[PATCH] jbd: revert checkpoint list changes

This patch reverts commit f93ea411b73594f7d144855fd34278bcf34a9afc:
  [PATCH] jbd: split checkpoint lists

This broke journal_flush() for OCFS2, which is its method of being sure
that metadata is sent to disk for another node.

And two related commits 8d3c7fce2d20ecc3264c8d8c91ae3beacdeaed1b and
43c3e6f5abdf6acac9b90c86bf03f995bf7d3d92 with the subjects:
  [PATCH] jbd: log_do_checkpoint fix
  [PATCH] jbd: remove_transaction fix

These seem to be incremental bugfixes on the original patch and as such are
no longer needed.

Signed-off-by: Mark Fasheh <mark.fasheh@oracle.com>
Cc: Jan Kara <jack@ucw.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

3 files changed, 179 insertions, 250 deletions

diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
index e6265a0b56b8..543ed543d1e5 100644
--- a/fs/jbd/checkpoint.c
+++ b/fs/jbd/checkpoint.c
@@ -24,75 +24,29 @@
 #include <linux/slab.h>
 
 /*
- * Unlink a buffer from a transaction checkpoint list.
+ * Unlink a buffer from a transaction.
  *
  * Called with j_list_lock held.
  */
 
-static void __buffer_unlink_first(struct journal_head *jh)
+static inline void __buffer_unlink(struct journal_head *jh)
 {
         transaction_t *transaction;
 
         transaction = jh->b_cp_transaction;
+        jh->b_cp_transaction = NULL;
 
         jh->b_cpnext->b_cpprev = jh->b_cpprev;
         jh->b_cpprev->b_cpnext = jh->b_cpnext;
-        if (transaction->t_checkpoint_list == jh) {
+        if (transaction->t_checkpoint_list == jh)
                 transaction->t_checkpoint_list = jh->b_cpnext;
-                if (transaction->t_checkpoint_list == jh)
-                        transaction->t_checkpoint_list = NULL;
-        }
-}
-
-/*
- * Unlink a buffer from a transaction checkpoint(io) list.
- *
- * Called with j_list_lock held.
- */
-
-static inline void __buffer_unlink(struct journal_head *jh)
-{
-        transaction_t *transaction;
-
-        transaction = jh->b_cp_transaction;
-
-        __buffer_unlink_first(jh);
-        if (transaction->t_checkpoint_io_list == jh) {
-                transaction->t_checkpoint_io_list = jh->b_cpnext;
-                if (transaction->t_checkpoint_io_list == jh)
-                        transaction->t_checkpoint_io_list = NULL;
-        }
-}
-
-/*
- * Move a buffer from the checkpoint list to the checkpoint io list
- *
- * Called with j_list_lock held
- */
-
-static inline void __buffer_relink_io(struct journal_head *jh)
-{
-        transaction_t *transaction;
-
-        transaction = jh->b_cp_transaction;
-        __buffer_unlink_first(jh);
-
-        if (!transaction->t_checkpoint_io_list) {
-                jh->b_cpnext = jh->b_cpprev = jh;
-        } else {
-                jh->b_cpnext = transaction->t_checkpoint_io_list;
-                jh->b_cpprev = transaction->t_checkpoint_io_list->b_cpprev;
-                jh->b_cpprev->b_cpnext = jh;
-                jh->b_cpnext->b_cpprev = jh;
-        }
-        transaction->t_checkpoint_io_list = jh;
+        if (transaction->t_checkpoint_list == jh)
+                transaction->t_checkpoint_list = NULL;
 }
 
 /*
  * Try to release a checkpointed buffer from its transaction.
- * Returns 1 if we released it and 2 if we also released the
- * whole transaction.
- *
+ * Returns 1 if we released it.
  * Requires j_list_lock
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
@@ -103,11 +57,12 @@ static int __try_to_free_cp_buf(struct journal_head *jh)
 
         if (jh->b_jlist == BJ_None && !buffer_locked(bh) && !buffer_dirty(bh)) {
                 JBUFFER_TRACE(jh, "remove from checkpoint list");
-                ret = __journal_remove_checkpoint(jh) + 1;
+                __journal_remove_checkpoint(jh);
                 jbd_unlock_bh_state(bh);
                 journal_remove_journal_head(bh);
                 BUFFER_TRACE(bh, "release");
                 __brelse(bh);
+                ret = 1;
         } else {
                 jbd_unlock_bh_state(bh);
         }
@@ -162,53 +117,83 @@ static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
 }
 
