jbd2: limit number of reserved credits

[cascardo/linux.git] / fs / jbd2 / transaction.c

diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c
index a6eec97..6b8338e 100644 (file)
--- a/fs/jbd2/transaction.c
+++ b/fs/jbd2/transaction.c
@@ -204,6 +204,20 @@ static int add_transaction_credits(journal_t *journal, int blocks,
                 * attach this handle to a new transaction.
                 */
                atomic_sub(total, &t->t_outstanding_credits);
+
+               /*
+                * Is the number of reserved credits in the current transaction too
+                * big to fit this handle? Wait until reserved credits are freed.
+                */
+               if (atomic_read(&journal->j_reserved_credits) + total >
+                   journal->j_max_transaction_buffers) {
+                       read_unlock(&journal->j_state_lock);
+                       wait_event(journal->j_wait_reserved,
+                                  atomic_read(&journal->j_reserved_credits) + total <=
+                                  journal->j_max_transaction_buffers);
+                       return 1;
+               }
+
                wait_transaction_locked(journal);
                return 1;
        }
@@ -262,20 +276,24 @@ static int start_this_handle(journal_t *journal, handle_t *handle,
        int             rsv_blocks = 0;
        unsigned long ts = jiffies;
 
+       if (handle->h_rsv_handle)
+               rsv_blocks = handle->h_rsv_handle->h_buffer_credits;
+
        /*
-        * 1/2 of transaction can be reserved so we can practically handle
-        * only 1/2 of maximum transaction size per operation
+        * Limit the number of reserved credits to 1/2 of maximum transaction
+        * size and limit the number of total credits to not exceed 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, blocks,
-                      journal->j_max_transaction_buffers / 2);
+       if ((rsv_blocks > journal->j_max_transaction_buffers / 2) ||
+           (rsv_blocks + blocks > journal->j_max_transaction_buffers)) {
+               printk(KERN_ERR "JBD2: %s wants too many credits "
+                      "credits:%d rsv_credits:%d max:%d\n",
+                      current->comm, blocks, rsv_blocks,
+                      journal->j_max_transaction_buffers);
+               WARN_ON(1);
                return -ENOSPC;
        }
 
-       if (handle->h_rsv_handle)
-               rsv_blocks = handle->h_rsv_handle->h_buffer_credits;
-
 alloc_transaction:
        if (!journal->j_running_transaction) {
                /*