1 files changed, 239 insertions, 180 deletions

diff --git a/fs/jbd/checkpoint.c b/fs/jbd/checkpoint.c
index 3f5102b069db..47678a26c13b 100644
--- a/fs/jbd/checkpoint.c
+++ b/fs/jbd/checkpoint.c
@@ -24,29 +24,67 @@
 #include <linux/slab.h>
 
 /*
- * Unlink a buffer from a transaction.
+ * Unlink a buffer from a transaction checkpoint list.
  *
  * Called with j_list_lock held.
  */
-
-static inline void __buffer_unlink(struct journal_head *jh)
+static inline void __buffer_unlink_first(struct journal_head *jh)
 {
-        transaction_t *transaction;
-
-        transaction = jh->b_cp_transaction;
-        jh->b_cp_transaction = NULL;
+        transaction_t *transaction = jh->b_cp_transaction;
 
         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;
+                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 = 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 = 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;
 }
 
 /*
  * Try to release a checkpointed buffer from its transaction.
- * Returns 1 if we released it.
+ * Returns 1 if we released it and 2 if we also released the
+ * whole transaction.
+ *
  * Requires j_list_lock
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
@@ -57,12 +95,11 @@ 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");
-                __journal_remove_checkpoint(jh);
+                ret = __journal_remove_checkpoint(jh) + 1;
                 jbd_unlock_bh_state(bh);
                 journal_remove_journal_head(bh);
                 BUFFER_TRACE(bh, "release");
                 __brelse(bh);
-                ret = 1;
         } else {
                 jbd_unlock_bh_state(bh);
         }
@@ -117,83 +154,54 @@ static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
 }
 
 /*
- * 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)
+ * 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.
  *
  * Called with j_list_lock held.
  */
-static int __cleanup_transaction(journal_t *journal, transaction_t *transaction)
+static void __wait_cp_io(journal_t *journal, transaction_t *transaction)
 {
-        struct journal_head *jh, *next_jh, *last_jh;
+        struct journal_head *jh;
         struct buffer_head *bh;
-        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;
+        tid_t this_tid;
+        int released = 0;
+
+        this_tid = transaction->t_tid;
+restart:
+        /* Did 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;
                 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);
-                        goto out_return_1;
+                        spin_lock(&journal->j_list_lock);
+                        goto restart;
                 }
-
                 /*
-                 * This is foul
+                 * 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
                  */
-                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;
+                released = __journal_remove_checkpoint(jh);
+                jbd_unlock_bh_state(bh);
+                journal_remove_journal_head(bh);
+                __brelse(bh);
+        }
 }
 
 #define NR_BATCH        64
@@ -203,9 +211,7 @@ __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);
@@ -221,19 +227,43 @@ __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.
+ * Called with j_list_lock held and drops it if 1 is returned
  * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
  */
-static int __flush_buffer(journal_t *journal, struct journal_head *jh,
-                        struct buffer_head **bhs, int *batch_count,
-                        int *drop_count)
+static int __process_buffer(journal_t *journal, struct journal_head *jh,
+                        struct buffer_head **bhs, int *batch_count)
 {
         struct buffer_head *bh = jh2bh(jh);
         int ret = 0;
 
-        if (buffer_dirty(bh) && !buffer_locked(bh) && jh->b_jlist == BJ_None) {
-                J_ASSERT_JH(jh, jh->b_transaction == NULL);
+        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);
+                ret = 1;
+        } else 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);
+                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);
+                __brelse(bh);
+                ret = 1;
+        } else {
                 /*
                  * Important: we are about to write the buffer, and
                  * possibly block, while still holding the journal lock.
@@ -246,45 +276,30 @@ static int __flush_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 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.
+ * 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.
  * 
- * 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");
 
@@ -299,79 +314,68 @@ int log_do_checkpoint(journal_t *journal)
                 return result;
 
