[GFS2] The core of GFS2

This patch contains all the core files for GFS2.

Signed-off-by: David Teigland <teigland@redhat.com>
Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>

1 files changed, 659 insertions, 0 deletions

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
new file mode 100644
index 000000000000..736d0d33dd1b
--- /dev/null
+++ b/fs/gfs2/log.c
@@ -0,0 +1,659 @@
+/*
+ * Copyright (C) Sistina Software, Inc.  1997-2003 All rights reserved.
+ * Copyright (C) 2004-2005 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 v.2.
+ */
+
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/completion.h>
+#include <linux/buffer_head.h>
+#include <asm/semaphore.h>
+
+#include "gfs2.h"
+#include "bmap.h"
+#include "glock.h"
+#include "log.h"
+#include "lops.h"
+#include "meta_io.h"
+
+#define PULL 1
+
+static inline int is_done(struct gfs2_sbd *sdp, atomic_t *a)
+{
+        int done;
+        gfs2_log_lock(sdp);
+        done = atomic_read(a) ? 0 : 1;
+        gfs2_log_unlock(sdp);
+        return done;
+}
+
+static void do_lock_wait(struct gfs2_sbd *sdp, wait_queue_head_t *wq,
+                         atomic_t *a)
+{
+        gfs2_log_unlock(sdp);
+        wait_event(*wq, is_done(sdp, a));
+        gfs2_log_lock(sdp);
+}
+
+static void lock_for_trans(struct gfs2_sbd *sdp)
+{
+        gfs2_log_lock(sdp);
+        do_lock_wait(sdp, &sdp->sd_log_trans_wq, &sdp->sd_log_flush_count);
+        atomic_inc(&sdp->sd_log_trans_count);
+        gfs2_log_unlock(sdp);
+}
+
+static void unlock_from_trans(struct gfs2_sbd *sdp)
+{
+        gfs2_assert_warn(sdp, atomic_read(&sdp->sd_log_trans_count));
+        if (atomic_dec_and_test(&sdp->sd_log_trans_count))
+                wake_up(&sdp->sd_log_flush_wq);
+}
+
+void gfs2_lock_for_flush(struct gfs2_sbd *sdp)
+{
+        gfs2_log_lock(sdp);
+        atomic_inc(&sdp->sd_log_flush_count);
+        do_lock_wait(sdp, &sdp->sd_log_flush_wq, &sdp->sd_log_trans_count);
+        gfs2_log_unlock(sdp);
+}
+
+void gfs2_unlock_from_flush(struct gfs2_sbd *sdp)
+{
+        gfs2_assert_warn(sdp, atomic_read(&sdp->sd_log_flush_count));
+        if (atomic_dec_and_test(&sdp->sd_log_flush_count))
+                wake_up(&sdp->sd_log_trans_wq);
+}
+
+/**
+ * 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_RU(nstruct - first, second);
+        }
+
+        return blks;
+}
+
+void gfs2_ail1_start(struct gfs2_sbd *sdp, int flags)
+{
+        struct list_head *head = &sdp->sd_ail1_list;
+        uint64_t sync_gen;
+        struct list_head *first, *tmp;
+        struct gfs2_ail *first_ai, *ai;
+
+        gfs2_log_lock(sdp);
+        if (list_empty(head)) {
+                gfs2_log_unlock(sdp);
+                return;
+        }
+        sync_gen = sdp->sd_ail_sync_gen++;
+
+        first = head->prev;
+        first_ai = list_entry(first, struct gfs2_ail, ai_list);
+        first_ai->ai_sync_gen = sync_gen;
+        gfs2_ail1_start_one(sdp, first_ai);
+
+        if (flags & DIO_ALL)
+                first = NULL;
+
+        for (;;) {
+                if (first &&
+                    (head->prev != first ||
+                     gfs2_ail1_empty_one(sdp, first_ai, 0)))
+                        break;
+
+                for (tmp = head->prev; tmp != head; tmp = tmp->prev) {
+                        ai = list_entry(tmp, struct gfs2_ail, ai_list);
+                        if (ai->ai_sync_gen >= sync_gen)
