transaction->t_expires = jiffies + journal->j_commit_interval;
spin_lock_init(&transaction->t_handle_lock);
atomic_set(&transaction->t_updates, 0);
- atomic_set(&transaction->t_outstanding_credits, 0);
+ atomic_set(&transaction->t_outstanding_credits,
+ atomic_read(&journal->j_reserved_credits));
atomic_set(&transaction->t_handle_count, 0);
INIT_LIST_HEAD(&transaction->t_inode_list);
INIT_LIST_HEAD(&transaction->t_private_list);
#endif
}
+/*
+ * Wait until running transaction passes T_LOCKED state. Also starts the commit
+ * if needed. The function expects running transaction to exist and releases
+ * j_state_lock.
+ */
+static void wait_transaction_locked(journal_t *journal)
+ __releases(journal->j_state_lock)
+{
+ DEFINE_WAIT(wait);
+ int need_to_start;
+ tid_t tid = journal->j_running_transaction->t_tid;
+
+ prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
+ TASK_UNINTERRUPTIBLE);
+ need_to_start = !tid_geq(journal->j_commit_request, tid);
+ read_unlock(&journal->j_state_lock);
+ if (need_to_start)
+ jbd2_log_start_commit(journal, tid);
+ schedule();
+ finish_wait(&journal->j_wait_transaction_locked, &wait);
+}
+
+static void sub_reserved_credits(journal_t *journal, int blocks)
+{
+ atomic_sub(blocks, &journal->j_reserved_credits);
+ wake_up(&journal->j_wait_reserved);
+}
+
+/*
+ * Wait until we can add credits for handle to the running transaction. Called
+ * with j_state_lock held for reading. Returns 0 if handle joined the running
+ * transaction. Returns 1 if we had to wait, j_state_lock is dropped, and
+ * caller must retry.
+ */
+static int add_transaction_credits(journal_t *journal, int blocks,
+ int rsv_blocks)
+{
+ transaction_t *t = journal->j_running_transaction;
+ int needed;
+ int total = blocks + rsv_blocks;
+
+ /*
+ * If the current transaction is locked down for commit, wait
+ * for the lock to be released.
+ */
+ if (t->t_state == T_LOCKED) {
+ wait_transaction_locked(journal);
+ return 1;
+ }
+
+ /*
+ * If there is not enough space left in the log to write all
+ * potential buffers requested by this operation, we need to
+ * stall pending a log checkpoint to free some more log space.
+ */
+ needed = atomic_add_return(total, &t->t_outstanding_credits);
+ if (needed > journal->j_max_transaction_buffers) {
+ /*
+ * If the current transaction is already too large,
+ * then start to commit it: we can then go back and
+ * attach this handle to a new transaction.
+ */
+ atomic_sub(total, &t->t_outstanding_credits);
+ wait_transaction_locked(journal);
+ return 1;
+ }
+
+ /*
+ * The commit code assumes that it can get enough log space
+ * without forcing a checkpoint. This is *critical* for
+ * correctness: a checkpoint of a buffer which is also
+ * associated with a committing transaction creates a deadlock,
+ * so commit simply cannot force through checkpoints.
+ *
+ * We must therefore ensure the necessary space in the journal
+ * *before* starting to dirty potentially checkpointed buffers
+ * in the new transaction.