 /*
- * Clean up transaction's list of buffers submitted for io.
- * We wait for any pending IO to complete and remove any clean
- * buffers. Note that we take the buffers in the opposite ordering
- * from the one in which they were submitted for IO.
+ * Clean up a transaction's checkpoint list.
+ *
+ * We wait for any pending IO to complete and make sure any clean
+ * buffers are removed from the transaction.
+ *
+ * Return 1 if we performed any actions which might have destroyed the
+ * checkpoint.  (journal_remove_checkpoint() deletes the transaction when
+ * the last checkpoint buffer is cleansed)
  *
  * Called with j_list_lock held.
  */
-
-static void __wait_cp_io(journal_t *journal, transaction_t *transaction)
+static int __cleanup_transaction(journal_t *journal, transaction_t *transaction)
 {
-        struct journal_head *jh;
+        struct journal_head *jh, *next_jh, *last_jh;
         struct buffer_head *bh;
-        tid_t this_tid;
-        int released = 0;
-
-        this_tid = transaction->t_tid;
-restart:
-        /* Didn't somebody clean up the transaction in the meanwhile */
-        if (journal->j_checkpoint_transactions != transaction ||
-                transaction->t_tid != this_tid)
-                return;
-        while (!released && transaction->t_checkpoint_io_list) {
-                jh = transaction->t_checkpoint_io_list;
+        int ret = 0;
+
+        assert_spin_locked(&journal->j_list_lock);
+        jh = transaction->t_checkpoint_list;
+        if (!jh)
+                return 0;
+
+        last_jh = jh->b_cpprev;
+        next_jh = jh;
+        do {
+                jh = next_jh;
                 bh = jh2bh(jh);
-                if (!jbd_trylock_bh_state(bh)) {
-                        jbd_sync_bh(journal, bh);
-                        spin_lock(&journal->j_list_lock);
-                        goto restart;
-                }
                 if (buffer_locked(bh)) {
                         atomic_inc(&bh->b_count);
                         spin_unlock(&journal->j_list_lock);
-                        jbd_unlock_bh_state(bh);
                         wait_on_buffer(bh);
                         /* the journal_head may have gone by now */
                         BUFFER_TRACE(bh, "brelse");
                         __brelse(bh);
-                        spin_lock(&journal->j_list_lock);
-                        goto restart;
+                        goto out_return_1;
                 }
+
                 /*
-                 * Now in whatever state the buffer currently is, we know that
-                 * it has been written out and so we can drop it from the list
+                 * This is foul
                  */
-                released = __journal_remove_checkpoint(jh);
-                jbd_unlock_bh_state(bh);
-        }
+                if (!jbd_trylock_bh_state(bh)) {
+                        jbd_sync_bh(journal, bh);
+                        goto out_return_1;
+                }
+
+                if (jh->b_transaction != NULL) {
+                        transaction_t *t = jh->b_transaction;
+                        tid_t tid = t->t_tid;
+
+                        spin_unlock(&journal->j_list_lock);
+                        jbd_unlock_bh_state(bh);
+                        log_start_commit(journal, tid);
+                        log_wait_commit(journal, tid);
+                        goto out_return_1;
+                }
+
+                /*
+                 * AKPM: I think the buffer_jbddirty test is redundant - it
+                 * shouldn't have NULL b_transaction?
+                 */
+                next_jh = jh->b_cpnext;
+                if (!buffer_dirty(bh) && !buffer_jbddirty(bh)) {
+                        BUFFER_TRACE(bh, "remove from checkpoint");
+                        __journal_remove_checkpoint(jh);
+                        jbd_unlock_bh_state(bh);
+                        journal_remove_journal_head(bh);
+                        __brelse(bh);
+                        ret = 1;
+                } else {
+                        jbd_unlock_bh_state(bh);
+                }
+        } while (jh != last_jh);
+
+        return ret;
+out_return_1:
+        spin_lock(&journal->j_list_lock);
+        return 1;
 }
 