+                                continue;
+                        ai->ai_sync_gen = sync_gen;
+                        gfs2_ail1_start_one(sdp, ai);
+                        break;
+                }
+
+                if (tmp == head)
+                        break;
+        }
+
+        gfs2_log_unlock(sdp);
+}
+
+int gfs2_ail1_empty(struct gfs2_sbd *sdp, int flags)
+{
+        struct gfs2_ail *ai, *s;
+        int ret;
+
+        gfs2_log_lock(sdp);
+
+        list_for_each_entry_safe_reverse(ai, s, &sdp->sd_ail1_list, ai_list) {
+                if (gfs2_ail1_empty_one(sdp, ai, flags))
+                        list_move(&ai->ai_list, &sdp->sd_ail2_list);
+                else if (!(flags & DIO_ALL))
+                        break;
+        }
+
+        ret = list_empty(&sdp->sd_ail1_list);
+
+        gfs2_log_unlock(sdp);
+
+        return ret;
+}
+
+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;
+
+        gfs2_log_lock(sdp);
+
+        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);
+        }
+
+        gfs2_log_unlock(sdp);
+}
+
+/**
+ * gfs2_log_reserve - Make a log reservation
+ * @sdp: The GFS2 superblock
+ * @blks: The number of blocks to reserve
+ *
+ * Returns: errno
+ */
+
+int gfs2_log_reserve(struct gfs2_sbd *sdp, unsigned int blks)
+{
+        LIST_HEAD(list);
+        unsigned int try = 0;
+
+        if (gfs2_assert_warn(sdp, blks) ||
+            gfs2_assert_warn(sdp, blks <= sdp->sd_jdesc->jd_blocks))
+                return -EINVAL;
+
+        for (;;) {
+                gfs2_log_lock(sdp);
+
+                if (list_empty(&list)) {
+                        list_add_tail(&list, &sdp->sd_log_blks_list);
+                        while (sdp->sd_log_blks_list.next != &list) {
+                                DECLARE_WAITQUEUE(__wait_chan, current);
+                                set_current_state(TASK_UNINTERRUPTIBLE);
+                                add_wait_queue(&sdp->sd_log_blks_wait,
+                                               &__wait_chan);
+                                gfs2_log_unlock(sdp);
+                                schedule();
+                                gfs2_log_lock(sdp);
+                                remove_wait_queue(&sdp->sd_log_blks_wait,
+                                                  &__wait_chan);
+                                set_current_state(TASK_RUNNING);
+                        }
+                }
+
+                /* Never give away the last block so we can
+                   always pull the tail if we need to. */
+                if (sdp->sd_log_blks_free > blks) {
+                        sdp->sd_log_blks_free -= blks;
+                        list_del(&list);
+                        gfs2_log_unlock(sdp);
+                        wake_up(&sdp->sd_log_blks_wait);
+                        break;
+                }
+
+                gfs2_log_unlock(sdp);
+
+                gfs2_ail1_empty(sdp, 0);
+                gfs2_log_flush(sdp);
+
+                if (try++)
+                        gfs2_ail1_start(sdp, 0);
+        }
+
+        lock_for_trans(sdp);
+
+        return 0;
+}
+
+/**
+ * gfs2_log_release - Release a given number of log blocks
+ * @sdp: The GFS2 superblock
+ * @blks: The number of blocks
+ *
+ */
+
+void gfs2_log_release(struct gfs2_sbd *sdp, unsigned int blks)
+{
+        unlock_from_trans(sdp);