+ */
+ if (jbd2_log_space_left(journal) < jbd2_space_needed(journal)) {
+ atomic_sub(total, &t->t_outstanding_credits);
+ read_unlock(&journal->j_state_lock);
+ write_lock(&journal->j_state_lock);
+ if (jbd2_log_space_left(journal) < jbd2_space_needed(journal))
+ __jbd2_log_wait_for_space(journal);
+ write_unlock(&journal->j_state_lock);
+ return 1;
+ }
+
+ /* No reservation? We are done... */
+ if (!rsv_blocks)
+ return 0;
+
+ needed = atomic_add_return(rsv_blocks, &journal->j_reserved_credits);
+ /* We allow at most half of a transaction to be reserved */
+ if (needed > journal->j_max_transaction_buffers / 2) {
+ sub_reserved_credits(journal, rsv_blocks);
+ atomic_sub(total, &t->t_outstanding_credits);
+ read_unlock(&journal->j_state_lock);
+ wait_event(journal->j_wait_reserved,
+ atomic_read(&journal->j_reserved_credits) + rsv_blocks
+ <= journal->j_max_transaction_buffers / 2);
+ return 1;
+ }
+ return 0;
+}
+
/*
* start_this_handle: Given a handle, deal with any locking or stalling
* needed to make sure that there is enough journal space for the handle
gfp_t gfp_mask)
{
transaction_t *transaction, *new_transaction = NULL;
- tid_t tid;
- int needed, need_to_start;
- int nblocks = handle->h_buffer_credits;
+ int blocks = handle->h_buffer_credits;
+ int rsv_blocks = 0;
unsigned long ts = jiffies;
- if (nblocks > journal->j_max_transaction_buffers) {
+ /*
+ * 1/2 of transaction can be reserved so we can practically handle
+ * only 1/2 of maximum transaction size per operation
+ */
+ if (WARN_ON(blocks > journal->j_max_transaction_buffers / 2)) {
printk(KERN_ERR "JBD2: %s wants too many credits (%d > %d)\n",
- current->comm, nblocks,
- journal->j_max_transaction_buffers);
+ current->comm, blocks,
+ journal->j_max_transaction_buffers / 2);
return -ENOSPC;
}
+ if (handle->h_rsv_handle)
+ rsv_blocks = handle->h_rsv_handle->h_buffer_credits;
+
alloc_transaction:
if (!journal->j_running_transaction) {
new_transaction = kmem_cache_zalloc(transaction_cache,
return -EROFS;
}
- /* Wait on the journal's transaction barrier if necessary */
- if (journal->j_barrier_count) {
+ /*
+ * Wait on the journal's transaction barrier if necessary. Specifically
+ * we allow reserved handles to proceed because otherwise commit could
+ * deadlock on page writeback not being able to complete.
+ */
+ if (!handle->h_reserved && journal->j_barrier_count) {
read_unlock(&journal->j_state_lock);
wait_event(journal->j_wait_transaction_locked,
journal->j_barrier_count == 0);
goto alloc_transaction;
write_lock(&journal->j_state_lock);
if (!journal->j_running_transaction &&
- !journal->j_barrier_count) {
+ (handle->h_reserved || !journal->j_barrier_count)) {
jbd2_get_transaction(journal, new_transaction);
new_transaction = NULL;
}
transaction = journal->j_running_transaction;
- /*
- * If the current transaction is locked down for commit, wait for the
- * lock to be released.
- */
- if (transaction->t_state == T_LOCKED) {
- DEFINE_WAIT(wait);
-
- prepare_to_wait(&journal->j_wait_transaction_locked,
- &wait, TASK_UNINTERRUPTIBLE);
- read_unlock(&journal->j_state_lock);
- schedule();
- finish_wait(&journal->j_wait_transaction_locked, &wait);
- goto repeat;
- }
-
- /*
- * If there is not enough space left in the log to write all potential
- * buffers requested by this operation, we need to stall pending a log
- * checkpoint to free some more log space.
- */
- needed = atomic_add_return(nblocks,
- &transaction->t_outstanding_credits);
-
- if (needed > journal->j_max_transaction_buffers) {
+ if (!handle->h_reserved) {
+ /* We may have dropped j_state_lock - restart in that case */
+ if (add_transaction_credits(journal, blocks, rsv_blocks))
+ goto repeat;
+ } else {
/*
- * If the current transaction is already too large, then start
- * to commit it: we can then go back and attach this handle to
- * a new transaction.
+ * We have handle reserved so we are allowed to join T_LOCKED
+ * transaction and we don't have to check for transaction size
+ * and journal space.
*/
- DEFINE_WAIT(wait);
-
- jbd_debug(2, "Handle %p starting new commit...\n", handle);
- atomic_sub(nblocks, &transaction->t_outstanding_credits);
- prepare_to_wait(&journal->j_wait_transaction_locked, &wait,
- TASK_UNINTERRUPTIBLE);
- tid = transaction->t_tid;
- need_to_start = !tid_geq(journal->j_commit_request, tid);
- read_unlock(&journal->j_state_lock);
- if (need_to_start)
- jbd2_log_start_commit(journal, tid);
- schedule();
- finish_wait(&journal->j_wait_transaction_locked, &wait);
- goto repeat;
- }
-
- /*
- * The commit code assumes that it can get enough log space
- * without forcing a checkpoint. This is *critical* for
- * correctness: a checkpoint of a buffer which is also
- * associated with a committing transaction creates a deadlock,
- * so commit simply cannot force through checkpoints.
