[GFS2] Clean up journaled data writing

This patch cleans up the code for writing journaled data into the log.
It also removes the need to allocate a small "tag" structure for each
block written into the log. Instead we just keep count of the outstanding
I/O so that we can be sure that its all been written at the correct time.
Another result of this patch is that a number of ll_rw_block() calls
have become submit_bh() calls, closing some races at the same time.

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

1 files changed, 83 insertions, 62 deletions

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 4d04e6f19706..ee704676b2f1 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -104,11 +104,8 @@ static void gfs2_ail1_start_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
                         gfs2_assert(sdp, bd->bd_ail == ai);
 
                         if (!buffer_busy(bh)) {
-                                if (!buffer_uptodate(bh)) {
-                                        gfs2_log_unlock(sdp);
+                                if (!buffer_uptodate(bh))
                                         gfs2_io_error_bh(sdp, bh);
-                                        gfs2_log_lock(sdp);
-                                }
                                 list_move(&bd->bd_ail_st_list, &ai->ai_ail2_list);
                                 continue;
                         }
@@ -118,9 +115,16 @@ static void gfs2_ail1_start_one(struct gfs2_sbd *sdp, struct gfs2_ail *ai)
 
                         list_move(&bd->bd_ail_st_list, &ai->ai_ail1_list);
 
+                        get_bh(bh);
                         gfs2_log_unlock(sdp);
-                        wait_on_buffer(bh);
-                        ll_rw_block(WRITE, 1, &bh);
+                        lock_buffer(bh);
+                        if (test_clear_buffer_dirty(bh)) {
+                                bh->b_end_io = end_buffer_write_sync;
+                                submit_bh(WRITE, bh);
+                        } else {
+                                unlock_buffer(bh);
+                                brelse(bh);
+                        }
                         gfs2_log_lock(sdp);
 
                         retry = 1;
@@ -446,10 +450,10 @@ static unsigned int current_tail(struct gfs2_sbd *sdp)
         return tail;
 }
 
-static inline void log_incr_head(struct gfs2_sbd *sdp)
+void gfs2_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);
+                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;
@@ -458,6 +462,23 @@ static inline void log_incr_head(struct gfs2_sbd *sdp)
 }
 
 /**
+ * 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
  *
@@ -467,25 +488,42 @@ static inline void log_incr_head(struct gfs2_sbd *sdp)
 struct buffer_head *gfs2_log_get_buf(struct gfs2_sbd *sdp)
 {
         u64 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_NOFS | __GFP_NOFAIL);
-        list_add(&lb->lb_list, &sdp->sd_log_flush_list);
-
-        bh = lb->lb_bh = sb_getblk(sdp->sd_vfs, blkno);
+        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);
+        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_sbd *sdp = GFS2_SB(real_bh->b_page->mapping->host);
+
+        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
@@ -497,22 +535,20 @@ 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 gfs2_log_buf *lb;
         struct buffer_head *bh;
 
-        lb = kzalloc(sizeof(struct gfs2_log_buf), GFP_NOFS | __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);
+        bh = alloc_buffer_head(GFP_NOFS | __GFP_NOFAIL);
         atomic_set(&bh->b_count, 1);
-        bh->b_state = (1 << BH_Mapped) | (1 << BH_Uptodate);
+        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;
 
-        log_incr_head(sdp);
+        gfs2_log_incr_head(sdp);
+        atomic_inc(&sdp->sd_log_in_flight);
 
         return bh;
 }
@@ -579,45 +615,24 @@ static void log_write_header(struct gfs2_sbd *sdp, u32 flags, int pull)
                 gfs2_assert_withdraw(sdp, !pull);
 
         sdp->sd_log_idle = (tail == sdp->sd_log_flush_head);
-        log_incr_head(sdp);
+        gfs2_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;
-        int flushcount = 0;
-
-        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);
-                flushcount++;
+        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);
         }
 
-        /* If nothing was journaled, the header is unplanned and unwanted. */
-        if (flushcount) {
-                log_write_header(sdp, 0, 0);
-        } else {
-                unsigned int tail;
-                tail = current_tail(sdp);
-
-                gfs2_ail1_empty(sdp, 0);
-                if (sdp->sd_log_tail != tail)
-                        log_pull_tail(sdp, tail);
-        }
+        log_write_header(sdp, 0, 0);
 }
 
 static void gfs2_ordered_write(struct gfs2_sbd *sdp)
@@ -698,10 +713,16 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl)
         INIT_LIST_HEAD(&ai->ai_ail1_list);
         INIT_LIST_HEAD(&ai->ai_ail2_list);
 
-        gfs2_assert_withdraw(sdp,
-                             sdp->sd_log_num_buf + sdp->sd_log_num_databuf ==
-                             sdp->sd_log_commited_buf +
-                             sdp->sd_log_commited_databuf);
+        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);
 
@@ -713,7 +734,7 @@ void gfs2_log_flush(struct gfs2_sbd *sdp, struct gfs2_glock *gl)
         lops_before_commit(sdp);
         gfs2_ordered_wait(sdp);
 
-        if (!list_empty(&sdp->sd_log_flush_list))
+        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);