 #define NR_BATCH        64
@@ -218,7 +203,9 @@ __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
 {
         int i;
 
+        spin_unlock(&journal->j_list_lock);
         ll_rw_block(SWRITE, *batch_count, bhs);
+        spin_lock(&journal->j_list_lock);
         for (i = 0; i < *batch_count; i++) {
                 struct buffer_head *bh = bhs[i];
                 clear_buffer_jwrite(bh);
@@ -234,46 +221,19 @@ __flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
  * Return 1 if something happened which requires us to abort the current
  * scan of the checkpoint list.  
  *
- * Called with j_list_lock held and drops it if 1 is returned
+ * Called with j_list_lock held.
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
-static int __process_buffer(journal_t *journal, struct journal_head *jh,
-                        struct buffer_head **bhs, int *batch_count)
+static int __flush_buffer(journal_t *journal, struct journal_head *jh,
+                        struct buffer_head **bhs, int *batch_count,
+                        int *drop_count)
 {
         struct buffer_head *bh = jh2bh(jh);
         int ret = 0;
 
-        if (buffer_locked(bh)) {
-                get_bh(bh);
-                spin_unlock(&journal->j_list_lock);
-                jbd_unlock_bh_state(bh);
-                wait_on_buffer(bh);
-                /* the journal_head may have gone by now */
-                BUFFER_TRACE(bh, "brelse");
-                put_bh(bh);
-                ret = 1;
-        }
-        else if (jh->b_transaction != NULL) {
-                transaction_t *t = jh->b_transaction;
-                tid_t tid = t->t_tid;
+        if (buffer_dirty(bh) && !buffer_locked(bh) && jh->b_jlist == BJ_None) {
+                J_ASSERT_JH(jh, jh->b_transaction == NULL);
 
-                spin_unlock(&journal->j_list_lock);
-                jbd_unlock_bh_state(bh);
-                log_start_commit(journal, tid);
-                log_wait_commit(journal, tid);
-                ret = 1;
-        }
-        else if (!buffer_dirty(bh)) {
-                J_ASSERT_JH(jh, !buffer_jbddirty(bh));
-                BUFFER_TRACE(bh, "remove from checkpoint");
-                __journal_remove_checkpoint(jh);
-                spin_unlock(&journal->j_list_lock);
-                jbd_unlock_bh_state(bh);
-                journal_remove_journal_head(bh);
-                put_bh(bh);
-                ret = 1;
-        }
-        else {
                 /*
                  * Important: we are about to write the buffer, and
                  * possibly block, while still holding the journal lock.
@@ -286,30 +246,45 @@ static int __process_buffer(journal_t *journal, struct journal_head *jh,
                 J_ASSERT_BH(bh, !buffer_jwrite(bh));
                 set_buffer_jwrite(bh);
                 bhs[*batch_count] = bh;
-                __buffer_relink_io(jh);
                 jbd_unlock_bh_state(bh);
                 (*batch_count)++;
                 if (*batch_count == NR_BATCH) {
-                        spin_unlock(&journal->j_list_lock);
                         __flush_batch(journal, bhs, batch_count);
                         ret = 1;
                 }
+        } else {
+                int last_buffer = 0;
+                if (jh->b_cpnext == jh) {
+                        /* We may be about to drop the transaction.  Tell the
+                         * caller that the lists have changed.
+                         */
+                        last_buffer = 1;
+                }
+                if (__try_to_free_cp_buf(jh)) {
+                        (*drop_count)++;
+                        ret = last_buffer;
+                }
         }
         return ret;
 }
 