- *
- * We must therefore ensure the necessary space in the journal
- * *before* starting to dirty potentially checkpointed buffers
- * in the new transaction.
- *
- * The worst part is, any transaction currently committing can
- * reduce the free space arbitrarily. Be careful to account for
- * those buffers when checkpointing.
- */
- if (jbd2_log_space_left(journal) < jbd2_space_needed(journal)) {
- jbd_debug(2, "Handle %p waiting for checkpoint...\n", handle);
- atomic_sub(nblocks, &transaction->t_outstanding_credits);
- read_unlock(&journal->j_state_lock);
- write_lock(&journal->j_state_lock);
- if (jbd2_log_space_left(journal) < jbd2_space_needed(journal))
- __jbd2_log_wait_for_space(journal);
- write_unlock(&journal->j_state_lock);
- goto repeat;
+ sub_reserved_credits(journal, blocks);
+ handle->h_reserved = 0;
}
/* OK, account for the buffers that this operation expects to
*/
update_t_max_wait(transaction, ts);
handle->h_transaction = transaction;
- handle->h_requested_credits = nblocks;
+ handle->h_requested_credits = blocks;
handle->h_start_jiffies = jiffies;
atomic_inc(&transaction->t_updates);
atomic_inc(&transaction->t_handle_count);
- jbd_debug(4, "Handle %p given %d credits (total %d, free %d)\n",
- handle, nblocks,
+ jbd_debug(4, "Handle %p given %d credits (total %d, free %lu)\n",
+ handle, blocks,
atomic_read(&transaction->t_outstanding_credits),
jbd2_log_space_left(journal));
read_unlock(&journal->j_state_lock);
*
* We make sure that the transaction can guarantee at least nblocks of
* modified buffers in the log. We block until the log can guarantee
- * that much space.
- *
- * This function is visible to journal users (like ext3fs), so is not
- * called with the journal already locked.
+ * that much space. Additionally, if rsv_blocks > 0, we also create another
+ * handle with rsv_blocks reserved blocks in the journal. This handle is
+ * is stored in h_rsv_handle. It is not attached to any particular transaction
+ * and thus doesn't block transaction commit. If the caller uses this reserved
+ * handle, it has to set h_rsv_handle to NULL as otherwise jbd2_journal_stop()
+ * on the parent handle will dispose the reserved one. Reserved handle has to
+ * be converted to a normal handle using jbd2_journal_start_reserved() before
+ * it can be used.
*
* Return a pointer to a newly allocated handle, or an ERR_PTR() value
* on failure.
*/
-handle_t *jbd2__journal_start(journal_t *journal, int nblocks, gfp_t gfp_mask,
- unsigned int type, unsigned int line_no)
+handle_t *jbd2__journal_start(journal_t *journal, int nblocks, int rsv_blocks,
+ gfp_t gfp_mask, unsigned int type,
+ unsigned int line_no)
{
handle_t *handle = journal_current_handle();
int err;
handle = new_handle(nblocks);
if (!handle)
return ERR_PTR(-ENOMEM);
+ if (rsv_blocks) {
+ handle_t *rsv_handle;
+
+ rsv_handle = new_handle(rsv_blocks);
+ if (!rsv_handle) {
+ jbd2_free_handle(handle);
+ return ERR_PTR(-ENOMEM);
+ }
+ rsv_handle->h_reserved = 1;
+ rsv_handle->h_journal = journal;
+ handle->h_rsv_handle = rsv_handle;
+ }
current->journal_info = handle;
err = start_this_handle(journal, handle, gfp_mask);
if (err < 0) {
+ if (handle->h_rsv_handle)
+ jbd2_free_handle(handle->h_rsv_handle);
jbd2_free_handle(handle);
current->journal_info = NULL;
return ERR_PTR(err);
handle_t *jbd2_journal_start(journal_t *journal, int nblocks)
{
- return jbd2__journal_start(journal, nblocks, GFP_NOFS, 0, 0);
+ return jbd2__journal_start(journal, nblocks, 0, GFP_NOFS, 0, 0);
}
EXPORT_SYMBOL(jbd2_journal_start);
+void jbd2_journal_free_reserved(handle_t *handle)
+{
+ journal_t *journal = handle->h_journal;
+
+ WARN_ON(!handle->h_reserved);
+ sub_reserved_credits(journal, handle->h_buffer_credits);
+ jbd2_free_handle(handle);
+}
+EXPORT_SYMBOL(jbd2_journal_free_reserved);
+
+/**
+ * int jbd2_journal_start_reserved(handle_t *handle) - start reserved handle
+ * @handle: handle to start
+ *
+ * Start handle that has been previously reserved with jbd2_journal_reserve().
