1 files changed, 697 insertions, 0 deletions

diff --git a/fs/jbd2/checkpoint.c b/fs/jbd2/checkpoint.c
new file mode 100644
index 000000000000..0208cc7ac5d0
--- /dev/null
+++ b/fs/jbd2/checkpoint.c
@@ -0,0 +1,697 @@
+/*
+ * linux/fs/checkpoint.c
+ *
+ * Written by Stephen C. Tweedie <sct@redhat.com>, 1999
+ *
+ * Copyright 1999 Red Hat Software --- All Rights Reserved
+ *
+ * This file is part of the Linux kernel and is made available under
+ * the terms of the GNU General Public License, version 2, or at your
+ * option, any later version, incorporated herein by reference.
+ *
+ * Checkpoint routines for the generic filesystem journaling code.
+ * Part of the ext2fs journaling system.
+ *
+ * Checkpointing is the process of ensuring that a section of the log is
+ * committed fully to disk, so that that portion of the log can be
+ * reused.
+ */
+
+#include <linux/time.h>
+#include <linux/fs.h>
+#include <linux/jbd.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+
+/*
+ * Unlink a buffer from a transaction checkpoint list.
+ *
+ * Called with j_list_lock held.
+ */
+static inline void __buffer_unlink_first(struct journal_head *jh)
+{
+        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) {
+                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 = 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 and 2 if we also released the
+ * whole transaction.
+ *
+ * Requires j_list_lock
+ * Called under jbd_lock_bh_state(jh2bh(jh)), and drops it
+ */
+static int __try_to_free_cp_buf(struct journal_head *jh)
+{
+        int ret = 0;
+        struct buffer_head *bh = jh2bh(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;
+                jbd_unlock_bh_state(bh);
+                journal_remove_journal_head(bh);
+                BUFFER_TRACE(bh, "release");
+                __brelse(bh);
+        } else {
+                jbd_unlock_bh_state(bh);
+        }
+        return ret;
+}
+
+/*
+ * __log_wait_for_space: wait until there is space in the journal.
+ *
+ * Called under j-state_lock *only*.  It will be unlocked if we have to wait
+ * for a checkpoint to free up some space in the log.
+ */
+void __log_wait_for_space(journal_t *journal)
+{
+        int nblocks;
+        assert_spin_locked(&journal->j_state_lock);
+
+        nblocks = jbd_space_needed(journal);
+        while (__log_space_left(journal) < nblocks) {
+                if (journal->j_flags & JFS_ABORT)
+                        return;
+                spin_unlock(&journal->j_state_lock);
+                mutex_lock(&journal->j_checkpoint_mutex);
+
+                /*
+                 * Test again, another process may have checkpointed while we
+                 * were waiting for the checkpoint lock
+                 */
+                spin_lock(&journal->j_state_lock);
+                nblocks = jbd_space_needed(journal);
+                if (__log_space_left(journal) < nblocks) {
+                        spin_unlock(&journal->j_state_lock);
+                        log_do_checkpoint(journal);
+                        spin_lock(&journal->j_state_lock);
+                }
+                mutex_unlock(&journal->j_checkpoint_mutex);
+        }
+}
+
+/*
+ * We were unable to perform jbd_trylock_bh_state() inside j_list_lock.
+ * The caller must restart a list walk.  Wait for someone else to run
+ * jbd_unlock_bh_state().
+ */
+static void jbd_sync_bh(journal_t *journal, struct buffer_head *bh)
+        __releases(journal->j_list_lock)
+{
+        get_bh(bh);
+        spin_unlock(&journal->j_list_lock);
+        jbd_lock_bh_state(bh);
+        jbd_unlock_bh_state(bh);
+        put_bh(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.
+ *
+ * Called with j_list_lock held.
+ */
+static void __wait_cp_io(journal_t *journal, transaction_t *transaction)
+{
+        struct journal_head *jh;
+        struct buffer_head *bh;
+        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);
+                        spin_lock(&journal->j_list_lock);
+                        goto restart;
+                }
+                /*
+                 * 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
+                 */
+                released = __journal_remove_checkpoint(jh);
+                jbd_unlock_bh_state(bh);
+                journal_remove_journal_head(bh);
+                __brelse(bh);
+        }
+}
+
+#define NR_BATCH        64
+
+static void
+__flush_batch(journal_t *journal, struct buffer_head **bhs, int *batch_count)
+{
+        int i;
+
+        ll_rw_block(SWRITE, *batch_count, bhs);
+        for (i = 0; i < *batch_count; i++) {
+                struct buffer_head *bh = bhs[i];
+                clear_buffer_jwrite(bh);
+                BUFFER_TRACE(bh, "brelse");
+                __brelse(bh);
+        }
+        *batch_count = 0;
+}
+
+/*
+ * Try to flush one buffer from the checkpoint list to disk.
