gfs2_ail *ai;

        down_write(&sdp->sd_log_flush_lock);

        /* Log might have been flushed while we waited for the flush lock */
        if (gl && !test_bit(GLF_LFLUSH, &gl->gl_flags)) {
                up_write(&sdp->sd_log_flush_lock);
                return;
        }
        trace_gfs2_log_flush(sdp, 1);

        ai = kzalloc(sizeof(struct gfs2_ail), GFP_NOFS | __GFP_NOFAIL);
        INIT_LIST_HEAD(&ai->ai_ail1_list);
        INIT_LIST_HEAD(&ai->ai_ail2_list);

        if (sdp->sd_log_num_buf != sdp->sd_log_commited_buf) {
                printk(KERN_INFO "GFS2: log buf %u %u\n", sdp->sd_log_num_buf,
                       sdp->sd_log_commited_buf);
                gfs2_assert_withdraw(sdp, 0);
        }
        if (sdp->sd_log_num_databuf != sdp->sd_log_commited_databuf) {
                printk(KERN_INFO "GFS2: log databuf %u %u\n",
                       sdp->sd_log_num_databuf, sdp->sd_log_commited_databuf);
                gfs2_assert_withdraw(sdp, 0);
        }
        gfs2_assert_withdraw(sdp,
                        sdp->sd_log_num_revoke == sdp->sd_log_commited_revoke);

        sdp->sd_log_flush_head = sdp->sd_log_head;
        sdp->sd_log_flush_wrapped = 0;
        ai->ai_first = sdp->sd_log_flush_head;

        gfs2_ordered_write(sdp);
        lops_before_commit(sdp);
        gfs2_ordered_wait(sdp);

        if (sdp->sd_log_head != sdp->sd_log_flush_head)
                log_flush_commit(sdp);
        else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle){
                gfs2_log_lock(sdp);
                atomic_dec(&sdp->sd_log_blks_free); /* Adjust for unreserved buffer */
                trace_gfs2_log_blocks(sdp, -1);
                gfs2_log_unlock(sdp);
                log_write_header(sdp, 0, PULL);
        }
        lops_after_commit(sdp, ai);

        gfs2_log_lock(sdp);
        sdp->sd_log_head = sdp->sd_log_flush_head;
        sdp->sd_log_blks_reserved = 0;
        sdp->sd_log_commited_buf = 0;
        sdp->sd_log_commited_databuf = 0;
        sdp->sd_log_commited_revoke = 0;

        spin_lock(&sdp->sd_ail_lock);
        if (!list_empty(&ai->ai_ail1_list)) {
                list_add(&ai->ai_list, &sdp->sd_ail1_list);
                ai = NULL;
        }
        spin_unlock(&sdp->sd_ail_lock);
        gfs2_log_unlock(sdp);
        trace_gfs2_log_flush(sdp, 0);
        up_write(&sdp->sd_log_flush_lock);

        kfree(ai);
}

static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
        unsigned int reserved;
        unsigned int unused;

        gfs2_log_lock(sdp);

        sdp->sd_log_commited_buf += tr->tr_num_buf_new - tr->tr_num_buf_rm;
        sdp->sd_log_commited_databuf += tr->tr_num_databuf_new -
                tr->tr_num_databuf_rm;
        gfs2_assert_withdraw(sdp, (((int)sdp->sd_log_commited_buf) >= 0) ||
                             (((int)sdp->sd_log_commited_databuf) >= 0));
        sdp->sd_log_commited_revoke += tr->tr_num_revoke - tr->tr_num_revoke_rm;
        reserved = calc_reserved(sdp);
        gfs2_assert_withdraw(sdp, sdp->sd_log_blks_reserved + tr->tr_reserved >= reserved);
        unused = sdp->sd_log_blks_reserved - reserved + tr->tr_reserved;
        atomic_add(unused, &sdp->sd_log_blks_free);
        trace_gfs2_log_blocks(sdp, unused);
        gfs2_assert_withdraw(sdp, atomic_read(&sdp->sd_log_blks_free) <=
                             sdp->sd_jdesc->jd_blocks);
        sdp->sd_log_blks_reserved = reserved;

        gfs2_log_unlock(sdp);
}

static void buf_lo_incore_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
        struct list_head *head = &tr->tr_list_buf;
        struct gfs2_bufdata *bd;

        gfs2_log_lock(sdp);
        while (!list_empty(head)) {
                bd = list_entry(head->next, struct gfs2_bufdata, bd_list_tr);
                list_del_init(&bd->bd_list_tr);
                tr->tr_num_buf--;
        }
        gfs2_log_unlock(sdp);
        gfs2_assert_warn(sdp, !tr->tr_num_buf);
}