+
+        gfs2_log_lock(sdp);
+        sdp->sd_log_blks_free += blks;
+        gfs2_assert_withdraw(sdp,
+                             sdp->sd_log_blks_free <= sdp->sd_jdesc->jd_blocks);
+        gfs2_log_unlock(sdp);
+}
+
+static uint64_t log_bmap(struct gfs2_sbd *sdp, unsigned int lbn)
+{
+        int new = 0;
+        uint64_t dbn;
+        int error;
+
+        error = gfs2_block_map(sdp->sd_jdesc->jd_inode, lbn, &new, &dbn, NULL);
+        gfs2_assert_withdraw(sdp, !error && dbn);
+
+        return dbn;
+}
+
+/**
+ * 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;
+}
+
+static unsigned int current_tail(struct gfs2_sbd *sdp)
+{
+        struct gfs2_ail *ai;
+        unsigned int tail;
+
+        gfs2_log_lock(sdp);
+
+        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;
+        }
+
+        gfs2_log_unlock(sdp);
+
+        return tail;
+}
+
+static inline void log_incr_head(struct gfs2_sbd *sdp)
+{
+        if (sdp->sd_log_flush_head == sdp->sd_log_tail)
+                gfs2_assert_withdraw(sdp,
+                                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_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)
+{
+        uint64_t blkno = log_bmap(sdp, sdp->sd_log_flush_head);
+        struct gfs2_log_buf *lb;
+        struct buffer_head *bh;
+
+        lb = kzalloc(sizeof(struct gfs2_log_buf), GFP_KERNEL | __GFP_NOFAIL);
+        list_add(&lb->lb_list, &sdp->sd_log_flush_list);
+
+        bh = lb->lb_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);
+        unlock_buffer(bh);
+
+        log_incr_head(sdp);
+
+        return bh;
+}
+
+/**
+ * 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)
+{
+        uint64_t blkno = log_bmap(sdp, sdp->sd_log_flush_head);
+        struct gfs2_log_buf *lb;
+        struct buffer_head *bh;
+
+        lb = kzalloc(sizeof(struct gfs2_log_buf), GFP_KERNEL | __GFP_NOFAIL);
+        list_add(&lb->lb_list, &sdp->sd_log_flush_list);
+        lb->lb_real = real;
+
+        bh = lb->lb_bh = alloc_buffer_head(GFP_NOFS | __GFP_NOFAIL);
+        atomic_set(&bh->b_count, 1);
+        bh->b_state = (1 << BH_Mapped) | (1 << BH_Uptodate);
+        set_bh_page(bh, virt_to_page(real->b_data),
+                    ((unsigned long)real->b_data) & (PAGE_SIZE - 1));
+        bh->b_blocknr = blkno;
+        bh->b_size = sdp->sd_sb.sb_bsize;
+        bh->b_bdev = sdp->sd_vfs->s_bdev;
+
+        log_incr_head(sdp);
+
+        return bh;
+}
+
+static void log_pull_tail(struct gfs2_sbd *sdp, unsigned int new_tail, int pull)
+{
+        unsigned int dist = log_distance(sdp, new_tail, sdp->sd_log_tail);
+
+        ail2_empty(sdp, new_tail);
+
+        gfs2_log_lock(sdp);
+        sdp->sd_log_blks_free += dist - ((pull) ? 1 : 0);
+        gfs2_assert_withdraw(sdp,
+                             sdp->sd_log_blks_free <= sdp->sd_jdesc->jd_blocks);
+        gfs2_log_unlock(sdp);
+
+        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, uint32_t flags, int pull)
+{
+        uint64_t blkno = log_bmap(sdp, sdp->sd_log_flush_head);
+        struct buffer_head *bh;
+        struct gfs2_log_header *lh;
+        unsigned int tail;
+        uint32_t hash;
+
+        atomic_inc(&sdp->sd_log_flush_ondisk);
+
+        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);
+        unlock_buffer(bh);
+
+        gfs2_ail1_empty(sdp, 0);