+ *
+ * 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 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)
+{
+        struct buffer_head *bh = jh2bh(jh);
+        int ret = 0;
+
+        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.
+                 * We cannot afford to let the transaction logic start
+                 * messing around with this buffer before we write it to
+                 * disk, as that would break recoverability.
+                 */
+                BUFFER_TRACE(bh, "queue");
+                get_bh(bh);
+                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;
+                }
+        }
+        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.
+ *
+ * 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;
+
+        jbd_debug(1, "Start checkpoint\n");
+
+        /*
+         * First thing: if there are any transactions in the log which
+         * don't need checkpointing, just eliminate them from the
+         * journal straight away.
+         */
+        result = cleanup_journal_tail(journal);
+        jbd_debug(1, "cleanup_journal_tail returned %d\n", result);
+        if (result <= 0)
+                return result;
+
+        /*
+         * 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:
+        /*
+         * 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).
+         */
+        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 = transaction->t_checkpoint_list;
+                        bh = jh2bh(jh);
+                        if (!jbd_trylock_bh_state(bh)) {
+                                jbd_sync_bh(journal, bh);
+                                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 = 1;
+                                break;
+                        }
+                }
+
+                if (batch_count) {
+                        if (!retry) {
+                                spin_unlock(&journal->j_list_lock);
+                                retry = 1;
+                        }
+                        __flush_batch(journal, bhs, &batch_count);
+                }
+
+                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
+                 */
+                __wait_cp_io(journal, transaction);
+        }
+out:
+        spin_unlock(&journal->j_list_lock);
+        result = cleanup_journal_tail(journal);
+        if (result < 0)
+                return result;
+        return 0;
+}
+
+/*
+ * Check the list of checkpoint transactions for the journal to see if
+ * we have already got rid of any since the last update of the log tail
+ * in the journal superblock.  If so, we can instantly roll the
+ * superblock forward to remove those transactions from the log.
+ *
+ * Return <0 on error, 0 on success, 1 if there was nothing to clean up.
+ *
+ * Called with the journal lock held.
+ *
+ * This is the only part of the journaling code which really needs to be
+ * aware of transaction aborts.  Checkpointing involves writing to the
+ * main filesystem area rather than to the journal, so it can proceed
+ * even in abort state, but we must not update the journal superblock if
+ * we have an abort error outstanding.
+ */
+
+int cleanup_journal_tail(journal_t *journal)
+{
+        transaction_t * transaction;
+        tid_t           first_tid;
+        unsigned long   blocknr, freed;
+
+        /* OK, work out the oldest transaction remaining in the log, and
+         * the log block it starts at.
+         *
+         * If the log is now empty, we need to work out which is the
+         * next transaction ID we will write, and where it will
+         * start. */
+
+        spin_lock(&journal->j_state_lock);
+        spin_lock(&journal->j_list_lock);
+        transaction = journal->j_checkpoint_transactions;
+        if (transaction) {
+                first_tid = transaction->t_tid;
+                blocknr = transaction->t_log_start;
+        } else if ((transaction = journal->j_committing_transaction) != NULL) {
+                first_tid = transaction->t_tid;
+                blocknr = transaction->t_log_start;
+        } else if ((transaction = journal->j_running_transaction) != NULL) {
+                first_tid = transaction->t_tid;
+                blocknr = journal->j_head;
+        } else {
+                first_tid = journal->j_transaction_sequence;
+                blocknr = journal->j_head;
+        }
+        spin_unlock(&journal->j_list_lock);
+        J_ASSERT(blocknr != 0);
+
+        /* If the oldest pinned transaction is at the tail of the log
+           already then there's not much we can do right now. */
+        if (journal->j_tail_sequence == first_tid) {
+                spin_unlock(&journal->j_state_lock);
+                return 1;
+        }
+
+        /* OK, update the superblock to recover the freed space.
+         * Physical blocks come first: have we wrapped beyond the end of
+         * the log?  */
+        freed = blocknr - journal->j_tail;
+        if (blocknr < journal->j_tail)
+                freed = freed + journal->j_last - journal->j_first;
+
+        jbd_debug(1,
+                  "Cleaning journal tail from %d to %d (offset %lu), "
+                  "freeing %lu\n",
+                  journal->j_tail_sequence, first_tid, blocknr, freed);
+
+        journal->j_free += freed;
+        journal->j_tail_sequence = first_tid;
+        journal->j_tail = blocknr;
+        spin_unlock(&journal->j_state_lock);
+        if (!(journal->j_flags & JFS_ABORT))
+                journal_update_superblock(journal, 1);
+        return 0;
+}
+
+
+/* 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)
+ */
+
+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)
+                goto out;
+
+        last_transaction = transaction->t_cpprev;
+        next_transaction = transaction;
+        do {
+                transaction = next_transaction;
+                next_transaction = transaction->t_cpnext;
+                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;
+}
+
+/*
+ * journal_remove_checkpoint: called after a buffer has been committed
+ * to disk (either by being write-back flushed to disk, or being
+ * committed to the log).