         /*
-         * OK, we need to start writing disk blocks.  Try to free up a
-         * quarter of the log in a single checkpoint if we can.
+         * OK, we need to start writing disk blocks.  Take one transaction
+         * and write it.
          */
+        spin_lock(&journal->j_list_lock);
+        if (!journal->j_checkpoint_transactions)
+                goto out;
+        transaction = journal->j_checkpoint_transactions;
+        this_tid = transaction->t_tid;
+restart:
         /*
-         * AKPM: check this code.  I had a feeling a while back that it
-         * degenerates into a busy loop at unmount time.
+         * 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).
          */
-        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 {
+        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) {
                         struct buffer_head *bh;
 
-                        jh = next_jh;
-                        next_jh = jh->b_cpnext;
+                        jh = transaction->t_checkpoint_list;
                         bh = jh2bh(jh);
                         if (!jbd_trylock_bh_state(bh)) {
                                 jbd_sync_bh(journal, bh);
-                                spin_lock(&journal->j_list_lock);
                                 retry = 1;
                                 break;
                         }
-                        retry = __flush_buffer(journal, jh, bhs, &batch_count, &drop_count);
-                        if (cond_resched_lock(&journal->j_list_lock)) {
+                        retry = __process_buffer(journal, jh, bhs,&batch_count);
+                        if (!retry && lock_need_resched(&journal->j_list_lock)){
+                                spin_unlock(&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;
+                }
                 /*
-                 * 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
-                 */
-                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.
+                 * Now we have cleaned up the first transaction's checkpoint
+                 * list. Let's clean up the second one
                  */
-                cleanup_ret = __cleanup_transaction(journal, transaction);
-                J_ASSERT(drop_count != 0 || cleanup_ret != 0);
-                if (journal->j_checkpoint_transactions != transaction)
-                        break;
+                __wait_cp_io(journal, transaction);
         }
+out:
         spin_unlock(&journal->j_list_lock);
         result = cleanup_journal_tail(journal);
         if (result < 0)
                 return result;
-
         return 0;
 }
 
@@ -456,52 +460,98 @@ 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 bufers reaped (for debug)
+ * Returns number of buffers reaped (for debug)
  */
 
 int __journal_clean_checkpoint_list(journal_t *journal)
 {
         transaction_t *transaction, *last_transaction, *next_transaction;
         int ret = 0;
+        int released;
 
         transaction = journal->j_checkpoint_transactions;
-        if (transaction == 0)
+        if (!transaction)
                 goto out;
 
         last_transaction = transaction->t_cpprev;
         next_transaction = transaction;
         do {
-                struct journal_head *jh;
-
                 transaction = next_transaction;
                 next_transaction = transaction->t_cpnext;
-                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);
-                }
+                ret += journal_clean_one_cp_list(transaction->
+                                t_checkpoint_list, &released);
+                /*
+                 * 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;
+                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;
         } while (transaction != last_transaction);
 out:
         return ret;
@@ -516,18 +566,22 @@ 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
- * list until they have been rewritten, at which point this function is
+ * lists until they have been rewritten, at which point this function is
  * called to remove the buffer from the existing transaction's
- * checkpoint list.
+ * checkpoint lists.
+ *
+ * The function returns 1 if it frees the transaction, 0 otherwise.
  *
  * 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))
  */
 
-void __journal_remove_checkpoint(struct journal_head *jh)
+int __journal_remove_checkpoint(struct journal_head *jh)
 {
         transaction_t *transaction;
         journal_t *journal;
+        int ret = 0;
 
         JBUFFER_TRACE(jh, "entry");
 
@@ -538,8 +592,10 @@ void __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)
+        if (transaction->t_checkpoint_list != NULL ||
+            transaction->t_checkpoint_io_list != NULL)
                 goto out;
         JBUFFER_TRACE(jh, "transaction has no more buffers");
 
@@ -565,8 +621,10 @@ void __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;
 }
 
 /*
@@ -628,6 +686,7 @@ 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);