 /*
- * Perform an actual checkpoint. We take the first transaction on the
- * list of transactions to be checkpointed and send all its buffers
- * to disk. We submit larger chunks of data at once.
+ * Perform an actual checkpoint.  We don't write out only enough to
+ * satisfy the current blocked requests: rather we submit a reasonably
+ * sized chunk of the outstanding data to disk at once for
+ * efficiency.  __log_wait_for_space() will retry if we didn't free enough.
  * 
+ * However, we _do_ take into account the amount requested so that once
+ * the IO has been queued, we can return as soon as enough of it has
+ * completed to disk.
+ *
  * The journal should be locked before calling this function.
  */
 int log_do_checkpoint(journal_t *journal)
 {
-        transaction_t *transaction;
-        tid_t this_tid;
         int result;
+        int batch_count = 0;
+        struct buffer_head *bhs[NR_BATCH];
 
         jbd_debug(1, "Start checkpoint\n");
 
@@ -324,70 +299,79 @@ int log_do_checkpoint(journal_t *journal)
                 return result;
 
         /*
-         * OK, we need to start writing disk blocks.  Take one transaction
-         * and write it.
+         * OK, we need to start writing disk blocks.  Try to free up a
+         * quarter of the log in a single checkpoint if we can.
          */
-        spin_lock(&journal->j_list_lock);
-        if (!journal->j_checkpoint_transactions)
-                goto out;
-        transaction = journal->j_checkpoint_transactions;
-        this_tid = transaction->t_tid;
-restart:
         /*
-         * If someone cleaned up this transaction while we slept, we're
-         * done (maybe it's a new transaction, but it fell at the same
-         * address).
+         * AKPM: check this code.  I had a feeling a while back that it
+         * degenerates into a busy loop at unmount time.
          */
-        if (journal->j_checkpoint_transactions == transaction &&
-                        transaction->t_tid == this_tid) {
-                int batch_count = 0;
-                struct buffer_head *bhs[NR_BATCH];
-                struct journal_head *jh;
-                int retry = 0;
-
-                while (!retry && transaction->t_checkpoint_list) {
+        spin_lock(&journal->j_list_lock);
+        while (journal->j_checkpoint_transactions) {
+                transaction_t *transaction;
+                struct journal_head *jh, *last_jh, *next_jh;
+                int drop_count = 0;
+                int cleanup_ret, retry = 0;
+                tid_t this_tid;
+
+                transaction = journal->j_checkpoint_transactions;
+                this_tid = transaction->t_tid;
+                jh = transaction->t_checkpoint_list;
+                last_jh = jh->b_cpprev;
+                next_jh = jh;
+                do {
                         struct buffer_head *bh;
 
-                        jh = transaction->t_checkpoint_list;
+                        jh = next_jh;
+                        next_jh = jh->b_cpnext;
                         bh = jh2bh(jh);
                         if (!jbd_trylock_bh_state(bh)) {
                                 jbd_sync_bh(journal, bh);
+                                spin_lock(&journal->j_list_lock);
                                 retry = 1;
                                 break;
                         }
-                        retry = __process_buffer(journal, jh, bhs,
-                                                &batch_count);
-                        if (!retry &&
-                            lock_need_resched(&journal->j_list_lock)) {
-                                spin_unlock(&journal->j_list_lock);
+                        retry = __flush_buffer(journal, jh, bhs, &batch_count, &drop_count);
+                        if (cond_resched_lock(&journal->j_list_lock)) {
                                 retry = 1;
                                 break;
                         }
-                }
+                } while (jh != last_jh && !retry);
 
                 if (batch_count) {
-                        if (!retry) {
-                                spin_unlock(&journal->j_list_lock);
-                                retry = 1;
-                        }
                         __flush_batch(journal, bhs, &batch_count);
+                        retry = 1;
                 }
 