+ * This attaches @handle to the running transaction (or creates one if there's
+ * not transaction running). Unlike jbd2_journal_start() this function cannot
+ * block on journal commit, checkpointing, or similar stuff. It can block on
+ * memory allocation or frozen journal though.
+ *
+ * Return 0 on success, non-zero on error - handle is freed in that case.
+ */
+int jbd2_journal_start_reserved(handle_t *handle, unsigned int type,
+ unsigned int line_no)
+{
+ journal_t *journal = handle->h_journal;
+ int ret = -EIO;
+
+ if (WARN_ON(!handle->h_reserved)) {
+ /* Someone passed in normal handle? Just stop it. */
+ jbd2_journal_stop(handle);
+ return ret;
+ }
+ /*
+ * Usefulness of mixing of reserved and unreserved handles is
+ * questionable. So far nobody seems to need it so just error out.
+ */
+ if (WARN_ON(current->journal_info)) {
+ jbd2_journal_free_reserved(handle);
+ return ret;
+ }
+
+ handle->h_journal = NULL;
+ current->journal_info = handle;
+ /*
+ * GFP_NOFS is here because callers are likely from writeback or
+ * similarly constrained call sites
+ */
+ ret = start_this_handle(journal, handle, GFP_NOFS);
+ if (ret < 0) {
+ current->journal_info = NULL;
+ jbd2_journal_free_reserved(handle);
+ }
+ handle->h_type = type;
+ handle->h_line_no = line_no;
+ return ret;
+}
+EXPORT_SYMBOL(jbd2_journal_start_reserved);
/**
* int jbd2_journal_extend() - extend buffer credits.
}
spin_lock(&transaction->t_handle_lock);
- wanted = atomic_read(&transaction->t_outstanding_credits) + nblocks;
+ wanted = atomic_add_return(nblocks,
+ &transaction->t_outstanding_credits);
if (wanted > journal->j_max_transaction_buffers) {
jbd_debug(3, "denied handle %p %d blocks: "
"transaction too large\n", handle, nblocks);
+ atomic_sub(nblocks, &transaction->t_outstanding_credits);
goto unlock;
}
jbd2_log_space_left(journal)) {
jbd_debug(3, "denied handle %p %d blocks: "
"insufficient log space\n", handle, nblocks);
+ atomic_sub(nblocks, &transaction->t_outstanding_credits);
goto unlock;
}
handle->h_buffer_credits += nblocks;
handle->h_requested_credits += nblocks;
- atomic_add(nblocks, &transaction->t_outstanding_credits);
result = 0;
jbd_debug(3, "extended handle %p by %d\n", handle, nblocks);
* to a running handle, a call to jbd2_journal_restart will commit the
* handle's transaction so far and reattach the handle to a new
* transaction capabable of guaranteeing the requested number of
- * credits.
+ * credits. We preserve reserved handle if there's any attached to the
+ * passed in handle.
*/
int jbd2__journal_restart(handle_t *handle, int nblocks, gfp_t gfp_mask)
{
spin_lock(&transaction->t_handle_lock);
atomic_sub(handle->h_buffer_credits,
&transaction->t_outstanding_credits);
+ if (handle->h_rsv_handle) {
+ sub_reserved_credits(journal,
+ handle->h_rsv_handle->h_buffer_credits);
+ }
if (atomic_dec_and_test(&transaction->t_updates))
wake_up(&journal->j_wait_updates);
spin_unlock(&transaction->t_handle_lock);
write_lock(&journal->j_state_lock);
++journal->j_barrier_count;
+ /* Wait until there are no reserved handles */
+ if (atomic_read(&journal->j_reserved_credits)) {
+ write_unlock(&journal->j_state_lock);
+ wait_event(journal->j_wait_reserved,
+ atomic_read(&journal->j_reserved_credits) == 0);
+ write_lock(&journal->j_state_lock);
+ }
+
/* Wait until there are no running updates */
while (1) {
transaction_t *transaction = journal->j_running_transaction;
lock_map_release(&handle->h_lockdep_map);
+ if (handle->h_rsv_handle)
+ jbd2_journal_free_reserved(handle->h_rsv_handle);
jbd2_free_handle(handle);
return err;
}
projects / ~andy / linux / blobdiff