+ *
+ * We cannot safely clean a transaction out of the log until all of the
+ * 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
+ * called to remove the buffer from the existing transaction's
+ * 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))
+ */
+
+int __journal_remove_checkpoint(struct journal_head *jh)
+{
+        transaction_t *transaction;
+        journal_t *journal;
+        int ret = 0;
+
+        JBUFFER_TRACE(jh, "entry");
+
+        if ((transaction = jh->b_cp_transaction) == NULL) {
+                JBUFFER_TRACE(jh, "not on transaction");
+                goto out;
+        }
+        journal = transaction->t_journal;
+
+        __buffer_unlink(jh);
+        jh->b_cp_transaction = NULL;
+
+        if (transaction->t_checkpoint_list != NULL ||
+            transaction->t_checkpoint_io_list != NULL)
+                goto out;
+        JBUFFER_TRACE(jh, "transaction has no more buffers");
+
+        /*
+         * There is one special case to worry about: if we have just pulled the
+         * buffer off a committing transaction's forget list, then even if the
+         * checkpoint list is empty, the transaction obviously cannot be
+         * dropped!
+         *
+         * The locking here around j_committing_transaction is a bit sleazy.
+         * See the comment at the end of journal_commit_transaction().
+         */
+        if (transaction == journal->j_committing_transaction) {
+                JBUFFER_TRACE(jh, "belongs to committing transaction");
+                goto out;
+        }
+
+        /* OK, that was the last buffer for the transaction: we can now
+           safely remove this transaction from the log */
+
+        __journal_drop_transaction(journal, transaction);
+
+        /* 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;
+}
+
+/*
+ * journal_insert_checkpoint: put a committed buffer onto a checkpoint
+ * list so that we know when it is safe to clean the transaction out of
+ * the log.
+ *
+ * Called with the journal locked.
+ * Called with j_list_lock held.
+ */
+void __journal_insert_checkpoint(struct journal_head *jh,
+                               transaction_t *transaction)
+{
+        JBUFFER_TRACE(jh, "entry");
+        J_ASSERT_JH(jh, buffer_dirty(jh2bh(jh)) || buffer_jbddirty(jh2bh(jh)));
+        J_ASSERT_JH(jh, jh->b_cp_transaction == NULL);
+
+        jh->b_cp_transaction = transaction;
+
+        if (!transaction->t_checkpoint_list) {
+                jh->b_cpnext = jh->b_cpprev = jh;
+        } else {
+                jh->b_cpnext = transaction->t_checkpoint_list;
+                jh->b_cpprev = transaction->t_checkpoint_list->b_cpprev;
+                jh->b_cpprev->b_cpnext = jh;
+                jh->b_cpnext->b_cpprev = jh;
+        }
+        transaction->t_checkpoint_list = jh;
+}
+
+/*
+ * We've finished with this transaction structure: adios...
+ *
+ * The transaction must have no links except for the checkpoint by this
+ * point.
+ *
+ * Called with the journal locked.
+ * Called with j_list_lock held.
+ */
+
+void __journal_drop_transaction(journal_t *journal, transaction_t *transaction)
+{
+        assert_spin_locked(&journal->j_list_lock);
+        if (transaction->t_cpnext) {
+                transaction->t_cpnext->t_cpprev = transaction->t_cpprev;
+                transaction->t_cpprev->t_cpnext = transaction->t_cpnext;
+                if (journal->j_checkpoint_transactions == transaction)
+                        journal->j_checkpoint_transactions =
+                                transaction->t_cpnext;
+                if (journal->j_checkpoint_transactions == transaction)
+                        journal->j_checkpoint_transactions = NULL;
+        }
+
+        J_ASSERT(transaction->t_state == T_FINISHED);
+        J_ASSERT(transaction->t_buffers == NULL);
+        J_ASSERT(transaction->t_sync_datalist == NULL);
+        J_ASSERT(transaction->t_forget == NULL);
+        J_ASSERT(transaction->t_iobuf_list == NULL);
+        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);
+
+        jbd_debug(1, "Dropping transaction %d, all done\n", transaction->t_tid);
+        kfree(transaction);
+}