-                if (retry) {
-                        spin_lock(&journal->j_list_lock);
-                        goto restart;
-                }
                 /*
-                 * Now we have cleaned up the first transaction's checkpoint
-                 * list.  Let's clean up the second one.
+                 * If someone cleaned up this transaction while we slept, we're
+                 * done
+                 */
+                if (journal->j_checkpoint_transactions != transaction)
+                        break;
+                if (retry)
+                        continue;
+                /*
+                 * Maybe it's a new transaction, but it fell at the same
+                 * address
                  */
-                __wait_cp_io(journal, transaction);
+                if (transaction->t_tid != this_tid)
+                        continue;
+                /*
+                 * We have walked the whole transaction list without
+                 * finding anything to write to disk.  We had better be
+                 * able to make some progress or we are in trouble.
+                 */
+                cleanup_ret = __cleanup_transaction(journal, transaction);
+                J_ASSERT(drop_count != 0 || cleanup_ret != 0);
+                if (journal->j_checkpoint_transactions != transaction)
+                        break;
         }
-out:
         spin_unlock(&journal->j_list_lock);
         result = cleanup_journal_tail(journal);
         if (result < 0)
                 return result;
+
         return 0;
 }
 
@@ -472,91 +456,52 @@ int cleanup_journal_tail(journal_t *journal)
 /* Checkpoint list management */
 
 /*
- * journal_clean_one_cp_list
- *
- * Find all the written-back checkpoint buffers in the given list and release them.
- *
- * Called with the journal locked.
- * Called with j_list_lock held.
- * Returns number of bufers reaped (for debug)
- */
-
-static int journal_clean_one_cp_list(struct journal_head *jh, int *released)
-{
-        struct journal_head *last_jh;
-        struct journal_head *next_jh = jh;
-        int ret, freed = 0;
-
-        *released = 0;
-        if (!jh)
-                return 0;
-
-        last_jh = jh->b_cpprev;
-        do {
-                jh = next_jh;
-                next_jh = jh->b_cpnext;
-                /* Use trylock because of the ranking */
-                if (jbd_trylock_bh_state(jh2bh(jh))) {
-                        ret = __try_to_free_cp_buf(jh);
-                        if (ret) {
-                                freed++;
-                                if (ret == 2) {
-                                        *released = 1;
-                                        return freed;
-                                }
-                        }
-                }
-                /*
-                 * This function only frees up some memory if possible so we
-                 * dont have an obligation to finish processing. Bail out if
-                 * preemption requested:
-                 */
-                if (need_resched())
-                        return freed;
-        } while (jh != last_jh);
-
-        return freed;
-}
-
-/*
  * journal_clean_checkpoint_list
  *
  * Find all the written-back checkpoint buffers in the journal and release them.
  *
  * Called with the journal locked.
  * Called with j_list_lock held.
- * Returns number of buffers reaped (for debug)
+ * Returns number of bufers reaped (for debug)
  */
 
 int __journal_clean_checkpoint_list(journal_t *journal)
 {
         transaction_t *transaction, *last_transaction, *next_transaction;
-        int ret = 0, released;
+        int ret = 0;
 
         transaction = journal->j_checkpoint_transactions;
-        if (!transaction)
+        if (transaction == 0)
                 goto out;
 
         last_transaction = transaction->t_cpprev;
         next_transaction = transaction;
         do {
+                struct journal_head *jh;
+
                 transaction = next_transaction;
                 next_transaction = transaction->t_cpnext;
-                ret += journal_clean_one_cp_list(transaction->
-                                t_checkpoint_list, &released);
-                if (need_resched())
-                        goto out;
-                if (released)
-                        continue;
-                /*
-                 * It is essential that we are as careful as in the case of
-                 * t_checkpoint_list with removing the buffer from the list as
-                 * we can possibly see not yet submitted buffers on io_list
-                 */
-                ret += journal_clean_one_cp_list(transaction->
-                                t_checkpoint_io_list, &released);
-                if (need_resched())
-                        goto out;
+                jh = transaction->t_checkpoint_list;
+                if (jh) {
+                        struct journal_head *last_jh = jh->b_cpprev;
+                        struct journal_head *next_jh = jh;
+
+                        do {
+                                jh = next_jh;
+                                next_jh = jh->b_cpnext;
+                                /* Use trylock because of the ranknig */
+                                if (jbd_trylock_bh_state(jh2bh(jh)))
+                                        ret += __try_to_free_cp_buf(jh);
+                                /*
+                                 * This function only frees up some memory
+                                 * if possible so we dont have an obligation
+                                 * to finish processing. Bail out if preemption
+                                 * requested:
+                                 */
+                                if (need_resched())
+                                        goto out;
+                        } while (jh != last_jh);
+                }
         } while (transaction != last_transaction);
 out:
         return ret;
@@ -571,22 +516,18 @@ out:
  * buffer updates committed in that transaction have safely been stored
  * elsewhere on disk.  To achieve this, all of the buffers in a
  * transaction need to be maintained on the transaction's checkpoint
- * lists until they have been rewritten, at which point this function is
+ * list until they have been rewritten, at which point this function is
  * called to remove the buffer from the existing transaction's
- * checkpoint lists.
- *
- * The function returns 1 if it frees the transaction, 0 otherwise.
+ * checkpoint list.
  *
  * This function is called with the journal locked.
  * This function is called with j_list_lock held.
- * This function is called with jbd_lock_bh_state(jh2bh(jh))
  */
 