+        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_be16(GFS2_METATYPE_LH);
+        lh->lh_header.mh_format = cpu_to_be16(GFS2_FORMAT_LH);
+        lh->lh_sequence = be64_to_cpu(sdp->sd_log_sequence++);
+        lh->lh_flags = be32_to_cpu(flags);
+        lh->lh_tail = be32_to_cpu(tail);
+        lh->lh_blkno = be32_to_cpu(sdp->sd_log_flush_head);
+        hash = gfs2_disk_hash(bh->b_data, sizeof(struct gfs2_log_header));
+        lh->lh_hash = cpu_to_be32(hash);
+
+        set_buffer_dirty(bh);
+        if (sync_dirty_buffer(bh))
+                gfs2_io_error_bh(sdp, bh);
+        brelse(bh);
+
+        if (sdp->sd_log_tail != tail)
+                log_pull_tail(sdp, tail, pull);
+        else
+                gfs2_assert_withdraw(sdp, !pull);
+
+        sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
+        log_incr_head(sdp);
+}
+
+static void log_flush_commit(struct gfs2_sbd *sdp)
+{
+        struct list_head *head = &sdp->sd_log_flush_list;
+        struct gfs2_log_buf *lb;
+        struct buffer_head *bh;
+        unsigned int d;
+
+        d = log_distance(sdp, sdp->sd_log_flush_head, sdp->sd_log_head);
+
+        gfs2_assert_withdraw(sdp, d + 1 == sdp->sd_log_blks_reserved);
+
+        while (!list_empty(head)) {
+                lb = list_entry(head->next, struct gfs2_log_buf, lb_list);
+                list_del(&lb->lb_list);
+                bh = lb->lb_bh;
+
+                wait_on_buffer(bh);
+                if (!buffer_uptodate(bh))
+                        gfs2_io_error_bh(sdp, bh);
+                if (lb->lb_real) {
+                        while (atomic_read(&bh->b_count) != 1)  /* Grrrr... */
+                                schedule();
+                        free_buffer_head(bh);
+                } else
+                        brelse(bh);
+                kfree(lb);
+        }
+
+        log_write_header(sdp, 0, 0);
+}
+
+/**
+ * gfs2_log_flush_i - flush incore transaction(s)
+ * @sdp: the filesystem
+ * @gl: The glock structure to flush.  If NULL, flush the whole incore log
+ *
+ */
+
+void gfs2_log_flush_i(struct gfs2_sbd *sdp, struct gfs2_glock *gl)
+{
+        struct gfs2_ail *ai;
+
+        atomic_inc(&sdp->sd_log_flush_incore);
+
+        ai = kzalloc(sizeof(struct gfs2_ail), GFP_KERNEL | __GFP_NOFAIL);
+        INIT_LIST_HEAD(&ai->ai_ail1_list);
+        INIT_LIST_HEAD(&ai->ai_ail2_list);
+
+        gfs2_lock_for_flush(sdp);
+        down(&sdp->sd_log_flush_lock);
+
+        gfs2_assert_withdraw(sdp,
+                        sdp->sd_log_num_buf == sdp->sd_log_commited_buf);
+        gfs2_assert_withdraw(sdp,
+                        sdp->sd_log_num_revoke == sdp->sd_log_commited_revoke);
+
+        if (gl && list_empty(&gl->gl_le.le_list)) {
+                up(&sdp->sd_log_flush_lock);
+                gfs2_unlock_from_flush(sdp);
+                kfree(ai);
+                return;
+        }
+
+        sdp->sd_log_flush_head = sdp->sd_log_head;
+        sdp->sd_log_flush_wrapped = 0;
+        ai->ai_first = sdp->sd_log_flush_head;
+
+        lops_before_commit(sdp);
+        if (!list_empty(&sdp->sd_log_flush_list))
+                log_flush_commit(sdp);
+        else if (sdp->sd_log_tail != current_tail(sdp) && !sdp->sd_log_idle)
+                log_write_header(sdp, 0, PULL);
+        lops_after_commit(sdp, ai);
+
+        sdp->sd_log_head = sdp->sd_log_flush_head;