/**
 * gfs2_log_commit - Commit a transaction to the log
 * @sdp: the filesystem
 * @tr: the transaction
 *
 * We wake up gfs2_logd if the number of pinned blocks exceed thresh1
 * or the total number of used blocks (pinned blocks plus AIL blocks)
 * is greater than thresh2.
 *
 * At mount time thresh1 is 1/3rd of journal size, thresh2 is 2/3rd of
 * journal size.
 *
 * Returns: errno
 */

void gfs2_log_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
{
        log_refund(sdp, tr);
        buf_lo_incore_commit(sdp, tr);

        up_read(&sdp->sd_log_flush_lock);

        if (atomic_read(&sdp->sd_log_pinned) > atomic_read(&sdp->sd_log_thresh1) ||
            ((sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free)) >
            atomic_read(&sdp->sd_log_thresh2)))
                wake_up(&sdp->sd_logd_waitq);
}

/**
 * gfs2_log_shutdown - write a shutdown header into a journal
 * @sdp: the filesystem
 *
 */

void gfs2_log_shutdown(struct gfs2_sbd *sdp)
{
        down_write(&sdp->sd_log_flush_lock);

        gfs2_assert_withdraw(sdp, !sdp->sd_log_blks_reserved);
        gfs2_assert_withdraw(sdp, !sdp->sd_log_num_buf);
        gfs2_assert_withdraw(sdp, !sdp->sd_log_num_revoke);
        gfs2_assert_withdraw(sdp, !sdp->sd_log_num_rg);
        gfs2_assert_withdraw(sdp, !sdp->sd_log_num_databuf);
        gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail1_list));

        sdp->sd_log_flush_head = sdp->sd_log_head;
        sdp->sd_log_flush_wrapped = 0;

        log_write_header(sdp, GFS2_LOG_HEAD_UNMOUNT,
                         (sdp->sd_log_tail == current_tail(sdp)) ? 0 : PULL);

        gfs2_assert_warn(sdp, atomic_read(&sdp->sd_log_blks_free) == sdp->sd_jdesc->jd_blocks);
        gfs2_assert_warn(sdp, sdp->sd_log_head == sdp->sd_log_tail);
        gfs2_assert_warn(sdp, list_empty(&sdp->sd_ail2_list));

        sdp->sd_log_head = sdp->sd_log_flush_head;
        sdp->sd_log_tail = sdp->sd_log_head;

        up_write(&sdp->sd_log_flush_lock);
}


/**
 * gfs2_meta_syncfs - sync all the buffers in a filesystem
 * @sdp: the filesystem
 *
 */

void gfs2_meta_syncfs(struct gfs2_sbd *sdp)
{
        gfs2_log_flush(sdp, NULL);
        for (;;) {
                gfs2_ail1_start(sdp);
                gfs2_ail1_wait(sdp);
                if (gfs2_ail1_empty(sdp))
                        break;
        }
        gfs2_log_flush(sdp, NULL);
}

static inline int gfs2_jrnl_flush_reqd(struct gfs2_sbd *sdp)
{
        return (atomic_read(&sdp->sd_log_pinned) >= atomic_read(&sdp->sd_log_thresh1));
}

static inline int gfs2_ail_flush_reqd(struct gfs2_sbd *sdp)
{
        unsigned int used_blocks = sdp->sd_jdesc->jd_blocks - atomic_read(&sdp->sd_log_blks_free);
        return used_blocks >= atomic_read(&sdp->sd_log_thresh2);
}

/**
 * gfs2_logd - Update log tail as Active Items get flushed to in-place blocks
 * @sdp: Pointer to GFS2 superblock
 *
 * Also, periodically check to make sure that we're using the most recent
 * journal index.
 */

int gfs2_logd(void *data)
{
        struct gfs2_sbd *sdp = data;
        unsigned long t = 1;
        DEFINE_WAIT(wait);
        unsigned preflush;

        while (!kthread_should_stop()) {

                preflush = atomic_read(&sdp->sd_log_pinned);
                if (gfs2_jrnl_flush_reqd(sdp) || t == 0) {
                        gfs2_ail1_empty(sdp);
                        gfs2_log_flush(sdp, NULL);
                }

                if (gfs2_ail_flush_reqd(sdp)) {
                        gfs2_ail1_start(sdp);
                        gfs2_ail1_wait(sdp);
                        gfs2_ail1_empty(sdp);
                        gfs2_log_flush(sdp, NULL);
                }

                if (!gfs2_ail_flush_reqd(sdp))
                        wake_up(&sdp->sd_log_waitq);

                t = gfs2_tune_get(sdp, gt_logd_secs) * HZ;
                if (freezing(current))
                        refrigerator();

                do {
                        prepare_to_wait(&sdp->sd_logd_waitq, &wait,
                                        TASK_INTERRUPTIBLE);
                        if (!gfs2_ail_flush_reqd(sdp) &&
                            !gfs2_jrnl_flush_reqd(sdp) &&
                            !kthread_should_stop())
                                t = schedule_timeout(t);
                } while(t && !gfs2_ail_flush_reqd(sdp) &&
                        !gfs2_jrnl_flush_reqd(sdp) &&
                        !kthread_should_stop());
                finish_wait(&sdp->sd_logd_waitq, &wait);
        }

        return 0;
}