-int __journal_remove_checkpoint(struct journal_head *jh)
+void __journal_remove_checkpoint(struct journal_head *jh)
 {
         transaction_t *transaction;
         journal_t *journal;
-        int ret = 0;
 
         JBUFFER_TRACE(jh, "entry");
 
@@ -597,10 +538,8 @@ int __journal_remove_checkpoint(struct journal_head *jh)
         journal = transaction->t_journal;
 
         __buffer_unlink(jh);
-        jh->b_cp_transaction = NULL;
 
-        if (transaction->t_checkpoint_list != NULL ||
-            transaction->t_checkpoint_io_list != NULL)
+        if (transaction->t_checkpoint_list != NULL)
                 goto out;
         JBUFFER_TRACE(jh, "transaction has no more buffers");
 
@@ -626,10 +565,8 @@ int __journal_remove_checkpoint(struct journal_head *jh)
         /* Just in case anybody was waiting for more transactions to be
            checkpointed... */
         wake_up(&journal->j_wait_logspace);
-        ret = 1;
 out:
         JBUFFER_TRACE(jh, "exit");
-        return ret;
 }
 
 /*
@@ -691,7 +628,6 @@ void __journal_drop_transaction(journal_t *journal, transaction_t *transaction)
         J_ASSERT(transaction->t_shadow_list == NULL);
         J_ASSERT(transaction->t_log_list == NULL);
         J_ASSERT(transaction->t_checkpoint_list == NULL);
-        J_ASSERT(transaction->t_checkpoint_io_list == NULL);
         J_ASSERT(transaction->t_updates == 0);
         J_ASSERT(journal->j_committing_transaction != transaction);
         J_ASSERT(journal->j_running_transaction != transaction);
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index 29e62d98bae6..002ad2bbc769 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -829,8 +829,7 @@ restart_loop:
         journal->j_committing_transaction = NULL;
         spin_unlock(&journal->j_state_lock);
 
-        if (commit_transaction->t_checkpoint_list == NULL &&
-            commit_transaction->t_checkpoint_io_list == NULL) {
+        if (commit_transaction->t_checkpoint_list == NULL) {
                 __journal_drop_transaction(journal, commit_transaction);
         } else {
                 if (journal->j_checkpoint_transactions == NULL) {
diff --git a/include/linux/jbd.h b/include/linux/jbd.h
index 0fe4aa891ddc..41ee79962bb2 100644
--- a/include/linux/jbd.h
+++ b/include/linux/jbd.h
@@ -498,12 +498,6 @@ struct transaction_s
         struct journal_head     *t_checkpoint_list;
 
         /*
-         * Doubly-linked circular list of all buffers submitted for IO while
-         * checkpointing. [j_list_lock]
-         */
-        struct journal_head     *t_checkpoint_io_list;
-
-        /*
          * Doubly-linked circular list of temporary buffers currently undergoing
          * IO in the log [j_list_lock]
          */
@@ -852,7 +846,7 @@ extern void journal_commit_transaction(journal_t *);
 
 /* Checkpoint list management */
 int __journal_clean_checkpoint_list(journal_t *journal);
-int __journal_remove_checkpoint(struct journal_head *);
+void __journal_remove_checkpoint(struct journal_head *);
 void __journal_insert_checkpoint(struct journal_head *, transaction_t *);
 
 /* Buffer IO */