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-rw-r--r--fs/jbd/transaction.c57
1 files changed, 55 insertions, 2 deletions
diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
index 67ff2024c23c..8dee32007500 100644
--- a/fs/jbd/transaction.c
+++ b/fs/jbd/transaction.c
@@ -1648,12 +1648,42 @@ out:
return;
}
+/*
+ * journal_try_to_free_buffers() could race with journal_commit_transaction()
+ * The latter might still hold the a count on buffers when inspecting
+ * them on t_syncdata_list or t_locked_list.
+ *
+ * journal_try_to_free_buffers() will call this function to
+ * wait for the current transaction to finish syncing data buffers, before
+ * tryinf to free that buffer.
+ *
+ * Called with journal->j_state_lock held.
+ */
+static void journal_wait_for_transaction_sync_data(journal_t *journal)
+{
+ transaction_t *transaction = NULL;
+ tid_t tid;
+
+ spin_lock(&journal->j_state_lock);
+ transaction = journal->j_committing_transaction;
+
+ if (!transaction) {
+ spin_unlock(&journal->j_state_lock);
+ return;
+ }
+
+ tid = transaction->t_tid;
+ spin_unlock(&journal->j_state_lock);
+ log_wait_commit(journal, tid);
+}
/**
* int journal_try_to_free_buffers() - try to free page buffers.
* @journal: journal for operation
* @page: to try and free
- * @unused_gfp_mask: unused
+ * @gfp_mask: we use the mask to detect how hard should we try to release
+ * buffers. If __GFP_WAIT and __GFP_FS is set, we wait for commit code to
+ * release the buffers.
*
*
* For all the buffers on this page,
@@ -1682,9 +1712,11 @@ out:
* journal_try_to_free_buffer() is changing its state. But that
* cannot happen because we never reallocate freed data as metadata
* while the data is part of a transaction. Yes?
+ *
+ * Return 0 on failure, 1 on success
*/
int journal_try_to_free_buffers(journal_t *journal,
- struct page *page, gfp_t unused_gfp_mask)
+ struct page *page, gfp_t gfp_mask)
{
struct buffer_head *head;
struct buffer_head *bh;
@@ -1713,7 +1745,28 @@ int journal_try_to_free_buffers(journal_t *journal,
if (buffer_jbd(bh))
goto busy;
} while ((bh = bh->b_this_page) != head);
+
ret = try_to_free_buffers(page);
+
+ /*
+ * There are a number of places where journal_try_to_free_buffers()
+ * could race with journal_commit_transaction(), the later still
+ * holds the reference to the buffers to free while processing them.
+ * try_to_free_buffers() failed to free those buffers. Some of the
+ * caller of releasepage() request page buffers to be dropped, otherwise
+ * treat the fail-to-free as errors (such as generic_file_direct_IO())
+ *
+ * So, if the caller of try_to_release_page() wants the synchronous
+ * behaviour(i.e make sure buffers are dropped upon return),
+ * let's wait for the current transaction to finish flush of
+ * dirty data buffers, then try to free those buffers again,
+ * with the journal locked.
+ */
+ if (ret == 0 && (gfp_mask & __GFP_WAIT) && (gfp_mask & __GFP_FS)) {
+ journal_wait_for_transaction_sync_data(journal);
+ ret = try_to_free_buffers(page);
+ }
+
busy:
return ret;
}