+        if (sdp->sd_log_flush_wrapped)
+                sdp->sd_log_wraps++;
+
+        sdp->sd_log_blks_reserved =
+                sdp->sd_log_commited_buf =
+                sdp->sd_log_commited_revoke = 0;
+
+        gfs2_log_lock(sdp);
+        if (!list_empty(&ai->ai_ail1_list)) {
+                list_add(&ai->ai_list, &sdp->sd_ail1_list);
+                ai = NULL;
+        }
+        gfs2_log_unlock(sdp);
+
+        up(&sdp->sd_log_flush_lock);
+        sdp->sd_vfs->s_dirt = 0;
+        gfs2_unlock_from_flush(sdp);
+
+        kfree(ai);
+}
+
+static void log_refund(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
+{
+        unsigned int reserved = 1;
+        unsigned int old;
+
+        gfs2_log_lock(sdp);
+
+        sdp->sd_log_commited_buf += tr->tr_num_buf_new - tr->tr_num_buf_rm;
+        gfs2_assert_withdraw(sdp, ((int)sdp->sd_log_commited_buf) >= 0);
+        sdp->sd_log_commited_revoke += tr->tr_num_revoke - tr->tr_num_revoke_rm;
+        gfs2_assert_withdraw(sdp, ((int)sdp->sd_log_commited_revoke) >= 0);
+
+        if (sdp->sd_log_commited_buf)
+                reserved += 1 + sdp->sd_log_commited_buf + sdp->sd_log_commited_buf/503;
+        if (sdp->sd_log_commited_revoke)
+                reserved += gfs2_struct2blk(sdp, sdp->sd_log_commited_revoke,
+                                            sizeof(uint64_t));
+
+        old = sdp->sd_log_blks_free;
+        sdp->sd_log_blks_free += tr->tr_reserved -
+                                 (reserved - sdp->sd_log_blks_reserved);
+
+        gfs2_assert_withdraw(sdp,
+                             sdp->sd_log_blks_free >= old);
+        gfs2_assert_withdraw(sdp,
+                             sdp->sd_log_blks_free <= sdp->sd_jdesc->jd_blocks);
+
+        sdp->sd_log_blks_reserved = reserved;
+
+        gfs2_log_unlock(sdp);
+}
+
+/**
+ * gfs2_log_commit - Commit a transaction to the log
+ * @sdp: the filesystem
+ * @tr: the transaction
+ *
+ * Returns: errno
+ */
+
+void gfs2_log_commit(struct gfs2_sbd *sdp, struct gfs2_trans *tr)
+{
+        log_refund(sdp, tr);
+        lops_incore_commit(sdp, tr);
+
+        sdp->sd_vfs->s_dirt = 1;
+        unlock_from_trans(sdp);
+
+        kfree(tr);
+
+        gfs2_log_lock(sdp);
+        if (sdp->sd_log_num_buf > gfs2_tune_get(sdp, gt_incore_log_blocks)) {
+                gfs2_log_unlock(sdp);
+                gfs2_log_flush(sdp);
+        } else
+                gfs2_log_unlock(sdp);
+}
+
+/**
+ * gfs2_log_shutdown - write a shutdown header into a journal
+ * @sdp: the filesystem
+ *
+ */
+
+void gfs2_log_shutdown(struct gfs2_sbd *sdp)
+{
+        down(&sdp->sd_log_flush_lock);
+
+        gfs2_assert_withdraw(sdp, !atomic_read(&sdp->sd_log_trans_count));
+        gfs2_assert_withdraw(sdp, !sdp->sd_log_blks_reserved);
+        gfs2_assert_withdraw(sdp, !sdp->sd_log_num_gl);
+        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, 0);
+
+        gfs2_assert_withdraw(sdp, sdp->sd_log_blks_free ==
+                             sdp->sd_jdesc->jd_blocks);
+        gfs2_assert_withdraw(sdp, sdp->sd_log_head == sdp->sd_log_tail);
+        gfs2_assert_withdraw(sdp, list_empty(&sdp->sd_ail2_list));
+
+        sdp->sd_log_head = sdp->sd_log_flush_head;
+        if (sdp->sd_log_flush_wrapped)
+                sdp->sd_log_wraps++;
+        sdp->sd_log_tail = sdp->sd_log_head;
+
+        up(&sdp->sd_log_flush_lock);
+}
+